Auto merge of #6188 - ebroto:primary_package, r=flip1995

Add --no-deps option to avoid running on path dependencies in workspaces

Since rust-lang/cargo#8758 has hit nightly, this allows us to address the second bullet point and [the concern related to `--fix`](https://github.com/rust-lang/cargo/issues/8143#issuecomment-619289546) in the [RUSTC_WORKSPACE_WRAPPER tracking issue](https://github.com/rust-lang/cargo/issues/8143).

As a reminder stabilizing that env var will solve #4612 (Clippy not running after `cargo check` in stable) and would allow to stabilize the `--fix` option in Clippy.

changelog: Add `--no-deps` option to avoid running on path dependencies in workspaces

Fixes #3025

7 files changed, 156 insertions, 19 deletions

diff --git a/README.md b/README.md
index fddf0614a0b..aaa55e11c7d 100644
--- a/README.md
+++ b/README.md
@@ -82,6 +82,22 @@ Note that this is still experimental and only supported on the nightly channel:
 cargo clippy --fix -Z unstable-options
 ```
 
+#### Workspaces
+
+All the usual workspace options should work with Clippy. For example the following command
+will run Clippy on the `example` crate:
+
+```terminal
+cargo clippy -p example
+```
+
+As with `cargo check`, this includes dependencies that are members of the workspace, like path dependencies.
+If you want to run Clippy **only** on the given crate, use the `--no-deps` option like this:
+
+```terminal
+cargo clippy -p example -- --no-deps 
+```
+
 ### Running Clippy from the command line without installing it
 
 To have cargo compile your crate with Clippy without Clippy installation
diff --git a/clippy_workspace_tests/path_dep/Cargo.toml b/clippy_workspace_tests/path_dep/Cargo.toml
new file mode 100644
index 00000000000..85a91cd2dec
--- /dev/null
+++ b/clippy_workspace_tests/path_dep/Cargo.toml
@@ -0,0 +1,3 @@
+[package]
+name = "path_dep"
+version = "0.1.0"
diff --git a/clippy_workspace_tests/path_dep/src/lib.rs b/clippy_workspace_tests/path_dep/src/lib.rs
new file mode 100644
index 00000000000..35ce524f2b1
--- /dev/null
+++ b/clippy_workspace_tests/path_dep/src/lib.rs
@@ -0,0 +1,6 @@
+#![deny(clippy::empty_loop)]
+
+#[cfg(feature = "primary_package_test")]
+pub fn lint_me() {
+    loop {}
+}
diff --git a/clippy_workspace_tests/subcrate/Cargo.toml b/clippy_workspace_tests/subcrate/Cargo.toml
index 83ea5868160..45362c11b85 100644
--- a/clippy_workspace_tests/subcrate/Cargo.toml
+++ b/clippy_workspace_tests/subcrate/Cargo.toml
@@ -1,3 +1,6 @@
 [package]
 name = "subcrate"
 version = "0.1.0"
+
+[dependencies]
+path_dep = { path = "../path_dep" }
diff --git a/src/driver.rs b/src/driver.rs
index ef31c72481a..e490ee54c0b 100644
--- a/src/driver.rs
+++ b/src/driver.rs
@@ -182,6 +182,7 @@ fn toolchain_path(home: Option<String>, toolchain: Option<String>) -> Option<Pat
     })
 }
 
+#[allow(clippy::too_many_lines)]
 pub fn main() {
     rustc_driver::init_rustc_env_logger();
     SyncLazy::force(&ICE_HOOK);
@@ -277,27 +278,40 @@ pub fn main() {
             args.extend(vec!["--sysroot".into(), sys_root]);
         };
 
-        // this check ensures that dependencies are built but not linted and the final
-        // crate is linted but not built
-        let clippy_enabled = env::var("CLIPPY_TESTS").map_or(false, |val| val == "true")
-            || arg_value(&orig_args, "--cap-lints", |val| val == "allow").is_none();
-
+        let mut no_deps = false;
+        let clippy_args = env::var("CLIPPY_ARGS")
+            .unwrap_or_default()
+            .split("__CLIPPY_HACKERY__")
+            .filter_map(|s| match s {
+                "" => None,
+                "--no-deps" => {
+                    no_deps = true;
+                    None
+                },
+                _ => Some(s.to_string()),
+            })
