Add apple_stub_binary rule.

This rule will be used by the Skylark bundling rules for product types that use
stub binaries copied out of the SDK instead of user-built binaries.

RELNOTES: None.
PiperOrigin-RevId: 159998782

6 files changed, 366 insertions, 42 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/BazelRuleClassProvider.java b/src/main/java/com/google/devtools/build/lib/bazel/rules/BazelRuleClassProvider.java
index 530a677674..ff1542b565 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/BazelRuleClassProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/BazelRuleClassProvider.java
@@ -121,6 +121,7 @@ import com.google.devtools.build.lib.rules.java.proto.JavaProtoSkylarkCommon;
 import com.google.devtools.build.lib.rules.objc.AppleBinaryRule;
 import com.google.devtools.build.lib.rules.objc.AppleSkylarkCommon;
 import com.google.devtools.build.lib.rules.objc.AppleStaticLibraryRule;
+import com.google.devtools.build.lib.rules.objc.AppleStubBinaryRule;
 import com.google.devtools.build.lib.rules.objc.AppleWatch1ExtensionRule;
 import com.google.devtools.build.lib.rules.objc.AppleWatch2ExtensionRule;
 import com.google.devtools.build.lib.rules.objc.AppleWatchExtensionBinaryRule;
@@ -563,6 +564,7 @@ public class BazelRuleClassProvider {
           builder.addNativeAspectClass(objcProtoAspect);
           builder.addRuleDefinition(new AppleBinaryRule(objcProtoAspect));
           builder.addRuleDefinition(new AppleStaticLibraryRule(objcProtoAspect));
+          builder.addRuleDefinition(new AppleStubBinaryRule());
           builder.addRuleDefinition(new ObjcProtoLibraryRule(objcProtoAspect));
 
           builder.addRuleDefinition(new AppleCcToolchainRule());
@@ -588,6 +590,7 @@ public class BazelRuleClassProvider {
           builder.addRuleDefinition(new ObjcRuleClasses.SimulatorRule());
           builder.addRuleDefinition(new ObjcRuleClasses.CompilingRule());
           builder.addRuleDefinition(new ObjcRuleClasses.LinkingRule(objcProtoAspect));
+          builder.addRuleDefinition(new ObjcRuleClasses.PlatformRule());
           builder.addRuleDefinition(new ObjcRuleClasses.MultiArchPlatformRule());
           builder.addRuleDefinition(new ObjcRuleClasses.ResourcesRule());
           builder.addRuleDefinition(new ObjcRuleClasses.AlwaysLinkRule());
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/AppleBinaryRule.java b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleBinaryRule.java
index 372aa6f851..bfe8193cce 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/AppleBinaryRule.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleBinaryRule.java
@@ -16,7 +16,6 @@ package com.google.devtools.build.lib.rules.objc;
 
 import static com.google.devtools.build.lib.packages.Attribute.attr;
 import static com.google.devtools.build.lib.packages.BuildType.LABEL;
-import static com.google.devtools.build.lib.packages.ImplicitOutputsFunction.fromTemplates;
 import static com.google.devtools.build.lib.syntax.Type.BOOLEAN;
 import static com.google.devtools.build.lib.syntax.Type.STRING;
 
@@ -26,7 +25,6 @@ import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
 import com.google.devtools.build.lib.packages.Attribute.AllowedValueSet;
 import com.google.devtools.build.lib.packages.ImplicitOutputsFunction;
-import com.google.devtools.build.lib.packages.ImplicitOutputsFunction.SafeImplicitOutputsFunction;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.RuleClass.Builder;
 import com.google.devtools.build.lib.packages.SkylarkProviderIdentifier;
@@ -52,12 +50,6 @@ public class AppleBinaryRule implements RuleDefinition {
   }
 
   /**
-   * Template for the fat binary output (using Apple's "lipo" tool to combine binaries of
-   * multiple architectures).
-   */
-  private static final SafeImplicitOutputsFunction LIPOBIN = fromTemplates("%{name}_lipobin");
-
-  /**
    * There are 3 classes of fully linked binaries in Mach: executable, dynamic library, and
    * loadable bundle.
