Allow to opt-out from library evolution

apple/build_settings/build_settings.bzl

@@ -38,6 +38,12 @@ Enables Bazel's tree artifacts for Apple bundle rules (instead of archives).
 """,
         default = False,
     ),
+    "use_library_evolution": struct(
+        doc = """
+Enables library evolution, allowing for the emission of .swiftinterface files.
+""",
+        default = True,
+    ),
 }
 
 _BUILD_SETTING_LABELS = {

apple/internal/partials/swift_framework.bzl

@@ -70,14 +70,25 @@ issue with a reproducible error case.
 
         found_module_name = swift_module.name
 
-        bundle_interface = swift_info_support.declare_swiftinterface(
-            actions = actions,
-            arch = arch,
-            label_name = label_name,
-            output_discriminator = output_discriminator,
-            swiftinterface = swift_module.swift.swiftinterface,
-        )
-        bundle_files.append((processor.location.bundle, modules_parent, depset([bundle_interface])))
+        # A swiftinterface will not be present when library evolution is disabled, if so, fallback to swiftmodule.
+        if swift_module.swift.swiftinterface:
+            bundle_interface = swift_info_support.declare_swiftinterface(
+                actions = actions,
+                arch = arch,
+                label_name = label_name,
+                output_discriminator = output_discriminator,
+                swiftinterface = swift_module.swift.swiftinterface,
+            )
+            bundle_files.append((processor.location.bundle, modules_parent, depset([bundle_interface])))
+        else:
+            bundle_swiftmodule = swift_info_support.declare_swiftmodule(
+                actions = actions,
+                arch = arch,
+                label_name = label_name,
+                output_discriminator = output_discriminator,
+                swiftmodule = swift_module.swift.swiftmodule,
+            )
+            bundle_files.append((processor.location.bundle, modules_parent, depset([bundle_swiftmodule])))
 
         bundle_doc = swift_info_support.declare_swiftdoc(
             actions = actions,

apple/internal/swift_info_support.bzl

@@ -81,7 +81,7 @@ swift_library dependencies.\
 """,
             )
 
-        if not all([module.name, module.swift.swiftdoc, module.swift.swiftinterface]):
+        if not all([module.name, module.swift.swiftdoc]) or not (module.swift.swiftmodule or module.swift.swiftinterface):
             fail(
                 """\
 error: Could not find all required artifacts and information to build a Swift framework. \
@@ -246,6 +246,38 @@ def _declare_swiftinterface(
     )
     return bundle_interface
 
+def _declare_swiftmodule(
+        *,
+        actions,
+        arch,
+        label_name,
+        output_discriminator,
+        swiftmodule):
+    """Declares the swiftmodule for this Swift framework.
+
+    Args:
+        actions: The actions provider from `ctx.actions`.
+        arch: The cpu architecture that the generated swiftdoc belongs to.
+        label_name: Name of the target being built.
+        output_discriminator: A string to differentiate between different target intermediate files
+            or `None`.
+        swiftmodule: A File referencing the swiftmodule file from a SwiftInfo provider.
+
+    Returns:
+        A File referencing the intermediate swiftmodule.
+    """
+    bundle_module = intermediates.file(
+        actions = actions,
+        target_name = label_name,
+        output_discriminator = output_discriminator,
+        file_name = "{}.swiftmodule".format(arch),
+    )
+    actions.symlink(
+        target_file = swiftmodule,
+        output = bundle_module,
+    )
+    return bundle_module
+
 swift_info_support = struct(
     verify_found_module_name = _verify_found_module_name,
     modules_from_avoid_deps = _modules_from_avoid_deps,
@@ -254,4 +286,5 @@ swift_info_support = struct(
     declare_generated_header = _declare_generated_header,
     declare_swiftdoc = _declare_swiftdoc,
     declare_swiftinterface = _declare_swiftinterface,
+    declare_swiftmodule = _declare_swiftmodule,
 )

