Include path to manifest in workspace warnings.

src/cargo/core/workspace.rs

@@ -741,6 +741,7 @@ impl<'cfg> Workspace<'cfg> {
                 MaybePackage::Package(pkg) => pkg.manifest().warnings().warnings(),
                 MaybePackage::Virtual(vm) => vm.warnings().warnings(),
             };
+            let path = path.join("Cargo.toml");
             for warning in warnings {
                 if warning.is_critical {
                     let err = format_err!("{}", warning.message);
@@ -750,7 +751,14 @@ impl<'cfg> Workspace<'cfg> {
                     );
                     return Err(err.context(cx).into());
                 } else {
-                    self.config.shell().warn(&warning.message)?
+                    let msg = if self.root_manifest.is_none() {
+                        warning.message.to_string()
+                    } else {
+                        // In a workspace, it can be confusing where a warning
+                        // originated, so include the path.
+                        format!("{}: {}", path.display(), warning.message)
+                    };
+                    self.config.shell().warn(msg)?
                 }
             }
         }

tests/testsuite/bad_config.rs

@@ -734,7 +734,7 @@ fn unused_keys_in_virtual_manifest() {
     p.cargo("build --all")
         .with_stderr(
             "\
-warning: unused manifest key: workspace.bulid
+[WARNING] [..]/foo/Cargo.toml: unused manifest key: workspace.bulid
 [COMPILING] bar [..]
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
 ",

tests/testsuite/workspaces.rs

@@ -1969,3 +1969,32 @@ workspace: [..]/foo/Cargo.toml
             .run();
     }
 }
+
+#[test]
+fn ws_warn_path() {
+    // Warnings include path to manifest.
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [workspace]
+            members = ["a"]
+            "#,
+        )
+        .file(
+            "a/Cargo.toml",
+            r#"
+            cargo-features = ["edition"]
+            [package]
+            name = "foo"
+            version = "0.1.0"
+            "#,
+        )
+        .file("a/src/lib.rs", "")
+        .build();
+
+    p.cargo("check")
+        .with_status(0)
+        .with_stderr_contains("[WARNING] [..]/foo/a/Cargo.toml: the cargo feature `edition`[..]")
+        .run();
+}