From aff1754b064898fde731a64622840535f8dd7165 Mon Sep 17 00:00:00 2001
From: Benjamin Peterson <benjamin@python.org>
Date: Fri, 6 Nov 2020 16:56:35 -0600
Subject: [PATCH] Migrate to the modern Starlark linker input API. (#512)

See https://github.com/bazelbuild/bazel/issues/10860.
---
 swift/internal/linking.bzl                 | 40 +++++++++++++-----
 swift/internal/swift_binary_test.bzl       |  1 +
 swift/internal/swift_grpc_library.bzl      | 11 +++--
 swift/internal/swift_import.bzl            | 22 ++++++----
 swift/internal/swift_library.bzl           | 13 +++---
 swift/internal/swift_module_alias.bzl      | 12 +++---
 swift/internal/swift_protoc_gen_aspect.bzl | 11 +++--
 swift/internal/utils.bzl                   | 49 +++++++---------------
 test/private_deps_tests.bzl                |  2 +-
 test/rules/provider_test.bzl               |  9 +++-
 test/split_derived_files_tests.bzl         |  6 +--
 11 files changed, 100 insertions(+), 76 deletions(-)

diff --git a/swift/internal/linking.bzl b/swift/internal/linking.bzl
index 613c77ff2..ac8a87c27 100644
--- a/swift/internal/linking.bzl
+++ b/swift/internal/linking.bzl
@@ -95,6 +95,7 @@ def _register_static_library_link_action(
     )
 
 def register_libraries_to_link(
+        owning_label,
         actions,
         alwayslink,
         cc_feature_configuration,
@@ -102,10 +103,13 @@ def register_libraries_to_link(
         is_static,
         library_name,
         objects,
-        swift_toolchain):
+        swift_toolchain,
+        user_link_flags,
+        additional_inputs):
     """Declares the requested libraries and registers actions to link them.
 
     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
@@ -120,9 +124,11 @@ def register_libraries_to_link(
             linked.
         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.
 
     Returns:
-        A `LibraryToLink` object containing the libraries that were created.
+        A `LinkerInput` object containing the libraries that were created.
     """
     dynamic_library = None
     if is_dynamic:
@@ -145,16 +151,24 @@ def register_libraries_to_link(
     else:
         static_library = None
 
-    return 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,
+    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),
     )
 
 def register_link_binary_action(
+        owning_label,
         actions,
         additional_inputs,
         additional_linking_contexts,
@@ -170,6 +184,7 @@ def register_link_binary_action(
     """Registers an action that invokes the linker to produce a binary.
 
     Args:
+        owning_label: Label of the rule creating the link action.
         actions: The object used to register actions.
         additional_inputs: A list of additional inputs to the link action,
             such as those used in `$(location ...)` substitution, linker
@@ -231,7 +246,12 @@ def register_link_binary_action(
 
             linking_contexts.append(
                 cc_common.create_linking_context(
-                    user_link_flags = dep_link_flags,
+                    linker_inputs = depset(direct = [
+                        cc_common.create_linker_input(
+                            owner = owning_label,
+                            user_link_flags = depset(direct = dep_link_flags),
+                        ),
+                    ])
                 ),
             )
 
diff --git a/swift/internal/swift_binary_test.bzl b/swift/internal/swift_binary_test.bzl
index 6d0d544d3..bfbc80d93 100644
--- a/swift/internal/swift_binary_test.bzl
+++ b/swift/internal/swift_binary_test.bzl
@@ -237,6 +237,7 @@ def _swift_linking_rule_impl(
     user_link_flags.extend(ctx.fragments.cpp.linkopts)
 
     linking_outputs = register_link_binary_action(
+        owning_label = ctx.label,
         actions = ctx.actions,
         additional_inputs = additional_inputs_to_linker,
         additional_linking_contexts = additional_linking_contexts,
diff --git a/swift/internal/swift_grpc_library.bzl b/swift/internal/swift_grpc_library.bzl
index 5688ac18c..29ffa6f46 100644
--- a/swift/internal/swift_grpc_library.bzl
+++ b/swift/internal/swift_grpc_library.bzl
@@ -293,7 +293,8 @@ def _swift_grpc_library_impl(ctx):
         target_name = ctx.label.name,
     )
 