+            .chain(vec!["--cfg".into(), r#"feature="cargo-clippy""#.into()])
+            .collect::<Vec<String>>();
+
+        // We enable Clippy if one of the following conditions is met
+        // - IF Clippy is run on its test suite OR
+        // - IF Clippy is run on the main crate, not on deps (`!cap_lints_allow`) THEN
+        //    - IF `--no-deps` is not set (`!no_deps`) OR
+        //    - IF `--no-deps` is set and Clippy is run on the specified primary package
+        let clippy_tests_set = env::var("CLIPPY_TESTS").map_or(false, |val| val == "true");
+        let cap_lints_allow = arg_value(&orig_args, "--cap-lints", |val| val == "allow").is_some();
+        let in_primary_package = env::var("CARGO_PRIMARY_PACKAGE").is_ok();
+
+        let clippy_enabled = clippy_tests_set || (!cap_lints_allow && (!no_deps || in_primary_package));
         if clippy_enabled {
-            args.extend(vec!["--cfg".into(), r#"feature="cargo-clippy""#.into()]);
-            if let Ok(extra_args) = env::var("CLIPPY_ARGS") {
-                args.extend(extra_args.split("__CLIPPY_HACKERY__").filter_map(|s| {
-                    if s.is_empty() {
-                        None
-                    } else {
-                        Some(s.to_string())
-                    }
-                }));
-            }
+            args.extend(clippy_args);
         }
+
         let mut clippy = ClippyCallbacks;
         let mut default = DefaultCallbacks;
         let callbacks: &mut (dyn rustc_driver::Callbacks + Send) =
             if clippy_enabled { &mut clippy } else { &mut default };
+
         rustc_driver::RunCompiler::new(&args, callbacks).run()
     }))
 }
diff --git a/src/main.rs b/src/main.rs
index 6739a4cf224..ea06743394d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -62,7 +62,7 @@ struct ClippyCmd {
     unstable_options: bool,
     cargo_subcommand: &'static str,
     args: Vec<String>,
-    clippy_args: String,
+    clippy_args: Vec<String>,
 }
 
 impl ClippyCmd {
@@ -99,7 +99,10 @@ impl ClippyCmd {
             args.insert(0, "+nightly".to_string());
         }
 
-        let clippy_args: String = old_args.map(|arg| format!("{}__CLIPPY_HACKERY__", arg)).collect();
+        let mut clippy_args: Vec<String> = old_args.collect();
+        if cargo_subcommand == "fix" && !clippy_args.iter().any(|arg| arg == "--no-deps") {
+            clippy_args.push("--no-deps".into());
+        }
 
         ClippyCmd {
             unstable_options,
@@ -147,10 +150,15 @@ impl ClippyCmd {
 
     fn into_std_cmd(self) -> Command {
         let mut cmd = Command::new("cargo");
+        let clippy_args: String = self
+            .clippy_args
+            .iter()
+            .map(|arg| format!("{}__CLIPPY_HACKERY__", arg))
+            .collect();
 
         cmd.env(self.path_env(), Self::path())
             .envs(ClippyCmd::target_dir())
-            .env("CLIPPY_ARGS", self.clippy_args)
+            .env("CLIPPY_ARGS", clippy_args)
             .arg(self.cargo_subcommand)
             .args(&self.args);
 
@@ -202,6 +210,24 @@ mod tests {
     }
 
     #[test]
+    fn fix_implies_no_deps() {
+        let args = "cargo clippy --fix -Zunstable-options"
+            .split_whitespace()
+            .map(ToString::to_string);
+        let cmd = ClippyCmd::new(args);
+        assert!(cmd.clippy_args.iter().any(|arg| arg == "--no-deps"));
+    }
+
+    #[test]
+    fn no_deps_not_duplicated_with_fix() {
+        let args = "cargo clippy --fix -Zunstable-options -- --no-deps"
+            .split_whitespace()
+            .map(ToString::to_string);
+        let cmd = ClippyCmd::new(args);
+        assert_eq!(cmd.clippy_args.iter().filter(|arg| *arg == "--no-deps").count(), 1);
+    }
+
+    #[test]
     fn check() {
