Add --print target-spec-json-schema

This schema is helpful for people writing custom target spec JSON. It
can provide autocomplete in the editor, and also serves as documentation
when there are documentation comments on the structs, as `schemars` will
put them in the schema.

2 files changed, 25 insertions, 0 deletions

diff --git a/src/bootstrap/src/core/build_steps/dist.rs b/src/bootstrap/src/core/build_steps/dist.rs
index a5f0718bc01..99a1062109a 100644
--- a/src/bootstrap/src/core/build_steps/dist.rs
+++ b/src/bootstrap/src/core/build_steps/dist.rs
@@ -590,6 +590,8 @@ impl Step for Rustc {
             // Debugger scripts
             builder.ensure(DebuggerScripts { sysroot: image.to_owned(), target });
 
+            generate_target_spec_json_schema(builder, image);
+
             // HTML copyright files
             let file_list = builder.ensure(super::run::GenerateCopyright);
             for file in file_list {
@@ -618,6 +620,28 @@ impl Step for Rustc {
     }
 }
 
+fn generate_target_spec_json_schema(builder: &Builder<'_>, sysroot: &Path) {
+    // Since we run rustc in bootstrap, we need to ensure that we use the host compiler.
+    // We do this by using the stage 1 compiler, which is always compiled for the host,
+    // even in a cross build.
+    let stage1_host = builder.compiler(1, builder.host_target);
+    let mut rustc = command(builder.rustc(stage1_host)).fail_fast();
+    rustc
+        .env("RUSTC_BOOTSTRAP", "1")
+        .args(["--print=target-spec-json-schema", "-Zunstable-options"]);
+    let schema = rustc.run_capture(builder).stdout();
+
+    let schema_dir = tmpdir(builder);
+    t!(fs::create_dir_all(&schema_dir));
+    let schema_file = schema_dir.join("target-spec-json-schema.json");
+    t!(std::fs::write(&schema_file, schema));
+
+    let dst = sysroot.join("etc");
+    t!(fs::create_dir_all(&dst));
+
+    builder.install(&schema_file, &dst, FileType::Regular);
+}
+
 /// Copies debugger scripts for `target` into the given compiler `sysroot`.
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 pub struct DebuggerScripts {
diff --git a/src/bootstrap/src/utils/proc_macro_deps.rs b/src/bootstrap/src/utils/proc_macro_deps.rs
index 777c8601aa1..db2369097d6 100644
--- a/src/bootstrap/src/utils/proc_macro_deps.rs
+++ b/src/bootstrap/src/utils/proc_macro_deps.rs
@@ -43,6 +43,7 @@ pub static CRATES: &[&str] = &[
     "rustc-hash",
     "self_cell",
     "serde",
+    "serde_derive_internals",
     "sha2",
     "smallvec",
     "stable_deref_trait",