Fix .swiftsourceinfo readonly bugs in version 3+

tools/worker/swift_runner.cc

@@ -27,6 +27,14 @@ bool ArgumentEnablesWMO(const std::string &arg) {
          arg == "-force-single-frontend-invocation";
 }
 
+bool StripPrefix(const std::string &prefix, std::string &str) {
+  if (str.find(prefix) != 0) {
+    return false;
+  }
+  str.erase(0, prefix.size());
+  return true;
+}
+
 namespace {
 
 // Creates a temporary file and writes the given arguments to it, one per line.
@@ -92,17 +100,6 @@ static std::string Unescape(const std::string &arg) {
   return result;
 }
 
-// If `str` starts with `prefix`, `str` is mutated to remove `prefix` and the
-// function returns true. Otherwise, `str` is left unmodified and the function
-// returns `false`.
-static bool StripPrefix(const std::string &prefix, std::string &str) {
-  if (str.find(prefix) != 0) {
-    return false;
-  }
-  str.erase(0, prefix.size());
-  return true;
-}
-
 }  // namespace
 
 SwiftRunner::SwiftRunner(const std::vector<std::string> &args,

tools/worker/swift_runner.h

@@ -29,6 +29,11 @@
 // optimization in the compiler.
 extern bool ArgumentEnablesWMO(const std::string &arg);
 
+// If `str` starts with `prefix`, `str` is mutated to remove `prefix` and the
+// function returns true. Otherwise, `str` is left unmodified and the function
+// returns `false`.
+extern bool StripPrefix(const std::string &prefix, std::string &str);
+
 // Handles spawning the Swift compiler driver, making any required substitutions
 // of the command line arguments (for example, Bazel's magic Xcode placeholder
 // strings).

tools/worker/work_processor.cc

@@ -86,13 +86,19 @@ void WorkProcessor::ProcessWorkRequest(
   std::string emit_objc_header_path;
   bool is_wmo = false;
   bool is_dump_ast = false;
+  bool emit_swift_source_info = false;
 
   std::string prev_arg;
   for (std::string arg : request.arguments) {
     std::string original_arg = arg;
     // Peel off the `-output-file-map` argument, so we can rewrite it if
     // necessary later.
-    if (arg == "-output-file-map") {
+    if (StripPrefix("-Xwrapped-swift=", arg)) {
+      if (arg == "-emit-swiftsourceinfo") {
+        emit_swift_source_info = true;
+      }
+      arg.clear();
+    } else if (arg == "-output-file-map") {
       arg.clear();
     } else if (arg == "-dump-ast") {
       is_dump_ast = true;
@@ -153,11 +159,23 @@ void WorkProcessor::ProcessWorkRequest(
 
     for (const auto &expected_object_pair :
          output_file_map.incremental_inputs()) {
+
+      const auto expected_object_path = std::filesystem::path(expected_object_pair.second);
+
+      // In rules_swift < 3.x the .swiftsourceinfo files are unconditionally written to the module path.
+      // In rules_swift >= 3.x these same files are no longer tracked by Bazel unless explicitly requested.
+      // When using non-sandboxed mode, previous builds will contain these files and cause build failures
+      // when Swift tries to use them, in order to work around this compatibility issue, we remove them if they are
+      // present but not requested.
+      if (expected_object_path.extension() == ".swiftsourceinfo" && !emit_swift_source_info) {
+        std::filesystem::remove(expected_object_path);
+      }
+
       // Bazel creates the intermediate directories for the files declared at
       // analysis time, but not any any deeper directories, like one can have
       // with -emit-objc-header-path, so we need to create those.
       const std::string dir_path =
-          std::filesystem::path(expected_object_pair.second)
+          expected_object_path
               .parent_path()
               .string();
       dir_paths.insert(dir_path);