internal: simplify handling of the build scripts

18 files changed, 404 insertions, 491 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 82c7c143ffa..89e48435fbb 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1181,6 +1181,7 @@ dependencies = [
  "proc_macro_api",
  "profile",
  "rustc-hash",
+ "semver",
  "serde",
  "serde_json",
  "stdx",
diff --git a/crates/project_model/Cargo.toml b/crates/project_model/Cargo.toml
index e8d33b055bf..5c85bc19c31 100644
--- a/crates/project_model/Cargo.toml
+++ b/crates/project_model/Cargo.toml
@@ -12,6 +12,7 @@ doctest = false
 log = "0.4.8"
 rustc-hash = "1.1.0"
 cargo_metadata = "0.14"
+semver = "1"
 serde = { version = "1.0.106", features = ["derive"] }
 serde_json = "1.0.48"
 anyhow = "1.0.26"
diff --git a/crates/project_model/src/build_data.rs b/crates/project_model/src/build_data.rs
deleted file mode 100644
index 92ead0c4356..00000000000
--- a/crates/project_model/src/build_data.rs
+++ /dev/null
@@ -1,323 +0,0 @@
-//! Handles build script specific information
-
-use std::{
-    path::PathBuf,
-    process::{Command, Stdio},
-    sync::Arc,
-};
-
-use anyhow::Result;
-use base_db::CrateName;
-use cargo_metadata::camino::Utf8Path;
-use cargo_metadata::{BuildScript, Message};
-use paths::{AbsPath, AbsPathBuf};
-use rustc_hash::FxHashMap;
-use serde::Deserialize;
-use stdx::format_to;
-
-use crate::{cfg_flag::CfgFlag, CargoConfig};
-
-#[derive(Debug, Clone, Default, PartialEq, Eq)]
-pub(crate) struct PackageBuildData {
-    /// List of config flags defined by this package's build script
-    pub(crate) cfgs: Vec<CfgFlag>,
-    /// List of cargo-related environment variables with their value
-    ///
-    /// If the package has a build script which defines environment variables,
-    /// they can also be found here.
-    pub(crate) envs: Vec<(String, String)>,
-    /// Directory where a build script might place its output
-    pub(crate) out_dir: Option<AbsPathBuf>,
-    /// Path to the proc-macro library file if this package exposes proc-macros
-    pub(crate) proc_macro_dylib_path: Option<AbsPathBuf>,
-}
-
-#[derive(Debug, Default, PartialEq, Eq, Clone)]
-pub(crate) struct WorkspaceBuildData {
-    per_package: FxHashMap<String, PackageBuildData>,
-    error: Option<String>,
-}
-
-#[derive(Debug, Default, PartialEq, Eq, Clone)]
-pub struct BuildDataResult {
-    per_workspace: FxHashMap<AbsPathBuf, WorkspaceBuildData>,
-}
-
-#[derive(Clone, Debug)]
-pub(crate) struct BuildDataConfig {
-    cargo_toml: AbsPathBuf,
-    cargo_features: CargoConfig,
-    packages: Arc<Vec<cargo_metadata::Package>>,
-}
-
-impl PartialEq for BuildDataConfig {
-    fn eq(&self, other: &Self) -> bool {
-        Arc::ptr_eq(&self.packages, &other.packages)
-    }
-}
-
-impl Eq for BuildDataConfig {}
-
-#[derive(Debug)]
-pub struct BuildDataCollector {
-    wrap_rustc: bool,
-    configs: FxHashMap<AbsPathBuf, BuildDataConfig>,
-}
-
-impl BuildDataCollector {
-    pub fn new(wrap_rustc: bool) -> Self {
-        Self { wrap_rustc, configs: FxHashMap::default() }
-    }
-
-    pub(crate) fn add_config(&mut self, workspace_root: &AbsPath, config: BuildDataConfig) {
-        self.configs.insert(workspace_root.to_path_buf(), config);
-    }
-
-    pub fn collect(&mut self, progress: &dyn Fn(String)) -> Result<BuildDataResult> {
-        let mut res = BuildDataResult::default();
-        for (path, config) in self.configs.iter() {
-            let workspace_build_data = WorkspaceBuildData::collect(
-                &config.cargo_toml,
-                &config.cargo_features,
-                &config.packages,
-                self.wrap_rustc,
-                progress,
-            )?;
-            res.per_workspace.insert(path.clone(), workspace_build_data);
-        }
-        Ok(res)
-    }
-}
-
-impl WorkspaceBuildData {
-    pub(crate) fn get(&self, package_id: &str) -> Option<&PackageBuildData> {
-        self.per_package.get(package_id)
-    }
-}
-
-impl BuildDataResult {
-    pub(crate) fn get(&self, workspace_root: &AbsPath) -> Option<&WorkspaceBuildData> {
-        self.per_workspace.get(workspace_root)
-    }
-    pub fn error(&self) -> Option<String> {
-        let mut buf = String::new();
-        for (_workspace_root, build_data) in &self.per_workspace {
-            if let Some(err) = &build_data.error {
-                format_to!(buf, "cargo check failed:\n{}", err);
-            }
-        }
-        if buf.is_empty() {
-            return None;
-        }
-
-        Some(buf)
-    }
-}
-
-impl BuildDataConfig {
-    pub(crate) fn new(
-        cargo_toml: AbsPathBuf,
-        cargo_features: CargoConfig,
-        packages: Arc<Vec<cargo_metadata::Package>>,
-    ) -> Self {
-        Self { cargo_toml, cargo_features, packages }
-    }
-}
-
-impl WorkspaceBuildData {
-    fn collect(
-        cargo_toml: &AbsPath,
-        cargo_features: &CargoConfig,
-        packages: &Vec<cargo_metadata::Package>,
-        wrap_rustc: bool,
-        progress: &dyn Fn(String),
-    ) -> Result<WorkspaceBuildData> {
-        let mut cmd = Command::new(toolchain::cargo());
-
-        if wrap_rustc {
-            // Setup RUSTC_WRAPPER to point to `rust-analyzer` binary itself. We use
-            // that to compile only proc macros and build scripts during the initial
-            // `cargo check`.
-            let myself = std::env::current_exe()?;
-            cmd.env("RUSTC_WRAPPER", myself);
-            cmd.env("RA_RUSTC_WRAPPER", "1");
-        }
-
-        cmd.current_dir(cargo_toml.parent().unwrap());
-        cmd.args(&["check", "--quiet", "--workspace", "--message-format=json", "--manifest-path"])
-            .arg(cargo_toml.as_ref());
-
-        // --all-targets includes tests, benches and examples in addition to the
-        // default lib and bins. This is an independent concept from the --targets
-        // flag below.
-        cmd.arg("--all-targets");
-
-        if let Some(target) = &cargo_features.target {
-            cmd.args(&["--target", target]);
-        }
-
-        if cargo_features.all_features {
-            cmd.arg("--all-features");
-        } else {
-            if cargo_features.no_default_features {
-                // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
-                // https://github.com/oli-obk/cargo_metadata/issues/79
-                cmd.arg("--no-default-features");
-            }
-            if !cargo_features.features.is_empty() {
-                cmd.arg("--features");
-                cmd.arg(cargo_features.features.join(" "));
-            }
-        }
-
-        cmd.stdout(Stdio::piped()).stderr(Stdio::piped()).stdin(Stdio::null());
-
-        let mut res = WorkspaceBuildData::default();
-
-        let mut callback_err = None;
-        let output = stdx::process::streaming_output(
-            cmd,
-            &mut |line| {
-                if callback_err.is_some() {
-                    return;
-                }
-
-                // Copy-pasted from existing cargo_metadata. It seems like we
-                // should be using sered_stacker here?
-                let mut deserializer = serde_json::Deserializer::from_str(line);
-                deserializer.disable_recursion_limit();
-                let message = Message::deserialize(&mut deserializer)
-                    .unwrap_or_else(|_| Message::TextLine(line.to_string()));
-
-                match message {
-                    Message::BuildScriptExecuted(BuildScript {
-                        package_id,
-                        out_dir,
-                        cfgs,
-                        env,
-                        ..
-                    }) => {
-                        let cfgs = {
-                            let mut acc = Vec::new();
-                            for cfg in cfgs {
-                                match cfg.parse::<CfgFlag>() {
-                                    Ok(it) => acc.push(it),
-                                    Err(err) => {
-                                        callback_err = Some(anyhow::format_err!(
-                                            "invalid cfg from cargo-metadata: {}",
-                                            err
-                                        ));
-                                        return;
-                                    }
-                                };
-                            }
-                            acc
-                        };
-                        let package_build_data =
-                            res.per_package.entry(package_id.repr).or_default();
-                        // cargo_metadata crate returns default (empty) path for
-                        // older cargos, which is not absolute, so work around that.
-                        if !out_dir.as_str().is_empty() {
-                            let out_dir =
-                                AbsPathBuf::assert(PathBuf::from(out_dir.into_os_string()));
-                            package_build_data.out_dir = Some(out_dir);
-                            package_build_data.cfgs = cfgs;
-                        }
-
-                        package_build_data.envs = env;
-                    }
-                    Message::CompilerArtifact(message) => {
-                        progress(format!("metadata {}", message.target.name));
-
-                        if message.target.kind.iter().any(|k| k == "proc-macro") {
-                            let package_id = message.package_id;
-                            // Skip rmeta file
-                            if let Some(filename) =
-                                message.filenames.iter().find(|name| is_dylib(name))
-                            {
-                                let filename = AbsPathBuf::assert(PathBuf::from(&filename));
-                                let package_build_data =
-                                    res.per_package.entry(package_id.repr).or_default();
-                                package_build_data.proc_macro_dylib_path = Some(filename);
-                            }
-                        }
-                    }
-                    Message::CompilerMessage(message) => {
-                        progress(message.target.name);
-                    }
-                    Message::BuildFinished(_) => {}
-                    Message::TextLine(_) => {}
-                    _ => {}
-                }
-            },
-            &mut |_| (),
-        )?;
-
-        for package in packages {
-            let package_build_data = res.per_package.entry(package.id.repr.clone()).or_default();
-            inject_cargo_env(package, package_build_data);
-            if let Some(out_dir) = &package_build_data.out_dir {
-                // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
-                if let Some(out_dir) = out_dir.as_os_str().to_str().map(|s| s.to_owned()) {
-                    package_build_data.envs.push(("OUT_DIR".to_string(), out_dir));
-                }
-            }
-        }
-
-        if !output.status.success() {
-            let mut stderr = String::from_utf8(output.stderr).unwrap_or_default();
-            if stderr.is_empty() {
-                stderr = "cargo check failed".to_string();
-            }
-            res.error = Some(stderr)
-        }
-
-        Ok(res)
-    }
-}
-
-// FIXME: File a better way to know if it is a dylib
