Extract swiftc argument generation from swift_library implementation

Make it possible to use compiler args that swift_library creates in
other rules that do not depend on it. Also rename _module_name to
swift_module_name and make it public because proper usage of
swiftc_args requires a module name to be passed in.

--
PiperOrigin-RevId: 141926959
MOS_MIGRATED_REVID=141926959

1 files changed, 120 insertions, 83 deletions

diff --git a/tools/build_defs/apple/swift.bzl b/tools/build_defs/apple/swift.bzl
index c1cf96eb8c..5c1b662d65 100644
--- a/tools/build_defs/apple/swift.bzl
+++ b/tools/build_defs/apple/swift.bzl
@@ -78,9 +78,9 @@ def _swift_bitcode_flags(ctx):
   return []
 
 
-def _module_name(ctx):
-  """Returns a module name for the given rule context."""
-  return ctx.label.package.lstrip("//").replace("/", "_") + "_" + ctx.label.name
+def swift_module_name(label):
+  """Returns a module name for the given label."""
+  return label.package.lstrip("//").replace("/", "_") + "_" + label.name
 
 
 def _swift_lib_dir(ctx):
@@ -160,23 +160,35 @@ def _validate_rule_and_deps(ctx):
       fail(name_error_str % dep.label)
 
 
-def _swift_library_impl(ctx):
-  """Implementation for swift_library Skylark rule."""
+def swiftc_args(ctx):
+  """Returns an almost compelete array of arguments to be passed to swiftc.
 
-  _validate_rule_and_deps(ctx)
+  This macro is intended to be used by the swift_library rule implementation
+  below but it also may be used by other rules outside this file. It has no
+  side effects and does not modify ctx. It expects ctx to contain the same
+  fragments and attributes as swift_library (you're encouraged to depend on
+  SWIFT_LIBRARY_ATTRS in your rule definition).
+
+  Args:
+    ctx: rule context
+
+  Returns:
+    A list of command line arguments for swiftc. The returned arguments
+    include everything except the arguments generation of which would require
+    adding new files or actions.
+  """
 
-  # TODO(b/29772303): Assert xcode version.
   apple_fragment = ctx.fragments.apple
 
   cpu = apple_fragment.single_arch_cpu
   platform = apple_fragment.single_arch_platform
 
-  target_os = ctx.fragments.apple.minimum_os_for_platform_type(
+  target_os = apple_fragment.minimum_os_for_platform_type(
       platform.platform_type)
   target = _swift_target(cpu, platform, target_os)
   apple_toolchain = apple_common.apple_toolchain()
 
-  module_name = ctx.attr.module_name or _module_name(ctx)
+  module_name = ctx.attr.module_name or swift_module_name(ctx.label)
 
   # A list of paths to pass with -F flag.
   framework_dirs = set([
@@ -184,31 +196,22 @@ def _swift_library_impl(ctx):
 
   # Collect transitive dependecies.
   dep_modules = []
-  dep_libs = []
   swiftc_defines = ctx.attr.defines
 
   swift_providers = [x.swift for x in ctx.attr.deps if hasattr(x, "swift")]
   objc_providers = [x.objc for x in ctx.attr.deps if hasattr(x, "objc")]
 
   for swift in swift_providers:
-    dep_libs += swift.transitive_libs
     dep_modules += swift.transitive_modules
     swiftc_defines += swift.transitive_defines
 
   objc_includes = set()     # Everything that needs to be included with -I
-  objc_files = set()        # All inputs required for the compile action
   objc_module_maps = set()  # Module maps for dependent targets
   objc_defines = set()
   for objc in objc_providers:
     objc_includes += objc.include
-
-    objc_files += objc.header
-    objc_files += objc.module_map
-
     objc_module_maps += objc.module_map
 
-    files = set(objc.static_framework_file) + set(objc.dynamic_framework_file)
-    objc_files += files
     framework_dirs += _parent_dirs(objc.framework_dir)
     # TODO(cparsons): Remove getattr call once dynamic_framework_dir is stable.
     framework_dirs += _parent_dirs(getattr(objc, "dynamic_framework_dir", []))
@@ -218,49 +221,11 @@ def _swift_library_impl(ctx):
     # their module cannot be compiled by clang), but did not occur in practice.
     objc_defines += objc.define
 
-  # A unique path for rule's outputs.
-  objs_outputs_path = label_scoped_path(ctx, "_objs/")
-
-  output_lib = ctx.new_file(objs_outputs_path + module_name + ".a")
-  output_module = ctx.new_file(objs_outputs_path + module_name + ".swiftmodule")
-
-  # These filenames are guaranteed to be unique, no need to scope.
-  output_header = ctx.new_file(ctx.label.name + "-Swift.h")
-  swiftc_output_map_file = ctx.new_file(ctx.label.name + ".output_file_map.json")
-
-  swiftc_output_map = struct()  # Maps output types to paths.
-  output_objs = []  # Object file outputs, used in archive action.
-  swiftc_outputs = []  # Other swiftc outputs that aren't processed further.
-  for source in ctx.files.srcs:
-    basename = source.basename
-    obj = ctx.new_file(objs_outputs_path + basename + ".o")
-    partial_module = ctx.new_file(objs_outputs_path + basename +
-                                  ".partial_swiftmodule")
-    output_objs.append(obj)
-    swiftc_outputs.append(partial_module)
-
-    swiftc_output_map += struct(**{
-        source.path: struct(object=obj.path, swiftmodule=partial_module.path)})
-
-  # Write down the intermediate outputs map for this compilation, to be used
-  # with -output-file-map flag.
-  # It's a JSON file that maps each source input (.swift) to its outputs
-  # (.o, .bc, .d, ...)
-  # Example:
-  #   {'foo.swift':
-  #       {'object': 'foo.o', 'bitcode': 'foo.bc', 'dependencies': 'foo.d'}}
-  # There's currently no documentation on this option, however all of the keys
-  # are listed here https://github.com/apple/swift/blob/swift-2.2.1-RELEASE/include/swift/Driver/Types.def
-  ctx.file_action(output=swiftc_output_map_file, content=swiftc_output_map.to_json())
-
   srcs_args = [f.path for f in ctx.files.srcs]
 
   # Include each swift module's parent directory for imports to work.
   include_dirs = set([x.dirname for x in dep_modules])
 
-  # Include the parent directory of the resulting module so LLDB can find it.
-  include_dirs += set([output_module.dirname])
-
   # Include the genfiles root so full-path imports can work for generated protos.
   include_dirs += set([ctx.configuration.genfiles_dir.path])
 
@@ -268,15 +233,6 @@ def _swift_library_impl(ctx):
   framework_args = ["-F%s" % x for x in framework_dirs]
   define_args = ["-D%s" % x for x in swiftc_defines]
 
-  # This tells the linker to write a reference to .swiftmodule as an AST symbol
-  # in the final binary.
-  # With dSYM enabled, this results in a __DWARF,__swift_ast section added to
-  # the dSYM binary, from where LLDB is able deserialize module information.
-  # Without dSYM, LLDB will follow the AST references, however there is a bug
-  # where it follows only the first one https://bugs.swift.org/browse/SR-2637
-  # This means that dSYM is required for debugging until that is resolved.
-  extra_linker_args = ["-Xlinker -add_ast_path -Xlinker " + output_module.path]
-
   clang_args = _intersperse(
       "-Xcc",
 
@@ -296,23 +252,16 @@ def _swift_library_impl(ctx):
       # https://llvm.org/bugs/show_bug.cgi?id=19501
       + ["-fmodule-map-file=%s" % x.path for x in objc_module_maps])
 
-  args = _swift_xcrun_args(ctx) + [
-      "swiftc",
+  args = [
       "-emit-object",
-      "-emit-module-path",
-      output_module.path,
       "-module-name",
       module_name,
-      "-emit-objc-header-path",
-      output_header.path,
       "-target",
       target,
       "-sdk",
       apple_toolchain.sdk_dir(),
       "-module-cache-path",
       module_cache_path(ctx),
-      "-output-file-map",
-      swiftc_output_map_file.path,
   ]
 
   if ctx.configuration.coverage_enabled:
@@ -328,6 +277,82 @@ def _swift_library_impl(ctx):
   args.extend(define_args)
   args.extend(ctx.attr.copts)
 
+  return args
+
+
+def _swift_library_impl(ctx):
+  """Implementation for swift_library Skylark rule."""
+
+  _validate_rule_and_deps(ctx)
+
+  # Collect transitive dependecies.
+  dep_modules = []
+  dep_libs = []
+  swiftc_defines = ctx.attr.defines
+
+  swift_providers = [x.swift for x in ctx.attr.deps if hasattr(x, "swift")]
+  objc_providers = [x.objc for x in ctx.attr.deps if hasattr(x, "objc")]
+
+  for swift in swift_providers:
+    dep_libs += swift.transitive_libs
+    dep_modules += swift.transitive_modules
+    swiftc_defines += swift.transitive_defines
+
+  objc_files = set()        # All inputs required for the compile action
+  for objc in objc_providers:
+    objc_files += objc.header
+    objc_files += objc.module_map
+
+    files = set(objc.static_framework_file) + set(objc.dynamic_framework_file)
+    objc_files += files
+
+  # A unique path for rule's outputs.
+  objs_outputs_path = label_scoped_path(ctx, "_objs/")
+
+  module_name = ctx.attr.module_name or swift_module_name(ctx.label)
+  output_lib = ctx.new_file(objs_outputs_path + module_name + ".a")
+  output_module = ctx.new_file(objs_outputs_path + module_name + ".swiftmodule")
+
+  # These filenames are guaranteed to be unique, no need to scope.
+  output_header = ctx.new_file(ctx.label.name + "-Swift.h")
+  swiftc_output_map_file = ctx.new_file(ctx.label.name + ".output_file_map.json")
+
+  swiftc_output_map = struct()  # Maps output types to paths.
+  output_objs = []  # Object file outputs, used in archive action.
+  swiftc_outputs = []  # Other swiftc outputs that aren't processed further.
+  for source in ctx.files.srcs:
+    basename = source.basename
+    obj = ctx.new_file(objs_outputs_path + basename + ".o")
+    partial_module = ctx.new_file(objs_outputs_path + basename +
+                                  ".partial_swiftmodule")
+    output_objs.append(obj)
+    swiftc_outputs.append(partial_module)
+
+    swiftc_output_map += struct(**{
+        source.path: struct(object=obj.path, swiftmodule=partial_module.path)})
+
+  # Write down the intermediate outputs map for this compilation, to be used
+  # with -output-file-map flag.
+  # It's a JSON file that maps each source input (.swift) to its outputs
+  # (.o, .bc, .d, ...)
+  # Example:
+  #   {'foo.swift':
+  #       {'object': 'foo.o', 'bitcode': 'foo.bc', 'dependencies': 'foo.d'}}
+  # There's currently no documentation on this option, however all of the keys
+  # are listed here https://github.com/apple/swift/blob/swift-2.2.1-RELEASE/include/swift/Driver/Types.def
+  ctx.file_action(output=swiftc_output_map_file, content=swiftc_output_map.to_json())
+
+  args = _swift_xcrun_args(ctx) + ["swiftc"] + swiftc_args(ctx)
+  args += [
+      "-I" + output_module.dirname,
+      "-emit-module-path",
+      output_module.path,
+      "-emit-objc-header-path",
+      output_header.path,
+      "-output-file-map",
+      swiftc_output_map_file.path,
+  ]
+
   xcrun_action(
       ctx,
       inputs=ctx.files.srcs + dep_modules + list(objc_files) +
@@ -348,6 +373,15 @@ def _swift_library_impl(ctx):
                ] + [x.path for x in output_objs],
                progress_message=("Archiving Swift objects %s" % ctx.label.name))
 
+  # This tells the linker to write a reference to .swiftmodule as an AST symbol
+  # in the final binary.
+  # With dSYM enabled, this results in a __DWARF,__swift_ast section added to
+  # the dSYM binary, from where LLDB is able deserialize module information.
+  # Without dSYM, LLDB will follow the AST references, however there is a bug
+  # where it follows only the first one https://bugs.swift.org/browse/SR-2637
+  # This means that dSYM is required for debugging until that is resolved.
+  extra_linker_args = ["-Xlinker -add_ast_path -Xlinker " + output_module.path]
+
   objc_provider = apple_common.new_objc_provider(
       library=set([output_lib] + dep_libs),
       header=set([output_header]),
@@ -364,18 +398,21 @@ def _swift_library_impl(ctx):
       objc=objc_provider,
       files=set([output_lib, output_module, output_header]))
 
+SWIFT_LIBRARY_ATTRS = {
+    "srcs": attr.label_list(allow_files = [".swift"], allow_empty=False),
+    "deps": attr.label_list(providers=[["swift"], ["objc"]]),
+    "module_name": attr.string(mandatory=False),
+    "defines": attr.string_list(mandatory=False, allow_empty=True),
+    "copts": attr.string_list(mandatory=False, allow_empty=True),
+    "_xcrunwrapper": attr.label(
+        executable=True,
+        cfg="host",
+        default=Label(XCRUNWRAPPER_LABEL))
+}
+
 swift_library = rule(
     _swift_library_impl,
-    attrs = {
-        "srcs": attr.label_list(allow_files = [".swift"], allow_empty=False),
-        "deps": attr.label_list(providers=[["swift"], ["objc"]]),
-        "module_name": attr.string(mandatory=False),
-        "defines": attr.string_list(mandatory=False, allow_empty=True),
-        "copts": attr.string_list(mandatory=False, allow_empty=True),
-        "_xcrunwrapper": attr.label(
-            executable=True,
-            cfg="host",
-            default=Label(XCRUNWRAPPER_LABEL))},
+    attrs = SWIFT_LIBRARY_ATTRS,
     fragments = ["apple", "objc"],
     output_to_genfiles=True,
 )