Add -file-prefix-map support

We can use -file-prefix-map instead of -debug-prefix-map starting in Xcode 14.
This has the main benefit of remapping debugging, indexing, and coverage paths, all with a single flag.

Keeping this opt-in for now, we'll test this out locally before a further rollout.

PiperOrigin-RevId: 477010867

Author: DavidGoldman

swift/internal/feature_names.bzl

@@ -44,6 +44,12 @@ SWIFT_FEATURE_BITCODE_EMBEDDED_MARKERS = "swift.bitcode_embedded_markers"
 # the note above about not depending on the C++ features.)
 SWIFT_FEATURE_COVERAGE = "swift.coverage"
 
+# If enabled, builds will use the `-file-prefix-map` feature to remap the
+# current working directory to `.`, which permits debugging remote or sandboxed
+# builds as well as hermetic index and coverage information. This requires
+# Xcode 14 or newer.
+SWIFT_FEATURE_FILE_PREFIX_MAP = "swift.file_prefix_map"
+
 # If enabled, debug builds will use the `-debug-prefix-map` feature to remap the
 # current working directory to `.`, which permits debugging remote or sandboxed
 # builds.

swift/toolchains/config/compile_config.bzl

@@ -34,6 +34,7 @@ load(
     "SWIFT_FEATURE_ENABLE_LIBRARY_EVOLUTION",
     "SWIFT_FEATURE_ENABLE_TESTING",
     "SWIFT_FEATURE_FASTBUILD",
+    "SWIFT_FEATURE_FILE_PREFIX_MAP",
     "SWIFT_FEATURE_FULL_DEBUG_INFO",
     "SWIFT_FEATURE_INDEX_SYSTEM_MODULES",
     "SWIFT_FEATURE_INDEX_WHILE_BUILDING",
@@ -340,6 +341,17 @@ def compile_action_configs(
                 [SWIFT_FEATURE_DEBUG_PREFIX_MAP, SWIFT_FEATURE_FASTBUILD],
                 [SWIFT_FEATURE_DEBUG_PREFIX_MAP, SWIFT_FEATURE_FULL_DEBUG_INFO],
             ],
+            not_features = [SWIFT_FEATURE_FILE_PREFIX_MAP],
+        ),
+        ActionConfigInfo(
+            actions = [
+                SWIFT_ACTION_COMPILE,
+                SWIFT_ACTION_PRECOMPILE_C_MODULE,
+            ],
+            configurators = [
+                add_arg("-Xwrapped-swift=-file-prefix-pwd-is-dot"),
+            ],
+            features = [SWIFT_FEATURE_FILE_PREFIX_MAP],
         ),
     ]
 

test/debug_settings_tests.bzl

@@ -26,6 +26,14 @@ DBG_CONFIG_SETTINGS = {
     ],
 }
 
+FILE_PREFIX_MAP_CONFIG_SETTINGS = {
+    "//command_line_option:compilation_mode": "dbg",
+    "//command_line_option:features": [
+        "swift.debug_prefix_map",
+        "swift.file_prefix_map",
+    ],
+}
+
 CACHEABLE_DBG_CONFIG_SETTINGS = {
     "//command_line_option:compilation_mode": "dbg",
     "//command_line_option:features": [
@@ -62,6 +70,10 @@ dbg_action_command_line_test = make_action_command_line_test_rule(
     config_settings = DBG_CONFIG_SETTINGS,
 )
 
+file_prefix_map_command_line_test = make_action_command_line_test_rule(
+    config_settings = FILE_PREFIX_MAP_CONFIG_SETTINGS,
+)
+
 cacheable_dbg_action_command_line_test = make_action_command_line_test_rule(
     config_settings = CACHEABLE_DBG_CONFIG_SETTINGS,
 )
@@ -107,6 +119,20 @@ def debug_settings_test_suite(name, tags = []):
         target_under_test = "@build_bazel_rules_swift//test/fixtures/debug_settings:simple",
     )
 
+    # Verify that the build is remapping paths with a file prefix map.
+    file_prefix_map_command_line_test(
+        name = "{}_file_prefix_map_build".format(name),
+        expected_argv = [
+            "-Xwrapped-swift=-file-prefix-pwd-is-dot",
+        ],
+        not_expected_argv = [
+            "-Xwrapped-swift=-debug-prefix-pwd-is-dot",
+        ],
+        mnemonic = "SwiftCompile",
+        tags = all_tags,
+        target_under_test = "@build_bazel_rules_swift//test/fixtures/debug_settings:simple",
+    )
+
     # Verify that `-c dbg` builds with `swift.cacheable_modules` do NOT
     # serialize debugging options, but are otherwise the same as regular `dbg`
     # builds.

tools/worker/swift_runner.cc

@@ -235,13 +235,21 @@ bool SwiftRunner::ProcessArgument(
   absl::string_view trimmed_arg = arg;
   if (absl::ConsumePrefix(&trimmed_arg, "-Xwrapped-swift=")) {
     if (trimmed_arg == "-debug-prefix-pwd-is-dot") {
-      // Get the actual current working directory (the workspace root), which
+      // Get the actual current working directory (the execution root), which
       // we didn't know at analysis time.
       consumer("-debug-prefix-map");
       consumer(GetCurrentDirectory() + "=.");
       return true;
     }
 
+    if (trimmed_arg == "-file-prefix-pwd-is-dot") {
+      // Get the actual current working directory (the execution root), which
+      // we didn't know at analysis time.
+      consumer("-file-prefix-map");
+      consumer(GetCurrentDirectory() + "=.");
+      return true;
+    }
+
     if (trimmed_arg == "-ephemeral-module-cache") {
       // Create a temporary directory to hold the module cache, which will be
       // deleted after compilation is finished.

tools/worker/swift_runner.h

@@ -45,6 +45,12 @@ namespace bazel_rules_swift {
 //     applied here because we do not know the current working directory at
 //     analysis time when the argument list is constructed.
 //
+// -Xwrapped-swift=-file-prefix-pwd-is-dot
+//     When specified, the Swift compiler will be directed to remap the current
+//     directory's path to the string "." in debug, coverage, and index info.
+//     This remapping must be applied here because we do not know the current
+//     working directory at analysis time when the argument list is constructed.
+//
 // -Xwrapped-swift=-ephemeral-module-cache
 //     When specified, the spawner will create a new temporary directory, pass
 //     that to the Swift compiler using `-module-cache-path`, and then delete