-    library_to_link = register_libraries_to_link(
+    linker_input = register_libraries_to_link(
+        owning_label = ctx.label,
         actions = ctx.actions,
         alwayslink = False,
         cc_feature_configuration = swift_common.cc_feature_configuration(
@@ -304,6 +305,8 @@ def _swift_grpc_library_impl(ctx):
         library_name = ctx.label.name,
         objects = compilation_outputs.object_files,
         swift_toolchain = swift_toolchain,
+        additional_inputs = compilation_outputs.linker_inputs,
+        user_link_flags = compilation_outputs.linker_flags,
     )
 
     providers = [
@@ -311,7 +314,7 @@ def _swift_grpc_library_impl(ctx):
             files = depset(direct = generated_files + compact([
                 compilation_outputs.swiftdoc,
                 compilation_outputs.swiftmodule,
-                library_to_link.pic_static_library,
+                linker_input.libraries[0].pic_static_library,
             ])),
         ),
         OutputGroupInfo(**output_groups_from_compilation_outputs(
@@ -320,7 +323,7 @@ def _swift_grpc_library_impl(ctx):
         create_cc_info(
             cc_infos = get_providers(compile_deps, CcInfo),
             compilation_outputs = compilation_outputs,
-            libraries_to_link = [library_to_link],
+            linker_inputs = [linker_input],
         ),
         deps[0][SwiftProtoInfo],
         swift_common.create_swift_info(
@@ -346,7 +349,7 @@ def _swift_grpc_library_impl(ctx):
             link_inputs = compilation_outputs.linker_inputs,
             linkopts = compilation_outputs.linker_flags,
             module_map = compilation_outputs.generated_module_map,
-            static_archives = compact([library_to_link.pic_static_library]),
+            static_archives = compact([linker_input.libraries[0].pic_static_library]),
             swiftmodules = [compilation_outputs.swiftmodule],
             objc_header = compilation_outputs.generated_header,
         ))
diff --git a/swift/internal/swift_import.bzl b/swift/internal/swift_import.bzl
index 7fdfd3f31..10fc0c7ec 100644
--- a/swift/internal/swift_import.bzl
+++ b/swift/internal/swift_import.bzl
@@ -38,14 +38,18 @@ def _swift_import_impl(ctx):
         unsupported_features = ctx.disabled_features,
     )
 
-    libraries_to_link = [
-        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_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
+            ]),
+        ),
     ]
 
     providers = [
@@ -59,7 +63,7 @@ def _swift_import_impl(ctx):
         ),
         create_cc_info(
             cc_infos = get_providers(deps, CcInfo),
-            libraries_to_link = libraries_to_link,
+            linker_inputs = linker_inputs,
         ),
         # Propagate an `Objc` provider so that Apple-specific rules like
         # apple_binary` will link the imported library properly. Typically we'd
diff --git a/swift/internal/swift_library.bzl b/swift/internal/swift_library.bzl
index 374b5184e..706eb6a1b 100644
--- a/swift/internal/swift_library.bzl
+++ b/swift/internal/swift_library.bzl
@@ -179,7 +179,8 @@ def _swift_library_impl(ctx):
     else:
         clang_module = None
 
-    library_to_link = register_libraries_to_link(
+    linker_input = register_libraries_to_link(
+        owning_label = ctx.label,
         actions = ctx.actions,
         alwayslink = ctx.attr.alwayslink,
         cc_feature_configuration = swift_common.cc_feature_configuration(
@@ -190,6 +191,8 @@ def _swift_library_impl(ctx):
         library_name = ctx.label.name,
         objects = compilation_outputs.object_files,
         swift_toolchain = swift_toolchain,
+        user_link_flags = linkopts,
+        additional_inputs = compilation_outputs.linker_inputs,
     )
 
     direct_output_files = compact([
@@ -197,7 +200,7 @@ def _swift_library_impl(ctx):
         compilation_outputs.swiftdoc,
         compilation_outputs.swiftinterface,
         compilation_outputs.swiftmodule,
-        library_to_link.pic_static_library,
+        linker_input.libraries[0].pic_static_library,
     ])
 
     providers = [
@@ -213,14 +216,12 @@ def _swift_library_impl(ctx):
             compilation_outputs = compilation_outputs,
         )),
         create_cc_info(
-            additional_inputs = additional_inputs,
             cc_infos = get_providers(deps, CcInfo),
             compilation_outputs = compilation_outputs,
             defines = ctx.attr.defines,
             includes = [ctx.bin_dir.path],
-            libraries_to_link = [library_to_link],
+            linker_inputs = [linker_input],
             private_cc_infos = get_providers(private_deps, CcInfo),
-            user_link_flags = linkopts,
         ),
         coverage_common.instrumented_files_info(
             ctx,
@@ -261,7 +262,7 @@ def _swift_library_impl(ctx):
             link_inputs = compilation_outputs.linker_inputs + additional_inputs,
             linkopts = compilation_outputs.linker_flags + linkopts,
             module_map = compilation_outputs.generated_module_map,
-            static_archives = compact([library_to_link.pic_static_library]),
+            static_archives = compact([linker_input.libraries[0].pic_static_library]),
             swiftmodules = [compilation_outputs.swiftmodule],
             objc_header = compilation_outputs.generated_header,
         ))
diff --git a/swift/internal/swift_module_alias.bzl b/swift/internal/swift_module_alias.bzl
index 55a57bf7c..217b7798c 100644
--- a/swift/internal/swift_module_alias.bzl
+++ b/swift/internal/swift_module_alias.bzl
@@ -72,7 +72,8 @@ def _swift_module_alias_impl(ctx):
         target_name = ctx.label.name,
     )
 
-    library_to_link = register_libraries_to_link(
+    linker_input = register_libraries_to_link(
+        owning_label = ctx.label,
         actions = ctx.actions,
         alwayslink = False,
         cc_feature_configuration = swift_common.cc_feature_configuration(
@@ -83,6 +84,7 @@ def _swift_module_alias_impl(ctx):
         library_name = ctx.label.name,
         objects = compilation_outputs.object_files,
         swift_toolchain = swift_toolchain,
+        additional_inputs = compilation_outputs.linker_inputs,
     )
 
     providers = [
@@ -90,8 +92,8 @@ def _swift_module_alias_impl(ctx):
             files = depset(compact([
                 compilation_outputs.swiftdoc,
                 compilation_outputs.swiftmodule,
-                library_to_link.dynamic_library,
-                library_to_link.pic_static_library,
+                linker_input.libraries[0].dynamic_library,
+                linker_input.libraries[0].pic_static_library,
             ])),
         ),
         OutputGroupInfo(**output_groups_from_compilation_outputs(
@@ -105,7 +107,7 @@ def _swift_module_alias_impl(ctx):
             cc_infos = get_providers(deps, CcInfo),
             compilation_outputs = compilation_outputs,
             includes = [ctx.bin_dir.path],
-            libraries_to_link = [library_to_link],
+            linker_inputs = [linker_input],
         ),
         swift_common.create_swift_info(
             modules = [
@@ -130,7 +132,7 @@ def _swift_module_alias_impl(ctx):
             link_inputs = compilation_outputs.linker_inputs,
             linkopts = compilation_outputs.linker_flags,
             module_map = compilation_outputs.generated_module_map,
-            static_archives = compact([library_to_link.pic_static_library]),
+            static_archives = compact([linker_input.libraries[0].pic_static_library]),
             swiftmodules = [compilation_outputs.swiftmodule],
             objc_header = compilation_outputs.generated_header,
         ))
diff --git a/swift/internal/swift_protoc_gen_aspect.bzl b/swift/internal/swift_protoc_gen_aspect.bzl
index 091013a9e..45f78837a 100644
--- a/swift/internal/swift_protoc_gen_aspect.bzl
+++ b/swift/internal/swift_protoc_gen_aspect.bzl
@@ -428,7 +428,8 @@ def _swift_protoc_gen_aspect_impl(target, aspect_ctx):
             target_name = target.label.name,
         )
 
