fix: deduplicate dependencies by artifact target

Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>

Author: rvolosatovs

src/cargo/core/compiler/standard_lib.rs

@@ -214,6 +214,7 @@ pub fn generate_std_roots(
                 /*is_std*/ true,
                 /*dep_hash*/ 0,
                 IsArtifact::No,
+                None,
             ));
         }
     }

src/cargo/core/compiler/unit.rs

@@ -1,6 +1,8 @@
-use crate::core::compiler::{unit_dependencies::IsArtifact, CompileKind, CompileMode, CrateType};
+use crate::core::compiler::unit_dependencies::IsArtifact;
+use crate::core::compiler::{CompileKind, CompileMode, CompileTarget, CrateType};
 use crate::core::manifest::{Target, TargetKind};
-use crate::core::{profiles::Profile, Package};
+use crate::core::profiles::Profile;
+use crate::core::Package;
 use crate::util::hex::short_hash;
 use crate::util::interning::InternedString;
 use crate::util::Config;
@@ -72,6 +74,12 @@ pub struct UnitInner {
     /// This value initially starts as 0, and then is filled in via a
     /// second-pass after all the unit dependencies have been computed.
     pub dep_hash: u64,
+
+    /// This is used for target-dependent feature resolution and is copied from
+    /// [`FeaturesFor::ArtifactDep`], if the enum matches the variant.
+    ///
+    /// [`FeaturesFor::ArtifactDep`]: crate::core::resolver::features::FeaturesFor::ArtifactDep
+    pub artifact_target_for_features: Option<CompileTarget>,
 }
 
 impl UnitInner {
@@ -139,6 +147,10 @@ impl fmt::Debug for Unit {
             .field("mode", &self.mode)
             .field("features", &self.features)
             .field("artifact", &self.artifact.is_true())
+            .field(
+                "artifact_target_for_features",
+                &self.artifact_target_for_features,
+            )
             .field("is_std", &self.is_std)
             .field("dep_hash", &self.dep_hash)
             .finish()
@@ -184,6 +196,7 @@ impl UnitInterner {
         is_std: bool,
         dep_hash: u64,
         artifact: IsArtifact,
+        artifact_target_for_features: Option<CompileTarget>,
     ) -> Unit {
         let target = match (is_std, target.kind()) {
             // This is a horrible hack to support build-std. `libstd` declares
@@ -216,6 +229,7 @@ impl UnitInterner {
             is_std,
             dep_hash,
             artifact,
+            artifact_target_for_features,
         });
         Unit { inner }
     }

src/cargo/core/compiler/unit_dependencies.rs

@@ -885,6 +885,10 @@ fn new_unit_dep_with_profile(
         .resolve()
         .is_public_dep(parent.pkg.package_id(), pkg.package_id());
     let features_for = unit_for.map_to_features_for(artifact);
+    let artifact_target = match features_for {
+        FeaturesFor::ArtifactDep(target) => Some(target),
+        _ => None,
+    };
     let features = state.activated_features(pkg.package_id(), features_for);
     let unit = state.interner.intern(
         pkg,
@@ -896,6 +900,7 @@ fn new_unit_dep_with_profile(
         state.is_std,
         /*dep_hash*/ 0,
         artifact.map_or(IsArtifact::No, |_| IsArtifact::Yes),
+        artifact_target,
     );
     Ok(UnitDep {
         unit,

src/cargo/ops/cargo_compile/mod.rs

@@ -630,6 +630,9 @@ fn traverse_and_share(
         unit.is_std,
         new_dep_hash,
         unit.artifact,
+        // Since `dep_hash` is now filled in, there's no need to specify the artifact target
+        // for target-dependent feature resolution
+        None,
     );
     assert!(memo.insert(unit.clone(), new_unit.clone()).is_none());
     new_graph.entry(new_unit.clone()).or_insert(new_deps);
@@ -788,6 +791,7 @@ fn override_rustc_crate_types(
             unit.is_std,
             unit.dep_hash,
             unit.artifact,
+            unit.artifact_target_for_features,
         )
     };
     units[0] = match unit.target.kind() {

src/cargo/ops/cargo_compile/unit_generator.rs

@@ -171,6 +171,7 @@ impl<'a> UnitGenerator<'a, '_> {
                     /*is_std*/ false,
                     /*dep_hash*/ 0,
                     IsArtifact::No,
+                    None,
                 )
             })
             .collect()