Add support for emitting serialized diagnostics (.dia) files

swift/internal/compiling.bzl

@@ -41,6 +41,7 @@ load(
     "SWIFT_FEATURE_DECLARE_SWIFTSOURCEINFO",
     "SWIFT_FEATURE_EMIT_BC",
     "SWIFT_FEATURE_EMIT_C_MODULE",
+    "SWIFT_FEATURE_EMIT_DIAGNOSTICS",
     "SWIFT_FEATURE_EMIT_PRIVATE_SWIFTINTERFACE",
     "SWIFT_FEATURE_EMIT_SWIFTDOC",
     "SWIFT_FEATURE_EMIT_SWIFTINTERFACE",
@@ -438,6 +439,10 @@ def compile(
                 representations of constant values extracted from the source
                 files, if requested via a direct dependency.
 
+            *   `diagnostics_files`: A list of `File`s that contains serialized
+                diagnostics (.dia) emitted by the compiler when the feature
+                `swift.emit_diagnostics` is enabled.
+
             *   `indexstore_directory`: A directory-type `File` that represents
                 the indexstore output files created when the feature
                 `swift.index_while_building` is enabled.
@@ -522,7 +527,7 @@ def compile(
     if split_derived_file_generation:
         all_compile_outputs = compact([
             compile_outputs.indexstore_directory,
-        ]) + compile_outputs.object_files + compile_outputs.const_values_files
+        ]) + compile_outputs.object_files + compile_outputs.const_values_files + compile_outputs.diagnostics_files
         all_derived_outputs = compact([
             # The `.swiftmodule` file is explicitly listed as the first output
             # because it will always exist and because Bazel uses it as a key for
@@ -550,7 +555,7 @@ def compile(
             compile_outputs.generated_header_file,
             compile_outputs.indexstore_directory,
             compile_outputs.macro_expansion_directory,
-        ]) + compile_outputs.object_files + compile_outputs.const_values_files
+        ]) + compile_outputs.object_files + compile_outputs.const_values_files + compile_outputs.diagnostics_files
         all_derived_outputs = []
 
     # In `upstream` they call `merge_compilation_contexts` on passed in
@@ -830,6 +835,7 @@ to use swift_common.compile(include_dev_srch_paths = ...) instead.\
         supplemental_outputs = struct(
             ast_files = compile_outputs.ast_files,
             const_values_files = compile_outputs.const_values_files,
+            diagnostics_files = compile_outputs.diagnostics_files,
             indexstore_directory = compile_outputs.indexstore_directory,
             macro_expansion_directory = compile_outputs.macro_expansion_directory,
         ),
@@ -1340,6 +1346,11 @@ def _declare_compile_outputs(
         indexstore_directory = None
         include_index_unit_paths = False
 
+    emit_diagnostics = is_feature_enabled(
+        feature_configuration = feature_configuration,
+        feature_name = SWIFT_FEATURE_EMIT_DIAGNOSTICS,
+    )
+
     if not output_nature.emits_multiple_objects:
         # If we're emitting a single object, we don't use an object map; we just
         # declare the output file that the compiler will generate and there are
@@ -1356,6 +1367,18 @@ def _declare_compile_outputs(
         const_values_files = [
             actions.declare_file("{}.swiftconstvalues".format(target_name)),
         ]
+        if emit_diagnostics:
+            diagnostics_files = [
+                _declare_per_source_output_file(
+                    actions = actions,
+                    extension = "dia",
+                    target_name = target_name,
+                    src = srcs[0],
+                ),
+                actions.declare_file("{}.dia".format(target_name)),
+            ]
+        else:
+            diagnostics_files = []
         output_file_map = None
         derived_files_output_file_map = None
         # TODO(b/147451378): Support indexing even with a single object file.
@@ -1389,6 +1412,7 @@ def _declare_compile_outputs(
         # object files so that we can pass them all to the archive action.
         output_info = _declare_multiple_outputs_and_write_output_file_map(
             actions = actions,
+            emit_diagnostics = emit_diagnostics,
             extract_const_values = extract_const_values,
             is_wmo = output_nature.is_wmo,
             emits_bc = emits_bc,
@@ -1400,6 +1424,7 @@ def _declare_compile_outputs(
         object_files = output_info.object_files
         ast_files = output_info.ast_files
         const_values_files = output_info.const_values_files
+        diagnostics_files = output_info.diagnostics_files
         output_file_map = output_info.output_file_map
         derived_files_output_file_map = output_info.derived_files_output_file_map
 
