Supply manifest path for path dependencies

Fixes #7483.

src/cargo/core/dependency.rs

@@ -4,6 +4,7 @@ use semver::ReqParseError;
 use semver::VersionReq;
 use serde::ser;
 use serde::Serialize;
+use std::path::PathBuf;
 use std::rc::Rc;
 
 use crate::core::{PackageId, SourceId, Summary};
@@ -61,6 +62,10 @@ struct SerializedDependency<'a> {
     /// The registry URL this dependency is from.
     /// If None, then it comes from the default registry (crates.io).
     registry: Option<&'a str>,
+
+    /// The path to the manifest for a local path dependency.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    manifest_path: Option<PathBuf>,
 }
 
 impl ser::Serialize for Dependency {
@@ -80,6 +85,7 @@ impl ser::Serialize for Dependency {
             target: self.platform(),
             rename: self.explicit_name_in_toml().map(|s| s.as_str()),
             registry: registry_id.as_ref().map(|sid| sid.url().as_str()),
+            manifest_path: self.source_id().manifest_path(),
         }
         .serialize(s)
     }

src/cargo/core/source/source_id.rs

@@ -9,7 +9,7 @@ use std::cmp::{self, Ordering};
 use std::collections::HashSet;
 use std::fmt::{self, Formatter};
 use std::hash::{self, Hash};
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::ptr;
 use std::sync::Mutex;
 use url::Url;
@@ -237,6 +237,15 @@ impl SourceId {
         self.inner.kind == SourceKind::Path
     }
 
+    /// Returns the manifest path if this is a path dependency.
+    pub fn manifest_path(self) -> Option<PathBuf> {
+        if self.inner.kind != SourceKind::Path {
+            return None;
+        }
+
+        Some(self.inner.url.to_file_path().unwrap().join("Cargo.toml"))
+    }
+
     /// Returns `true` if this source is from a registry (either local or not).
     pub fn is_registry(self) -> bool {
         matches!(

tests/testsuite/metadata.rs

@@ -1984,6 +1984,7 @@ fn deps_with_bin_only() {
                       "rename": null,
                       "optional": false,
                       "uses_default_features": true,
+                      "manifest_path": "[..]/bdep/Cargo.toml",
                       "features": [],
                       "target": null,
                       "registry": null