add application_extension attribute to apple_binary

Summary: We need a way to determine between extension binaries and app binaries. Add a boolean attribute that we can set on `apple_binary`.

Reviewed By: d16r

Differential Revision: D68783951

fbshipit-source-id: a259e26910aa4eb5ba829a6d039f4188335be60e

prelude/apple/apple_binary.bzl

@@ -105,6 +105,16 @@ def apple_binary_impl(ctx: AnalysisContext) -> [list[Provider], Promise]:
         swift_preprocessor = [swift_compile.pre] if swift_compile else []
         extra_link_flags = entitlements_link_flags(ctx)
 
+        # Extensions have custom entry points and API restrictions
+        extension_compiler_flags = []
+        if ctx.attrs.application_extension:
+            extra_link_flags += [
+                "-fapplication-extension",
+                "-e",
+                "_NSExtensionMain",
+            ]
+            extension_compiler_flags = ["-fapplication-extension"]
+
         framework_search_path_pre = CPreprocessor(
             args = CPreprocessorArgs(args = [framework_search_path_flags]),
         )
@@ -153,7 +163,7 @@ def apple_binary_impl(ctx: AnalysisContext) -> [list[Provider], Promise]:
             # Some apple rules rely on `static` libs *not* following dependents.
             link_groups_force_static_follows_dependents = False,
             swiftmodule_linkable = get_swiftmodule_linkable(swift_compile),
-            compiler_flags = ctx.attrs.compiler_flags,
+            compiler_flags = ctx.attrs.compiler_flags + extension_compiler_flags,
             lang_compiler_flags = ctx.attrs.lang_compiler_flags,
             platform_compiler_flags = ctx.attrs.platform_compiler_flags,
             lang_platform_compiler_flags = ctx.attrs.lang_platform_compiler_flags,

prelude/apple/apple_rules_impl.bzl

@@ -68,6 +68,7 @@ _APPLE_TOOLCHAIN_ATTR = get_apple_toolchain_attr()
 
 def _apple_binary_extra_attrs():
     attribs = {
+        "application_extension": attrs.bool(default = False),
         "binary_linker_flags": attrs.list(attrs.arg(), default = []),
         "dist_thin_lto_codegen_flags": attrs.list(attrs.arg(), default = []),
         "enable_distributed_thinlto": attrs.bool(default = False),

prelude/apple/swift/swift_compilation.bzl

@@ -863,6 +863,9 @@ def _get_shared_flags(
     if ctx.attrs._swift_enable_testing:
         cmd.add("-enable-testing")
 
+    if getattr(ctx.attrs, "application_extension", False):
+        cmd.add("-application-extension")
+
     pcm_deps_tset = get_compiled_pcm_deps_tset(ctx, deps_providers)
 
     # If Swift Explicit Modules are enabled, a few things must be provided to a compilation job: