diff --git a/src/cargo/core/source/source_id.rs b/src/cargo/core/source/source_id.rs
index 5e6322d9e9c..dae09cb6ee7 100644
--- a/src/cargo/core/source/source_id.rs
+++ b/src/cargo/core/source/source_id.rs
@@ -5,6 +5,7 @@ use crate::util::{CanonicalUrl, CargoResult, Config, IntoUrl};
 use log::trace;
 use serde::de;
 use serde::ser;
+use std::cell::Cell;
 use std::cmp::{self, Ordering};
 use std::collections::HashSet;
 use std::fmt::{self, Formatter};
@@ -437,12 +438,30 @@ impl Ord for SourceId {
     }
 }
 
+thread_local! {
+    static SERIALIZE_STRIP_PATHS: Cell<bool> = Cell::new(false);
+}
+
+#[must_use]
+#[allow(dead_code)]
+pub fn disable_path_serialization() -> impl Drop {
+    // Ensure that we reset the setting eventually.
+    struct DropGuard;
+    impl Drop for DropGuard {
+        fn drop(&mut self) {
+            SERIALIZE_STRIP_PATHS.with(|ssp| ssp.set(false));
+        }
+    }
+    SERIALIZE_STRIP_PATHS.with(|ssp| ssp.set(true));
+    DropGuard
+}
+
 impl ser::Serialize for SourceId {
     fn serialize<S>(&self, s: S) -> Result<S::Ok, S::Error>
     where
         S: ser::Serializer,
     {
-        if self.is_path() {
+        if self.is_path() && SERIALIZE_STRIP_PATHS.with(|ssp| ssp.get()) {
             None::<String>.serialize(s)
         } else {
             s.collect_str(&self.as_url())
diff --git a/tests/testsuite/alt_registry.rs b/tests/testsuite/alt_registry.rs
index 748d5dcaaa5..5fd7958a7d2 100644
--- a/tests/testsuite/alt_registry.rs
+++ b/tests/testsuite/alt_registry.rs
@@ -783,7 +783,7 @@ fn alt_reg_metadata() {
                         "license": null,
                         "license_file": null,
                         "description": null,
-                        "source": null,
+                        "source": "path+file://[..]/foo",
                         "dependencies": [
                             {
                                 "name": "altdep",
@@ -936,7 +936,7 @@ fn alt_reg_metadata() {
                         "license": null,
                         "license_file": null,
                         "description": null,
-                        "source": null,
+                        "source": "path+file://[..]/foo",
                         "dependencies": [
                             {
                                 "name": "altdep",
@@ -1141,7 +1141,7 @@ fn unknown_registry() {
                   "license": null,
                   "license_file": null,
                   "description": null,
-                  "source": null,
+                  "source": "path+file://[..]/foo",
                   "dependencies": [
                     {
                       "name": "bar",
diff --git a/tests/testsuite/features_namespaced.rs b/tests/testsuite/features_namespaced.rs
index 55078f1c28e..4d7397515e3 100644
--- a/tests/testsuite/features_namespaced.rs
+++ b/tests/testsuite/features_namespaced.rs
@@ -741,7 +741,7 @@ fn json_exposed() {
                       "description": null,
                       "homepage": null,
                       "documentation": null,
-                      "source": null,
+                      "source": "path+file://[..]/foo",
                       "dependencies": "{...}",
                       "targets": "{...}",
                       "features": {
diff --git a/tests/testsuite/git.rs b/tests/testsuite/git.rs
index 548d7264c2a..aadc5e93327 100644
--- a/tests/testsuite/git.rs
+++ b/tests/testsuite/git.rs
@@ -3106,7 +3106,7 @@ fn metadata_master_consistency() {
                   "license": null,
                   "license_file": null,
                   "description": null,
-                  "source": null,
+                  "source": "path+file://[..]/foo",
                   "dependencies": [
                     {
                       "name": "bar",
diff --git a/tests/testsuite/metadata.rs b/tests/testsuite/metadata.rs
index 3c4ba6bf59b..c65ae5e80f5 100644
--- a/tests/testsuite/metadata.rs
+++ b/tests/testsuite/metadata.rs
@@ -24,7 +24,7 @@ fn cargo_metadata_simple() {
                 "version": "0.5.0",
                 "id": "foo[..]",
                 "keywords": [],
-                "source": null,
+                "source": "path+file://[..]/foo",
                 "dependencies": [],
                 "edition": "2015",
                 "license": null,
@@ -125,7 +125,7 @@ crate-type = ["lib", "staticlib"]
                 "version": "0.5.0",
                 "id": "foo[..]",
                 "keywords": [],
-                "source": null,
+                "source": "path+file://[..]/foo",
                 "dependencies": [],
                 "edition": "2015",
                 "license": null,
@@ -212,7 +212,7 @@ optional_feat = []
                 "version": "0.5.0",
                 "id": "foo[..]",
                 "keywords": [],
-                "source": null,
+                "source": "path+file://[..]/foo",
                 "dependencies": [],
                 "edition": "2015",
                 "license": null,
@@ -440,7 +440,7 @@ fn cargo_metadata_with_deps_and_version() {
                 "repository": null,
                 "homepage": null,
                 "documentation": null,
-                "source": null,
+                "source": "path+file://[..]/foo",
                 "targets": [
                     {
                         "crate_types": [
@@ -616,7 +616,7 @@ name = "ex"
                 "links": null,
                 "description": null,
                 "edition": "2015",
-                "source": null,
+                "source": "path+file://[..]/foo",
                 "dependencies": [],
                 "targets": [
                     {
@@ -709,7 +709,7 @@ crate-type = ["rlib", "dylib"]
                 "links": null,
                 "description": null,
                 "edition": "2015",
-                "source": null,
+                "source": "path+file://[..]/foo",
                 "dependencies": [],
                 "targets": [
