fix(doc): respect public-dependency when documenting deps

Author: ojuschugh1

src/cargo/core/compiler/unit_dependencies.rs

@@ -637,6 +637,16 @@ fn compute_deps_doc(
     // built. If we're documenting *all* libraries, then we also depend on
     // the documentation of the library being built.
     let mut ret = Vec::new();
+    let is_member = state.ws.is_member(&unit.pkg);
+
+    // Check if public-dependency feature is enabled
+    let public_deps_enabled = state.gctx.cli_unstable().public_dependency
+        || unit
+            .pkg
+            .manifest()
+            .unstable_features()
+            .is_enabled(Feature::public_dependency());
+
     for (id, deps) in state.deps(unit, unit_for) {
         let Some(dep_lib) = calc_artifact_deps(unit, unit_for, id, &deps, state, &mut ret)? else {
             continue;
@@ -657,7 +667,20 @@ fn compute_deps_doc(
             IS_NO_ARTIFACT_DEP,
         )?;
         ret.push(lib_unit_dep);
-        if dep_lib.documented() && state.intent.wants_deps_docs() {
+
+        // Decide whether to document this dependency.
+        // When public-dependency is enabled, only document:
+        // - Direct dependencies of workspace members
+        // - Public dependencies (recursively)
+        // This dramatically speeds up documentation builds by excluding indirect
+        // private dependencies that cannot be used by readers of the docs.
+        let should_doc_dep = if is_member || !public_deps_enabled {
+            true
+        } else {
+            state.resolve().is_public_dep(unit.pkg.package_id(), id)
+        };
+
+        if dep_lib.documented() && state.intent.wants_deps_docs() && should_doc_dep {
             // Document this lib as well.
             let doc_unit_dep = new_unit_dep(
                 state,

tests/testsuite/doc.rs

@@ -4205,7 +4205,6 @@ fn doc_with_private_dependency() {
 [DOWNLOADING] crates ...
 [DOWNLOADED] baz v0.0.1 (registry `dummy-registry`)
 [DOWNLOADED] bar v0.0.1 (registry `dummy-registry`)
-[DOCUMENTING] baz v0.0.1
 [CHECKING] baz v0.0.1
 [DOCUMENTING] bar v0.0.1
 [CHECKING] bar v0.0.1
@@ -4220,7 +4219,7 @@ fn doc_with_private_dependency() {
 
     assert!(p.root().join("target/doc/foo/index.html").is_file());
     assert!(p.root().join("target/doc/bar/index.html").is_file());
-    assert!(p.root().join("target/doc/baz/index.html").is_file());
+    assert!(!p.root().join("target/doc/baz/index.html").is_file());
 }
 
 #[cargo_test(nightly, reason = "public-dependency feature is unstable")]
@@ -4277,5 +4276,78 @@ fn doc_mixed_public_private_deps() {
             .join("target/doc/priv_dep_with_dep/index.html")
             .is_file()
     );
-    assert!(p.root().join("target/doc/transitive/index.html").is_file());
+    assert!(!p.root().join("target/doc/transitive/index.html").is_file());
+}
+
+#[cargo_test(nightly, reason = "public-dependency feature is unstable")]
+fn doc_workspace_member_private_dep() {
+    // selected -> skipped (private dep), skipped -> transitive (registry dep)
+    // Both selected and skipped are workspace members.
+    // Running `cargo doc -p selected`:
+    // - skipped is documented because it is a workspace member (is_member = true),
+    //   even though selected declares it as a private dep
+    // - transitive is documented because skipped is a workspace member, so
+    //   is_member is true when computing skipped's deps
+
+    Package::new("transitive", "0.0.1")
+        .file("src/lib.rs", "pub fn transitive() {}")
+        .publish();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [workspace]
+                members = ["selected", "skipped"]
+            "#,
+        )
+        .file(
+            "selected/Cargo.toml",
+            r#"
+                cargo-features = ["public-dependency"]
+
+                [package]
+                name = "selected"
+                version = "0.0.1"
+                edition = "2021"
+
+                [dependencies]
+                skipped = { path = "../skipped", public = false }
+            "#,
+        )
+        .file("selected/src/lib.rs", "pub fn selected() {}")
+        .file(
+            "skipped/Cargo.toml",
+            r#"
+                [package]
+                name = "skipped"
+                version = "0.0.1"
+                edition = "2021"
+
+                [dependencies]
+                transitive = "0.0.1"
+            "#,
+        )
+        .file("skipped/src/lib.rs", "pub fn skipped() {}")
+        .build();
+
+    p.cargo("doc -p selected -Zpublic-dependency")
+        .masquerade_as_nightly_cargo(&["public-dependency"])
+        .run();
+
+    // selected is documented
+    assert!(p
+        .root()
+        .join("target/doc/selected/index.html")
+        .is_file());
+    // skipped is a workspace member so it is documented even though selected marks it private
+    assert!(p
+        .root()
+        .join("target/doc/skipped/index.html")
+        .is_file());
+    // transitive is documented because skipped is a workspace member
+    assert!(p
+        .root()
+        .join("target/doc/transitive/index.html")
+        .is_file());
 }