Add Apple static library linking Starlark API

Introduces new Apple static library linking API refactoring existing
`apple_static_library` Starlark rule, and exposing linking logic under:
  - `apple_common.link_multi_arch_static_library`

RELNOTES: Introduces experimental static library linking API under apple_common.link_multi_arch_static_library
PiperOrigin-RevId: 431539590

src/main/java/com/google/devtools/build/lib/rules/objc/AppleLinkingOutputs.java

@@ -20,8 +20,14 @@
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
+import com.google.devtools.build.lib.packages.BuiltinProvider;
+import com.google.devtools.build.lib.packages.Provider;
+import com.google.devtools.build.lib.packages.StarlarkInfo;
+import com.google.devtools.build.lib.packages.StructImpl;
+import java.util.HashMap;
 import java.util.Map;
 import javax.annotation.Nullable;
+import net.starlark.java.syntax.Location;
 
 /**
  * The providers and artifact outputs returned by the {@code apple_common.link_multi_arch_binary}
@@ -41,6 +47,16 @@ static TargetTriplet create(String architecture, String platform, String environ
     abstract String platform();
 
     abstract String environment();
+
+    /** Returns a Starlark Dict representation of a {@link TargetTriplet} */
+    public final StructImpl toStarlarkStruct() {
+      Provider constructor = new BuiltinProvider<StructImpl>("target_triplet", StructImpl.class) {};
+      HashMap<String, Object> fields = new HashMap<>();
+      fields.put("architecture", architecture());
+      fields.put("environment", environment());
+      fields.put("platform", platform());
+      return StarlarkInfo.create(constructor, fields, Location.BUILTIN);
+    }
   }
 
   /**

src/main/java/com/google/devtools/build/lib/rules/objc/AppleStarlarkCommon.java

@@ -45,12 +45,14 @@
 import com.google.devtools.build.lib.rules.objc.ObjcProvider.Flag;
 import com.google.devtools.build.lib.starlarkbuildapi.SplitTransitionProviderApi;
 import com.google.devtools.build.lib.starlarkbuildapi.apple.AppleCommonApi;
+import java.util.HashMap;
 import java.util.Map;
 import javax.annotation.Nullable;
 import net.starlark.java.eval.Dict;
 import net.starlark.java.eval.EvalException;
 import net.starlark.java.eval.Sequence;
 import net.starlark.java.eval.Starlark;
+import net.starlark.java.eval.StarlarkFunction;
 import net.starlark.java.eval.StarlarkInt;
 import net.starlark.java.eval.StarlarkList;
 import net.starlark.java.eval.StarlarkThread;
@@ -285,6 +287,29 @@ public StructImpl linkMultiArchBinary(
     }
   }
 
+  @Override
+  public StructImpl linkMultiArchStaticLibrary(
+      StarlarkRuleContext starlarkRuleContext, StarlarkThread thread)
+      throws EvalException, InterruptedException {
+    try {
+      RuleContext ruleContext = starlarkRuleContext.getRuleContext();
+      StarlarkFunction linkMultiArchLibrary =
+          (StarlarkFunction)
+              ruleContext.getStarlarkDefinedBuiltin("link_multi_arch_static_library");
+      Dict<String, StructImpl> splitTargetTriplets =
+          MultiArchBinarySupport.getSplitTargetTripletFromCtads(
+              ruleContext.getSplitPrerequisiteConfiguredTargetAndTargets(
+                  ObjcRuleClasses.CHILD_CONFIG_ATTR));
+      return (StructImpl)
+          ruleContext.callStarlarkOrThrowRuleError(
+              linkMultiArchLibrary,
+              ImmutableList.of(ruleContext.getStarlarkRuleContext(), splitTargetTriplets),
+              new HashMap<>());
+    } catch (RuleErrorException exception) {
+      throw new EvalException(exception);
+    }
+  }
+
   @Override
   public DottedVersion dottedVersion(String version) throws EvalException {
     try {

src/main/java/com/google/devtools/build/lib/rules/objc/MultiArchBinarySupport.java

@@ -36,6 +36,7 @@
 import com.google.devtools.build.lib.packages.BuiltinProvider;
 import com.google.devtools.build.lib.packages.Info;
 import com.google.devtools.build.lib.packages.RuleClass.ConfiguredTargetFactory.RuleErrorException;
+import com.google.devtools.build.lib.packages.StructImpl;
 import com.google.devtools.build.lib.rules.apple.AppleCommandLineOptions;
 import com.google.devtools.build.lib.rules.apple.AppleConfiguration;
 import com.google.devtools.build.lib.rules.apple.AppleConfiguration.ConfigurationDistinguisher;
@@ -52,6 +53,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
+import net.starlark.java.eval.Dict;
 
