Implement compilation support for swift_module_mapping

doc/api.md

@@ -479,9 +479,9 @@ A provider whose type/layout is an implementation detail and should not
 ## swift_common.create_swift_module
 
 <pre>
-swift_common.create_swift_module(<a href="#swift_common.create_swift_module-swiftdoc">swiftdoc</a>, <a href="#swift_common.create_swift_module-swiftmodule">swiftmodule</a>, <a href="#swift_common.create_swift_module-ast_files">ast_files</a>, <a href="#swift_common.create_swift_module-defines">defines</a>, <a href="#swift_common.create_swift_module-generated_header">generated_header</a>,
-                                 <a href="#swift_common.create_swift_module-indexstore">indexstore</a>, <a href="#swift_common.create_swift_module-plugins">plugins</a>, <a href="#swift_common.create_swift_module-swiftsourceinfo">swiftsourceinfo</a>, <a href="#swift_common.create_swift_module-swiftinterface">swiftinterface</a>,
-                                 <a href="#swift_common.create_swift_module-private_swiftinterface">private_swiftinterface</a>, <a href="#swift_common.create_swift_module-const_protocols_to_gather">const_protocols_to_gather</a>)
+swift_common.create_swift_module(<a href="#swift_common.create_swift_module-ast_files">ast_files</a>, <a href="#swift_common.create_swift_module-const_protocols_to_gather">const_protocols_to_gather</a>, <a href="#swift_common.create_swift_module-defines">defines</a>, <a href="#swift_common.create_swift_module-generated_header">generated_header</a>,
+                                 <a href="#swift_common.create_swift_module-indexstore">indexstore</a>, <a href="#swift_common.create_swift_module-original_module_name">original_module_name</a>, <a href="#swift_common.create_swift_module-plugins">plugins</a>, <a href="#swift_common.create_swift_module-private_swiftinterface">private_swiftinterface</a>,
+                                 <a href="#swift_common.create_swift_module-swiftdoc">swiftdoc</a>, <a href="#swift_common.create_swift_module-swiftinterface">swiftinterface</a>, <a href="#swift_common.create_swift_module-swiftmodule">swiftmodule</a>, <a href="#swift_common.create_swift_module-swiftsourceinfo">swiftsourceinfo</a>)
 </pre>
 
 Creates a value representing a Swift module use as a Swift dependency.
@@ -491,17 +491,18 @@ Creates a value representing a Swift module use as a Swift dependency.
 
 | Name  | Description | Default Value |
 | :------------- | :------------- | :------------- |
-| <a id="swift_common.create_swift_module-swiftdoc"></a>swiftdoc |  The `.swiftdoc` file emitted by the compiler for this module.   |  none |
-| <a id="swift_common.create_swift_module-swiftmodule"></a>swiftmodule |  The `.swiftmodule` file emitted by the compiler for this module.   |  none |
 | <a id="swift_common.create_swift_module-ast_files"></a>ast_files |  A list of `File`s output from the `DUMP_AST` action.   |  `[]` |
+| <a id="swift_common.create_swift_module-const_protocols_to_gather"></a>const_protocols_to_gather |  A list of protocol names from which constant values should be extracted from source code that takes this module as a *direct* dependency.   |  `[]` |
 | <a id="swift_common.create_swift_module-defines"></a>defines |  A list of defines that will be provided as `copts` to targets that depend on this module. If omitted, the empty list will be used.   |  `[]` |
 | <a id="swift_common.create_swift_module-generated_header"></a>generated_header |  A `File` representing the Swift generated header.   |  `None` |
 | <a id="swift_common.create_swift_module-indexstore"></a>indexstore |  A `File` representing the directory that contains the index store data generated by the compiler if the `"swift.index_while_building"` feature is enabled, otherwise this will be `None`.   |  `None` |
+| <a id="swift_common.create_swift_module-original_module_name"></a>original_module_name |  The original name of the module if it was changed by a module mapping; otherwise, `None`.   |  `None` |
 | <a id="swift_common.create_swift_module-plugins"></a>plugins |  A list of `SwiftCompilerPluginInfo` providers representing compiler plugins that are required by this module and should be loaded by the compiler when this module is directly depended on.   |  `[]` |
-| <a id="swift_common.create_swift_module-swiftsourceinfo"></a>swiftsourceinfo |  The `.swiftsourceinfo` file emitted by the compiler for this module. May be `None` if no source info file was emitted.   |  `None` |
-| <a id="swift_common.create_swift_module-swiftinterface"></a>swiftinterface |  The `.swiftinterface` file emitted by the compiler for this module. May be `None` if no module interface file was emitted.   |  `None` |
 | <a id="swift_common.create_swift_module-private_swiftinterface"></a>private_swiftinterface |  The `.private.swiftinterface` file emitted by the compiler for this module. May be `None` if no private module interface file was emitted.   |  `None` |
-| <a id="swift_common.create_swift_module-const_protocols_to_gather"></a>const_protocols_to_gather |  A list of protocol names from which constant values should be extracted from source code that takes this module as a *direct* dependency.   |  `[]` |
+| <a id="swift_common.create_swift_module-swiftdoc"></a>swiftdoc |  The `.swiftdoc` file emitted by the compiler for this module.   |  none |
+| <a id="swift_common.create_swift_module-swiftinterface"></a>swiftinterface |  The `.swiftinterface` file emitted by the compiler for this module. May be `None` if no module interface file was emitted.   |  `None` |
+| <a id="swift_common.create_swift_module-swiftmodule"></a>swiftmodule |  The `.swiftmodule` file emitted by the compiler for this module.   |  none |
+| <a id="swift_common.create_swift_module-swiftsourceinfo"></a>swiftsourceinfo |  The `.swiftsourceinfo` file emitted by the compiler for this module. May be `None` if no source info file was emitted.   |  `None` |
 
