v3: compare complete fallback input sets

Author: medvednikov

vlib/v/builder/c_error_report.v

@@ -474,9 +474,10 @@ pub fn take_external_v3_report_from_env() ?ExternalCErrorBugReport {
 	return report
 }
 
-// matches_v3_fallback_inputs confirms that every source V3 recorded was parsed from the
-// same bytes by the stable compiler. Report paths are never opened: they are compared
-// only with canonical paths belonging to the stable parser's own AST files.
+// matches_v3_fallback_inputs confirms that the stable compiler parsed the same set of
+// project sources from the same bytes that V3 recorded. Report paths are never opened:
+// they are compared only with canonical paths belonging to the stable parser's own AST
+// files.
 fn (b &Builder) matches_v3_fallback_inputs(report ExternalCErrorBugReport) bool {
 	if report.kind == external_v3_notice_only_kind {
 		return true
@@ -485,11 +486,27 @@ fn (b &Builder) matches_v3_fallback_inputs(report ExternalCErrorBugReport) bool
 		return false
 	}
 	mut stable_digests := map[string]string{}
+	vlib_root := os.real_path(os.join_path(b.pref.vroot, 'vlib')).trim_right(os.path_separator)
 	for file in b.parsed_files {
 		if file.path == '' || file.source_digest == '' {
 			continue
 		}
-		stable_digests[os.real_path(file.path)] = file.source_digest
+		path := os.real_path(file.path)
+		// Mirror macos_v3_fallback_report_sources: V1 and V3 intentionally parse
+		// different bundled compiler-support files, so compare only caller/project and
+		// installed-module inputs.
+		if path == vlib_root || path.starts_with(vlib_root + os.path_separator) {
+			continue
+		}
+		if previous := stable_digests[path] {
+			if previous != file.source_digest {
+				return false
+			}
+		}
+		stable_digests[path] = file.source_digest
+	}
+	if stable_digests.len != report.input_digests.len {
+		return false
 	}
 	for path, v3_digest in report.input_digests {
 		if stable_digests[path] != v3_digest {

vlib/v/builder/c_error_report_test.v

@@ -375,14 +375,24 @@ fn test_external_v3_report_env_round_trip() {
 }
 
 fn test_v3_fallback_input_verification_uses_stable_parser_digests() {
-	path := os.real_path(@FILE)
+	vroot := os.real_path(@VEXEROOT)
+	path := os.real_path(os.join_path(os.temp_dir(), 'v3_retry_input_main.v'))
 	parsed_digest := sha256.hexhash('the exact stable parser bytes')
 	b := &Builder{
+		pref:         &pref.Preferences{
+			vroot: vroot
+		}
 		parsed_files: [
 			&ast.File{
 				path:          path
 				source_digest: parsed_digest
 			},
+			// Bundled vlib support files intentionally differ between V1 and V3 and are
+			// excluded from both input sets.
+			&ast.File{
+				path:          os.join_path(vroot, 'vlib', 'builtin', 'builtin.v')
+				source_digest: sha256.hexhash('stable compiler builtin')
+			},
 		]
 	}
 	matching := ExternalCErrorBugReport{
@@ -404,6 +414,17 @@ fn test_v3_fallback_input_verification_uses_stable_parser_digests() {
 			os.join_path(os.dir(path), 'not-parsed.v'): parsed_digest
 		}
 	})
+	mut b_with_extra_input := &Builder{
+		pref:         &pref.Preferences{
+			vroot: vroot
+		}
+		parsed_files: b.parsed_files.clone()
+	}
+	b_with_extra_input.parsed_files << &ast.File{
+		path:          os.join_path(os.dir(path), 'added-after-v3-failed.v')
+		source_digest: sha256.hexhash('new stable-only input')
+	}
+	assert !b_with_extra_input.matches_v3_fallback_inputs(matching)
 	assert !b.matches_v3_fallback_inputs(ExternalCErrorBugReport{
 		...matching
 		input_digests_complete: false