Migrate Swift build rules to the new C++ LinkerInput APIs.

swift/internal/linking.bzl

@@ -94,41 +94,49 @@ def _register_static_library_link_action(
         progress_message = "Linking {}".format(output.short_path),
     )
 
-def register_libraries_to_link(
-        owning_label,
+def create_linker_input(
+        *,
         actions,
         alwayslink,
         cc_feature_configuration,
+        compilation_outputs,
         is_dynamic,
         is_static,
         library_name,
         objects,
+        owner,
         swift_toolchain,
-        user_link_flags,
-        additional_inputs):
-    """Declares the requested libraries and registers actions to link them.
+        additional_inputs = [],
+        user_link_flags = []):
+    """Creates a linker input for a library to link and additional inputs/flags.
 
     Args:
-        owning_label: Label executing rule (i.e., ctx.label).
         actions: The object used to register actions.
         alwayslink: If True, create a static library that should be
             always-linked (having a `.lo` extension instead of `.a`). This
             argument is ignored if `is_static` is False.
         cc_feature_configuration: The C++ feature configuration to use when
             constructing the action.
+        compilation_outputs: The compilation outputs from a Swift compile
+            action, as returned by `swift_common.compile`, or None.
         is_dynamic: If True, declare and link a dynamic library.
         is_static: If True, declare and link a static library.
         library_name: The basename (without extension) of the libraries to
             declare.
         objects: A list of `File`s denoting object (`.o`) files that will be
             linked.
+        owner: The `Label` of the target that owns this linker input.
         swift_toolchain: The Swift toolchain provider to use when constructing
             the action.
-        user_link_flags: Extra link flags to be passed with the library.
-        additional_inputs: Extra inputs for a link action involving the library.
+        additional_inputs: A list of extra `File` inputs passed to the linking
+            action.
+        user_link_flags: A list of extra flags to pass to the linking command.
 
     Returns:
-        A `LinkerInput` object containing the libraries that were created.
+        A tuple containing two elements:
+
+        1.  A `LinkerInput` object containing the library that was created.
+        2.  The single `LibraryToLink` object that is inside the linker input.
     """
     dynamic_library = None
     if is_dynamic:
@@ -151,21 +159,26 @@ def register_libraries_to_link(
     else:
         static_library = None
 
-    return cc_common.create_linker_input(
-        owner = owning_label,
-        libraries = depset(direct = [
-            cc_common.create_library_to_link(
-                actions = actions,
-                alwayslink = alwayslink,
-                cc_toolchain = swift_toolchain.cc_toolchain_info,
-                feature_configuration = cc_feature_configuration,
-                pic_static_library = static_library,
-                dynamic_library = dynamic_library,
-            ),
-        ]),
-        additional_inputs = depset(direct = additional_inputs),
-        user_link_flags = depset(direct = user_link_flags),
+    library_to_link = cc_common.create_library_to_link(
+        actions = actions,
+        alwayslink = alwayslink,
+        cc_toolchain = swift_toolchain.cc_toolchain_info,
+        feature_configuration = cc_feature_configuration,
+        pic_static_library = static_library,
+        dynamic_library = dynamic_library,
     )
+    linker_input = cc_common.create_linker_input(
+        owner = owner,
+        libraries = depset([library_to_link]),
+        additional_inputs = depset(
+            compilation_outputs.linker_inputs + additional_inputs,
+        ),
+        user_link_flags = depset(
+            compilation_outputs.linker_flags + user_link_flags,
+        ),
+    )
+
+    return linker_input, library_to_link
 
 def register_link_binary_action(
         owning_label,
@@ -178,6 +191,7 @@ def register_link_binary_action(
         name,
         objects,
         output_type,
+        owner,
         stamp,
         swift_toolchain,
         user_link_flags):
@@ -201,6 +215,7 @@ def register_link_binary_action(
         objects: A list of object (.o) files that will be passed to the linker.
         output_type: A string indicating the output type; "executable" or
             "dynamic_library".
+        owner: The `Label` of the target that owns this linker input.
         stamp: A tri-state value (-1, 0, or 1) that specifies whether link
             stamping is enabled. See `cc_common.link` for details about the
             behavior of this argument.
@@ -246,12 +261,12 @@ def register_link_binary_action(
 
             linking_contexts.append(
                 cc_common.create_linking_context(
-                    linker_inputs = depset(direct = [
+                    linker_inputs = depset([
                         cc_common.create_linker_input(
-                            owner = owning_label,
-                            user_link_flags = depset(direct = dep_link_flags),
+                            owner = owner,
+                            user_link_flags = depset(dep_link_flags),
                         ),
-                    ])
+                    ]),
                 ),
             )
 

swift/internal/swift_binary_test.bzl

@@ -247,6 +247,7 @@ def _swift_linking_rule_impl(
         name = ctx.label.name,
         objects = objects_to_link,
         output_type = "executable",
+        owner = ctx.label,
         stamp = ctx.attr.stamp,
         swift_toolchain = swift_toolchain,
         user_link_flags = user_link_flags,

swift/internal/swift_grpc_library.bzl

@@ -27,7 +27,7 @@ load(
     "SWIFT_FEATURE_GENERATE_FROM_RAW_PROTO_FILES",
     "SWIFT_FEATURE_NO_GENERATED_HEADER",
 )
-load(":linking.bzl", "register_libraries_to_link")
+load(":linking.bzl", "create_linker_input")
 load(
     ":proto_gen_utils.bzl",
     "declare_generated_files",
@@ -293,17 +293,18 @@ def _swift_grpc_library_impl(ctx):
         target_name = ctx.label.name,
     )
 
-    linker_input = register_libraries_to_link(
-        owning_label = ctx.label,
+    linker_input, library_to_link = create_linker_input(
         actions = ctx.actions,
         alwayslink = False,
         cc_feature_configuration = swift_common.cc_feature_configuration(
             feature_configuration = feature_configuration,
         ),
+        compilation_outputs = compilation_outputs,
         is_dynamic = False,
         is_static = True,
         library_name = ctx.label.name,
         objects = compilation_outputs.object_files,
+        owner = ctx.label,
         swift_toolchain = swift_toolchain,
         additional_inputs = compilation_outputs.linker_inputs,
         user_link_flags = compilation_outputs.linker_flags,

swift/internal/swift_import.bzl

@@ -38,19 +38,18 @@ def _swift_import_impl(ctx):
         unsupported_features = ctx.disabled_features,
     )
 
-    linker_inputs = [
-        cc_common.create_linker_input(
-            libraries = depset(direct = [
-                cc_common.create_library_to_link(
-                    actions = ctx.actions,
-                    cc_toolchain = cc_toolchain,
-                    feature_configuration = cc_feature_configuration,
-                    static_library = archive,
-                )
-                for archive in archives
-            ]),
-        ),
-    ]
+    linker_input = cc_common.create_linker_input(
+        owner = ctx.label,
+        libraries = depset([
+            cc_common.create_library_to_link(
+                actions = ctx.actions,
+                cc_toolchain = cc_toolchain,
+                feature_configuration = cc_feature_configuration,
+                static_library = archive,
+            )
+            for archive in archives
+        ]),
+    )
 
     providers = [
         DefaultInfo(
@@ -63,7 +62,7 @@ def _swift_import_impl(ctx):
         ),
         create_cc_info(
             cc_infos = get_providers(deps, CcInfo),
-            linker_inputs = linker_inputs,
+            linker_inputs = [linker_input],
         ),
         # Propagate an `Objc` provider so that Apple-specific rules like
         # apple_binary` will link the imported library properly. Typically we'd

swift/internal/swift_library.bzl

@@ -28,7 +28,7 @@ load(
     "SWIFT_FEATURE_ENABLE_LIBRARY_EVOLUTION",
     "SWIFT_FEATURE_SUPPORTS_PRIVATE_DEPS",
 )
-load(":linking.bzl", "register_libraries_to_link")
+load(":linking.bzl", "create_linker_input")
 load(":providers.bzl", "SwiftInfo", "SwiftToolchainInfo")
 load(":swift_common.bzl", "swift_common")
 load(
@@ -179,20 +179,21 @@ def _swift_library_impl(ctx):
     else:
         clang_module = None
 
-    linker_input = register_libraries_to_link(
-        owning_label = ctx.label,
+    linker_input, library_to_link = create_linker_input(
         actions = ctx.actions,
+        additional_inputs = additional_inputs,
         alwayslink = ctx.attr.alwayslink,
         cc_feature_configuration = swift_common.cc_feature_configuration(
             feature_configuration = feature_configuration,
         ),
+        compilation_outputs = compilation_outputs,
         is_dynamic = False,
         is_static = True,
         library_name = ctx.label.name,
         objects = compilation_outputs.object_files,
+        owner = ctx.label,
         swift_toolchain = swift_toolchain,
         user_link_flags = linkopts,
-        additional_inputs = compilation_outputs.linker_inputs,
     )
 
     direct_output_files = compact([

swift/internal/swift_module_alias.bzl

@@ -21,7 +21,7 @@ load(
     "output_groups_from_compilation_outputs",
 )
 load(":derived_files.bzl", "derived_files")
-load(":linking.bzl", "register_libraries_to_link")
+load(":linking.bzl", "create_linker_input")
 load(":providers.bzl", "SwiftInfo", "SwiftToolchainInfo")
 load(":swift_common.bzl", "swift_common")
 load(":utils.bzl", "compact", "create_cc_info", "get_providers")
@@ -72,17 +72,18 @@ def _swift_module_alias_impl(ctx):
         target_name = ctx.label.name,
     )
 
-    linker_input = register_libraries_to_link(
-        owning_label = ctx.label,
+    linker_input, library_to_link = create_linker_input(
         actions = ctx.actions,
         alwayslink = False,
         cc_feature_configuration = swift_common.cc_feature_configuration(
             feature_configuration = feature_configuration,
         ),
+        compilation_outputs = compilation_outputs,
         is_dynamic = False,
         is_static = True,
         library_name = ctx.label.name,
         objects = compilation_outputs.object_files,
+        owner = ctx.label,
         swift_toolchain = swift_toolchain,
         additional_inputs = compilation_outputs.linker_inputs,
     )

swift/internal/swift_protoc_gen_aspect.bzl

@@ -27,7 +27,7 @@ load(
     "SWIFT_FEATURE_GENERATE_FROM_RAW_PROTO_FILES",
     "SWIFT_FEATURE_NO_GENERATED_HEADER",
 )
-load(":linking.bzl", "register_libraries_to_link")
+load(":linking.bzl", "create_linker_input")
 load(
     ":proto_gen_utils.bzl",
     "declare_generated_files",
@@ -428,20 +428,21 @@ def _swift_protoc_gen_aspect_impl(target, aspect_ctx):
             target_name = target.label.name,
         )
 
-        linker_input = register_libraries_to_link(
-            owning_label = aspect_ctx.label,
+        linker_input, library_to_link = create_linker_input(
             actions = aspect_ctx.actions,
             alwayslink = False,
             cc_feature_configuration = swift_common.cc_feature_configuration(
                 feature_configuration = feature_configuration,
             ),
+            compilation_outputs = compilation_outputs,
             is_dynamic = False,
             is_static = True,
             # Prevent conflicts with C++ protos in the same output directory,
             # which use the `lib{name}.a` pattern. This will produce
             # `lib{name}.swift.a` instead.
             library_name = "{}.swift".format(target.label.name),
             objects = compilation_outputs.object_files,
+            owner = target.label,
             swift_toolchain = swift_toolchain,
             additional_inputs = compilation_outputs.linker_inputs,
             user_link_flags = compilation_outputs.linker_flags,

swift/internal/utils.bzl

@@ -41,8 +41,8 @@ def collect_cc_libraries(
     """
     libraries = []
 
-    for li in cc_info.linking_context.linker_inputs.to_list():
-        for library in li.libraries:
+    for linker_input in cc_info.linking_context.linker_inputs.to_list():
+        for library in linker_input.libraries:
             if include_pic_static:
                 if library.pic_static_library:
                     libraries.append(library.pic_static_library)
@@ -69,6 +69,7 @@ def compact(sequence):
     return [item for item in sequence if item != None]
 
 def create_cc_info(
+        *,
         cc_infos = [],
         compilation_outputs = None,
         defines = [],
@@ -88,7 +89,8 @@ def create_cc_info(
         includes: The list of include paths to insert into the compilation
             context.
         linker_inputs: A list of `LinkerInput` objects that represent the
-            libraries that should be linked into the final binary.
+            libraries that should be linked into the final binary as well as any
+            additional inputs and flags that should be passed to the linker.
         private_cc_infos: A list of `CcInfo` providers from private
             (implementation-only) dependencies, whose linking contexts should be
             merged into the new provider but whose compilation contexts should
@@ -104,7 +106,7 @@ def create_cc_info(
     local_cc_infos = [
         CcInfo(
             linking_context = cc_common.create_linking_context(
-                linker_inputs = depset(direct = linker_inputs),
+                linker_inputs = depset(linker_inputs),
             ),
             compilation_context = cc_common.create_compilation_context(
                 defines = depset(defines),

test/rules/provider_test.bzl

@@ -85,14 +85,16 @@ def _evaluate_field(env, source, field):
                 )
                 return _EVALUATE_FIELD_FAILED
 
-            expanded = []
+            # If the elements are lists or depsets, flatten the whole thing into
+            # a single list.
+            flattened = []
             for item in source:
                 item = _normalize_collection(item)
                 if types.is_list(item):
-                    expanded.extend(item)
+                    flattened.extend(item)
                 else:
-                    expanded.append(item)
-            source = [getattr(item, component, None) for item in expanded]
+                    flattened.append(item)
+            source = [getattr(item, component, None) for item in flattened]
             if filter_nones:
                 source = [item for item in source if item != None]
         else: