Auto merge of #10341 - hi-rustin:rustin-patch-doc-deps, r=ehuss

Compute non custom build and non transitive deps for doc

### What does this PR try to resolve?

close #10318 and close #9198
### How should we test and review this PR?

Compute non custom build and non transitive deps for doc.
Add test for it.

src/cargo/core/compiler/unit_dependencies.rs

@@ -18,7 +18,6 @@
 use crate::core::compiler::unit_graph::{UnitDep, UnitGraph};
 use crate::core::compiler::UnitInterner;
 use crate::core::compiler::{CompileKind, CompileMode, RustcTargetData, Unit};
-use crate::core::dependency::DepKind;
 use crate::core::profiles::{Profile, Profiles, UnitFor};
 use crate::core::resolver::features::{FeaturesFor, ResolvedFeatures};
 use crate::core::resolver::Resolve;
@@ -243,29 +242,7 @@ fn compute_deps(
     }
 
     let id = unit.pkg.package_id();
-    let filtered_deps = state.deps(unit, unit_for, &|dep| {
-        // If this target is a build command, then we only want build
-        // dependencies, otherwise we want everything *other than* build
-        // dependencies.
-        if unit.target.is_custom_build() != dep.is_build() {
-            return false;
-        }
-
-        // If this dependency is **not** a transitive dependency, then it
-        // only applies to test/example targets.
-        if !dep.is_transitive()
-            && !unit.target.is_test()
-            && !unit.target.is_example()
-            && !unit.mode.is_doc_scrape()
-            && !unit.mode.is_any_test()
-        {
-            return false;
-        }
-
-        // If we've gotten past all that, then this dependency is
-        // actually used!
-        true
-    });
+    let filtered_deps = state.deps(unit, unit_for);
 
     let mut ret = Vec::new();
     let mut dev_deps = Vec::new();
@@ -423,7 +400,7 @@ fn compute_deps_doc(
     state: &mut State<'_, '_>,
     unit_for: UnitFor,
 ) -> CargoResult<Vec<UnitDep>> {
-    let deps = state.deps(unit, unit_for, &|dep| dep.kind() == DepKind::Normal);
+    let deps = state.deps(unit, unit_for);
 
     // To document a library, we depend on dependencies actually being
     // built. If we're documenting *all* libraries, then we also depend on
@@ -831,22 +808,32 @@ impl<'a, 'cfg> State<'a, 'cfg> {
     }
 
     /// Returns a filtered set of dependencies for the given unit.
-    fn deps(
-        &self,
-        unit: &Unit,
-        unit_for: UnitFor,
-        filter: &dyn Fn(&Dependency) -> bool,
-    ) -> Vec<(PackageId, &HashSet<Dependency>)> {
+    fn deps(&self, unit: &Unit, unit_for: UnitFor) -> Vec<(PackageId, &HashSet<Dependency>)> {
         let pkg_id = unit.pkg.package_id();
         let kind = unit.kind;
         self.resolve()
             .deps(pkg_id)
             .filter(|&(_id, deps)| {
                 assert!(!deps.is_empty());
                 deps.iter().any(|dep| {
-                    if !filter(dep) {
+                    // If this target is a build command, then we only want build
+                    // dependencies, otherwise we want everything *other than* build
+                    // dependencies.
+                    if unit.target.is_custom_build() != dep.is_build() {
                         return false;
                     }
+
+                    // If this dependency is **not** a transitive dependency, then it
+                    // only applies to test/example targets.
+                    if !dep.is_transitive()
+                        && !unit.target.is_test()
+                        && !unit.target.is_example()
+                        && !unit.mode.is_doc_scrape()
+                        && !unit.mode.is_any_test()
+                    {
+                        return false;
+                    }
+
                     // If this dependency is only available for certain platforms,
                     // make sure we're only enabling it for that platform.
                     if !self.target_data.dep_platform_activated(dep, kind) {
@@ -862,6 +849,8 @@ impl<'a, 'cfg> State<'a, 'cfg> {
                         }
                     }
 
+                    // If we've gotten past all that, then this dependency is
+                    // actually used!
                     true
                 })
             })

tests/testsuite/doc.rs

@@ -1815,6 +1815,70 @@ fn doc_example() {
         .exists());
 }
 
+#[cargo_test]
+fn doc_example_with_deps() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "foo"
+            version = "0.1.0"
+            edition = "2018"
+
+            [[example]]
+            crate-type = ["lib"]
+            name = "ex"
+            doc = true
+
+            [dev-dependencies]
+            a = {path = "a"}
+            b = {path = "b"}
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .file(
+            "examples/ex.rs",
+            r#"
+            use a::fun;
+
+            /// Example
+            pub fn x() { fun(); }
+            "#,
+        )
+        .file(
+            "a/Cargo.toml",
+            r#"
+            [package]
+            name = "a"
+            version = "0.0.1"
+
+            [dependencies]
+            b = {path = "../b"}
+            "#,
+        )
+        .file("a/src/fun.rs", "pub fn fun() {}")
+        .file("a/src/lib.rs", "pub mod fun;")
+        .file(
+            "b/Cargo.toml",
+            r#"
+            [package]
+            name = "b"
+            version = "0.0.1"
+            "#,
+        )
+        .file("b/src/lib.rs", "")
+        .build();
+
+    p.cargo("doc --examples").run();
+    assert!(p
+        .build_dir()
+        .join("doc")
+        .join("ex")
+        .join("fn.x.html")
+        .exists());
+}
+
 #[cargo_test]
 fn bin_private_items() {
     let p = project()