                     {
@@ -804,7 +804,7 @@ fn workspace_metadata() {
                 "homepage": null,
                 "documentation": null,
                 "keywords": [],
-                "source": null,
+                "source": "path+file://[..]/bar",
                 "dependencies": [],
                 "license": null,
                 "license_file": null,
@@ -841,7 +841,7 @@ fn workspace_metadata() {
                 "version": "0.5.0",
                 "id": "baz[..]",
                 "keywords": [],
-                "source": null,
+                "source": "path+file://[..]/baz",
                 "dependencies": [],
                 "license": null,
                 "license_file": null,
@@ -933,7 +933,7 @@ fn workspace_metadata_no_deps() {
                 "version": "0.5.0",
                 "id": "bar[..]",
                 "keywords": [],
-                "source": null,
+                "source": "path+file://[..]/bar",
                 "dependencies": [],
                 "license": null,
                 "license_file": null,
@@ -970,7 +970,7 @@ fn workspace_metadata_no_deps() {
                 "version": "0.5.0",
                 "id": "baz[..]",
                 "keywords": [],
-                "source": null,
+                "source": "path+file://[..]/baz",
                 "dependencies": [],
                 "license": null,
                 "license_file": null,
@@ -1032,7 +1032,7 @@ const MANIFEST_OUTPUT: &str = r#"
         "name":"foo",
         "version":"0.5.0",
         "id":"foo[..]0.5.0[..](path+file://[..]/foo)",
-        "source":null,
+        "source":"path+file://[..]/foo",
         "dependencies":[],
         "keywords": [],
         "license": null,
@@ -1222,7 +1222,7 @@ fn package_metadata() {
                 "version": "0.1.0",
                 "id": "foo[..]",
                 "keywords": ["database"],
-                "source": null,
+                "source": "path+file://[..]/foo",
                 "dependencies": [],
                 "edition": "2015",
                 "license": null,
@@ -1299,7 +1299,7 @@ fn package_publish() {
                 "version": "0.1.0",
                 "id": "foo[..]",
                 "keywords": ["database"],
-                "source": null,
+                "source": "path+file://[..]/foo",
                 "dependencies": [],
                 "edition": "2015",
                 "license": null,
@@ -1382,7 +1382,7 @@ fn cargo_metadata_path_to_cargo_toml_project() {
                     "repository": null,
                     "homepage": null,
                     "documentation": null,
-                    "source": null,
+                    "source": "path+file://[..]/bar-0.5.0",
                     "targets": [
                     {
                         "crate_types": [
@@ -1468,7 +1468,7 @@ fn package_edition_2018() {
                         "repository": null,
                         "homepage": null,
                         "documentation": null,
-                        "source": null,
+                        "source": "path+file://[..]/foo",
                         "targets": [
                             {
                                 "crate_types": [
@@ -1558,7 +1558,7 @@ fn target_edition_2018() {
                         "repository": null,
                         "homepage": null,
                         "documentation": null,
-                        "source": null,
+                        "source": "path+file://[..]/foo",
                         "targets": [
                             {
                                 "crate_types": [
@@ -1766,7 +1766,7 @@ fn rename_dependency() {
             "repository": null,
             "homepage": null,
             "documentation": null,
-            "source": null,
+            "source": "path+file://[..]/foo",
             "targets": [
                 {
                     "crate_types": [
@@ -1886,7 +1886,7 @@ fn metadata_links() {
                   "repository": null,
                   "homepage": null,
                   "documentation": null,
-                  "source": null,
+                  "source": "path+file://[..]/foo",
                   "targets": [
                     {
                       "crate_types": [
@@ -1974,11 +1974,11 @@ fn deps_with_bin_only() {
                   "license": null,
                   "license_file": null,
                   "description": null,
-                  "source": null,
+                  "source": "path+file://[..]/foo",
                   "dependencies": [
                     {
                       "name": "bdep",
-                      "source": null,
+                      "source": "path+file://[..]/bdep",
                       "req": "*",
                       "kind": null,
                       "rename": null,
@@ -2258,7 +2258,7 @@ fn filter_platform() {
       "license": null,
       "license_file": null,
       "description": null,
-      "source": null,
+      "source": "path+file://[..]/foo",
       "dependencies": [
         {
           "name": "normal-dep",
diff --git a/tests/testsuite/read_manifest.rs b/tests/testsuite/read_manifest.rs
index 24d855eb029..5686d513703 100644
--- a/tests/testsuite/read_manifest.rs
+++ b/tests/testsuite/read_manifest.rs
@@ -23,7 +23,7 @@ fn manifest_output(readme_value: &str) -> String {
     "links": null,
     "description": null,
     "edition": "2015",
-    "source":null,
+    "source": "path+file://[..]/foo",
     "dependencies":[],
     "targets":[{{
         "kind":["bin"],
diff --git a/tests/testsuite/update.rs b/tests/testsuite/update.rs
index 93f6eb6846c..e1c1d0891fb 100644
--- a/tests/testsuite/update.rs
+++ b/tests/testsuite/update.rs
@@ -463,7 +463,7 @@ fn update_precise_first_run() {
       "name": "bar",
       "readme": null,
       "repository": null,
-      "source": null,
+      "source": "path+file://[..]/foo",
       "targets": [
         {
           "crate_types": [