Add test host app transition marker

Summary:
If `embed_xctest_frameworks_in_test_host_app` is set on an `apple_test()`, the `config//marker/apple/constraints:embed_xctest_frameworks_enabled` constraint is then added to the `test_host_app` via a transition.

This constraint is then used in `apple_bundle()` to embed XCTest frameworks.

Reviewed By: manicaesar

Differential Revision: D62936576

fbshipit-source-id: 62f95834503eee2dfac8ec71286b0f54c4dd5293

apple/apple_test_host_app_transition.bzl

@@ -0,0 +1,38 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under both the MIT license found in the
+# LICENSE-MIT file in the root directory of this source tree and the Apache
+# License, Version 2.0 found in the LICENSE-APACHE file in the root directory
+# of this source tree.
+
+def _apple_test_host_app_transition_impl(platform: PlatformInfo, refs: struct, attrs: struct) -> PlatformInfo:
+    if not attrs.embed_xctest_frameworks_in_test_host_app:
+        return platform
+
+    updated_constraints = dict(platform.configuration.constraints)
+
+    test_host_marker_setting_label = refs.embed_xctest_frameworks_constraint_setting[ConstraintSettingInfo].label
+    if test_host_marker_setting_label in updated_constraints:
+        return platform
+
+    test_host_marker_value_info = refs.embed_xctest_frameworks_marker_constraint_value[ConstraintValueInfo]
+    updated_constraints[test_host_marker_setting_label] = test_host_marker_value_info
+
+    return PlatformInfo(
+        label = platform.label + "-test-host-app",
+        configuration = ConfigurationInfo(
+            constraints = updated_constraints,
+            values = platform.configuration.values,
+        ),
+    )
+
+apple_test_host_app_transition = transition(
+    impl = _apple_test_host_app_transition_impl,
+    refs = {
+        "embed_xctest_frameworks_constraint_setting": "config//marker/apple/constraints:embed_xctest_frameworks",
+        "embed_xctest_frameworks_marker_constraint_value": "config//marker/apple/constraints:embed_xctest_frameworks_enabled",
+    },
+    attrs = [
+        "embed_xctest_frameworks_in_test_host_app",
+    ],
+)

decls/ios_rules.bzl

@@ -12,6 +12,7 @@
 
 load("@prelude//apple:apple_common.bzl", "apple_common")
 load("@prelude//apple:apple_rules_impl_utility.bzl", "apple_dsymutil_attrs", "get_apple_toolchain_attr")
+load("@prelude//apple:apple_test_host_app_transition.bzl", "apple_test_host_app_transition")
 load("@prelude//apple:apple_toolchain_types.bzl", "AppleToolsInfo")
 load("@prelude//apple:apple_universal_executable.bzl", "apple_universal_executable_impl")
 load("@prelude//apple:cxx_universal_executable.bzl", "cxx_universal_executable_impl")
@@ -673,7 +674,7 @@ apple_test = prelude_rule(
         apple_common.info_plist_arg() |
         apple_common.info_plist_substitutions_arg() |
         {
-            "test_host_app": attrs.option(attrs.dep(), default = None, doc = """
+            "test_host_app": attrs.option(attrs.transition_dep(cfg = apple_test_host_app_transition), default = None, doc = """
                 A build target identifying
                  an `apple_bundle()` rule that builds an
                  application bundle. Output of the specified rule will be used as a test host of this test. This
@@ -684,6 +685,9 @@ apple_test = prelude_rule(
                  reference errors during compilation, but if the symbols do not exist, it might result in runtime
                  crashes).
             """),
+            "embed_xctest_frameworks_in_test_host_app": attrs.option(attrs.bool(), default = None, doc = """
+                Controls whether a marker constraint is added to the `test_host_app`.
+            """),
         } |
         cxx_common.srcs_arg() |
         cxx_common.platform_srcs_arg() |