Add a mechanism to provide a list of protocol names for constant valu…

…e extraction.

If a module populates `const_gather_protocols` when calling `create_swift_module_context`, any target that directly depends on that module will automatically have that list of protocols passed to the compiler via `-const-gather-protocols-file`. The output group `const_values` will then contain the JSON file with the extracted constant information.

This is meant to support Apple's AppIntents framework, which uses the output from `-emit-const-values-path` as an input to the AppIntent bundling tool.

PiperOrigin-RevId: 588388131
(cherry picked from commit 18f2f87)

# Conflicts:
#	swift/internal/compiling.bzl
#	swift/internal/output_groups.bzl
#	swift/providers.bzl
#	swift/toolchains/config/compile_config.bzl
#	test/rules/provider_test.bzl
#	tools/worker/swift_runner.cc

swift/internal/compiling.bzl

@@ -376,6 +376,12 @@ def compile_action_configs(
             actions = [swift_action_names.DERIVE_FILES],
             configurators = [_emit_objc_header_path_configurator],
         ),
+        swift_toolchain_config.action_config(
+            actions = [
+                swift_action_names.COMPILE,
+            ],
+            configurators = [_constant_value_extraction_configurator],
+        ),
     ]
 
     if generated_header_rewriter:
@@ -1351,6 +1357,10 @@ def _emit_module_interface_path_configurator(prerequisites, args):
     """Adds the `.swiftinterface` output path to the command line."""
     args.add("-emit-module-interface-path", prerequisites.swiftinterface_file)
 
+def _emit_const_values_path_configurator(prerequisites, args):
+    """Adds the `.swiftconst` output path to the command line."""
+    args.add("-emit-const-values-path", prerequisites.swiftconst_values)
+
 def _emit_objc_header_path_configurator(prerequisites, args):
     """Adds the generated header output path to the command line."""
     if prerequisites.generated_header_file:
@@ -1969,6 +1979,23 @@ def _conditional_compilation_flag_configurator(prerequisites, args):
         format_each = "-D%s",
     )
 
+def _constant_value_extraction_configurator(prerequisites, args):
+    """Adds flags related to constant value extraction to the command line."""
+    if not prerequisites.const_gather_protocols_file:
+        return None
+
+    args.add("-emit-const-values")
+    args.add_all(
+        [
+            "-const-gather-protocols-file",
+            prerequisites.const_gather_protocols_file,
+        ],
+        before_each = "-Xfrontend",
+    )
+    return swift_toolchain_config.config_result(
+        inputs = [prerequisites.const_gather_protocols_file],
+    )
+
 def _additional_inputs_configurator(prerequisites, _args):
     """Propagates additional input files to the action.
 
@@ -2342,6 +2369,9 @@ def compile(
                 contains the symbol graph data generated by the compiler if the
                 `"swift.emit_symbol_graph"` feature is enabled, otherwise this
                 will be `None`.
+            *   `const_values_files`: A list of `File`s that contains JSON
+                representations of constant values extracted from the source
+                files, if requested via a direct dependency.
     """
 
     # Collect the `SwiftInfo` providers that represent the dependencies of the
@@ -2356,9 +2386,15 @@ def compile(
         swift_toolchain.generated_header_module_implicit_deps_providers.swift_infos
     )
 
+    const_gather_protocols_file = _maybe_create_const_protocols_file(
+        actions = actions,
+        swift_infos = generated_module_deps_swift_infos,
+        target_name = target_name,
+    )
     compile_outputs, other_outputs = _declare_compile_outputs(
         srcs = srcs,
         actions = actions,
+        extract_const_values = bool(const_gather_protocols_file),
         feature_configuration = feature_configuration,
         generated_header_name = generated_header_name,
         generated_module_deps_swift_infos = generated_module_deps_swift_infos,
@@ -2377,7 +2413,7 @@ def compile(
             compile_outputs.swiftinterface_file,
             compile_outputs.indexstore_directory,
             compile_outputs.macro_expansion_directory,
-        ]) + compile_outputs.object_files
+        ]) + compile_outputs.object_files + compile_outputs.const_values_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
@@ -2403,7 +2439,7 @@ def compile(
             compile_outputs.indexstore_directory,
             compile_outputs.macro_expansion_directory,
             compile_outputs.symbol_graph_directory,
-        ]) + compile_outputs.object_files + other_outputs
+        ]) + compile_outputs.object_files + compile_outputs.const_values_files + other_outputs
         all_derived_outputs = []
 
     # Merge the providers from our dependencies so that we have one each for
@@ -2510,6 +2546,7 @@ to use swift_common.compile(include_dev_srch_paths = ...) instead.\
         additional_inputs = additional_inputs,
         bin_dir = feature_configuration._bin_dir,
         cc_compilation_context = merged_providers.cc_info.compilation_context,
+        const_gather_protocols_file = const_gather_protocols_file,
         cc_linking_context = merged_providers.cc_info.linking_context,
         defines = sets.to_list(defines_set),
         explicit_swift_module_map_file = explicit_swift_module_map_file,
@@ -2646,6 +2683,7 @@ to use swift_common.compile(include_dev_srch_paths = ...) instead.\
         indexstore = compile_outputs.indexstore_directory,
         macro_expansion_directory = compile_outputs.macro_expansion_directory,
         symbol_graph = compile_outputs.symbol_graph_directory,
+        const_values_files = compile_outputs.const_values_files,
     )
 
     return module_context, cc_compilation_outputs, other_compilation_outputs
@@ -2899,6 +2937,7 @@ def _create_cc_compilation_context(
 def _declare_compile_outputs(
         *,
         actions,
+        extract_const_values,
         feature_configuration,
         generated_header_name,
         generated_module_deps_swift_infos,
@@ -2910,6 +2949,8 @@ def _declare_compile_outputs(
 
     Args:
         actions: The object used to register actions.
+        extract_const_values: A Boolean value indicating whether constant values
+            should be extracted during this compilation.
         feature_configuration: A feature configuration obtained from
             `swift_common.configure_features`.
         generated_header_name: The desired name of the generated header for this
@@ -3038,6 +3079,9 @@ def _declare_compile_outputs(
             src = srcs[0],
         )]
         other_outputs = []
+        const_values_files = [
+            actions.declare_file("{}.swiftconstvalues".format(target_name)),
+        ]
         output_file_map = None
         derived_files_output_file_map = None
     else:
@@ -3050,6 +3094,8 @@ 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,
+            extract_const_values = extract_const_values,
+            is_wmo = output_nature.is_wmo,
             emits_bc = emits_bc,
             split_derived_file_generation = split_derived_file_generation,
             srcs = srcs,
@@ -3058,6 +3104,7 @@ def _declare_compile_outputs(
         object_files = output_info.object_files
         ast_files = output_info.ast_files
         other_outputs = output_info.other_outputs
+        const_values_files = output_info.const_values_files
         output_file_map = output_info.output_file_map
         derived_files_output_file_map = output_info.derived_files_output_file_map
 
@@ -3106,6 +3153,7 @@ def _declare_compile_outputs(
 
     compile_outputs = struct(
         ast_files = ast_files,
+        const_values_files = const_values_files,
         generated_header_file = generated_header,
         generated_module_map_file = generated_module_map,
         indexstore_directory = indexstore_directory,
@@ -3123,6 +3171,8 @@ def _declare_compile_outputs(
 
 def _declare_multiple_outputs_and_write_output_file_map(
         actions,
+        extract_const_values,
+        is_wmo,
         emits_bc,
         split_derived_file_generation,
         srcs,
@@ -3131,6 +3181,10 @@ def _declare_multiple_outputs_and_write_output_file_map(
 
     Args:
         actions: The object used to register actions.
+        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
+            requested.
         emits_bc: If `True` the compiler will generate LLVM BC files instead of
             object files.
         split_derived_file_generation: Whether objects and modules are produced
@@ -3172,17 +3226,25 @@ def _declare_multiple_outputs_and_write_output_file_map(
     # The output map data, which is keyed by source path and will be written to
     # `output_map_file` and `derived_files_output_map_file`.
     output_map = {}
+    whole_module_map = {}
     derived_files_output_map = {}
 
-    # Object files that will be used to build the archive.
+    # Output files that will be emitted by the compiler.
     output_objs = []
+    const_values_files = []
 
     # Additional files, such as partial Swift modules, that must be declared as
     # action outputs although they are not processed further.
     other_outputs = []
 
     # AST files that are available in the swift_ast_file output group
     ast_files = []
+    if extract_const_values and is_wmo:
+        const_value_file = actions.declare_file(
+            "{}.swiftconstvalues".format(target_name),
+        )
+        const_values_files.append(const_value_file)
+        whole_module_map["const-values"] = const_value_file.path
 
     for src in srcs:
         src_output_map = {}
@@ -3227,6 +3289,7 @@ def _declare_multiple_outputs_and_write_output_file_map(
         )
 
     return struct(
+        const_values_files = const_values_files,
         ast_files = ast_files,
         object_files = output_objs,
         other_outputs = other_outputs,
@@ -3344,6 +3407,12 @@ def output_groups_from_other_compilation_outputs(*, other_compilation_outputs):
             other_compilation_outputs.macro_expansion_directory,
         ])
 