apple/internal/transition_support.bzl

@@ -249,6 +249,7 @@ def _command_line_options(
     default_platforms = [settings[_CPU_TO_DEFAULT_PLATFORM_FLAG[cpu]]] if _is_bazel_7 else []
     return {
         build_settings_labels.use_tree_artifacts_outputs: force_bundle_outputs if force_bundle_outputs else settings[build_settings_labels.use_tree_artifacts_outputs],
+        build_settings_labels.use_library_evolution: settings[build_settings_labels.use_library_evolution],
         "//command_line_option:apple configuration distinguisher": "applebin_" + platform_type,
         "//command_line_option:apple_platform_type": platform_type,
         "//command_line_option:apple_platforms": apple_platforms,
@@ -361,7 +362,10 @@ def _command_line_options_for_xcframework_platform(
                     environment = target_environment,
                     platform_type = platform_type,
                 ): _command_line_options(
-                    emit_swiftinterface = True,
+                    emit_swiftinterface = _should_emit_swiftinterface(
+                        settings,
+                        is_xcframework = True,
+                    ),
                     environment_arch = resolved_environment_arch,
                     minimum_os_version = minimum_os_version,
                     platform_type = platform_type,
@@ -372,11 +376,28 @@ def _command_line_options_for_xcframework_platform(
 
     return output_dictionary
 
+def _should_emit_swiftinterface(settings, is_xcframework = False):
+    """Determines if a .swiftinterface file should be generated for Swift dependencies.
+
+    By providing the option to disable the emission of these files, it allows consumers to opt out
+    of library evolution features, offering flexibility in how Swift dependencies are integrated and managed.
+    """
+
+    # Do not emit swiftinterface file when library evolution is disabled for a given build
+    if not settings[build_settings_labels.use_library_evolution]:
+        return False
+
+    # For iOS and tvOS static frameworks, it's historically been required for the underlying swift_library targets
+    # to generate a Swift interface file, though this is primarily for legacy support. `swiftmodule` files may
+    # be used as an alternative. The introduction of a private attribute `_emitswiftinterface` within these
+    # rules allows for selective configuration of Swift build settings across the build graph.
+    return is_xcframework or hasattr(attr, "_emitswiftinterface")
+
 def _apple_rule_base_transition_impl(settings, attr):
     """Rule transition for Apple rules using Bazel CPUs and a valid Apple split transition."""
     platform_type = attr.platform_type
     return _command_line_options(
-        emit_swiftinterface = hasattr(attr, "_emitswiftinterface"),
+        emit_swiftinterface = _should_emit_swiftinterface(settings),
         environment_arch = _environment_archs(platform_type, settings)[0],
         minimum_os_version = attr.minimum_os_version,
         platform_type = platform_type,
@@ -389,6 +410,7 @@ def _apple_rule_base_transition_impl(settings, attr):
 # - https://github.com/bazelbuild/bazel/blob/master/src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java
 _apple_rule_common_transition_inputs = [
     build_settings_labels.use_tree_artifacts_outputs,
+    build_settings_labels.use_library_evolution,
     "//command_line_option:apple_crosstool_top",
 ] + _CPU_TO_DEFAULT_PLATFORM_FLAG.values()
 _apple_rule_base_transition_inputs = _apple_rule_common_transition_inputs + [
@@ -407,6 +429,7 @@ _apple_platform_transition_inputs = _apple_platforms_rule_base_transition_inputs
 ]
 _apple_rule_base_transition_outputs = [
     build_settings_labels.use_tree_artifacts_outputs,
+    build_settings_labels.use_library_evolution,
     "//command_line_option:apple configuration distinguisher",
     "//command_line_option:apple_platform_type",
     "//command_line_option:apple_platforms",
@@ -447,7 +470,7 @@ def _apple_platforms_rule_base_transition_impl(settings, attr):
         environment_arch = _environment_archs(platform_type, settings)[0]
     return _command_line_options(
         apple_platforms = settings["//command_line_option:apple_platforms"],
-        emit_swiftinterface = hasattr(attr, "_emitswiftinterface"),
+        emit_swiftinterface = _should_emit_swiftinterface(settings),
         environment_arch = environment_arch,
         minimum_os_version = minimum_os_version,
         platform_type = platform_type,
@@ -470,7 +493,7 @@ def _apple_platforms_rule_bundle_output_base_transition_impl(settings, attr):
         environment_arch = _environment_archs(platform_type, settings)[0]
     return _command_line_options(
         apple_platforms = settings["//command_line_option:apple_platforms"],
-        emit_swiftinterface = hasattr(attr, "_emitswiftinterface"),
+        emit_swiftinterface = _should_emit_swiftinterface(settings),
         environment_arch = environment_arch,
         force_bundle_outputs = True,
         minimum_os_version = minimum_os_version,
@@ -547,10 +570,7 @@ def _apple_platform_split_transition_impl(settings, attr):
     output_dictionary = {}
     invalid_requested_archs = []
 