-fn is_dylib(path: &Utf8Path) -> bool {
-    match path.extension().map(|e| e.to_string().to_lowercase()) {
-        None => false,
-        Some(ext) => matches!(ext.as_str(), "dll" | "dylib" | "so"),
-    }
-}
-
-/// Recreates the compile-time environment variables that Cargo sets.
-///
-/// Should be synced with <https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates>
-fn inject_cargo_env(package: &cargo_metadata::Package, build_data: &mut PackageBuildData) {
-    let env = &mut build_data.envs;
-
-    // FIXME: Missing variables:
-    // CARGO_BIN_NAME, CARGO_BIN_EXE_<name>
-
-    let mut manifest_dir = package.manifest_path.clone();
-    manifest_dir.pop();
-    env.push(("CARGO_MANIFEST_DIR".into(), manifest_dir.into_string()));
-
-    // Not always right, but works for common cases.
-    env.push(("CARGO".into(), "cargo".into()));
-
-    env.push(("CARGO_PKG_VERSION".into(), package.version.to_string()));
-    env.push(("CARGO_PKG_VERSION_MAJOR".into(), package.version.major.to_string()));
-    env.push(("CARGO_PKG_VERSION_MINOR".into(), package.version.minor.to_string()));
-    env.push(("CARGO_PKG_VERSION_PATCH".into(), package.version.patch.to_string()));
-    env.push(("CARGO_PKG_VERSION_PRE".into(), package.version.pre.to_string()));
-
-    let authors = package.authors.join(";");
-    env.push(("CARGO_PKG_AUTHORS".into(), authors));
-
-    env.push(("CARGO_PKG_NAME".into(), package.name.clone()));
-    // FIXME: This isn't really correct (a package can have many crates with different names), but
-    // it's better than leaving the variable unset.
-    env.push(("CARGO_CRATE_NAME".into(), CrateName::normalize_dashes(&package.name).to_string()));
-    env.push(("CARGO_PKG_DESCRIPTION".into(), package.description.clone().unwrap_or_default()));
-    env.push(("CARGO_PKG_HOMEPAGE".into(), package.homepage.clone().unwrap_or_default()));
-    env.push(("CARGO_PKG_REPOSITORY".into(), package.repository.clone().unwrap_or_default()));
-    env.push(("CARGO_PKG_LICENSE".into(), package.license.clone().unwrap_or_default()));
-
-    let license_file = package.license_file.as_ref().map(|buf| buf.to_string()).unwrap_or_default();
-    env.push(("CARGO_PKG_LICENSE_FILE".into(), license_file));
-}
diff --git a/crates/project_model/src/build_scripts.rs b/crates/project_model/src/build_scripts.rs
new file mode 100644
index 00000000000..fb8cc271c51
--- /dev/null
+++ b/crates/project_model/src/build_scripts.rs
@@ -0,0 +1,207 @@
+//! Workspace information we get from cargo consists of two pieces. The first is
+//! the output of `cargo metadata`. The second is the output of running
+//! `build.rs` files (`OUT_DIR` env var, extra cfg flags) and compiling proc
+//! macro.
+//!
+//! This module implements this second part. We use "build script" terminology
+//! here, but it covers procedural macros as well.
+
+use std::{
+    path::PathBuf,
+    process::{Command, Stdio},
+};
+
+use anyhow::Result;
+use cargo_metadata::{camino::Utf8Path, Message};
+use la_arena::ArenaMap;
+use paths::AbsPathBuf;
+use rustc_hash::FxHashMap;
+use serde::Deserialize;
+
+use crate::{cfg_flag::CfgFlag, CargoConfig, CargoWorkspace, Package};
+
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
+pub struct WorkspaceBuildScripts {
+    pub(crate) outputs: ArenaMap<Package, BuildScriptOutput>,
+    error: Option<String>,
+}
+
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+pub(crate) struct BuildScriptOutput {
+    /// List of config flags defined by this package's build script.
+    pub(crate) cfgs: Vec<CfgFlag>,
+    /// List of cargo-related environment variables with their value.
+    ///
+    /// If the package has a build script which defines environment variables,
+    /// they can also be found here.
+    pub(crate) envs: Vec<(String, String)>,
+    /// Directory where a build script might place its output.
+    pub(crate) out_dir: Option<AbsPathBuf>,
+    /// Path to the proc-macro library file if this package exposes proc-macros.
+    pub(crate) proc_macro_dylib_path: Option<AbsPathBuf>,
+}
+
+impl WorkspaceBuildScripts {
+    pub fn run(
+        config: &CargoConfig,
+        workspace: &CargoWorkspace,
+        progress: &dyn Fn(String),
+    ) -> Result<WorkspaceBuildScripts> {
+        let mut cmd = Command::new(toolchain::cargo());
+
+        if config.wrap_rustc_in_build_scripts {
+            // Setup RUSTC_WRAPPER to point to `rust-analyzer` binary itself. We use
+            // that to compile only proc macros and build scripts during the initial
+            // `cargo check`.
+            let myself = std::env::current_exe()?;
+            cmd.env("RUSTC_WRAPPER", myself);
+            cmd.env("RA_RUSTC_WRAPPER", "1");
+        }
+        cmd.current_dir(workspace.workspace_root());
+        cmd.args(&["check", "--quiet", "--workspace", "--message-format=json"]);
+
+        // --all-targets includes tests, benches and examples in addition to the
+        // default lib and bins. This is an independent concept from the --targets
+        // flag below.
+        cmd.arg("--all-targets");
+
+        if let Some(target) = &config.target {
+            cmd.args(&["--target", target]);
+        }
+
+        if config.all_features {
+            cmd.arg("--all-features");
+        } else {
+            if config.no_default_features {
+                cmd.arg("--no-default-features");
+            }
+            if !config.features.is_empty() {
+                cmd.arg("--features");
+                cmd.arg(config.features.join(" "));
+            }
+        }
+
+        cmd.stdout(Stdio::piped()).stderr(Stdio::piped()).stdin(Stdio::null());
+
+        let mut res = WorkspaceBuildScripts::default();
+        // NB: Cargo.toml could have been modified between `cargo metadata` and
+        // `cargo check`. We shouldn't assume that package ids we see here are
+        // exactly those from `config`.
+        let mut by_id: FxHashMap<String, Package> = FxHashMap::default();
+
+        for package in workspace.packages() {
+            res.outputs.insert(package, BuildScriptOutput::default());
+            by_id.insert(workspace[package].id.clone(), package);
+        }
+
+        let mut callback_err = None;
+        let mut stderr = String::new();
+        let output = stdx::process::streaming_output(
+            cmd,
+            &mut |line| {
+                if callback_err.is_some() {
+                    return;
+                }
+
+                // Copy-pasted from existing cargo_metadata. It seems like we
+                // should be using sered_stacker here?
+                let mut deserializer = serde_json::Deserializer::from_str(line);
+                deserializer.disable_recursion_limit();
+                let message = Message::deserialize(&mut deserializer)
+                    .unwrap_or_else(|_| Message::TextLine(line.to_string()));
+
+                match message {
+                    Message::BuildScriptExecuted(message) => {
+                        let package = match by_id.get(&message.package_id.repr) {
+                            Some(it) => *it,
+                            None => return,
+                        };
+                        let cfgs = {
+                            let mut acc = Vec::new();
+                            for cfg in message.cfgs {
+                                match cfg.parse::<CfgFlag>() {
+                                    Ok(it) => acc.push(it),
+                                    Err(err) => {
+                                        callback_err = Some(anyhow::format_err!(
+                                            "invalid cfg from cargo-metadata: {}",
+                                            err
+                                        ));
+                                        return;
+                                    }
+                                };
+                            }
+                            acc
+                        };
+                        let package_build_data = &mut res.outputs[package];
+                        // cargo_metadata crate returns default (empty) path for
+                        // older cargos, which is not absolute, so work around that.
+                        if !message.out_dir.as_str().is_empty() {
+                            let out_dir =
+                                AbsPathBuf::assert(PathBuf::from(message.out_dir.into_os_string()));
+                            package_build_data.out_dir = Some(out_dir);
+                            package_build_data.cfgs = cfgs;
+                        }
+
+                        package_build_data.envs = message.env;
+                    }
+                    Message::CompilerArtifact(message) => {
+                        let package = match by_id.get(&message.package_id.repr) {
+                            Some(it) => *it,
+                            None => return,
+                        };
+
+                        progress(format!("metadata {}", message.target.name));
+
+                        if message.target.kind.iter().any(|k| k == "proc-macro") {
+                            // Skip rmeta file
+                            if let Some(filename) =
+                                message.filenames.iter().find(|name| is_dylib(name))
+                            {
+                                let filename = AbsPathBuf::assert(PathBuf::from(&filename));
+                                res.outputs[package].proc_macro_dylib_path = Some(filename);
+                            }
+                        }
+                    }
+                    Message::CompilerMessage(message) => {
+                        progress(message.target.name);
+                    }
+                    Message::BuildFinished(_) => {}
+                    Message::TextLine(_) => {}
+                    _ => {}
+                }
+            },
+            &mut |line| {
+                stderr.push_str(line);
+                stderr.push('\n');
+            },
+        )?;
+
+        for package in workspace.packages() {
+            let package_build_data = &mut res.outputs[package];
+            // inject_cargo_env(package, package_build_data);
+            if let Some(out_dir) = &package_build_data.out_dir {
+                // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
+                if let Some(out_dir) = out_dir.as_os_str().to_str().map(|s| s.to_owned()) {
+                    package_build_data.envs.push(("OUT_DIR".to_string(), out_dir));
+                }
+            }
+        }
+
+        if !output.status.success() {
+            if stderr.is_empty() {
+                stderr = "cargo check failed".to_string();
+            }
+            res.error = Some(stderr)
+        }
+
+        Ok(res)
+    }
+}
+
+// FIXME: File a better way to know if it is a dylib.
+fn is_dylib(path: &Utf8Path) -> bool {
+    match path.extension().map(|e| e.to_string().to_lowercase()) {
+        None => false,
+        Some(ext) => matches!(ext.as_str(), "dll" | "dylib" | "so"),
+    }
+}
diff --git a/crates/project_model/src/cargo_workspace.rs b/crates/project_model/src/cargo_workspace.rs
index 4ee720a53ab..c88bafb0baf 100644
--- a/crates/project_model/src/cargo_workspace.rs
+++ b/crates/project_model/src/cargo_workspace.rs
@@ -2,7 +2,7 @@
 
 use std::iter;
 use std::path::PathBuf;
-use std::{convert::TryInto, ops, process::Command, sync::Arc};
+use std::{convert::TryInto, ops, process::Command};
 
 use anyhow::{Context, Result};
 use base_db::Edition;
@@ -13,8 +13,8 @@ use rustc_hash::FxHashMap;
 use serde::Deserialize;
 use serde_json::from_value;
 
+use crate::utf8_stdout;
 use crate::CfgOverrides;
-use crate::{build_data::BuildDataConfig, utf8_stdout};
 
 /// [`CargoWorkspace`] represents the logical structure of, well, a Cargo
 /// workspace. It pretty closely mirrors `cargo metadata` output.
@@ -31,7 +31,6 @@ pub struct CargoWorkspace {
     packages: Arena<PackageData>,
     targets: Arena<TargetData>,
     workspace_root: AbsPathBuf,
-    build_data_config: BuildDataConfig,
 }
 
 impl ops::Index<Package> for CargoWorkspace {
@@ -81,6 +80,8 @@ pub struct CargoConfig {
 
     /// crates to disable `#[cfg(test)]` on
     pub unset_test_crates: Vec<String>,
+
+    pub wrap_rustc_in_build_scripts: bool,
 }
 
 impl CargoConfig {
@@ -103,7 +104,7 @@ pub type Target = Idx<TargetData>;
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct PackageData {
     /// Version given in the `Cargo.toml`
-    pub version: String,
+    pub version: semver::Version,
     /// Name as given in the `Cargo.toml`
     pub name: String,
     /// Path containing the `Cargo.toml`
@@ -288,11 +289,7 @@ impl CargoWorkspace {
         Ok(meta)
     }
 
-    pub fn new(
-        cargo_toml: &AbsPath,
-        config: &CargoConfig,
-        mut meta: cargo_metadata::Metadata,
-    ) -> CargoWorkspace {
+    pub fn new(mut meta: cargo_metadata::Metadata) -> CargoWorkspace {
         let mut pkg_by_id = FxHashMap::default();
         let mut packages = Arena::default();
         let mut targets = Arena::default();
@@ -314,7 +311,7 @@ impl CargoWorkspace {
             let pkg = packages.alloc(PackageData {
                 id: id.repr.clone(),
                 name: name.clone(),
-                version: version.to_string(),
+                version: version.clone(),
                 manifest: AbsPathBuf::assert(PathBuf::from(&manifest_path)),
                 targets: Vec::new(),
                 is_member,
@@ -374,10 +371,8 @@ impl CargoWorkspace {
 
         let workspace_root =
             AbsPathBuf::assert(PathBuf::from(meta.workspace_root.into_os_string()));
-        let build_data_config =
-            BuildDataConfig::new(cargo_toml.to_path_buf(), config.clone(), Arc::new(meta.packages));
 
-        CargoWorkspace { packages, targets, workspace_root, build_data_config }
+        CargoWorkspace { packages, targets, workspace_root }
     }
 
     pub fn from_cargo_metadata3(
@@ -386,7 +381,7 @@ impl CargoWorkspace {
         progress: &dyn Fn(String),
     ) -> Result<CargoWorkspace> {
         let meta = CargoWorkspace::fetch_metadata(cargo_toml, config, progress)?;
-        Ok(CargoWorkspace::new(cargo_toml, config, meta))
+        Ok(CargoWorkspace::new(meta))
     }
 
     pub fn packages<'a>(&'a self) -> impl Iterator<Item = Package> + ExactSizeIterator + 'a {
@@ -412,10 +407,6 @@ impl CargoWorkspace {
         }
     }
 
-    pub(crate) fn build_data_config(&self) -> &BuildDataConfig {
-        &self.build_data_config
-    }
-
     fn is_unique(&self, name: &str) -> bool {
         self.packages.iter().filter(|(_, v)| v.name == name).count() == 1
     }
diff --git a/crates/project_model/src/lib.rs b/crates/project_model/src/lib.rs
index 22364cfd04c..7be4e04907e 100644
--- a/crates/project_model/src/lib.rs
+++ b/crates/project_model/src/lib.rs
@@ -21,7 +21,7 @@ mod project_json;
 mod sysroot;
 mod workspace;
 mod rustc_cfg;
-mod build_data;
+mod build_scripts;
 
 use std::{
     fs::{self, read_dir, ReadDir},
@@ -34,7 +34,7 @@ use paths::{AbsPath, AbsPathBuf};
 use rustc_hash::FxHashSet;
 
 pub use crate::{
-    build_data::{BuildDataCollector, BuildDataResult},
+    build_scripts::WorkspaceBuildScripts,
     cargo_workspace::{
         CargoConfig, CargoWorkspace, Package, PackageData, PackageDependency, RustcSource, Target,
         TargetData, TargetKind,
diff --git a/crates/project_model/src/workspace.rs b/crates/project_model/src/workspace.rs
index 76c4388f193..7a47fd7a5c0 100644
--- a/crates/project_model/src/workspace.rs
+++ b/crates/project_model/src/workspace.rs
@@ -6,20 +6,19 @@ use std::{collections::VecDeque, fmt, fs, process::Command};
 
 use anyhow::{format_err, Context, Result};
 use base_db::{CrateDisplayName, CrateGraph, CrateId, CrateName, Edition, Env, FileId, ProcMacro};
-use cargo_workspace::DepKind;
 use cfg::{CfgDiff, CfgOptions};
 use paths::{AbsPath, AbsPathBuf};
 use proc_macro_api::ProcMacroClient;
 use rustc_hash::{FxHashMap, FxHashSet};
 
 use crate::{
-    build_data::{BuildDataResult, PackageBuildData, WorkspaceBuildData},
-    cargo_workspace,
+    build_scripts::BuildScriptOutput,
+    cargo_workspace::{DepKind, PackageData, RustcSource},
     cfg_flag::CfgFlag,
     rustc_cfg,
     sysroot::SysrootCrate,
-    utf8_stdout, BuildDataCollector, CargoConfig, CargoWorkspace, ProjectJson, ProjectManifest,
-    Sysroot, TargetKind,
+    utf8_stdout, CargoConfig, CargoWorkspace, ProjectJson, ProjectManifest, Sysroot, TargetKind,
+    WorkspaceBuildScripts,
 };
 
 pub type CfgOverrides = FxHashMap<String, CfgDiff>;
@@ -134,7 +133,7 @@ impl ProjectWorkspace {
                             cargo_version
                         )
                     })?;
-                let cargo = CargoWorkspace::new(&cargo_toml, config, meta);
+                let cargo = CargoWorkspace::new(meta);
 
                 let sysroot = if config.no_sysroot {
                     Sysroot::default()
@@ -148,7 +147,6 @@ impl ProjectWorkspace {
                 };
 
                 let rustc_dir = if let Some(rustc_source) = &config.rustc_source {
-                    use cargo_workspace::RustcSource;
                     match rustc_source {
                         RustcSource::Path(path) => Some(path.clone()),
                         RustcSource::Discover => Sysroot::discover_rustc(&cargo_toml),
@@ -163,7 +161,7 @@ impl ProjectWorkspace {
                             .with_context(|| {
                                 format!("Failed to read Cargo metadata for Rust sources")
                             })?;
-                        CargoWorkspace::new(&rustc_dir, config, meta)
+                        CargoWorkspace::new(meta)
                     }),
                     None => None,
                 };
@@ -201,7 +199,7 @@ impl ProjectWorkspace {
     /// Returns the roots for the current `ProjectWorkspace`
     /// The return type contains the path and whether or not
     /// the root is a member of the current workspace
-    pub fn to_roots(&self, build_data: Option<&BuildDataResult>) -> Vec<PackageRoot> {
+    pub fn to_roots(&self, build_scripts: &WorkspaceBuildScripts) -> Vec<PackageRoot> {
         match self {
             ProjectWorkspace::Json { project, sysroot, rustc_cfg: _ } => project
                 .crates()
@@ -229,10 +227,7 @@ impl ProjectWorkspace {
 
                         let mut include = vec![pkg_root.clone()];
                         include.extend(
-                            build_data
-                                .and_then(|it| it.get(cargo.workspace_root()))
-                                .and_then(|map| map.get(&cargo[pkg].id))
-                                .and_then(|it| it.out_dir.clone()),
+                            build_scripts.outputs.get(pkg).and_then(|it| it.out_dir.clone()),
                         );
 
                         // In case target's path is manually set in Cargo.toml to be
@@ -307,7 +302,7 @@ impl ProjectWorkspace {
 
     pub fn to_crate_graph(
         &self,
-        build_data: Option<&BuildDataResult>,
+        build_scripts: &WorkspaceBuildScripts,
         proc_macro_client: Option<&ProcMacroClient>,
         load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
     ) -> CrateGraph {
@@ -332,13 +327,9 @@ impl ProjectWorkspace {
                     &proc_macro_loader,
                     load,
                     cargo,
-                    build_data.and_then(|it| it.get(cargo.workspace_root())),
+                    build_scripts,
                     sysroot,
                     rustc,
-                    rustc
-                        .as_ref()
-                        .zip(build_data)
-                        .and_then(|(it, map)| map.get(it.workspace_root())),
                 )
             }
             ProjectWorkspace::DetachedFiles { files, sysroot, rustc_cfg } => {
@@ -352,15 +343,6 @@ impl ProjectWorkspace {
         }
         crate_graph
     }
-
-    pub fn collect_build_data_configs(&self, collector: &mut BuildDataCollector) {
-        match self {
-            ProjectWorkspace::Cargo { cargo, .. } => {
-                collector.add_config(cargo.workspace_root(), cargo.build_data_config().clone());
-            }
-            _ => {}
-        }
-    }
 }
 
 fn project_json_to_crate_graph(
@@ -435,10 +417,9 @@ fn cargo_to_crate_graph(
     proc_macro_loader: &dyn Fn(&AbsPath) -> Vec<ProcMacro>,
     load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
     cargo: &CargoWorkspace,
-    build_data_map: Option<&WorkspaceBuildData>,
+    build_scripts: &WorkspaceBuildScripts,
     sysroot: &Sysroot,
     rustc: &Option<CargoWorkspace>,
-    rustc_build_data_map: Option<&WorkspaceBuildData>,
 ) -> CrateGraph {
     let _p = profile::span("cargo_to_crate_graph");
     let mut crate_graph = CrateGraph::default();
@@ -481,7 +462,7 @@ fn cargo_to_crate_graph(
                 let crate_id = add_target_crate_root(
                     &mut crate_graph,
                     &cargo[pkg],
-                    build_data_map.and_then(|it| it.get(&cargo[pkg].id)),
+                    build_scripts.outputs.get(pkg),
                     &cfg_options,
                     proc_macro_loader,
                     file_id,
@@ -555,7 +536,6 @@ fn cargo_to_crate_graph(
                 rustc_workspace,
                 load,
                 &mut crate_graph,
-                rustc_build_data_map,
                 &cfg_options,
                 proc_macro_loader,
                 &mut pkg_to_lib_crate,
@@ -615,7 +595,6 @@ fn handle_rustc_crates(
     rustc_workspace: &CargoWorkspace,
     load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
     crate_graph: &mut CrateGraph,
-    rustc_build_data_map: Option<&WorkspaceBuildData>,
     cfg_options: &CfgOptions,
     proc_macro_loader: &dyn Fn(&AbsPath) -> Vec<ProcMacro>,
     pkg_to_lib_crate: &mut FxHashMap<la_arena::Idx<crate::PackageData>, CrateId>,
@@ -651,7 +630,7 @@ fn handle_rustc_crates(
                     let crate_id = add_target_crate_root(
                         crate_graph,
                         &rustc_workspace[pkg],
-                        rustc_build_data_map.and_then(|it| it.get(&rustc_workspace[pkg].id)),
+                        None,
                         cfg_options,
                         proc_macro_loader,
                         file_id,
@@ -706,8 +685,8 @@ fn handle_rustc_crates(
 
 fn add_target_crate_root(
     crate_graph: &mut CrateGraph,
-    pkg: &cargo_workspace::PackageData,
-    build_data: Option<&PackageBuildData>,
+    pkg: &PackageData,
+    build_data: Option<&BuildScriptOutput>,
     cfg_options: &CfgOptions,
     proc_macro_loader: &dyn Fn(&AbsPath) -> Vec<ProcMacro>,
     file_id: FileId,
@@ -726,6 +705,8 @@ fn add_target_crate_root(
     };
 
     let mut env = Env::default();
+    inject_cargo_env(pkg, &mut env);
+
     if let Some(envs) = build_data.map(|it| &it.envs) {
         for (k, v) in envs {
             env.set(k, v.clone());
@@ -812,3 +793,40 @@ fn add_dep(graph: &mut CrateGraph, from: CrateId, name: CrateName, to: CrateId)
         log::error!("{}", err)
     }
 }
+
+/// Recreates the compile-time environment variables that Cargo sets.
+///
+/// Should be synced with
+/// <https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates>
+///
+/// FIXME: ask Cargo to provide this data instead of re-deriving.
+fn inject_cargo_env(package: &PackageData, env: &mut Env) {
+    // FIXME: Missing variables:
+    // CARGO_BIN_NAME, CARGO_BIN_EXE_<name>
+
+    let mut manifest_dir = package.manifest.clone();
+    manifest_dir.pop();
+    env.set("CARGO_MANIFEST_DIR".into(), manifest_dir.as_os_str().to_string_lossy().into_owned());
+
+    // Not always right, but works for common cases.
+    env.set("CARGO".into(), "cargo".into());
+
+    env.set("CARGO_PKG_VERSION".into(), package.version.to_string());
+    env.set("CARGO_PKG_VERSION_MAJOR".into(), package.version.major.to_string());
+    env.set("CARGO_PKG_VERSION_MINOR".into(), package.version.minor.to_string());
+    env.set("CARGO_PKG_VERSION_PATCH".into(), package.version.patch.to_string());
+    env.set("CARGO_PKG_VERSION_PRE".into(), package.version.pre.to_string());
+
+    env.set("CARGO_PKG_AUTHORS".into(), String::new());
+
+    env.set("CARGO_PKG_NAME".into(), package.name.clone());
+    // FIXME: This isn't really correct (a package can have many crates with different names), but
+    // it's better than leaving the variable unset.
+    env.set("CARGO_CRATE_NAME".into(), CrateName::normalize_dashes(&package.name).to_string());
+    env.set("CARGO_PKG_DESCRIPTION".into(), String::new());
+    env.set("CARGO_PKG_HOMEPAGE".into(), String::new());
+    env.set("CARGO_PKG_REPOSITORY".into(), String::new());
+    env.set("CARGO_PKG_LICENSE".into(), String::new());
+
+    env.set("CARGO_PKG_LICENSE_FILE".into(), String::new());
+}
diff --git a/crates/rust-analyzer/src/cli/analysis_stats.rs b/crates/rust-analyzer/src/cli/analysis_stats.rs
index 843c0ca37b0..37da24f30e1 100644
--- a/crates/rust-analyzer/src/cli/analysis_stats.rs
+++ b/crates/rust-analyzer/src/cli/analysis_stats.rs
@@ -68,7 +68,6 @@ impl AnalysisStatsCmd {
         cargo_config.no_sysroot = self.no_sysroot;
         let load_cargo_config = LoadCargoConfig {
             load_out_dirs_from_check: self.enable_build_scripts,
-            wrap_rustc: false,
             with_proc_macro: self.enable_proc_macros,
             prefill_caches: false,
         };
diff --git a/crates/rust-analyzer/src/cli/diagnostics.rs b/crates/rust-analyzer/src/cli/diagnostics.rs
index dc9a390fe99..84aaf1d5055 100644
--- a/crates/rust-analyzer/src/cli/diagnostics.rs
+++ b/crates/rust-analyzer/src/cli/diagnostics.rs
@@ -34,12 +34,8 @@ pub fn diagnostics(
     with_proc_macro: bool,
 ) -> Result<()> {
     let cargo_config = Default::default();
-    let load_cargo_config = LoadCargoConfig {
-        load_out_dirs_from_check,
-        with_proc_macro,
-        wrap_rustc: false,
-        prefill_caches: false,
-    };
+    let load_cargo_config =
+        LoadCargoConfig { load_out_dirs_from_check, with_proc_macro, prefill_caches: false };
     let (host, _vfs, _proc_macro) =
         load_workspace_at(path, &cargo_config, &load_cargo_config, &|_| {})?;
     let db = host.raw_database();
diff --git a/crates/rust-analyzer/src/cli/load_cargo.rs b/crates/rust-analyzer/src/cli/load_cargo.rs
index b8f47f2b985..c3ab6c107cf 100644
--- a/crates/rust-analyzer/src/cli/load_cargo.rs
+++ b/crates/rust-analyzer/src/cli/load_cargo.rs
@@ -8,7 +8,7 @@ use hir::db::DefDatabase;
 use ide::{AnalysisHost, Change};
 use ide_db::base_db::CrateGraph;
 use project_model::{
-    BuildDataCollector, CargoConfig, ProcMacroClient, ProjectManifest, ProjectWorkspace,
+    CargoConfig, ProcMacroClient, ProjectManifest, ProjectWorkspace, WorkspaceBuildScripts,
 };
 use vfs::{loader::Handle, AbsPath, AbsPathBuf};
 
@@ -16,7 +16,6 @@ use crate::reload::{ProjectFolders, SourceRootConfig};
 
 pub(crate) struct LoadCargoConfig {
     pub(crate) load_out_dirs_from_check: bool,
-    pub(crate) wrap_rustc: bool,
     pub(crate) with_proc_macro: bool,
     pub(crate) prefill_caches: bool,
 }
@@ -33,12 +32,13 @@ pub(crate) fn load_workspace_at(
     eprintln!("root = {:?}", root);
     let workspace = ProjectWorkspace::load(root, cargo_config, progress)?;
 