@@ -1416,6 +1441,7 @@ def _declare_compile_outputs(
     compile_outputs = struct(
         ast_files = ast_files,
         const_values_files = const_values_files,
+        diagnostics_files = diagnostics_files,
         generated_header_file = generated_header,
         generated_module_map_file = generated_module_map,
         indexstore_directory = indexstore_directory,
@@ -1459,6 +1485,7 @@ def _declare_per_source_output_file(actions, extension, target_name, src):
 
 def _declare_multiple_outputs_and_write_output_file_map(
         actions,
+        emit_diagnostics,
         extract_const_values,
         is_wmo,
         emits_bc,
@@ -1470,6 +1497,8 @@ def _declare_multiple_outputs_and_write_output_file_map(
 
     Args:
         actions: The object used to register actions.
+        emit_diagnostics: A Boolean value indicating whether serialized
+            diagnostics files (.dia) should be emitted during this compilation.
         extract_const_values: A Boolean value indicating whether constant values
             should be extracted during this compilation.
         is_wmo: A Boolean value indicating whether whole-module-optimization was
@@ -1516,6 +1545,7 @@ def _declare_multiple_outputs_and_write_output_file_map(
 
     # Output files that will be emitted by the compiler.
     ast_files = []
+    diagnostics_files = []
     output_objs = []
     const_values_files = []
 
@@ -1526,6 +1556,13 @@ def _declare_multiple_outputs_and_write_output_file_map(
         const_values_files.append(const_values_file)
         whole_module_map["const-values"] = const_values_file.path
 
+    if emit_diagnostics and is_wmo:
+        diagnostics_file = actions.declare_file(
+            "{}.dia".format(target_name),
+        )
+        diagnostics_files.append(diagnostics_file)
+        whole_module_map["diagnostics"] = diagnostics_file.path
+
     for src in srcs:
         file_outputs = {}
 
@@ -1572,6 +1609,16 @@ def _declare_multiple_outputs_and_write_output_file_map(
             const_values_files.append(const_values_file)
             file_outputs["const-values"] = const_values_file.path
 
+        if emit_diagnostics and not is_wmo:
+            diagnostics_file = _declare_per_source_output_file(
+                actions = actions,
+                extension = "dia",
+                target_name = target_name,
+                src = src,
+            )
+            diagnostics_files.append(diagnostics_file)
+            file_outputs["diagnostics"] = diagnostics_file.path
+
         output_map[src.path] = file_outputs
 
     if whole_module_map:
@@ -1592,6 +1639,7 @@ def _declare_multiple_outputs_and_write_output_file_map(
         ast_files = ast_files,
         const_values_files = const_values_files,
         derived_files_output_file_map = derived_files_output_map_file,
+        diagnostics_files = diagnostics_files,
         object_files = output_objs,
         output_file_map = output_map_file,
     )

swift/internal/feature_names.bzl

@@ -432,3 +432,8 @@ SWIFT_FEATURE_ENABLE_CPP23_INTEROP = "swift.enable_cpp23_interop"
 #   automatically include it at compile time, and provide it to the linker at link time
 # * alwayslink on swift_library() target will now default to False, as it is not required in embedded mode
 SWIFT_FEATURE_ENABLE_EMBEDDED = "swift.enable_embedded"
+
+# If enabled, requests the compiler to emit serialized diagnostics files (.dia)
+# for each source file. These files contain machine-readable compiler
+# diagnostics that can be consumed by IDEs and other tools.
+SWIFT_FEATURE_EMIT_DIAGNOSTICS = "swift.emit_diagnostics"

swift/internal/output_groups.bzl

@@ -37,6 +37,7 @@ def supplemental_compilation_output_groups(
     """
     ast_files = []
     const_values_files = []
+    diagnostics_files = []
     indexstore_files = list(additional_indexstore_files)
     macro_expansions_files = []
 
