fix: update resolve_all_features() to filter pkg deps

src/cargo/core/compiler/unit_dependencies.rs

@@ -28,8 +28,8 @@ use crate::core::compiler::{
 };
 use crate::core::dependency::{Artifact, ArtifactKind, ArtifactTarget, DepKind};
 use crate::core::profiles::{Profile, Profiles, UnitFor};
-use crate::core::resolver::Resolve;
 use crate::core::resolver::features::{FeaturesFor, ResolvedFeatures};
+use crate::core::resolver::{ForceAllTargets, HasDevUnits, Resolve};
 use crate::core::{
     Dependency, Feature, Package, PackageId, PackageSet, Target, TargetKind, Workspace,
 };
@@ -399,6 +399,10 @@ fn compute_deps(
                                 state.features(),
                                 state.package_set,
                                 id,
+                                HasDevUnits::No, // FIXME: see if anywhere specifies this
+                                &[unit.kind],
+                                state.target_data,
+                                ForceAllTargets::No, // FIXME: see if anywhere specifies this
                             );
                             rf.iter().all(|f| features.contains(f))
                         }

src/cargo/core/package.rs

@@ -629,7 +629,7 @@ impl<'gctx> PackageSet<'gctx> {
         Ok(())
     }
 
-    fn filter_deps<'a>(
+    pub fn filter_deps<'a>(
         pkg_id: PackageId,
         resolve: &'a Resolve,
         has_dev_units: HasDevUnits,

src/cargo/ops/cargo_compile/mod.rs

@@ -48,7 +48,7 @@ use crate::core::compiler::{CrateType, TargetInfo, apply_env_config, standard_li
 use crate::core::compiler::{DefaultExecutor, Executor, UnitInterner};
 use crate::core::profiles::Profiles;
 use crate::core::resolver::features::{self, CliFeatures, FeaturesFor};
-use crate::core::resolver::{HasDevUnits, Resolve};
+use crate::core::resolver::{ForceAllTargets, HasDevUnits, Resolve};
 use crate::core::{PackageId, PackageSet, SourceId, TargetKind, Workspace};
 use crate::drop_println;
 use crate::ops;
@@ -278,7 +278,7 @@ pub fn create_bcx<'a, 'gctx>(
         cli_features,
         &specs,
         has_dev_units,
-        crate::core::resolver::features::ForceAllTargets::No,
+        ForceAllTargets::No,
         dry_run,
     )?;
     let WorkspaceResolve {
@@ -974,6 +974,10 @@ pub fn resolve_all_features(
     resolved_features: &features::ResolvedFeatures,
     package_set: &PackageSet<'_>,
     package_id: PackageId,
+    has_dev_units: HasDevUnits,
+    requested_kinds: &[CompileKind],
+    target_data: &RustcTargetData<'_>,
+    force_all_targets: ForceAllTargets,
 ) -> HashSet<String> {
     let mut features: HashSet<String> = resolved_features
         .activated_features(package_id, FeaturesFor::NormalOrDev)
@@ -983,7 +987,15 @@ pub fn resolve_all_features(
 
     // Include features enabled for use by dependencies so targets can also use them with the
     // required-features field when deciding whether to be built or skipped.
-    for (dep_id, deps) in resolve_with_overrides.deps(package_id) {
+    let filtered_deps = PackageSet::filter_deps(
+        package_id,
+        resolve_with_overrides,
+        has_dev_units,
+        requested_kinds,
+        target_data,
+        force_all_targets,
+    );
+    for (dep_id, deps) in filtered_deps {
         let is_proc_macro = package_set
             .get_one(dep_id)
             .expect("packages downloaded")

src/cargo/ops/cargo_compile/unit_generator.rs

@@ -11,7 +11,7 @@ use crate::core::compiler::{RustcTargetData, UnitInterner};
 use crate::core::dependency::DepKind;
 use crate::core::profiles::{Profiles, UnitFor};
 use crate::core::resolver::features::{self, FeaturesFor};
-use crate::core::resolver::{HasDevUnits, Resolve};
+use crate::core::resolver::{ForceAllTargets, HasDevUnits, Resolve};
 use crate::core::{FeatureValue, Package, PackageSet, Summary, Target};
 use crate::util::restricted_names::is_glob_pattern;
 use crate::util::{CargoResult, closest_msg};
@@ -716,6 +716,10 @@ Rustdoc did not scrape the following examples because they require dev-dependenc
                             self.resolved_features,
                             self.package_set,
                             pkg.package_id(),
+                            self.has_dev_units,
+                            self.requested_kinds,
+                            self.target_data,
+                            ForceAllTargets::No,
                         )
                     });
                     rf.iter().filter(|f| !features.contains(*f)).collect()

tests/testsuite/main.rs

@@ -164,6 +164,7 @@ mod registry_overlay;
 mod rename_deps;
 mod replace;
 mod required_features;
+mod resolve_optional_dependency;
 mod run;
 mod rust_version;
 mod rustc;

tests/testsuite/resolve_optional_dependency.rs

@@ -0,0 +1,50 @@
+use crate::prelude::*;
+use cargo_test_support::project;
+
+#[cargo_test(ignore_windows = "test windows only dependency on unix systems")]
+fn cargo_test_should_not_demand_not_required_dep() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+[package]
+name = "sample"
+version = "0.1.0"
+edition = "2024"
+
+[features]
+default = ["feat"]
+feat = ["dep:ipconfig"]
+
+[target.'cfg(windows)'.dependencies]
+ipconfig = { version = "0.3.2", optional = true }
+
+[[example]]
+name = "demo"
+required-features = ["feat"]
+"#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .file("examples/demo.rs", "fn main() {}")
+        .build();
+
+    #[cfg(all(target_os = "linux", target_arch = "x86_64"))]
+    {
+        p.cargo("fetch --target=x86_64-unknown-linux-gnu").run();
+        p.cargo("test --target=x86_64-unknown-linux-gnu --frozen")
+            .run();
+    }
+
+    #[cfg(all(target_os = "linux", target_arch = "aarch64"))]
+    {
+        p.cargo("fetch --target=aarch64-unknown-linux-gnu").run();
+        p.cargo("test --target=aarch64-unknown-linux-gnu --frozen")
+            .run();
+    }
+
+    #[cfg(all(target_os = "macos", target_arch = "aarch64"))]
+    {
+        p.cargo("fetch --target=aarch64-apple-darwin").run();
+        p.cargo("test --target=aarch64-apple-darwin --frozen").run();
+    }
+}