-    load_workspace(workspace, load_config, progress)
+    load_workspace(workspace, cargo_config, load_config, progress)
 }
 
 fn load_workspace(
     ws: ProjectWorkspace,
-    config: &LoadCargoConfig,
+    cargo_config: &CargoConfig,
+    load_config: &LoadCargoConfig,
     progress: &dyn Fn(String),
 ) -> Result<(AnalysisHost, vfs::Vfs, Option<ProcMacroClient>)> {
     let (sender, receiver) = unbounded();
@@ -49,33 +49,29 @@ fn load_workspace(
         Box::new(loader)
     };
 
-    let proc_macro_client = if config.with_proc_macro {
+    let proc_macro_client = if load_config.with_proc_macro {
         let path = AbsPathBuf::assert(std::env::current_exe()?);
         Some(ProcMacroClient::extern_process(path, &["proc-macro"]).unwrap())
     } else {
         None
     };
 
-    let build_data = if config.load_out_dirs_from_check {
-        let mut collector = BuildDataCollector::new(config.wrap_rustc);
-        ws.collect_build_data_configs(&mut collector);
-        Some(collector.collect(progress)?)
-    } else {
-        None
+    let build_scripts = match &ws {
+        ProjectWorkspace::Cargo { cargo, .. } if load_config.load_out_dirs_from_check => {
+            WorkspaceBuildScripts::run(cargo_config, cargo, progress)?
+        }
+        _ => WorkspaceBuildScripts::default(),
     };
 
-    let crate_graph = ws.to_crate_graph(
-        build_data.as_ref(),
-        proc_macro_client.as_ref(),
-        &mut |path: &AbsPath| {
+    let crate_graph =
+        ws.to_crate_graph(&build_scripts, proc_macro_client.as_ref(), &mut |path: &AbsPath| {
             let contents = loader.load_sync(path);
             let path = vfs::VfsPath::from(path.to_path_buf());
             vfs.set_file_contents(path.clone(), contents);
             vfs.file_id(&path)
-        },
-    );
+        });
 
-    let project_folders = ProjectFolders::new(&[ws], &[], build_data.as_ref());
+    let project_folders = ProjectFolders::new(&[ws], &[build_scripts], &[]);
     loader.set_config(vfs::loader::Config {
         load: project_folders.load,
         watch: vec![],
@@ -86,7 +82,7 @@ fn load_workspace(
     let host =
         load_crate_graph(crate_graph, project_folders.source_root_config, &mut vfs, &receiver);
 
-    if config.prefill_caches {
+    if load_config.prefill_caches {
         host.analysis().prime_caches(|_| {})?;
     }
     Ok((host, vfs, proc_macro_client))
@@ -146,10 +142,9 @@ mod tests {
     #[test]
     fn test_loading_rust_analyzer() {
         let path = Path::new(env!("CARGO_MANIFEST_DIR")).parent().unwrap().parent().unwrap();
-        let cargo_config = Default::default();
+        let cargo_config = CargoConfig::default();
         let load_cargo_config = LoadCargoConfig {
             load_out_dirs_from_check: false,
-            wrap_rustc: false,
             with_proc_macro: false,
             prefill_caches: false,
         };
diff --git a/crates/rust-analyzer/src/cli/ssr.rs b/crates/rust-analyzer/src/cli/ssr.rs
index 0b3475e0928..60092127d96 100644
--- a/crates/rust-analyzer/src/cli/ssr.rs
+++ b/crates/rust-analyzer/src/cli/ssr.rs
@@ -5,13 +5,13 @@ use crate::cli::{
     Result,
 };
 use ide_ssr::{MatchFinder, SsrPattern, SsrRule};
+use project_model::CargoConfig;
 
 pub fn apply_ssr_rules(rules: Vec<SsrRule>) -> Result<()> {
     use ide_db::base_db::SourceDatabaseExt;
-    let cargo_config = Default::default();
+    let cargo_config = CargoConfig::default();
     let load_cargo_config = LoadCargoConfig {
         load_out_dirs_from_check: true,
-        wrap_rustc: false,
         with_proc_macro: true,
         prefill_caches: false,
     };
@@ -39,10 +39,9 @@ pub fn apply_ssr_rules(rules: Vec<SsrRule>) -> Result<()> {
 pub fn search_for_patterns(patterns: Vec<SsrPattern>, debug_snippet: Option<String>) -> Result<()> {
     use ide_db::base_db::SourceDatabaseExt;
     use ide_db::symbol_index::SymbolsDatabase;
-    let cargo_config = Default::default();
+    let cargo_config = CargoConfig::default();
     let load_cargo_config = LoadCargoConfig {
         load_out_dirs_from_check: true,
-        wrap_rustc: true,
         with_proc_macro: true,
         prefill_caches: false,
     };
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 7df60229648..2f10f7b6c89 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -628,9 +628,6 @@ impl Config {
     pub fn run_build_scripts(&self) -> bool {
         self.data.cargo_runBuildScripts || self.data.procMacro_enable
     }
-    pub fn wrap_rustc(&self) -> bool {
-        self.data.cargo_useRustcWrapperForBuildScripts
-    }
     pub fn cargo(&self) -> CargoConfig {
         let rustc_source = self.data.rustcSource.as_ref().map(|rustc_src| {
             if rustc_src == "discover" {
@@ -648,6 +645,7 @@ impl Config {
             rustc_source,
             no_sysroot: self.data.cargo_noSysroot,
             unset_test_crates: self.data.cargo_unsetTest.clone(),
+            wrap_rustc_in_build_scripts: self.data.cargo_useRustcWrapperForBuildScripts,
         }
     }
 
diff --git a/crates/rust-analyzer/src/global_state.rs b/crates/rust-analyzer/src/global_state.rs
index 583900cfeef..c188d26a796 100644
--- a/crates/rust-analyzer/src/global_state.rs
+++ b/crates/rust-analyzer/src/global_state.rs
@@ -12,7 +12,7 @@ use ide_db::base_db::{CrateId, VfsPath};
 use lsp_types::{SemanticTokens, Url};
 use parking_lot::{Mutex, RwLock};
 use project_model::{
-    BuildDataCollector, BuildDataResult, CargoWorkspace, ProcMacroClient, ProjectWorkspace, Target,
+    CargoWorkspace, ProcMacroClient, ProjectWorkspace, Target, WorkspaceBuildScripts,
 };
 use rustc_hash::FxHashMap;
 use vfs::AnchoredPathBuf;
@@ -79,12 +79,15 @@ pub(crate) struct GlobalState {
     /// fetch.
     ///
     /// If the fetch (partially) fails, we do not update the values.
+    ///
+    /// Invariant: workspaces.len() == workspace_build_data
     pub(crate) workspaces: Arc<Vec<ProjectWorkspace>>,
-    pub(crate) fetch_workspaces_queue: OpQueue<(), Vec<anyhow::Result<ProjectWorkspace>>>,
-    pub(crate) workspace_build_data: Option<BuildDataResult>,
-    pub(crate) fetch_build_data_queue:
-        OpQueue<BuildDataCollector, Option<anyhow::Result<BuildDataResult>>>,
-    pub(crate) prime_caches_queue: OpQueue<(), ()>,
+    pub(crate) fetch_workspaces_queue: OpQueue<Vec<anyhow::Result<ProjectWorkspace>>>,
+
+    pub(crate) workspace_build_data: Vec<WorkspaceBuildScripts>,
+    pub(crate) fetch_build_data_queue: OpQueue<Vec<anyhow::Result<WorkspaceBuildScripts>>>,
+
+    pub(crate) prime_caches_queue: OpQueue<()>,
 
     latest_requests: Arc<RwLock<LatestRequests>>,
 }
@@ -146,7 +149,7 @@ impl GlobalState {
 
             workspaces: Arc::new(Vec::new()),
             fetch_workspaces_queue: OpQueue::default(),
-            workspace_build_data: None,
+            workspace_build_data: Vec::new(),
             prime_caches_queue: OpQueue::default(),
 
             fetch_build_data_queue: OpQueue::default(),
diff --git a/crates/rust-analyzer/src/integrated_benchmarks.rs b/crates/rust-analyzer/src/integrated_benchmarks.rs
index f8afc930aaa..036cfe157b4 100644
--- a/crates/rust-analyzer/src/integrated_benchmarks.rs
+++ b/crates/rust-analyzer/src/integrated_benchmarks.rs
@@ -17,6 +17,7 @@ use ide_db::helpers::{
     insert_use::{ImportGranularity, InsertUseConfig},
     SnippetCap,
 };
+use project_model::CargoConfig;
 use test_utils::project_root;
 use vfs::{AbsPathBuf, VfsPath};
 