+    if other_compilation_outputs.const_values_files:
+        if other_compilation_outputs.const_values_files:
+            output_groups["const_values"] = depset([
+                other_compilation_outputs.const_values_files,
+            ])
+
     return output_groups
 
 def swift_library_output_map(name):
@@ -3463,6 +3532,7 @@ def _emitted_output_nature(feature_configuration, user_compile_flags):
         *   `emits_multiple_objects`: `True` if the Swift frontend emits an
             object file per source file, instead of a single object file for the
             whole module, in a compilation action with the given flags.
+        *   `is_wmo`: `True` if whole-module-optimization was requested.
     """
     is_wmo = (
         is_feature_enabled(
@@ -3487,7 +3557,42 @@ def _emitted_output_nature(feature_configuration, user_compile_flags):
 
     return struct(
         emits_multiple_objects = not (is_wmo and is_single_threaded),
+        is_wmo = is_wmo,
+    )
+
+def _maybe_create_const_protocols_file(actions, swift_infos, target_name):
+    """Create the const extraction protocols file, if necessary.
+    Args:
+        actions: The object used to register actions.
+        swift_infos: A list of `SwiftInfo` providers describing the dependencies
+            of the code being compiled.
+        target_name: The name of the build target, which is used to generate
+            output file names.
+    Returns:
+        A file passed as an input to the compiler that lists the protocols whose
+        conforming types should have values extracted.
+    """
+    const_gather_protocols = []
+    for swift_info in swift_infos:
+        for module_context in swift_info.direct_modules:
+            const_gather_protocols.extend(
+                module_context.const_gather_protocols,
+            )
+
+    # If there are no protocols to extract, return early.
+    if not const_gather_protocols:
+        return None
+
+    # Create the input file to the compiler, which contains a JSON array of
+    # protocol names.
+    const_gather_protocols_file = actions.declare_file(
+        "{}_const_extract_protocols.json".format(target_name),
+    )
+    actions.write(
+        content = json.encode(const_gather_protocols),
+        output = const_gather_protocols_file,
     )
+    return const_gather_protocols_file
 
 def _exclude_swift_incompatible_define(define):
     """A `map_each` helper that excludes a define if it is not Swift-compatible.

swift/internal/providers.bzl

@@ -322,6 +322,7 @@ def create_module(
         *,
         name,
         clang = None,
+        const_gather_protocols = [],
         compilation_context = None,
         is_system = False,
         swift = None):
@@ -349,6 +350,9 @@ def create_module(
             contains artifacts related to Clang modules, such as a module map or
             precompiled module. This may be `None` if the module is a pure Swift
             module with no generated Objective-C interface.
+        const_gather_protocols: A list of protocol names from which constant
+            values should be extracted from source code that takes this module
+            as a *direct* dependency.
         compilation_context: A value returned from
             `swift_common.create_compilation_context` that contains the
             context needed to compile the module being built. This may be `None`
@@ -379,6 +383,7 @@ def create_module(
     """
     return struct(
         clang = clang,
+        const_gather_protocols = tuple(const_gather_protocols),
         compilation_context = compilation_context,
         is_system = is_system,
         name = name,

test/rules/provider_test.bzl

@@ -65,6 +65,11 @@ def _evaluate_field(env, source, field):
         component that was not the final component, then the special value
         `_EVALUATE_FIELD_FAILED` is returned.
     """
+    def evaluate_component(source, component):
+        if types.is_dict(source):
+            return source.get(component)
+        return getattr(source, component, None)
+
     components = field.split(".")
 
     for component in components:
@@ -93,7 +98,7 @@ def _evaluate_field(env, source, field):
                     flattened.extend(item)
                 else:
                     flattened.append(item)
-            source = [getattr(item, component, None) for item in flattened]
+            source = [evaluate_component(item, component) for item in flattened]
             if filter_nones:
                 source = [item for item in source if item != None]
         else:
@@ -107,7 +112,7 @@ def _evaluate_field(env, source, field):
                 )
                 return _EVALUATE_FIELD_FAILED
 
-            source = getattr(source, component, None)
+            source = evaluate_component(source, component)
             if filter_nones:
                 source = _normalize_collection(source)
                 if types.is_list(source):
@@ -400,6 +405,10 @@ evaluated on every item in that list, not on the list itself. Likewise, if such
 a field path component is followed by `!`, then any `None` elements that may
 have resulted during evaluation will be removed from the list before evaluating
 the next component.
+
+If a value along the field path is a dictionary and the next component
+is a valid key in that dictionary, then the value of that dictionary key is
+retrieved instead of it being treated as a struct field access.
 """,
             ),
             "provider": attr.string(