@@ -45,6 +46,8 @@ def supplemental_compilation_output_groups(
             ast_files.extend(outputs.ast_files)
         if outputs.const_values_files:
             const_values_files.extend(outputs.const_values_files)
+        if hasattr(outputs, "diagnostics_files") and outputs.diagnostics_files:
+            diagnostics_files.extend(outputs.diagnostics_files)
         if outputs.indexstore_directory:
             indexstore_files.append(outputs.indexstore_directory)
         if outputs.macro_expansion_directory:
@@ -55,6 +58,8 @@ def supplemental_compilation_output_groups(
         output_groups["swift_ast_file"] = depset(ast_files)
     if const_values_files:
         output_groups["const_values"] = depset(const_values_files)
+    if diagnostics_files:
+        output_groups["swift_diagnostics"] = depset(diagnostics_files)
     if indexstore_files:
         output_groups["swift_index_store"] = depset(indexstore_files)
     if macro_expansions_files:

swift/toolchains/config/compile_config.bzl

@@ -49,6 +49,7 @@ load(
     "SWIFT_FEATURE_DISABLE_SYSTEM_INDEX",
     "SWIFT_FEATURE_EMIT_BC",
     "SWIFT_FEATURE_EMIT_C_MODULE",
+    "SWIFT_FEATURE_EMIT_DIAGNOSTICS",
     "SWIFT_FEATURE_EMIT_PRIVATE_SWIFTINTERFACE",
     "SWIFT_FEATURE_EMIT_SWIFTDOC",
     "SWIFT_FEATURE_EMIT_SWIFTINTERFACE",
@@ -159,6 +160,13 @@ def compile_action_configs(
             features = [SWIFT_FEATURE_EMIT_BC],
         ),
 
+        # Emit serialized diagnostics file(s).
+        ActionConfigInfo(
+            actions = [SWIFT_ACTION_COMPILE],
+            configurators = [add_arg("-serialize-diagnostics")],
+            features = [SWIFT_FEATURE_EMIT_DIAGNOSTICS],
+        ),
+
         # Add the single object file or object file map, whichever is needed.
         ActionConfigInfo(
             actions = [SWIFT_ACTION_COMPILE],

test/BUILD

@@ -7,6 +7,7 @@ load(":compiler_arguments_tests.bzl", "compiler_arguments_test_suite")
 load(":const_values_tests.bzl", "const_values_test_suite")
 load(":coverage_settings_tests.bzl", "coverage_settings_test_suite")
 load(":debug_settings_tests.bzl", "debug_settings_test_suite")
+load(":diagnostics_tests.bzl", "diagnostics_test_suite")
 load(":environment_tests.bzl", "environment_test_suite")
 load(":features_tests.bzl", "features_test_suite")
 load(":generated_header_tests.bzl", "generated_header_test_suite")
@@ -45,6 +46,8 @@ coverage_settings_test_suite(name = "coverage_settings")
 
 debug_settings_test_suite(name = "debug_settings")
 
+diagnostics_test_suite(name = "diagnostics")
+
 environment_test_suite(name = "environment")
 
 features_test_suite(name = "features")

test/diagnostics_tests.bzl

@@ -0,0 +1,57 @@
+# Copyright 2024 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for `swift.emit_diagnostics` feature."""
+
+load(
+    "//test/rules:action_command_line_test.bzl",
+    "make_action_command_line_test_rule",
+)
+load(
+    "//test/rules:provider_test.bzl",
+    "provider_test",
+)
+
+diagnostics_command_line_test = make_action_command_line_test_rule(
+    config_settings = {
+        "//command_line_option:features": [
+            "swift.emit_diagnostics",
+        ],
+    },
+)
+
+def diagnostics_test_suite(name, tags = []):
+    """Test suite for `swift_library` producing .dia files.
+
+    Args:
+        name: The base name to be used in things created by this macro.
+        tags: Additional tags to apply to each test.
+    """
+    all_tags = [name] + tags
+
+    diagnostics_command_line_test(
+        name = "{}_serialize_diagnostics_flag".format(name),
+        expected_argv = [
+            "-serialize-diagnostics",
+        ],
+        mnemonic = "SwiftCompile",
+        tags = all_tags,
+        target_under_test = "//test/fixtures/basic:first",
+    )
+
+    native.test_suite(
+        name = name,
+        tags = all_tags,
+    )
+