Fix handling of std crates for no_std targets

Author: Kobzol

src/bootstrap/src/core/build_steps/compile.rs

@@ -449,21 +449,24 @@ fn copy_self_contained_objects(
     target_deps
 }
 
-/// Resolves standard library crates for `Std::run_make` for any build kind (like check, build, clippy, etc.).
+/// Resolves standard library crates for `Std::run_make` for any build kind (like check, doc,
+/// build, clippy, etc.).
 pub fn std_crates_for_run_make(run: &RunConfig<'_>) -> Vec<String> {
-    let has_alias = run.paths.iter().any(|set| set.assert_single_path().path.ends_with("library"));
+    let mut crates = run.make_run_crates(builder::Alias::Library);
+
+    // For no_std targets, we only want to check core and alloc
+    // Regardless of core/alloc being selected explicitly or via the "library" default alias,
+    // we only want to keep these two crates.
+    // The set of no_std crates should be kept in sync with what `Builder::std_cargo` does.
+    // Note: an alternative design would be to return an enum from this function (Default vs Subset)
+    // of crates. However, several steps currently pass `-p <package>` even if all crates are
+    // selected, because Cargo behaves differently in that case. To keep that behavior without
+    // making further changes, we pre-filter the no-std crates here.
     let target_is_no_std = run.builder.no_std(run.target).unwrap_or(false);
-
-    // For no_std targets, do not add any additional crates to the compilation other than what `compile::std_cargo` already adds for no_std targets.
     if target_is_no_std {
-        vec![]
-    }
-    // If the paths include "library", build the entire standard library.
-    else if has_alias {
-        run.make_run_crates(builder::Alias::Library)
-    } else {
-        run.cargo_crates_in_set()
+        crates.retain(|c| c == "core" || c == "alloc");
     }
+    crates
 }
 
 /// Tries to find LLVM's `compiler-rt` source directory, for building `library/profiler_builtins`.

src/bootstrap/src/core/builder/tests.rs

@@ -1521,6 +1521,60 @@ mod snapshot {
         steps.assert_contains(StepMetadata::test("CrateLibrustc", host));
         steps.assert_contains_fuzzy(StepMetadata::build("rustc", host));
     }
+
+    #[test]
+    fn doc_library() {
+        let ctx = TestCtx::new();
+        insta::assert_snapshot!(
+            ctx.config("doc")
+                .path("library")
+                .targets(&["x86_64-unknown-linux-gnu"])
+                .get_steps()
+                .render_with(RenderConfig {
+                    normalize_host: false,
+                }), @r"
+        [build] llvm <x86_64-unknown-linux-gnu>
+        [build] rustc 0 <x86_64-unknown-linux-gnu> -> rustc 1 <x86_64-unknown-linux-gnu>
+        [build] rustdoc 0 <x86_64-unknown-linux-gnu>
+        [doc] std 1 <x86_64-unknown-linux-gnu> crates=[alloc,compiler_builtins,core,panic_abort,panic_unwind,proc_macro,std,sysroot,test,unwind]
+        ");
+    }
+
+    #[test]
+    fn doc_core() {
+        let ctx = TestCtx::new();
+        insta::assert_snapshot!(
+            ctx.config("doc")
+                .path("core")
+                .targets(&["x86_64-unknown-linux-gnu"])
+                .get_steps()
+                .render_with(RenderConfig {
+                    normalize_host: false,
+                }), @r"
+        [build] llvm <x86_64-unknown-linux-gnu>
+        [build] rustc 0 <x86_64-unknown-linux-gnu> -> rustc 1 <x86_64-unknown-linux-gnu>
+        [build] rustdoc 0 <x86_64-unknown-linux-gnu>
+        [doc] std 1 <x86_64-unknown-linux-gnu> crates=[core]
+        ");
+    }
+
+    #[test]
+    fn doc_library_no_std_target() {
+        let ctx = TestCtx::new();
+        insta::assert_snapshot!(
+            ctx.config("doc")
+                .path("core")
+                .targets(&["aarch64-unknown-none"])
+                .get_steps()
+                .render_with(RenderConfig {
+                    normalize_host: false,
+                }), @r"
+        [build] llvm <x86_64-unknown-linux-gnu>
+        [build] rustc 0 <x86_64-unknown-linux-gnu> -> rustc 1 <x86_64-unknown-linux-gnu>
+        [build] rustdoc 0 <x86_64-unknown-linux-gnu>
+        [doc] std 1 <aarch64-unknown-none> crates=[core]
+        ");
+    }
 }
 
 struct ExecutedSteps {