-        library_to_link = register_libraries_to_link(
+        linker_input = register_libraries_to_link(
+            owning_label = aspect_ctx.label,
             actions = aspect_ctx.actions,
             alwayslink = False,
             cc_feature_configuration = swift_common.cc_feature_configuration(
@@ -442,6 +443,8 @@ def _swift_protoc_gen_aspect_impl(target, aspect_ctx):
             library_name = "{}.swift".format(target.label.name),
             objects = compilation_outputs.object_files,
             swift_toolchain = swift_toolchain,
+            additional_inputs = compilation_outputs.linker_inputs,
+            user_link_flags = compilation_outputs.linker_flags,
         )
 
         # It's bad practice to attach providers you don't own to other targets,
@@ -477,9 +480,9 @@ def _swift_protoc_gen_aspect_impl(target, aspect_ctx):
                 objc_info_args["header"] = depset([
                     compilation_outputs.generated_header,
                 ])
-            if library_to_link.pic_static_library:
+            if linker_input.libraries[0].pic_static_library:
                 objc_info_args["library"] = depset(
-                    [library_to_link.pic_static_library],
+                    [linker_input.libraries[0].pic_static_library],
                     order = "topological",
                 )
             if compilation_outputs.linker_flags:
@@ -516,7 +519,7 @@ def _swift_protoc_gen_aspect_impl(target, aspect_ctx):
                     cc_infos = cc_infos,
                     compilation_outputs = compilation_outputs,
                     includes = includes,
-                    libraries_to_link = [library_to_link],
+                    linker_inputs = [linker_input],
                 ),
                 objc_info = objc_info,
             ),
diff --git a/swift/internal/utils.bzl b/swift/internal/utils.bzl
index b4e41d85f..fcda609af 100644
--- a/swift/internal/utils.bzl
+++ b/swift/internal/utils.bzl
@@ -41,25 +41,20 @@ def collect_cc_libraries(
     """
     libraries = []
 
-    # TODO(https://github.com/bazelbuild/bazel/issues/8118): Remove once flag is
-    # flipped.
-    libraries_to_link = cc_info.linking_context.libraries_to_link
-    if hasattr(libraries_to_link, "to_list"):
-        libraries_to_link = libraries_to_link.to_list()
-
-    for library in libraries_to_link:
-        if include_pic_static:
-            if library.pic_static_library:
-                libraries.append(library.pic_static_library)
-            elif library.static_library:
+    for li in cc_info.linking_context.linker_inputs.to_list():
+        for library in li.libraries:
+            if include_pic_static:
+                if library.pic_static_library:
+                    libraries.append(library.pic_static_library)
+                elif library.static_library:
+                    libraries.append(library.static_library)
+            elif include_static and library.static_library:
                 libraries.append(library.static_library)
-        elif include_static and library.static_library:
-            libraries.append(library.static_library)
 
-        if include_dynamic and library.dynamic_library:
-            libraries.append(library.dynamic_library)
-        if include_interface and library.interface_library:
-            libraries.append(library.interface_library)
+            if include_dynamic and library.dynamic_library:
+                libraries.append(library.dynamic_library)
+            if include_interface and library.interface_library:
+                libraries.append(library.interface_library)
 
     return libraries
 
@@ -74,19 +69,15 @@ def compact(sequence):
     return [item for item in sequence if item != None]
 
 def create_cc_info(
-        additional_inputs = [],
         cc_infos = [],
         compilation_outputs = None,
         defines = [],
         includes = [],
-        libraries_to_link = [],
-        private_cc_infos = [],
-        user_link_flags = []):
+        linker_inputs = [],
+        private_cc_infos = []):
     """Creates a `CcInfo` provider from Swift compilation info and deps.
 
     Args:
-        additional_inputs: A list of additional files that should be passed as
-            inputs to the final link action.
         cc_infos: A list of `CcInfo` providers from public dependencies, whose
             compilation and linking contexts should both be merged into the new
             provider.
@@ -96,32 +87,24 @@ def create_cc_info(
             context.
         includes: The list of include paths to insert into the compilation
             context.
-        libraries_to_link: A list of `LibraryToLink` objects that represent the
+        linker_inputs: A list of `LinkerInput` objects that represent the
             libraries that should be linked into the final binary.
         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
             be excluded.
-        user_link_flags: A list of flags that should be passed to the final link
-            action.
 