@@ -32,10 +33,9 @@ fn integrated_highlighting_benchmark() {
     let workspace_to_load = project_root();
     let file = "./crates/ide_db/src/apply_change.rs";
 
-    let cargo_config = Default::default();
+    let cargo_config = CargoConfig::default();
     let load_cargo_config = LoadCargoConfig {
         load_out_dirs_from_check: true,
-        wrap_rustc: false,
         with_proc_macro: false,
         prefill_caches: false,
     };
@@ -87,10 +87,9 @@ fn integrated_completion_benchmark() {
     let workspace_to_load = project_root();
     let file = "./crates/hir/src/lib.rs";
 
-    let cargo_config = Default::default();
+    let cargo_config = CargoConfig::default();
     let load_cargo_config = LoadCargoConfig {
         load_out_dirs_from_check: true,
-        wrap_rustc: false,
         with_proc_macro: false,
         prefill_caches: true,
     };
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 82a31362af6..3214bbd9e0c 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -12,7 +12,6 @@ use ide::{FileId, PrimeCachesProgress};
 use ide_db::base_db::VfsPath;
 use lsp_server::{Connection, Notification, Request, Response};
 use lsp_types::notification::Notification as _;
-use project_model::BuildDataCollector;
 use vfs::ChangeKind;
 
 use crate::{
@@ -236,12 +235,7 @@ impl GlobalState {
                                     let workspaces_updated = !Arc::ptr_eq(&old, &self.workspaces);
 
                                     if self.config.run_build_scripts() && workspaces_updated {
-                                        let mut collector =
-                                            BuildDataCollector::new(self.config.wrap_rustc());
-                                        for ws in self.workspaces.iter() {
-                                            ws.collect_build_data_configs(&mut collector);
-                                        }
-                                        self.fetch_build_data_request(collector)
+                                        self.fetch_build_data_request()
                                     }
 
                                     (Progress::End, None)
@@ -719,23 +713,21 @@ impl GlobalState {
         self.maybe_update_diagnostics();
 
         // Ensure that only one cache priming task can run at a time
-        self.prime_caches_queue.request_op(());
-        if self.prime_caches_queue.should_start_op().is_none() {
-            return;
-        }
-
-        self.task_pool.handle.spawn_with_sender({
-            let snap = self.snapshot();
-            move |sender| {
-                let cb = |progress| {
-                    sender.send(Task::PrimeCaches(progress)).unwrap();
-                };
-                match snap.analysis.prime_caches(cb) {
-                    Ok(()) => (),
-                    Err(_canceled) => (),
+        self.prime_caches_queue.request_op();
+        if self.prime_caches_queue.should_start_op() {
+            self.task_pool.handle.spawn_with_sender({
+                let snap = self.snapshot();
+                move |sender| {
+                    let cb = |progress| {
+                        sender.send(Task::PrimeCaches(progress)).unwrap();
+                    };
+                    match snap.analysis.prime_caches(cb) {
+                        Ok(()) => (),
+                        Err(_canceled) => (),
+                    }
                 }
-            }
-        });
+            });
+        }
     }
     fn maybe_update_diagnostics(&mut self) {
         let subscriptions = self
diff --git a/crates/rust-analyzer/src/op_queue.rs b/crates/rust-analyzer/src/op_queue.rs
index 1d612a93376..e2894b3ff2c 100644
--- a/crates/rust-analyzer/src/op_queue.rs
+++ b/crates/rust-analyzer/src/op_queue.rs
@@ -1,28 +1,29 @@
 //! Bookkeeping to make sure only one long-running operation is being executed
 //! at a time.
 
-pub(crate) struct OpQueue<Args, Output> {
-    op_requested: Option<Args>,
+pub(crate) struct OpQueue<Output> {
+    op_requested: bool,
     op_in_progress: bool,
     last_op_result: Output,
 }
 
-impl<Args, Output: Default> Default for OpQueue<Args, Output> {
+impl<Output: Default> Default for OpQueue<Output> {
     fn default() -> Self {
-        Self { op_requested: None, op_in_progress: false, last_op_result: Default::default() }
+        Self { op_requested: false, op_in_progress: false, last_op_result: Default::default() }
     }
 }
 
-impl<Args, Output> OpQueue<Args, Output> {
-    pub(crate) fn request_op(&mut self, data: Args) {
-        self.op_requested = Some(data);
+impl<Output> OpQueue<Output> {
+    pub(crate) fn request_op(&mut self) {
+        self.op_requested = true;
     }
-    pub(crate) fn should_start_op(&mut self) -> Option<Args> {
+    pub(crate) fn should_start_op(&mut self) -> bool {
         if self.op_in_progress {
-            return None;
+            return false;
         }
-        self.op_in_progress = self.op_requested.is_some();
-        self.op_requested.take()
+        self.op_in_progress = self.op_requested;
+        self.op_requested = false;
+        self.op_in_progress
     }
     pub(crate) fn op_completed(&mut self, result: Output) {
         assert!(self.op_in_progress);
@@ -30,7 +31,6 @@ impl<Args, Output> OpQueue<Args, Output> {
         self.last_op_result = result;
     }
 
-    #[allow(unused)]
     pub(crate) fn last_op_result(&self) -> &Output {
         &self.last_op_result
     }
@@ -38,6 +38,6 @@ impl<Args, Output> OpQueue<Args, Output> {
         self.op_in_progress
     }
     pub(crate) fn op_requested(&self) -> bool {
-        self.op_requested.is_some()
+        self.op_requested
     }
 }
diff --git a/crates/rust-analyzer/src/reload.rs b/crates/rust-analyzer/src/reload.rs
index 95751cae6db..ce0e79e848f 100644
--- a/crates/rust-analyzer/src/reload.rs
+++ b/crates/rust-analyzer/src/reload.rs
@@ -1,11 +1,12 @@
 //! Project loading & configuration updates
 use std::{mem, sync::Arc};
 
+use always_assert::always;
 use flycheck::{FlycheckConfig, FlycheckHandle};
 use hir::db::DefDatabase;
 use ide::Change;
 use ide_db::base_db::{CrateGraph, SourceRoot, VfsPath};
-use project_model::{BuildDataCollector, BuildDataResult, ProcMacroClient, ProjectWorkspace};
+use project_model::{ProcMacroClient, ProjectWorkspace, WorkspaceBuildScripts};
 use vfs::{file_set::FileSetConfig, AbsPath, AbsPathBuf, ChangeKind};
 
 use crate::{
@@ -26,7 +27,7 @@ pub(crate) enum ProjectWorkspaceProgress {
 pub(crate) enum BuildDataProgress {
     Begin,
     Report(String),
-    End(anyhow::Result<BuildDataResult>),
+    End(Vec<anyhow::Result<WorkspaceBuildScripts>>),
 }
 
 impl GlobalState {
@@ -144,10 +145,10 @@ impl GlobalState {
     }
 
     pub(crate) fn fetch_workspaces_request(&mut self) {
-        self.fetch_workspaces_queue.request_op(())
+        self.fetch_workspaces_queue.request_op()
     }
     pub(crate) fn fetch_workspaces_if_needed(&mut self) {
-        if self.fetch_workspaces_queue.should_start_op().is_none() {
+        if !self.fetch_workspaces_queue.should_start_op() {
             return;
         }
         log::info!("will fetch workspaces");
@@ -207,14 +208,16 @@ impl GlobalState {
         self.fetch_workspaces_queue.op_completed(workspaces)
     }
 