-    # iOS and tvOS static frameworks require underlying swift_library targets generate a Swift
-    # interface file. These rules define a private attribute called `_emitswiftinterface` that
-    # let's this transition flip rules_swift config down the build graph.
-    emit_swiftinterface = hasattr(attr, "_emitswiftinterface")
+    emit_swiftinterface = _should_emit_swiftinterface(settings)
 
     if settings["//command_line_option:incompatible_enable_apple_toolchain_resolution"]:
         platforms = (

test/starlark_tests/apple_static_xcframework_tests.bzl

@@ -18,6 +18,10 @@ load(
     ":common.bzl",
     "common",
 )
+load(
+    "@build_bazel_rules_apple//apple/build_settings:build_settings.bzl",
+    "build_settings_labels",
+)
 load(
     "//test/starlark_tests/rules:common_verification_tests.bzl",
     "archive_contents_test",
@@ -127,6 +131,9 @@ def apple_static_xcframework_test_suite(name):
         name = "{}_swift_generates_header_test".format(name),
         build_type = "device",
         target_under_test = "//test/starlark_tests/targets_under_test/apple:ios_static_xcfmwk_with_swift_generated_headers",
+        build_settings = {
+            build_settings_labels.use_library_evolution: "True",
+        },
         contains = [
             "$BUNDLE_ROOT/Info.plist",
             "$BUNDLE_ROOT/ios-arm64/ios_static_xcfmwk_with_swift_generated_headers.framework/Headers/ios_static_xcfmwk_with_swift_generated_headers.h",

test/starlark_tests/apple_xcframework_tests.bzl

@@ -18,6 +18,10 @@ load(
     ":common.bzl",
     "common",
 )
+load(
+    "@build_bazel_rules_apple//apple/build_settings:build_settings.bzl",
+    "build_settings_labels",
+)
 load(
     "//test/starlark_tests/rules:analysis_failure_message_test.bzl",
     "analysis_failure_message_test",
@@ -485,6 +489,9 @@ def apple_xcframework_test_suite(name):
         build_type = "simulator",
         compilation_mode = "opt",
         target_under_test = "//test/starlark_tests/targets_under_test/apple:ios_swift_xcframework_with_generated_header",
+        build_settings = {
+            build_settings_labels.use_library_evolution: "True",
+        },
         contains = [
             "$BUNDLE_ROOT/ios-arm64_x86_64-simulator/SwiftFmwkWithGenHeader.framework/Headers/SwiftFmwkWithGenHeader.h",
             "$BUNDLE_ROOT/ios-arm64_x86_64-simulator/SwiftFmwkWithGenHeader.framework/Modules/module.modulemap",

test/starlark_tests/ios_framework_tests.bzl

@@ -18,6 +18,10 @@ load(
     ":common.bzl",
     "common",
 )
+load(
+    "@build_bazel_rules_apple//apple/build_settings:build_settings.bzl",
+    "build_settings_labels",
+)
 load(
     "//test/starlark_tests/rules:analysis_failure_message_test.bzl",
     "analysis_failure_message_test",
@@ -411,6 +415,9 @@ def ios_framework_test_suite(name):
         name = "{}_static_framework_contains_swiftinterface".format(name),
         build_type = "simulator",
         target_under_test = "//test/starlark_tests/targets_under_test/ios:swift_static_framework",
+        build_settings = {
+            build_settings_labels.use_library_evolution: "True",
+        },
         contains = [
             "$BUNDLE_ROOT/Headers/swift_framework_lib.h",
             "$BUNDLE_ROOT/Modules/swift_framework_lib.swiftmodule/x86_64.swiftdoc",