     Returns:
         A new `CcInfo`.
     """
-    all_additional_inputs = list(additional_inputs)
-    all_user_link_flags = list(user_link_flags)
     all_headers = []
     if compilation_outputs:
-        all_additional_inputs.extend(compilation_outputs.linker_inputs)
-        all_user_link_flags.extend(compilation_outputs.linker_flags)
         all_headers = compact([compilation_outputs.generated_header])
 
     local_cc_infos = [
         CcInfo(
             linking_context = cc_common.create_linking_context(
-                additional_inputs = all_additional_inputs,
-                libraries_to_link = libraries_to_link,
-                user_link_flags = all_user_link_flags,
+                linker_inputs = depset(direct = linker_inputs),
             ),
             compilation_context = cc_common.create_compilation_context(
                 defines = depset(defines),
diff --git a/test/private_deps_tests.bzl b/test/private_deps_tests.bzl
index 1afd6b10e..148777462 100644
--- a/test/private_deps_tests.bzl
+++ b/test/private_deps_tests.bzl
@@ -115,7 +115,7 @@ def private_deps_test_suite(name = "private_deps"):
             # dependencies, which we need to ignore.
             "*",
         ],
-        field = "linking_context.libraries_to_link.static_library!",
+        field = "linking_context.linker_inputs.libraries.static_library!",
         provider = "CcInfo",
         tags = [name],
         target_under_test = "@build_bazel_rules_swift//test/fixtures/private_deps:client_cc_deps",
diff --git a/test/rules/provider_test.bzl b/test/rules/provider_test.bzl
index 42799fa79..b9cf0b762 100644
--- a/test/rules/provider_test.bzl
+++ b/test/rules/provider_test.bzl
@@ -85,7 +85,14 @@ def _evaluate_field(env, source, field):
                 )
                 return _EVALUATE_FIELD_FAILED
 
-            source = [getattr(item, component, None) for item in source]
+            expanded = []
+            for item in source:
+                item = _normalize_collection(item)
+                if types.is_list(item):
+                    expanded.extend(item)
+                else:
+                    expanded.append(item)
+            source = [getattr(item, component, None) for item in expanded]
             if filter_nones:
                 source = [item for item in source if item != None]
         else:
diff --git a/test/split_derived_files_tests.bzl b/test/split_derived_files_tests.bzl
index 2eeb17664..34839ebae 100644
--- a/test/split_derived_files_tests.bzl
+++ b/test/split_derived_files_tests.bzl
@@ -114,7 +114,7 @@ def split_derived_files_test_suite(name = "split_derived_files"):
         expected_files = [
             "libsimple.a",
         ],
-        field = "linking_context.libraries_to_link.pic_static_library!",
+        field = "linking_context.linker_inputs.libraries.pic_static_library!",
         provider = "CcInfo",
         tags = [name],
         target_under_test = "@build_bazel_rules_swift//test/fixtures/debug_settings:simple",
@@ -162,7 +162,7 @@ def split_derived_files_test_suite(name = "split_derived_files"):
         expected_files = [
             "libsimple.a",
         ],
-        field = "linking_context.libraries_to_link.pic_static_library!",
+        field = "linking_context.linker_inputs.libraries.pic_static_library!",
         provider = "CcInfo",
         tags = [name],
         target_under_test = "@build_bazel_rules_swift//test/fixtures/debug_settings:simple",
@@ -212,7 +212,7 @@ def split_derived_files_test_suite(name = "split_derived_files"):
         expected_files = [
             "libsimple.a",
         ],
-        field = "linking_context.libraries_to_link.pic_static_library!",
+        field = "linking_context.linker_inputs.libraries.pic_static_library!",
         provider = "CcInfo",
         tags = [name],
         target_under_test = "@build_bazel_rules_swift//test/fixtures/debug_settings:simple",