 **RETURNS**
 

swift/internal/compiling.bzl

@@ -477,6 +477,14 @@ def compile(
                 macros).
     """
 
+    # Apply the module alias for the module being compiled, if present.
+    module_alias = swift_toolchain.module_aliases.get(module_name)
+    if module_alias:
+        original_module_name = module_name
+        module_name = module_alias
+    else:
+        original_module_name = None
+
     # Collect the `SwiftInfo` providers that represent the dependencies of the
     # Objective-C generated header module -- this includes the dependencies of
     # the Swift module, plus any additional dependencies that the toolchain says
@@ -687,8 +695,9 @@ to use swift_common.compile(include_dev_srch_paths = ...) instead.\
         include_dev_srch_paths = include_dev_srch_paths_value,
         is_swift = True,
         module_name = module_name,
-        package_name = package_name,
         objc_info = merged_objc_info,
+        original_module_name = original_module_name,
+        package_name = package_name,
         plugins = depset(used_plugins),
         source_files = srcs,
         target_label = feature_configuration._label,
@@ -822,6 +831,7 @@ to use swift_common.compile(include_dev_srch_paths = ...) instead.\
             defines = defines,
             generated_header = compile_outputs.generated_header_file,
             indexstore = compile_outputs.indexstore_directory,
+            original_module_name = original_module_name,
             plugins = depset(plugins),
             private_swiftinterface = compile_outputs.private_swiftinterface_file,
             swiftdoc = compile_outputs.swiftdoc_file,

swift/internal/providers.bzl

@@ -148,44 +148,47 @@ def create_clang_module(
 
 def create_swift_module(
         *,
-        swiftdoc,
-        swiftmodule,
         ast_files = [],
+        const_protocols_to_gather = [],
         defines = [],
         generated_header = None,
         indexstore = None,
+        original_module_name = None,
         plugins = [],
-        swiftsourceinfo = None,
-        swiftinterface = None,
         private_swiftinterface = None,
-        const_protocols_to_gather = []):
+        swiftdoc,
+        swiftinterface = None,
+        swiftmodule,
+        swiftsourceinfo = None):
     """Creates a value representing a Swift module use as a Swift dependency.
 
     Args:
-        swiftdoc: The `.swiftdoc` file emitted by the compiler for this module.
-        swiftmodule: The `.swiftmodule` file emitted by the compiler for this
-            module.
         ast_files: A list of `File`s output from the `DUMP_AST` action.
+        const_protocols_to_gather: A list of protocol names from which constant
+            values should be extracted from source code that takes this module
+            as a *direct* dependency.
         defines: A list of defines that will be provided as `copts` to targets
             that depend on this module. If omitted, the empty list will be used.
         generated_header: A `File` representing the Swift generated header.
         indexstore: A `File` representing the directory that contains the index
             store data generated by the compiler if the
             `"swift.index_while_building"` feature is enabled, otherwise this
             will be `None`.
+        original_module_name: The original name of the module if it was changed
+            by a module mapping; otherwise, `None`.
         plugins: A list of `SwiftCompilerPluginInfo` providers representing
             compiler plugins that are required by this module and should be
             loaded by the compiler when this module is directly depended on.
         private_swiftinterface: The `.private.swiftinterface` file emitted by
             the compiler for this module. May be `None` if no private module
             interface file was emitted.
-        swiftsourceinfo: The `.swiftsourceinfo` file emitted by the compiler for
-            this module. May be `None` if no source info file was emitted.
+        swiftdoc: The `.swiftdoc` file emitted by the compiler for this module.
         swiftinterface: The `.swiftinterface` file emitted by the compiler for
             this module. May be `None` if no module interface file was emitted.
-        const_protocols_to_gather: A list of protocol names from which constant
-            values should be extracted from source code that takes this module
-            as a *direct* dependency.
+        swiftmodule: The `.swiftmodule` file emitted by the compiler for this
+            module.
+        swiftsourceinfo: The `.swiftsourceinfo` file emitted by the compiler for
+            this module. May be `None` if no source info file was emitted.
 
     Returns:
         A `struct` containing the `ast_files`, `defines`, `indexstore,
@@ -194,16 +197,17 @@ def create_swift_module(
     """
     return struct(
         ast_files = tuple(ast_files),
+        const_protocols_to_gather = tuple(const_protocols_to_gather),
         defines = tuple(defines),
         generated_header = generated_header,
+        indexstore = indexstore,
         plugins = plugins,
         private_swiftinterface = private_swiftinterface,
-        indexstore = indexstore,
+        original_module_name = original_module_name,
         swiftdoc = swiftdoc,
         swiftinterface = swiftinterface,
         swiftmodule = swiftmodule,
         swiftsourceinfo = swiftsourceinfo,
-        const_protocols_to_gather = tuple(const_protocols_to_gather),
     )
 
 def create_swift_info(

swift/toolchains/config/compile_config.bzl

@@ -798,6 +798,10 @@ def compile_action_configs(
             ],
             features = [SWIFT_FEATURE_VFSOVERLAY],
         ),
+        ActionConfigInfo(
+            actions = [SWIFT_ACTION_COMPILE],
+            configurators = [_module_aliases_configurator],
+        ),
         ActionConfigInfo(
             actions = [
                 SWIFT_ACTION_COMPILE,
@@ -1717,6 +1721,44 @@ def _swift_module_search_path_map_fn(module):
     else:
         return None
 
+def _module_alias_flags(name, original):
+    """Returns compiler flags to set the given module alias."""
+
+    # TODO(b/257269318): Remove `-Xfrontend`; this is only needed to workaround
+    # a bug in toolchains still using the legacy C++ driver.
+    return [
+        "-Xfrontend",
+        "-module-alias",
+        "-Xfrontend",
+        "{original}={name}".format(
+            name = name,
+            original = original,
+        ),
+    ]
+
+def _module_alias_map_fn(module):
+    """Returns compiler flags to alias the given module.
+
+    This function is intended to be used as a mapping function for modules
+    passed into `Args.add_all`.
+
+    Args:
+        module: The module structure (as returned by
+            `swift_common.create_module`) extracted from the transitive
+            modules of a `SwiftInfo` provider.
+
+    Returns:
+        The flags to pass to the compiler to alias the given module, or `None`
+        if no alias applies.
+    """
+    if module.swift and module.swift.original_module_name:
+        return _module_alias_flags(
+            original = module.swift.original_module_name,
+            name = module.name,
+        )
+    else:
+        return None
+
 def _dependencies_swiftmodules_and_swiftdocs_configurator(prerequisites, args):
     """Adds `.swiftmodule` and `.swiftdoc` files from the transitive modules to search paths and action inputs."""
     args.add_all(
@@ -1744,6 +1786,21 @@ def _dependencies_swiftmodules_configurator(prerequisites, args):
         inputs = prerequisites.transitive_swiftmodules,
     )
 