test/starlark_tests/ios_static_framework_tests.bzl

@@ -18,6 +18,10 @@ load(
     ":common.bzl",
     "common",
 )
+load(
+    "@build_bazel_rules_apple//apple/build_settings:build_settings.bzl",
+    "build_settings_labels",
+)
 load(
     "//test/starlark_tests/rules:analysis_failure_message_test.bzl",
     "analysis_failure_message_test",
@@ -118,6 +122,9 @@ def ios_static_framework_test_suite(name):
         build_type = "simulator",
         compilation_mode = "opt",
         target_under_test = "//test/starlark_tests/targets_under_test/ios:static_fmwk_with_swift_and_avoid_deps",
+        build_settings = {
+            build_settings_labels.use_library_evolution: "True",
+        },
         contains = [
             "$BUNDLE_ROOT/Modules/SwiftFmwkUpperLib.swiftmodule/x86_64.swiftdoc",
             "$BUNDLE_ROOT/Modules/SwiftFmwkUpperLib.swiftmodule/x86_64.swiftinterface",
@@ -184,6 +191,9 @@ def ios_static_framework_test_suite(name):
         build_type = "simulator",
         compilation_mode = "opt",
         target_under_test = "//test/starlark_tests/targets_under_test/ios:static_framework_with_generated_header",
+        build_settings = {
+            build_settings_labels.use_library_evolution: "True",
+        },
         contains = [
             "$BUNDLE_ROOT/Headers/SwiftStaticFmwkWithGenHeader.h",
             "$BUNDLE_ROOT/Modules/module.modulemap",

test/starlark_tests/macos_framework_tests.bzl

@@ -18,6 +18,10 @@ load(
     ":common.bzl",
     "common",
 )
+load(
+    "@build_bazel_rules_apple//apple/build_settings:build_settings.bzl",
+    "build_settings_labels",
+)
 load(
     "//test/starlark_tests/rules:common_verification_tests.bzl",
     "archive_contents_test",
@@ -337,6 +341,9 @@ def macos_framework_test_suite(name):
         name = "{}_static_framework_contains_swiftinterface".format(name),
         build_type = "simulator",
         target_under_test = "//test/starlark_tests/targets_under_test/macos:swift_static_framework",
+        build_settings = {
+            build_settings_labels.use_library_evolution: "True",
+        },
         contains = [
             "$BUNDLE_ROOT/Headers/swift_framework_lib.h",
             "$BUNDLE_ROOT/Modules/swift_framework_lib.swiftmodule/x86_64.swiftdoc",

test/starlark_tests/macos_static_framework_tests.bzl

@@ -18,6 +18,10 @@ load(
     ":common.bzl",
     "common",
 )
+load(
+    "@build_bazel_rules_apple//apple/build_settings:build_settings.bzl",
+    "build_settings_labels",
+)
 load(
     "//test/starlark_tests/rules:analysis_failure_message_test.bzl",
     "analysis_failure_message_test",
@@ -88,6 +92,9 @@ def macos_static_framework_test_suite(name):
         build_type = "simulator",
         compilation_mode = "opt",
         target_under_test = "//test/starlark_tests/targets_under_test/macos:static_fmwk_with_swift_and_avoid_deps",
+        build_settings = {
+            build_settings_labels.use_library_evolution: "True",
+        },
         contains = [
             "$BUNDLE_ROOT/Modules/SwiftFmwkUpperLib.swiftmodule/x86_64.swiftdoc",
             "$BUNDLE_ROOT/Modules/SwiftFmwkUpperLib.swiftmodule/x86_64.swiftinterface",
@@ -154,6 +161,9 @@ def macos_static_framework_test_suite(name):
         build_type = "simulator",
         compilation_mode = "opt",
         target_under_test = "//test/starlark_tests/targets_under_test/macos:static_framework_with_generated_header",
+        build_settings = {
+            build_settings_labels.use_library_evolution: "True",
+        },
         contains = [
             "$BUNDLE_ROOT/Headers/SwiftFmwkWithGenHeader.h",
             "$BUNDLE_ROOT/Modules/module.modulemap",