Add the path to the manifest in json output

This allows consumers of the json messages to avoid guessing where
exactly the package root is. Having access to the package root is
difficult by virtue of requiring logic to guess its location by e.g.
walking filesystem from the source file.

This guessing logic becomes further complicated in presence of
workspaces and nigh impossible to implement correctly in instances where
artifacts end up produced from paths above the package root (e.g.
`../foo.rs`).

Since Cargo has access to this data in the first place, there doesn't
seem to be much reason to force consumers to invent their own, possibly
flawed, logic.

src/cargo/core/compiler/mod.rs

@@ -175,6 +175,7 @@ fn compile<'cfg>(
             let work = if unit.show_warnings(bcx.config) {
                 replay_output_cache(
                     unit.pkg.package_id(),
+                    PathBuf::from(unit.pkg.manifest_path()),
                     &unit.target,
                     cx.files().message_cache_path(unit),
                     cx.bcx.build_config.message_format,
@@ -219,6 +220,7 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
     // Prepare the native lib state (extra `-L` and `-l` flags).
     let build_script_outputs = Arc::clone(&cx.build_script_outputs);
     let current_id = unit.pkg.package_id();
+    let manifest_path = PathBuf::from(unit.pkg.manifest_path());
     let build_scripts = cx.build_scripts.get(unit).cloned();
 
     // If we are a binary and the package also contains a library, then we
@@ -316,7 +318,16 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
                 &target,
                 mode,
                 &mut |line| on_stdout_line(state, line, package_id, &target),
-                &mut |line| on_stderr_line(state, line, package_id, &target, &mut output_options),
+                &mut |line| {
+                    on_stderr_line(
+                        state,
+                        line,
+                        package_id,
+                        &manifest_path,
+                        &target,
+                        &mut output_options,
+                    )
+                },
             )
             .map_err(verbose_if_simple_exit_code)
             .chain_err(|| format!("could not compile `{}`", name))?;
@@ -414,6 +425,7 @@ fn link_targets(cx: &mut Context<'_, '_>, unit: &Unit, fresh: bool) -> CargoResu
     let outputs = cx.outputs(unit)?;
     let export_dir = cx.files().export_dir();
     let package_id = unit.pkg.package_id();
+    let manifest_path = PathBuf::from(unit.pkg.manifest_path());
     let profile = unit.profile;
     let unit_mode = unit.mode;
     let features = unit.features.iter().map(|s| s.to_string()).collect();
@@ -467,6 +479,7 @@ fn link_targets(cx: &mut Context<'_, '_>, unit: &Unit, fresh: bool) -> CargoResu
 
             let msg = machine_message::Artifact {
                 package_id,
+                manifest_path,
                 target: &target,
                 profile: art_profile,
                 features,
@@ -618,10 +631,10 @@ fn rustdoc(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Work> {
     let name = unit.pkg.name().to_string();
     let build_script_outputs = Arc::clone(&cx.build_script_outputs);
     let package_id = unit.pkg.package_id();
+    let manifest_path = PathBuf::from(unit.pkg.manifest_path());
     let target = Target::clone(&unit.target);
     let mut output_options = OutputOptions::new(cx, unit);
     let script_metadata = cx.find_build_script_metadata(unit);
-
     Ok(Work::new(move |state| {
         if let Some(script_metadata) = script_metadata {
             if let Some(output) = build_script_outputs.lock().unwrap().get(script_metadata) {
@@ -638,7 +651,16 @@ fn rustdoc(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Work> {
         rustdoc
             .exec_with_streaming(
                 &mut |line| on_stdout_line(state, line, package_id, &target),
-                &mut |line| on_stderr_line(state, line, package_id, &target, &mut output_options),
+                &mut |line| {
+                    on_stderr_line(
+                        state,
+                        line,
+                        package_id,
+                        &manifest_path,
+                        &target,
+                        &mut output_options,
+                    )
+                },
                 false,
             )
             .chain_err(|| format!("could not document `{}`", name))?;
@@ -1139,10 +1161,11 @@ fn on_stderr_line(
     state: &JobState<'_>,
     line: &str,
     package_id: PackageId,
+    manifest_path: &std::path::Path,
     target: &Target,
     options: &mut OutputOptions,
 ) -> CargoResult<()> {
-    if on_stderr_line_inner(state, line, package_id, target, options)? {
+    if on_stderr_line_inner(state, line, package_id, manifest_path, target, options)? {
         // Check if caching is enabled.
         if let Some((path, cell)) = &mut options.cache_cell {
             // Cache the output, which will be replayed later when Fresh.
@@ -1160,6 +1183,7 @@ fn on_stderr_line_inner(
     state: &JobState<'_>,
     line: &str,
     package_id: PackageId,
+    manifest_path: &std::path::Path,
     target: &Target,
     options: &mut OutputOptions,
 ) -> CargoResult<bool> {
@@ -1300,6 +1324,7 @@ fn on_stderr_line_inner(
     // indicating which package it came from and then emit it.
     let msg = machine_message::FromCompiler {
         package_id,
+        manifest_path,
         target,
         message: compiler_message,
     }
@@ -1314,6 +1339,7 @@ fn on_stderr_line_inner(
 
 fn replay_output_cache(
     package_id: PackageId,
+    manifest_path: PathBuf,
     target: &Target,
     path: PathBuf,
     format: MessageFormat,
@@ -1343,7 +1369,14 @@ fn replay_output_cache(
                 break;
             }
             let trimmed = line.trim_end_matches(&['\n', '\r'][..]);
-            on_stderr_line(state, trimmed, package_id, &target, &mut options)?;
+            on_stderr_line(
+                state,
+                trimmed,
+                package_id,
+                &manifest_path,
+                &target,
+                &mut options,
+            )?;
             line.clear();
         }
         Ok(())