 /** Support utility for creating multi-arch Apple binaries. */
 public class MultiArchBinarySupport {
@@ -562,4 +564,25 @@ public static AppleLinkingOutputs.TargetTriplet getTargetTriplet(BuildConfigurat
         cpuPlatform.getTargetPlatform(),
         cpuPlatform.getTargetEnvironment());
   }
+
+  /**
+   * Transforms a {@link Map<Optional<String>, List<ConfiguredTargetAndData>>}, to a Starlark Dict
+   * keyed by split transition keys with {@link AppleLinkingOutputs.TargetTriplet} Starlark struct
+   * definition.
+   *
+   * @param ctads a {@link Map<Optional<String>, List<ConfiguredTargetAndData>>} from rule context
+   * @return a Starlark {@link Dict<String, StructImpl>} representing split transition keys with
+   *     their target triplet (architecture, platform, environment)
+   */
+  public static Dict<String, StructImpl> getSplitTargetTripletFromCtads(
+      Map<Optional<String>, List<ConfiguredTargetAndData>> ctads) {
+    Dict.Builder<String, StructImpl> result = Dict.builder();
+    for (Optional<String> splitTransitionKey : ctads.keySet()) {
+      TargetTriplet targetTriplet =
+          getTargetTriplet(
+              Iterables.getOnlyElement(ctads.get(splitTransitionKey)).getConfiguration());
+      result.put(splitTransitionKey.get(), targetTriplet.toStarlarkStruct());
+    }
+    return result.buildImmutable();
+  }
 }

src/main/java/com/google/devtools/build/lib/starlarkbuildapi/apple/AppleCommonApi.java

@@ -426,6 +426,22 @@ StructApi linkMultiArchBinary(
       StarlarkThread thread)
       throws EvalException, InterruptedException;
 
+  @StarlarkMethod(
+      name = "link_multi_arch_static_library",
+      doc =
+          "Links a (potentially multi-architecture) static library targeting Apple platforms."
+              + " This method comprises a part of the <code>apple_static_library</code> rule logic,"
+              + " and is exposed as an API to iterate on XCFrameworks support on Starlark.\n"
+              + "<p>This API is <b>highly experimental</b> and subject to change at any time."
+              + " Do not depend on the stability of this function at this time.",
+      parameters = {
+        @Param(name = "ctx", named = true, positional = false, doc = "The Starlark rule context."),
+      },
+      useStarlarkThread = true)
+  StructApi linkMultiArchStaticLibrary(
+      StarlarkRuleContextT starlarkRuleContext, StarlarkThread thread)
+      throws EvalException, InterruptedException;
+
   @StarlarkMethod(
       name = "dotted_version",
       doc = "Creates a new <a href=\"DottedVersion.html\">DottedVersion</a> instance.",

src/main/starlark/builtins_bzl/common/exports.bzl

@@ -22,6 +22,7 @@ load("@_builtins//:common/objc/objc_import.bzl", "objc_import")
 load("@_builtins//:common/objc/objc_library.bzl", "objc_library")
 load("@_builtins//:common/objc/apple_static_library.bzl", "apple_static_library")
 load("@_builtins//:common/objc/compilation_support.bzl", "compilation_support")
+load("@_builtins//:common/objc/linking_support.bzl", "linking_support")
 load("@_builtins//:common/proto/proto_common.bzl", "proto_common")
 load("@_builtins//:common/proto/proto_library.bzl", "proto_library")
 load("@_builtins//:common/java/proto/java_lite_proto_library.bzl", "java_lite_proto_library")
@@ -58,4 +59,5 @@ exported_rules = {
 exported_to_java = {
     "register_compile_and_archive_actions_for_j2objc": compilation_support.register_compile_and_archive_actions_for_j2objc,
     "create_proto_compile_action": proto_common.create_proto_compile_action,
+    "link_multi_arch_static_library": linking_support.link_multi_arch_static_library,
 }

src/main/starlark/builtins_bzl/common/objc/apple_static_library.bzl

@@ -12,11 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""objc_library Starlark implementation replacing native"""
+"""apple_static_library Starlark implementation"""
 
-load("@_builtins//:common/objc/semantics.bzl", "semantics")
-load("@_builtins//:common/objc/compilation_support.bzl", "compilation_support")
 load("@_builtins//:common/objc/attrs.bzl", "common_attrs")
+load("@_builtins//:common/objc/linking_support.bzl", "linking_support")
+load("@_builtins//:common/objc/semantics.bzl", "semantics")
 load("@_builtins//:common/objc/transitions.bzl", "apple_crosstool_transition")
 
 objc_internal = _builtins.internal.objc_internal
@@ -33,65 +33,10 @@ def _apple_static_library_impl(ctx):
     platform_type = getattr(apple_common.platform_type, ctx.attr.platform_type)
     platform = ctx.fragments.apple.multi_arch_platform(platform_type)
 