-    pub(crate) fn fetch_build_data_request(&mut self, build_data_collector: BuildDataCollector) {
-        self.fetch_build_data_queue.request_op(build_data_collector);
+    pub(crate) fn fetch_build_data_request(&mut self) {
+        self.fetch_build_data_queue.request_op();
     }
     pub(crate) fn fetch_build_data_if_needed(&mut self) {
-        let mut build_data_collector = match self.fetch_build_data_queue.should_start_op() {
-            Some(it) => it,
-            None => return,
-        };
+        if !self.fetch_build_data_queue.should_start_op() {
+            return;
+        }
+
+        let workspaces = Arc::clone(&self.workspaces);
+        let config = self.config.cargo();
         self.task_pool.handle.spawn_with_sender(move |sender| {
             sender.send(Task::FetchBuildData(BuildDataProgress::Begin)).unwrap();
 
@@ -224,15 +227,25 @@ impl GlobalState {
                     sender.send(Task::FetchBuildData(BuildDataProgress::Report(msg))).unwrap()
                 }
             };
-            let res = build_data_collector.collect(&progress);
+            let mut res = Vec::new();
+            for ws in workspaces.iter() {
+                let ws = match ws {
+                    ProjectWorkspace::Cargo { cargo, .. } => cargo,
+                    ProjectWorkspace::DetachedFiles { .. } | ProjectWorkspace::Json { .. } => {
+                        res.push(Ok(WorkspaceBuildScripts::default()));
+                        continue;
+                    }
+                };
+                res.push(WorkspaceBuildScripts::run(&config, ws, &progress))
+            }
             sender.send(Task::FetchBuildData(BuildDataProgress::End(res))).unwrap();
         });
     }
     pub(crate) fn fetch_build_data_completed(
         &mut self,
-        build_data: anyhow::Result<BuildDataResult>,
+        build_data: Vec<anyhow::Result<WorkspaceBuildScripts>>,
     ) {
-        self.fetch_build_data_queue.op_completed(Some(build_data))
+        self.fetch_build_data_queue.op_completed(build_data)
     }
 
     pub(crate) fn switch_workspaces(&mut self) {
@@ -257,12 +270,22 @@ impl GlobalState {
             .filter_map(|res| res.as_ref().ok().cloned())
             .collect::<Vec<_>>();
 
-        let workspace_build_data = match self.fetch_build_data_queue.last_op_result() {
-            Some(Ok(it)) => Some(it.clone()),
-            None | Some(Err(_)) => None,
-        };
+        let mut build_scripts = self
+            .fetch_build_data_queue
+            .last_op_result()
+            .iter()
+            .map(|res| res.as_ref().ok().cloned().unwrap_or_default())
+            .collect::<Vec<_>>();
+
+        // FIXME: This is not even remotely correct. I do hope that this is
+        // eventually consistent though. We need to figure a better way to map
+        // `cargo metadata` to `cargo check` in the future.
+        //
+        // I *think* what we need here is an extra field on `ProjectWorkspace`,
+        // and a workflow to set it, once build data is ready.
+        build_scripts.resize_with(workspaces.len(), WorkspaceBuildScripts::default);
 
-        if *self.workspaces == workspaces && self.workspace_build_data == workspace_build_data {
+        if *self.workspaces == workspaces && self.workspace_build_data == build_scripts {
             return;
         }
 
@@ -271,7 +294,8 @@ impl GlobalState {
                 let registration_options = lsp_types::DidChangeWatchedFilesRegistrationOptions {
                     watchers: workspaces
                         .iter()
-                        .flat_map(|it| it.to_roots(workspace_build_data.as_ref()))
+                        .zip(&build_scripts)
+                        .flat_map(|(ws, bs)| ws.to_roots(bs))
                         .filter(|it| it.is_member)
                         .flat_map(|root| {
                             root.include.into_iter().flat_map(|it| {
@@ -304,7 +328,7 @@ impl GlobalState {
 
         let files_config = self.config.files();
         let project_folders =
-            ProjectFolders::new(&workspaces, &files_config.exclude, workspace_build_data.as_ref());
+            ProjectFolders::new(&workspaces, &build_scripts, &files_config.exclude);
 
         if self.proc_macro_client.is_none() {
             self.proc_macro_client = match self.config.proc_macro_srv() {
@@ -353,9 +377,9 @@ impl GlobalState {
                 }
                 res
             };
-            for ws in workspaces.iter() {
+            for (ws, bs) in workspaces.iter().zip(&build_scripts) {
                 crate_graph.extend(ws.to_crate_graph(
-                    workspace_build_data.as_ref(),
+                    bs,
                     self.proc_macro_client.as_ref(),
                     &mut load,
                 ));
@@ -367,7 +391,7 @@ impl GlobalState {
 
         self.source_root_config = project_folders.source_root_config;
         self.workspaces = Arc::new(workspaces);
-        self.workspace_build_data = workspace_build_data;
+        self.workspace_build_data = build_scripts;
 
         self.analysis_host.apply_change(change);
         self.process_changes();
@@ -392,13 +416,19 @@ impl GlobalState {
     }
 
     fn build_data_error(&self) -> Option<String> {
-        match self.fetch_build_data_queue.last_op_result() {
-            Some(Err(err)) => {
-                Some(format!("rust-analyzer failed to fetch build data: {:#}\n", err))
+        let mut buf = String::new();
+
+        for ws in self.fetch_build_data_queue.last_op_result() {
+            if let Err(err) = ws {
+                stdx::format_to!(buf, "rust-analyzer failed to run custom build: {:#}\n", err);
             }
-            Some(Ok(data)) => data.error(),
-            None => None,
         }
+
+        if buf.is_empty() {
+            return None;
+        }
+
+        Some(buf)
     }
 
     fn reload_flycheck(&mut self) {
@@ -451,14 +481,15 @@ pub(crate) struct ProjectFolders {
 impl ProjectFolders {
     pub(crate) fn new(
         workspaces: &[ProjectWorkspace],
+        build_scripts: &[WorkspaceBuildScripts],
         global_excludes: &[AbsPathBuf],
-        build_data: Option<&BuildDataResult>,
     ) -> ProjectFolders {
+        always!(workspaces.len() == build_scripts.len());
         let mut res = ProjectFolders::default();
         let mut fsc = FileSetConfig::builder();
         let mut local_filesets = vec![];
 
-        for root in workspaces.iter().flat_map(|it| it.to_roots(build_data)) {
+        for root in workspaces.iter().zip(build_scripts).flat_map(|(ws, bs)| ws.to_roots(bs)) {
             let file_set_roots: Vec<VfsPath> =
                 root.include.iter().cloned().map(VfsPath::from).collect();
 
diff --git a/lib/arena/src/map.rs b/lib/arena/src/map.rs
index d8acfe0518d..d27f086d37b 100644
--- a/lib/arena/src/map.rs
+++ b/lib/arena/src/map.rs
@@ -62,6 +62,12 @@ impl<T, V> std::ops::Index<Idx<V>> for ArenaMap<Idx<V>, T> {
     }
 }
 
+impl<T, V> std::ops::IndexMut<Idx<V>> for ArenaMap<Idx<V>, T> {
+    fn index_mut(&mut self, idx: Idx<V>) -> &mut T {
+        self.v[Self::to_idx(idx)].as_mut().unwrap()
+    }
+}
+
 impl<T, V> Default for ArenaMap<Idx<V>, T> {
     fn default() -> Self {
         ArenaMap { v: Vec::new(), _ty: PhantomData }