Make ./x.py <cmd> compiler/<crate> aware of the crate's features

src/bootstrap/src/core/build_steps/check.rs

@@ -228,7 +228,7 @@ impl Step for Rustc {
             self.override_build_kind.unwrap_or(builder.kind),
         );
 
-        rustc_cargo(builder, &mut cargo, target, &compiler);
+        rustc_cargo(builder, &mut cargo, target, &compiler, &self.crates);
 
         // For ./x.py clippy, don't run with --all-targets because
         // linting tests and benchmarks can produce very noisy results

src/bootstrap/src/core/build_steps/clippy.rs

@@ -197,7 +197,7 @@ impl Step for Rustc {
             Kind::Clippy,
         );
 
-        rustc_cargo(builder, &mut cargo, target, &compiler);
+        rustc_cargo(builder, &mut cargo, target, &compiler, &self.crates);
 
         // Explicitly pass -p for all compiler crates -- this will force cargo
         // to also lint the tests/benches/examples for these crates, rather

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

@@ -983,7 +983,7 @@ impl Step for Rustc {
             Kind::Build,
         );
 
-        rustc_cargo(builder, &mut cargo, target, &compiler);
+        rustc_cargo(builder, &mut cargo, target, &compiler, &self.crates);
 
         // NB: all RUSTFLAGS should be added to `rustc_cargo()` so they will be
         // consistently applied by check/doc/test modes too.
@@ -1042,10 +1042,11 @@ pub fn rustc_cargo(
     cargo: &mut Cargo,
     target: TargetSelection,
     compiler: &Compiler,
+    crates: &[String],
 ) {
     cargo
         .arg("--features")
-        .arg(builder.rustc_features(builder.kind, target))
+        .arg(builder.rustc_features(builder.kind, target, crates))
         .arg("--manifest-path")
         .arg(builder.src.join("compiler/rustc/Cargo.toml"));
 

src/bootstrap/src/core/build_steps/doc.rs

@@ -826,7 +826,7 @@ impl Step for Rustc {
         // see https://github.com/rust-lang/rust/pull/122066#issuecomment-1983049222
         // cargo.rustdocflag("--generate-link-to-definition");
 
-        compile::rustc_cargo(builder, &mut cargo, target, &compiler);
+        compile::rustc_cargo(builder, &mut cargo, target, &compiler, &self.crates);
         cargo.arg("-Zskip-rustdoc-fingerprint");
 
         // Only include compiler crates, no dependencies of those, such as `libc`.

src/bootstrap/src/core/build_steps/test.rs

@@ -2692,7 +2692,7 @@ impl Step for Crate {
                 }
             }
             Mode::Rustc => {
-                compile::rustc_cargo(builder, &mut cargo, target, &compiler);
+                compile::rustc_cargo(builder, &mut cargo, target, &compiler, &self.crates);
             }
             _ => panic!("can only test libraries"),
         };

src/bootstrap/src/core/metadata.rs

@@ -1,3 +1,4 @@
+use std::collections::BTreeMap;
 use std::path::PathBuf;
 
 use serde_derive::Deserialize;
@@ -21,6 +22,7 @@ struct Package {
     manifest_path: String,
     dependencies: Vec<Dependency>,
     targets: Vec<Target>,
+    features: BTreeMap<String, Vec<String>>,
 }
 
 /// For more information, see the output of
@@ -51,7 +53,13 @@ pub fn build(build: &mut Build) {
                 .map(|dep| dep.name)
                 .collect();
             let has_lib = package.targets.iter().any(|t| t.kind.iter().any(|k| k == "lib"));
-            let krate = Crate { name: name.clone(), deps, path, has_lib };
+            let krate = Crate {
+                name: name.clone(),
+                deps,
+                path,
+                has_lib,
+                features: package.features.keys().cloned().collect(),
+            };
             let relative_path = krate.local_path(build);
             build.crates.insert(name.clone(), krate);
             let existing_path = build.crate_paths.insert(relative_path, name);

src/bootstrap/src/lib.rs

@@ -183,6 +183,7 @@ struct Crate {
     deps: HashSet<String>,
     path: PathBuf,
     has_lib: bool,
+    features: Vec<String>,
 }
 
 impl Crate {
@@ -666,16 +667,25 @@ impl Build {
     }
 
     /// Gets the space-separated set of activated features for the compiler.
-    fn rustc_features(&self, kind: Kind, target: TargetSelection) -> String {
+    fn rustc_features(&self, kind: Kind, target: TargetSelection, crates: &[String]) -> String {
+        let possible_features_by_crates: HashSet<_> = crates
+            .iter()
+            .flat_map(|krate| &self.crates[krate].features)
+            .map(std::ops::Deref::deref)
+            .collect();
         let mut features = vec![];
-        if self.config.jemalloc {
+        if self.config.jemalloc && possible_features_by_crates.contains("jemalloc") {
             features.push("jemalloc");
         }
-        if self.config.llvm_enabled(target) || kind == Kind::Check {
+        if (self.config.llvm_enabled(target) || kind == Kind::Check)
+            && possible_features_by_crates.contains("llvm")
+        {
             features.push("llvm");
         }
         // keep in sync with `bootstrap/compile.rs:rustc_cargo_env`
-        if self.config.rustc_parallel {
+        if self.config.rustc_parallel
+            && possible_features_by_crates.contains("rustc_use_parallel_compiler")
+        {
             features.push("rustc_use_parallel_compiler");
         }
 
@@ -684,7 +694,8 @@ impl Build {
         // which is everything (including debug/trace/etc.)
         // if its unset, if debug_assertions is on, then debug_logging will also be on
         // as well as tracing *ignoring* this feature when debug_assertions is on
-        if !self.config.rust_debug_logging {
+        if !self.config.rust_debug_logging && possible_features_by_crates.contains("max_level_info")
+        {
             features.push("max_level_info");
         }