+def _module_aliases_configurator(prerequisites, args):
+    """Adds `-module-alias` flags for the active module mapping, if any."""
+    args.add_all(
+        prerequisites.transitive_modules,
+        map_each = _module_alias_map_fn,
+    )
+
+    if prerequisites.original_module_name:
+        args.add_all(
+            _module_alias_flags(
+                original = prerequisites.original_module_name,
+                name = prerequisites.module_name,
+            ),
+        )
+
 def _load_executable_plugin_map_fn(plugin):
     """Returns frontend flags to load compiler plugins."""
     return [

test/BUILD

@@ -13,6 +13,7 @@ load(":interop_hints_tests.bzl", "interop_hints_test_suite")
 load(":mainattr_tests.bzl", "mainattr_test_suite")
 load(":module_cache_settings_tests.bzl", "module_cache_settings_test_suite")
 load(":module_interface_tests.bzl", "module_interface_test_suite")
+load(":module_mapping_tests.bzl", "module_mapping_test_suite")
 load(":output_file_map_tests.bzl", "output_file_map_test_suite")
 load(":pch_output_dir_tests.bzl", "pch_output_dir_test_suite")
 load(":private_deps_tests.bzl", "private_deps_test_suite")
@@ -52,6 +53,8 @@ module_cache_settings_test_suite(name = "module_cache_settings")
 
 module_interface_test_suite(name = "module_interface")
 
+module_mapping_test_suite(name = "module_mapping")
+
 output_file_map_test_suite(name = "output_file_map")
 
 private_deps_test_suite(name = "private_deps")

test/fixtures/module_mapping/BUILD

@@ -0,0 +1,47 @@
+load("//swift:swift_library.bzl", "swift_library")
+load("//swift:swift_module_mapping.bzl", "swift_module_mapping")
+load(
+    "//test/fixtures:common.bzl",
+    "FIXTURE_TAGS",
+)
+load(":apply_mapping.bzl", "apply_mapping")
+
+package(
+    default_testonly = True,
+    default_visibility = ["//test:__subpackages__"],
+)
+
+licenses(["notice"])
+
+swift_library(
+    name = "Common",
+    srcs = ["Common.swift"],
+    module_name = "Common",
+    tags = FIXTURE_TAGS,
+)
+
+swift_library(
+    name = "MySDK",
+    srcs = ["MySDK.swift"],
+    module_name = "MySDK",
+    tags = FIXTURE_TAGS,
+    deps = [":Common"],
+)
+
+swift_module_mapping(
+    name = "MySDK_module_mapping",
+    # This must not be testonly because it is used by the toolchain through the
+    # `:module_mapping` label flag.
+    testonly = False,
+    aliases = {
+        "Common": "MySDKInternal_Common",
+    },
+)
+
+# This is the target that will be tested in `module_mapping.bzl`, to force the
+# `MySDK` target to build in a configuration that sets the flag.
+apply_mapping(
+    name = "MySDK_with_mapping",
+    mapping = ":MySDK_module_mapping",
+    target = ":MySDK",
+)

test/fixtures/module_mapping/Common.swift

@@ -0,0 +1,19 @@
+// Copyright 2022 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.
+
+public final class Cat {
+  public class var standardIssue: Common.Cat { Common.Cat() }
+
+  public init() {}
+}

test/fixtures/module_mapping/MySDK.swift

@@ -0,0 +1,19 @@
+// Copyright 2022 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.
+
+import Common
+
+public func makeStandardIssueCat() -> Common.Cat {
+  return Common.Cat.standardIssue
+}

test/fixtures/module_mapping/apply_mapping.bzl

@@ -0,0 +1,40 @@
+# Copyright 2022 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.
+
+"""Rule and transition to force a specific module mapping in tests."""
+
+def _apply_mapping_transition_impl(settings, attr):
+    settings = dict(settings)
+    settings["@build_bazel_rules_swift//swift:module_mapping"] = attr.mapping
+    return settings
+
+apply_mapping_transition = transition(
+    implementation = _apply_mapping_transition_impl,
+    inputs = [],
+    outputs = ["@build_bazel_rules_swift//swift:module_mapping"],
+)
+
+def _apply_mapping_impl(ctx):
+    return [ctx.attr.target[0][DefaultInfo]]
+
+apply_mapping = rule(
+    attrs = {
+        "mapping": attr.label(),
+        "target": attr.label(cfg = apply_mapping_transition),
+        "_allowlist_function_transition": attr.label(
+            default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
+        ),
+    },
+    implementation = _apply_mapping_impl,
+)