Use ConfigResultInfo to set additional tools

swift/internal/actions.bzl

@@ -44,6 +44,7 @@ def _apply_action_configs(
         A `ConfigResultInfo` value that contains the files that are required
         inputs of the action, as determined by the configurators.
     """
+    additional_tools = []
     inputs = []
     transitive_inputs = []
 
@@ -82,26 +83,32 @@ def _apply_action_configs(
                     should_apply_configurators = False
                     break
 
+        if not should_apply_configurators:
+            continue
+
         # If one of the feature lists is completely satisfied, invoke the
         # configurators.
-        if should_apply_configurators:
-            for configurator in action_config.configurators:
-                action_inputs = configurator(prerequisites, args)
-
-                # If we create an action configurator from a lambda that calls
-                # `Args.add*`, the result will be the `Args` objects (rather
-                # than `None`) because those methods return the same `Args`
-                # object for chaining. We can guard against this (and possibly
-                # other errors) by checking that the value is a struct. If it
-                # is, then it's not `None` and it probably came from the
-                # provider used by `ConfigResultInfo`. If it's some other kind
-                # of struct, then we'll error out trying to access the fields.
-                if type(action_inputs) == "struct":
-                    inputs.extend(action_inputs.inputs)
-                    transitive_inputs.extend(action_inputs.transitive_inputs)
+        for configurator in action_config.configurators:
+            action_inputs = configurator(prerequisites, args)
+
+            # If we create an action configurator from a lambda that calls
+            # `Args.add*`, the result will be the `Args` objects (rather than
+            # `None`) because those methods return the same `Args` object for
+            # chaining. We can guard against this (and possibly other errors) by
+            # checking that the value is a struct. If it is, then it's not
+            # `None` and it probably came from the provider used by
+            # `ConfigResultInfo`. If it's some other kind of struct, then we'll
+            # error out trying to access the fields.
+            if not type(action_inputs) == "struct":
+                continue
+
+            additional_tools.extend(action_inputs.additional_tools)
+            inputs.extend(action_inputs.inputs)
+            transitive_inputs.extend(action_inputs.transitive_inputs)
 
     # Merge the action results into a single result that we return.
     return ConfigResultInfo(
+        additional_tools = additional_tools,
         inputs = inputs,
         transitive_inputs = transitive_inputs,
     )
@@ -219,7 +226,10 @@ def run_toolchain_action(
         ),
         mnemonic = mnemonic if mnemonic else action_name,
         resource_set = tool_config.resource_set,
-        tools = tools,
+        tools = depset(
+            tools,
+            transitive = action_inputs.additional_tools,
+        ),
         use_default_shell_env = USE_DEFAULT_SHELL_ENV,
         **kwargs
     )

swift/toolchains/config/action_config.bzl

@@ -118,10 +118,16 @@ def _action_config_init(
         "not_features": _normalize_action_config_features(not_features),
     }
 
-def _config_result_init(*, inputs = [], transitive_inputs = []):
+def _config_result_init(
+        *,
+        additional_tools = [],
+        inputs = [],
+        transitive_inputs = []):
     """Validates and initializes an action configurator result.
 
     Args:
+        additional_tools: A list of `depset`s of `File`s that should be passed
+            as additional tool inputs to the action being configured.
         inputs: A list of `File`s that should be passed as inputs to the action
             being configured.
         transitive_inputs: A list of `depset`s of `File`s that should be passed
@@ -131,6 +137,7 @@ def _config_result_init(*, inputs = [], transitive_inputs = []):
         A new config result that can be returned from a configurator.
     """
     return {
+        "additional_tools": additional_tools,
         "inputs": inputs,
         "transitive_inputs": transitive_inputs,
     }
@@ -184,8 +191,9 @@ ActionConfigInfo, _action_config_init_unchecked = provider(
 ConfigResultInfo, _config_result_init_unchecked = provider(
     doc = "The inputs required by an action configurator.",
     fields = [
-        "inputs",
-        "transitive_inputs",
+        "additional_tools",  # List[depset[File]]
+        "inputs",  # list[File]
+        "transitive_inputs",  # List[depset[File]]
     ],
     init = _config_result_init,
 )

swift/toolchains/config/compile_config.bzl

@@ -265,15 +265,21 @@ def compile_action_configs(
     ]
 
     if generated_header_rewriter:
-        # Only add the generated header rewriter to the command line only if the
-        # toolchain provides one, the relevant feature is requested, and the
-        # particular compilation action is generating a header.
+        # Only add the generated header rewriter to the command line and to the
+        # action's tool inputs only if the toolchain provides one, the relevant
+        # feature is requested, and the particular compilation action is
+        # generating a header.
         def generated_header_rewriter_configurator(prerequisites, args):
+            additional_tools = []
             if prerequisites.generated_header_file:
+                additional_tools.append(depset([generated_header_rewriter]))
                 args.add(
                     generated_header_rewriter,
                     format = "-Xwrapped-swift=-generated-header-rewriter=%s",
                 )
+            return ConfigResultInfo(
+                additional_tools = additional_tools,
+            )
 
         action_configs.append(
             ActionConfigInfo(

swift/toolchains/xcode_swift_toolchain.bzl

@@ -490,7 +490,6 @@ def _all_tool_configs(
         custom_toolchain,
         env,
         execution_requirements,
-        generated_header_rewriter,
         swift_executable,
         toolchain_root):
     """Returns the tool configurations for the Swift toolchain.
@@ -500,8 +499,6 @@ def _all_tool_configs(
             one was requested.
         env: The environment variables to set when launching tools.
         execution_requirements: The execution requirements for tools.
-        generated_header_rewriter: The optional executable that will be invoked
-            after compilation to rewrite the generated header.
         swift_executable: A custom Swift driver executable to be used during the
             build, if provided.
         toolchain_root: The root directory of the toolchain, if provided.
@@ -525,9 +522,6 @@ def _all_tool_configs(
         }
 
     tool_config = ToolConfigInfo(
-        additional_tools = (
-            [generated_header_rewriter] if generated_header_rewriter else []
-        ),
         driver_config = _driver_config(mode = "swiftc"),
         env = env,
         execution_requirements = execution_requirements,
@@ -551,9 +545,6 @@ def _all_tool_configs(
         ),
         SWIFT_ACTION_COMPILE_MODULE_INTERFACE: (
             ToolConfigInfo(
-                additional_tools = (
-                    [generated_header_rewriter] if generated_header_rewriter else []
-                ),
                 driver_config = _driver_config(mode = "swiftc"),
                 args = ["-frontend"],
                 env = env,
@@ -739,7 +730,6 @@ def _xcode_swift_toolchain_impl(ctx):
         custom_toolchain = custom_toolchain,
         env = env,
         execution_requirements = execution_requirements,
-        generated_header_rewriter = generated_header_rewriter,
         swift_executable = swift_executable,
         toolchain_root = toolchain_root,
     )
@@ -897,8 +887,7 @@ generated header.
 
 This tool is expected to have a command line interface such that the Swift
 compiler invocation is passed to it following a `"--"` argument, and any
-arguments preceding the `"--"` can be defined by the tool itself (however, at
-this time the worker does not support passing additional flags to the tool).
+arguments preceding the `"--"` can be defined by the tool itself.
 """,
                 executable = True,
             ),