src/cargo/util/machine_message.rs

@@ -20,6 +20,7 @@ pub trait Message: ser::Serialize {
 #[derive(Serialize)]
 pub struct FromCompiler<'a> {
     pub package_id: PackageId,
+    pub manifest_path: &'a Path,
     pub target: &'a Target,
     pub message: Box<RawValue>,
 }
@@ -33,6 +34,7 @@ impl<'a> Message for FromCompiler<'a> {
 #[derive(Serialize)]
 pub struct Artifact<'a> {
     pub package_id: PackageId,
+    pub manifest_path: PathBuf,
     pub target: &'a Target,
     pub profile: ArtifactProfile,
     pub features: Vec<String>,

tests/testsuite/bench.rs

@@ -1736,6 +1736,7 @@ fn json_artifact_includes_executable_for_benchmark() {
                     "filenames": "{...}",
                     "fresh": false,
                     "package_id": "foo 0.0.1 ([..])",
+                    "manifest_path": "[..]",
                     "profile": "{...}",
                     "reason": "compiler-artifact",
                     "target": {

tests/testsuite/build.rs

@@ -3140,6 +3140,7 @@ fn compiler_json_error_format() {
             {
                 "reason":"compiler-artifact",
                 "package_id":"foo 0.5.0 ([..])",
+                "manifest_path": "[..]",
                 "target":{
                     "kind":["custom-build"],
                     "crate_types":["bin"],
@@ -3166,6 +3167,7 @@ fn compiler_json_error_format() {
             {
                 "reason":"compiler-message",
                 "package_id":"bar 0.5.0 ([..])",
+                "manifest_path": "[..]",
                 "target":{
                     "kind":["lib"],
                     "crate_types":["lib"],
@@ -3191,6 +3193,7 @@ fn compiler_json_error_format() {
                 "executable": null,
                 "features": [],
                 "package_id":"bar 0.5.0 ([..])",
+                "manifest_path": "[..]",
                 "target":{
                     "kind":["lib"],
                     "crate_types":["lib"],
@@ -3221,6 +3224,7 @@ fn compiler_json_error_format() {
             {
                 "reason":"compiler-message",
                 "package_id":"foo 0.5.0 ([..])",
+                "manifest_path": "[..]",
                 "target":{
                     "kind":["bin"],
                     "crate_types":["bin"],
@@ -3237,6 +3241,7 @@ fn compiler_json_error_format() {
             {
                 "reason":"compiler-artifact",
                 "package_id":"foo 0.5.0 ([..])",
+                "manifest_path": "[..]",
                 "target":{
                     "kind":["bin"],
                     "crate_types":["bin"],
@@ -3307,6 +3312,7 @@ fn message_format_json_forward_stderr() {
                 {
                     "reason":"compiler-message",
                     "package_id":"foo 0.5.0 ([..])",
+                    "manifest_path": "[..]",
                     "target":{
                         "kind":["bin"],
                         "crate_types":["bin"],
@@ -3323,6 +3329,7 @@ fn message_format_json_forward_stderr() {
                 {
                     "reason":"compiler-artifact",
                     "package_id":"foo 0.5.0 ([..])",
+                    "manifest_path": "[..]",
                     "target":{
                         "kind":["bin"],
                         "crate_types":["bin"],

tests/testsuite/doc.rs

@@ -1414,6 +1414,7 @@ fn doc_message_format() {
                     "spans": "{...}"
                 },
                 "package_id": "foo [..]",
+                "manifest_path": "[..]",
                 "reason": "compiler-message",
                 "target": "{...}"
             }

tests/testsuite/metabuild.rs

@@ -691,6 +691,7 @@ fn metabuild_json_artifact() {
               "filenames": "{...}",
               "fresh": false,
               "package_id": "foo [..]",
+              "manifest_path": "[..]",
               "profile": "{...}",
               "reason": "compiler-artifact",
               "target": {
@@ -743,6 +744,7 @@ fn metabuild_failed_build_json() {
                 "spans": "{...}"
               },
               "package_id": "foo [..]",
+              "manifest_path": "[..]",
               "reason": "compiler-message",
               "target": {
                 "crate_types": [

tests/testsuite/test.rs

@@ -3536,6 +3536,7 @@ fn json_artifact_includes_test_flag() {
                     "executable": "[..]/foo-[..]",
                     "features": [],
                     "package_id":"foo 0.0.1 ([..])",
+                    "manifest_path": "[..]",
                     "target":{
                         "kind":["lib"],
                         "crate_types":["lib"],
@@ -3572,6 +3573,7 @@ fn json_artifact_includes_executable_for_library_tests() {
                     "filenames": "{...}",
                     "fresh": false,
                     "package_id": "foo 0.0.1 ([..])",
+                    "manifest_path": "[..]",
                     "profile": "{...}",
                     "reason": "compiler-artifact",
                     "target": {
@@ -3610,6 +3612,7 @@ fn json_artifact_includes_executable_for_integration_tests() {
                     "filenames": "{...}",
                     "fresh": false,
                     "package_id": "foo 0.0.1 ([..])",
+                    "manifest_path": "[..]",
                     "profile": "{...}",
                     "reason": "compiler-artifact",
                     "target": {