         let args = "cargo clippy".split_whitespace().map(ToString::to_string);
         let cmd = ClippyCmd::new(args);
diff --git a/tests/dogfood.rs b/tests/dogfood.rs
index a6163a83d76..052223d6d6f 100644
--- a/tests/dogfood.rs
+++ b/tests/dogfood.rs
@@ -3,7 +3,7 @@
 #![feature(once_cell)]
 
 use std::lazy::SyncLazy;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::process::Command;
 
 mod cargo;
@@ -47,12 +47,77 @@ fn dogfood_clippy() {
 
 #[test]
 fn dogfood_subprojects() {
+    fn test_no_deps_ignores_path_deps_in_workspaces() {
+        fn clean(cwd: &Path, target_dir: &Path) {
+            Command::new("cargo")
+                .current_dir(cwd)
+                .env("CARGO_TARGET_DIR", target_dir)
+                .arg("clean")
+                .args(&["-p", "subcrate"])
+                .args(&["-p", "path_dep"])
+                .output()
+                .unwrap();
+        }
+
+        if cargo::is_rustc_test_suite() {
+            return;
+        }
+        let root = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+        let target_dir = root.join("target").join("dogfood");
+        let cwd = root.join("clippy_workspace_tests");
+
+        // Make sure we start with a clean state
+        clean(&cwd, &target_dir);
+
+        // `path_dep` is a path dependency of `subcrate` that would trigger a denied lint.
+        // Make sure that with the `--no-deps` argument Clippy does not run on `path_dep`.
+        let output = Command::new(&*CLIPPY_PATH)
+            .current_dir(&cwd)
+            .env("CLIPPY_DOGFOOD", "1")
+            .env("CARGO_INCREMENTAL", "0")
+            .arg("clippy")
+            .args(&["-p", "subcrate"])
+            .arg("--")
+            .arg("--no-deps")
+            .arg("-Cdebuginfo=0") // disable debuginfo to generate less data in the target dir
+            .args(&["--cfg", r#"feature="primary_package_test""#])
+            .output()
+            .unwrap();
+        println!("status: {}", output.status);
+        println!("stdout: {}", String::from_utf8_lossy(&output.stdout));
+        println!("stderr: {}", String::from_utf8_lossy(&output.stderr));
+
+        assert!(output.status.success());
+
+        // Make sure we start with a clean state
+        clean(&cwd, &target_dir);
+
+        // Test that without the `--no-deps` argument, `path_dep` is linted.
+        let output = Command::new(&*CLIPPY_PATH)
+            .current_dir(&cwd)
+            .env("CLIPPY_DOGFOOD", "1")
+            .env("CARGO_INCREMENTAL", "0")
+            .arg("clippy")
+            .args(&["-p", "subcrate"])
+            .arg("--")
+            .arg("-Cdebuginfo=0") // disable debuginfo to generate less data in the target dir
+            .args(&["--cfg", r#"feature="primary_package_test""#])
+            .output()
+            .unwrap();
+        println!("status: {}", output.status);
+        println!("stdout: {}", String::from_utf8_lossy(&output.stdout));
+        println!("stderr: {}", String::from_utf8_lossy(&output.stderr));
+
+        assert!(!output.status.success());
+    }
+
     // run clippy on remaining subprojects and fail the test if lint warnings are reported
     if cargo::is_rustc_test_suite() {
         return;
     }
     let root_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
 
+    // NOTE: `path_dep` crate is omitted on purpose here
     for d in &[
         "clippy_workspace_tests",
         "clippy_workspace_tests/src",
@@ -78,4 +143,8 @@ fn dogfood_subprojects() {
 
         assert!(output.status.success());
     }
+
+    // NOTE: Since tests run in parallel we can't run cargo commands on the same workspace at the
+    // same time, so we test this immediately after the dogfood for workspaces.
+    test_no_deps_ignores_path_deps_in_workspaces();
 }