enable cxx interop in sdk pcm compilation

Summary:
Traverse the correct SDK dep tree when cxx interop is enabled, and add handling for the std and Darwin modules.

This adds very basic support for cxx interop with explicit modules, there are remaining issues importing parts of the cxx stdlib.

Reviewed By: drodriguez

Differential Revision: D60546682

fbshipit-source-id: 049c6b8a0679bf5605ad0a3faa58c80645fa7b97

prelude/apple/swift/swift_compilation.bzl

@@ -132,7 +132,9 @@ SwiftDebugInfo = record(
     shared = list[ArtifactTSet],
 )
 
-REQUIRED_SDK_MODULES = ["Swift", "SwiftOnoneSupport", "Darwin", "_Concurrency", "_StringProcessing"]
+_REQUIRED_SDK_MODULES = ["Swift", "SwiftOnoneSupport", "Darwin", "_Concurrency", "_StringProcessing"]
+
+_REQUIRED_SDK_CXX_MODULES = _REQUIRED_SDK_MODULES + ["std"]
 
 def get_swift_anonymous_targets(ctx: AnalysisContext, get_apple_library_providers: typing.Callable) -> Promise:
     swift_cxx_flags = get_swift_cxx_flags(ctx)
@@ -141,7 +143,7 @@ def get_swift_anonymous_targets(ctx: AnalysisContext, get_apple_library_provider
     # all transitive deps will be compiled recursively.
     direct_uncompiled_sdk_deps = get_uncompiled_sdk_deps(
         ctx.attrs.sdk_modules,
-        REQUIRED_SDK_MODULES,
+        _REQUIRED_SDK_CXX_MODULES if ctx.attrs.enable_cxx_interop else _REQUIRED_SDK_MODULES,
         ctx.attrs._apple_toolchain[AppleToolchainInfo].swift_toolchain_info,
     )
 
@@ -157,6 +159,7 @@ def get_swift_anonymous_targets(ctx: AnalysisContext, get_apple_library_provider
     # passing apple_library's cxx flags through that must be used for all downward PCM compilations.
     sdk_pcm_targets = get_swift_sdk_pcm_anon_targets(
         ctx,
+        ctx.attrs.enable_cxx_interop,
         direct_uncompiled_sdk_deps,
         swift_cxx_flags,
     )

prelude/apple/swift/swift_pcm_compilation.bzl

@@ -38,6 +38,7 @@ def get_swift_pcm_anon_targets(
     deps = [
         {
             "dep": uncompiled_dep,
+            "enable_cxx_interop": ctx.attrs.enable_cxx_interop,
             "name": uncompiled_dep.label,
             "swift_cxx_args": swift_cxx_args,
             "_apple_toolchain": ctx.attrs._apple_toolchain,
@@ -196,6 +197,7 @@ def _swift_pcm_compilation_impl(ctx: AnalysisContext) -> [Promise, list[Provider
     # Recursively compiling SDK's Clang dependencies
     sdk_pcm_deps_anon_targets = get_swift_sdk_pcm_anon_targets(
         ctx,
+        ctx.attrs.enable_cxx_interop,
         direct_uncompiled_sdk_deps,
         ctx.attrs.swift_cxx_args,
     )
@@ -212,6 +214,7 @@ _swift_pcm_compilation = rule(
     impl = _swift_pcm_compilation_impl,
     attrs = {
         "dep": attrs.dep(),
+        "enable_cxx_interop": attrs.bool(),
         "swift_cxx_args": attrs.list(attrs.string(), default = []),
         "_apple_toolchain": attrs.dep(),
     },

prelude/apple/swift/swift_sdk_pcm_compilation.bzl

@@ -90,13 +90,15 @@ def _add_sdk_module_search_path(cmd, uncompiled_sdk_module_info, apple_toolchain
 
 def get_swift_sdk_pcm_anon_targets(
         ctx: AnalysisContext,
+        enable_cxx_interop: bool,
         uncompiled_sdk_deps: list[Dependency],
         swift_cxx_args: list[str]):
     # We include the Swift deps here too as we need
     # to include their transitive clang deps.
     return [
         (_swift_sdk_pcm_compilation, {
             "dep": module_dep,
+            "enable_cxx_interop": enable_cxx_interop,
             "name": module_dep.label,
             "swift_cxx_args": swift_cxx_args,
             "_apple_toolchain": ctx.attrs._apple_toolchain,
@@ -172,6 +174,19 @@ def _swift_sdk_pcm_compilation_impl(ctx: AnalysisContext) -> [Promise, list[Prov
 
         cmd.add(ctx.attrs.swift_cxx_args)
 
+        if module_name == "Darwin" and ctx.attrs.enable_cxx_interop:
+            # The Darwin module requires special handling with cxx interop
+            # to ensure that it does not include the c++ headers. The module
+            # is marked with [no_undeclared_includes] which will prevent
+            # including headers declared in other modulemaps. So that the
+            # cxx modules are visible we need to pass the module map path
+            # without the corresponding module file, which we cannot build
+            # until the Darwin module is available.
+            cmd.add([
+                "-Xcc",
+                cmd_args(swift_toolchain.sdk_path, format = "-fmodule-map-file={}/usr/include/c++/v1/module.modulemap"),
+            ])
+
         _add_sdk_module_search_path(cmd, uncompiled_sdk_module_info, apple_toolchain)
 
         ctx.actions.run(
@@ -226,9 +241,11 @@ def _swift_sdk_pcm_compilation_impl(ctx: AnalysisContext) -> [Promise, list[Prov
         ]
 
     # Compile the transitive clang module deps of this target.
+    deps = ctx.attrs.dep[SdkUncompiledModuleInfo].cxx_deps if ctx.attrs.enable_cxx_interop else ctx.attrs.dep[SdkUncompiledModuleInfo].deps
     clang_module_deps = get_swift_sdk_pcm_anon_targets(
         ctx,
-        ctx.attrs.dep[SdkUncompiledModuleInfo].deps,
+        ctx.attrs.enable_cxx_interop,
+        deps,
         ctx.attrs.swift_cxx_args,
     )
 
@@ -238,6 +255,7 @@ _swift_sdk_pcm_compilation = rule(
     impl = _swift_sdk_pcm_compilation_impl,
     attrs = {
         "dep": attrs.dep(),
+        "enable_cxx_interop": attrs.bool(),
         "swift_cxx_args": attrs.list(attrs.string(), default = []),
         "_apple_toolchain": attrs.dep(),
     },

prelude/apple/swift/swift_sdk_swiftinterface_compilation.bzl

@@ -99,6 +99,7 @@ def _swift_interface_compilation_impl(ctx: AnalysisContext) -> [Promise, list[Pr
     module_info = ctx.attrs.dep[SdkUncompiledModuleInfo]
     clang_module_deps = get_swift_sdk_pcm_anon_targets(
         ctx,
+        False,
         module_info.deps,
         ["-target", module_info.target],
     )