-    cpu_to_deps_map = ctx.split_attr.deps
-    cpu_to_avoid_deps_map = ctx.split_attr.avoid_deps
-    child_configs_and_toolchains = ctx.split_attr._child_configuration_dummmy
-    rule_intermediate_artifacts = objc_internal.create_intermediate_artifacts(ctx = ctx)
-
-    libraries_to_lipo = []
-    files_to_build = [rule_intermediate_artifacts.combined_architecture_archive]
-    sdk_dylib = []
-    sdk_framework = []
-    weak_sdk_framework = []
-
-    for key, child_toolchain in ctx.split_attr._child_configuration_dummmy.items():
-        intermediate_artifacts = objc_internal.create_intermediate_artifacts(ctx = ctx)
-
-        deps = cpu_to_deps_map[key]
-
-        common_variables = compilation_support.build_common_variables(
-            ctx = ctx,
-            toolchain = child_toolchain[cc_common.CcToolchainInfo],
-            use_pch = True,
-            deps = cpu_to_deps_map[key],
-        )
-
-        avoid_objc_providers = []
-        avoid_cc_providers = []
-
-        if len(cpu_to_avoid_deps_map.keys()):
-            for dep in cpu_to_avoid_deps_map[key]:
-                if apple_common.Objc in dep:
-                    avoid_objc_providers.append(dep[apple_common.Objc])
-                if CcInfo in dep:
-                    avoid_cc_providers.append(dep[CcInfo])
-
-        objc_provider = common_variables.objc_provider.subtract_subtrees(avoid_objc_providers = avoid_objc_providers, avoid_cc_providers = avoid_cc_providers)
-
-        name = ctx.label.name + "-" + key + "-fl"
-
-        linking_outputs = compilation_support.register_fully_link_action(common_variables, objc_provider, name)
-
-        libraries_to_lipo.append(linking_outputs.library_to_link.static_library)
-
-        sdk_dylib.append(objc_provider.sdk_dylib)
-        sdk_framework.append(objc_provider.sdk_framework)
-        weak_sdk_framework.append(objc_provider.weak_sdk_framework)
-
-    objc_provider = apple_common.new_objc_provider(
-        sdk_dylib = depset(transitive = sdk_dylib),
-        sdk_framework = depset(transitive = sdk_framework),
-        weak_sdk_framework = depset(transitive = weak_sdk_framework),
-    )
-
-    header_tokens = []
-    for key, deps in cpu_to_deps_map.items():
-        for dep in deps:
-            if CcInfo in dep:
-                header_tokens.append(dep[CcInfo].compilation_context.validation_artifacts)
-
-    output_groups = {"_validation": depset(transitive = header_tokens)}
+    linking_outputs = linking_support.link_multi_arch_static_library(ctx = ctx)
+    libraries_to_lipo = [output.library for output in linking_outputs.outputs]
 
+    rule_intermediate_artifacts = objc_internal.create_intermediate_artifacts(ctx = ctx)
     output_archive = rule_intermediate_artifacts.combined_architecture_archive
     _register_combine_architectures_action(
         ctx,
@@ -100,13 +45,21 @@ def _apple_static_library_impl(ctx):
         platform,
     )
 
-    runfiles = ctx.runfiles(files = files_to_build, collect_default = True, collect_data = True)
+    files_to_build = [output_archive]
+    runfiles = ctx.runfiles(
+        files = files_to_build,
+        collect_default = True,
+        collect_data = True,
+    )
 
     return [
         DefaultInfo(files = depset(files_to_build), runfiles = runfiles),
-        objc_provider,
-        OutputGroupInfo(**output_groups),
-        apple_common.AppleStaticLibrary(archive = output_archive, objc = objc_provider),
+        linking_outputs.objc,
+        linking_outputs.output_groups,
+        apple_common.AppleStaticLibrary(
+            archive = output_archive,
+            objc = linking_outputs.objc,
+        ),
     ]
 
 def _validate_minimum_os(ctx):
@@ -116,7 +69,7 @@ def _validate_minimum_os(ctx):
         else:
             return
 
-    minimum_os_version = apple_common.dotted_version(ctx.attr.minimum_os_version)
+    apple_common.dotted_version(ctx.attr.minimum_os_version)
     components = ctx.attr.minimum_os_version.split(".")
     for i in range(len(components) - 1, 0, -1):
         if components[i] == "0":
@@ -179,8 +132,11 @@ apple_static_library = rule(
                 allow_rules = ["cc_library", "cc_inc_library"],
             ),
             "linkopts": attr.string_list(),
-            "additional_linker_inputs": attr.label_list(flags = ["DIRECT_COMPILE_TIME_INPUT"], allow_files = True),
-            "_child_configuration_dummmy": attr.label(
+            "additional_linker_inputs": attr.label_list(
+                flags = ["DIRECT_COMPILE_TIME_INPUT"],
+                allow_files = True,
+            ),
+            "_child_configuration_dummy": attr.label(
                 cfg = apple_common.multi_arch_split,
                 default = "@" + semantics.get_repo() + "//tools/cpp:current_cc_toolchain",
             ),