    *
@@ -89,7 +81,9 @@ public class AppleBinaryRule implements RuleDefinition {
         new MultiArchSplitTransitionProvider();
     return builder
         .requiresConfigurationFragments(
-            ObjcConfiguration.class, J2ObjcConfiguration.class, AppleConfiguration.class,
+            ObjcConfiguration.class,
+            J2ObjcConfiguration.class,
+            AppleConfiguration.class,
             CppConfiguration.class)
         .add(
             attr("$is_executable", BOOLEAN)
@@ -123,8 +117,10 @@ public class AppleBinaryRule implements RuleDefinition {
         This attribute is deprecated and will be removed soon. It currently has no effect.
         "Extension-safe" link options may be added using the <code>linkopts</code> attribute.
         <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
-        .add(attr(EXTENSION_SAFE_ATTR_NAME, BOOLEAN).value(false)
-            .nonconfigurable("Determines the configuration transition on deps"))
+        .add(
+            attr(EXTENSION_SAFE_ATTR_NAME, BOOLEAN)
+                .value(false)
+                .nonconfigurable("Determines the configuration transition on deps"))
         .add(
             attr(BUNDLE_LOADER_ATTR_NAME, LABEL)
                 .direct_compile_time_input()
@@ -143,7 +139,8 @@ public class AppleBinaryRule implements RuleDefinition {
              binary. All transitive dependencies and <code>srcs</code> are linked.</li>
         </ul>
         <!-- #END_BLAZE_RULE.IMPLICIT_OUTPUTS -->*/
-        .setImplicitOutputsFunction(ImplicitOutputsFunction.fromFunctions(LIPOBIN))
+        .setImplicitOutputsFunction(
+            ImplicitOutputsFunction.fromFunctions(ObjcRuleClasses.LIPOBIN_OUTPUT))
         .cfg(AppleCrosstoolTransition.APPLE_CROSSTOOL_TRANSITION)
         .build();
   }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/AppleStubBinary.java b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleStubBinary.java
new file mode 100644
index 0000000000..537cb9e561
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleStubBinary.java
@@ -0,0 +1,198 @@
+// Copyright 2017 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.devtools.build.lib.rules.objc;
+
+import static com.google.devtools.build.lib.rules.objc.ObjcProvider.MULTI_ARCH_LINKED_BINARIES;
+import static com.google.devtools.build.lib.syntax.Type.STRING;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableListMultimap;
+import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.analysis.ConfigurationMakeVariableContext;
+import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.FilesToRunProvider;
+import com.google.devtools.build.lib.analysis.MakeVariableExpander;
+import com.google.devtools.build.lib.analysis.MakeVariableExpander.ExpansionException;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTarget.Mode;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
+import com.google.devtools.build.lib.analysis.RuleContext;
+import com.google.devtools.build.lib.analysis.actions.CustomCommandLine;
+import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
+import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
+import com.google.devtools.build.lib.rules.RuleConfiguredTargetFactory;
+import com.google.devtools.build.lib.rules.apple.AppleConfiguration;
+import com.google.devtools.build.lib.rules.apple.AppleToolchain;
+import com.google.devtools.build.lib.rules.apple.Platform;
+import com.google.devtools.build.lib.rules.apple.Platform.PlatformType;
+import com.google.devtools.build.lib.util.StringUtil;
+import com.google.devtools.build.lib.vfs.PathFragment;
+
+/** Implementation for the "apple_stub_binary" rule. */
+public class AppleStubBinary implements RuleConfiguredTargetFactory {
+
+  /** Provides substitutions for the make variables that can be used in an xcenv_based_path */
+  private static class XcenvBasedPathVariableContext extends ConfigurationMakeVariableContext {
+    private final RuleContext ruleContext;
+
+    /** The platform used to build $(PLATFORM_DIR). */
+    private final Platform platform;
+
+    /** The complete set of variables that may be used in paths. */
+    public static final ImmutableList<String> DEFINED_VARS =
+        ImmutableList.of("$(SDKROOT)", "$(PLATFORM_DIR)");
+
+    public XcenvBasedPathVariableContext(RuleContext ruleContext, Platform platform) {
+      super(
+          ImmutableMap.<String, String>of(),
+          ruleContext.getRule().getPackage(),
+          ruleContext.getConfiguration());
+      this.ruleContext = ruleContext;
+      this.platform = platform;
+    }
+
+    /** Throws an exception if the given path is not rooted at a defined Make variable. */
+    public void validatePathRoot(String path) throws RuleErrorException {
+      for (String var : DEFINED_VARS) {
+        if (path.startsWith(var)) {
+          return;
+        }
+      }
+
+      throw ruleContext.throwWithAttributeError(
+          AppleStubBinaryRule.XCENV_BASED_PATH_ATTR,
+          String.format(
+              PATH_INCORRECTLY_ROOTED_ERROR_FORMAT,
+              StringUtil.joinEnglishList(XcenvBasedPathVariableContext.DEFINED_VARS, "or")));
+    }
+
+    @Override
+    public String lookupMakeVariable(String var) throws ExpansionException {
+      if (var.equals("SDKROOT")) {
+        return "__BAZEL_XCODE_SDKROOT__";
+      }
+      if (var.equals("PLATFORM_DIR")) {
+        return AppleToolchain.platformDir(platform.getNameInPlist());
+      }
+      // Intentionally do not call super, because we only want to allow these specific variables and
+      // discard any that might be inherited from toolchains and other contexts.
+      throw new MakeVariableExpander.ExpansionException("$(" + var + ") not defined");
+    }
+  }
+
+  @VisibleForTesting
+  public static final String PATH_INCORRECTLY_ROOTED_ERROR_FORMAT =
+      "The stub binary path must be rooted at %s";
+
+  @VisibleForTesting
+  public static final String PATH_NOT_NORMALIZED_ERROR =
+      "The stub binary path must be normalized (i.e., not contain \".\" or \"..\")";
+
+  @Override
+  public final ConfiguredTarget create(RuleContext ruleContext)
+      throws InterruptedException, RuleErrorException {
+    MultiArchSplitTransitionProvider.validateMinimumOs(ruleContext);
+    PlatformType platformType = MultiArchSplitTransitionProvider.getPlatformType(ruleContext);
+
+    AppleConfiguration appleConfiguration = ruleContext.getFragment(AppleConfiguration.class);
+
+    Platform platform = appleConfiguration.getMultiArchPlatform(platformType);
+    ImmutableListMultimap<BuildConfiguration, ObjcProvider> configurationToDepsMap =
+        ruleContext.getPrerequisitesByConfiguration("deps", Mode.SPLIT, ObjcProvider.class);
+
+    Artifact outputArtifact =
+        ObjcRuleClasses.intermediateArtifacts(ruleContext).combinedArchitectureBinary();
+
+    registerActions(ruleContext, appleConfiguration, platform, outputArtifact);
+
+    NestedSetBuilder<Artifact> filesToBuild =
+        NestedSetBuilder.<Artifact>stableOrder().add(outputArtifact);
+    RuleConfiguredTargetBuilder targetBuilder =
+        ObjcRuleClasses.ruleConfiguredTarget(ruleContext, filesToBuild.build());
+
+    ObjcProvider.Builder objcProviderBuilder = new ObjcProvider.Builder();
+    for (ObjcProvider depProvider : configurationToDepsMap.values()) {
+      objcProviderBuilder.addTransitiveAndPropagate(depProvider);
+    }
+    objcProviderBuilder.add(MULTI_ARCH_LINKED_BINARIES, outputArtifact);
+
+    ObjcProvider objcProvider = objcProviderBuilder.build();
+    // TODO(cparsons): Stop propagating ObjcProvider directly from this rule.
+    targetBuilder.addProvider(ObjcProvider.class, objcProvider);
+
+    targetBuilder.addNativeDeclaredProvider(
+        new AppleExecutableBinaryProvider(outputArtifact, objcProvider));
+
+    return targetBuilder.build();
+  }
+
+  private static FilesToRunProvider xcrunwrapper(RuleContext ruleContext) {
+    return ruleContext.getExecutablePrerequisite("$xcrunwrapper", Mode.HOST);
+  }
+
+  /** Registers the actions that copy the stub binary to the target's output. */
+  private static void registerActions(
+      RuleContext ruleContext,
+      AppleConfiguration appleConfiguration,
+      Platform platform,
+      Artifact outputBinary)
+      throws RuleErrorException {
+    CustomCommandLine copyCommandLine =
+        new CustomCommandLine.Builder()
+            .add("/bin/cp")
+            .add(resolveXcenvBasedPath(ruleContext, platform))
+            .addExecPaths(ImmutableList.of(outputBinary))
+            .build();
+
+    ruleContext.registerAction(
+        ObjcRuleClasses.spawnAppleEnvActionBuilder(appleConfiguration, platform)
+            .setExecutable(xcrunwrapper(ruleContext))
+            .setCommandLine(copyCommandLine)
+            .setMnemonic("CopyStubExecutable")
+            .addOutput(outputBinary)
+            .disableSandboxing()
+            .build(ruleContext));
+  }
+
+  /**
+   * Returns the value of the xcenv_based_path attribute, emitting an error if its format is
+   * invalid.
+   *
+   * @param ruleContext the rule context
+   * @param platform the Apple platform
+   * @return the path string, if it was valid
+   * @throws RuleErrorException If the path string was invalid because it was not rooted at one of
+   *     the allowed environment variables or it was not normalized
+   */
+  private static String resolveXcenvBasedPath(RuleContext ruleContext, Platform platform)
+      throws RuleErrorException {
+    String pathString =
+        ruleContext.attributes().get(AppleStubBinaryRule.XCENV_BASED_PATH_ATTR, STRING);
+    XcenvBasedPathVariableContext makeVariableContext =
+        new XcenvBasedPathVariableContext(ruleContext, platform);
+
+    makeVariableContext.validatePathRoot(pathString);
+
+    PathFragment pathFragment = PathFragment.create(pathString);
+    if (!pathFragment.isNormalized()) {
+      throw ruleContext.throwWithAttributeError(
+          AppleStubBinaryRule.XCENV_BASED_PATH_ATTR, PATH_NOT_NORMALIZED_ERROR);
+    }
+
+    return ruleContext.expandMakeVariables(
+        AppleStubBinaryRule.XCENV_BASED_PATH_ATTR, pathString, makeVariableContext);
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/AppleStubBinaryRule.java b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleStubBinaryRule.java
new file mode 100644
index 0000000000..f2e2c59a2d
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleStubBinaryRule.java
@@ -0,0 +1,95 @@
+// Copyright 2017 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.devtools.build.lib.rules.objc;
+
+import static com.google.devtools.build.lib.packages.Attribute.attr;
+import static com.google.devtools.build.lib.packages.BuildType.LABEL_LIST;
+import static com.google.devtools.build.lib.syntax.Type.STRING;
+
+import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.analysis.BaseRuleClasses;
+import com.google.devtools.build.lib.analysis.RuleDefinition;
+import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
+import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
+import com.google.devtools.build.lib.packages.ImplicitOutputsFunction;
+import com.google.devtools.build.lib.packages.RuleClass;
+import com.google.devtools.build.lib.packages.RuleClass.Builder;
+import com.google.devtools.build.lib.rules.apple.AppleConfiguration;
+
+/** Rule definition for apple_stub_binary. */
+public class AppleStubBinaryRule implements RuleDefinition {
+
+  public static final String XCENV_BASED_PATH_ATTR = "xcenv_based_path";
+
+  @Override
+  public RuleClass build(Builder builder, RuleDefinitionEnvironment env) {
+    MultiArchSplitTransitionProvider splitTransitionProvider =
+        new MultiArchSplitTransitionProvider();
+    return builder
+        .requiresConfigurationFragments(ObjcConfiguration.class, AppleConfiguration.class)
+        /* <!-- #BLAZE_RULE(apple_stub_binary).ATTRIBUTE(xcenv_based_path) -->
+        The path to the stub executable within an Xcode platform or SDK bundle. This path must be
+        rooted at either <code>$(SDKROOT)</code> or <code>$(PLATFORM_DIR)</code> (written with
+        parentheses, as they are "Make" variables, not shell variables).
+        <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
+        .add(attr(XCENV_BASED_PATH_ATTR, STRING))
+        /* <!-- #BLAZE_RULE(apple_stub_binary).ATTRIBUTE(deps) -->
+        The list of targets whose resources will be included in the final bundle.
+        <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
+        .add(
+            attr("deps", LABEL_LIST)
+                .direct_compile_time_input()
+                .mandatoryNativeProviders(
+                    ImmutableList.<Class<? extends TransitiveInfoProvider>>of(ObjcProvider.class))
+                .allowedFileTypes()
+                .cfg(splitTransitionProvider))
+        /*<!-- #BLAZE_RULE(apple_stub_binary).IMPLICIT_OUTPUTS -->
+        <ul>
+         <li><code><var>name</var></code>: the stub executable copied from the Xcode
+             platform/SDK location.</li>
+        </ul>
+        <!-- #END_BLAZE_RULE.IMPLICIT_OUTPUTS -->*/
+        .setImplicitOutputsFunction(
+            ImplicitOutputsFunction.fromFunctions(ObjcRuleClasses.LIPOBIN_OUTPUT))
+        .build();
+  }
+
+  @Override
+  public Metadata getMetadata() {
+    return RuleDefinition.Metadata.builder()
+        .name("apple_stub_binary")
+        .factoryClass(AppleStubBinary.class)
+        .ancestors(
+            BaseRuleClasses.BaseRule.class,
+            ObjcRuleClasses.PlatformRule.class,
+            ObjcRuleClasses.XcrunRule.class)
+        .build();
+  }
+}
+
+/*<!-- #BLAZE_RULE (NAME = apple_stub_binary, TYPE = BINARY, FAMILY = Objective-C) -->
+
+<p>This rule copies a stub executable (such as that used by a watchOS application or an iMessage
+sticker pack) from a location in an Xcode platform or SDK bundle to the output.</p>
+
+<p>This rule is meant to be used internally by the Apple bundling rules and does has limited use
+outside of that. Its purpose is to provide target uniformity across all Apple bundles whether they
+contain a user binary or a stub binary and to ensure that the platform transition is still present
+for those stubs so that platform selection works as expected in downstream resource dependencies.
+</p>
+
+${IMPLICIT_OUTPUTS}
+
+<!-- #END_BLAZE_RULE -->*/
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/MultiArchSplitTransitionProvider.java b/src/main/java/com/google/devtools/build/lib/rules/objc/MultiArchSplitTransitionProvider.java
index 49f2dcaeaa..8c72933334 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/MultiArchSplitTransitionProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/MultiArchSplitTransitionProvider.java
@@ -33,7 +33,7 @@ import com.google.devtools.build.lib.rules.apple.AppleConfiguration.Configuratio
 import com.google.devtools.build.lib.rules.apple.DottedVersion;
 import com.google.devtools.build.lib.rules.apple.Platform;
 import com.google.devtools.build.lib.rules.apple.Platform.PlatformType;
-import com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.MultiArchPlatformRule;
+import com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.PlatformRule;
 import java.util.List;
 
 /**
@@ -63,11 +63,12 @@ public class MultiArchSplitTransitionProvider implements SplitTransitionProvider
    */
   public static PlatformType getPlatformType(RuleContext ruleContext) throws RuleErrorException {
     String attributeValue =
-        ruleContext.attributes().get(MultiArchPlatformRule.PLATFORM_TYPE_ATTR_NAME, STRING);
+        ruleContext.attributes().get(PlatformRule.PLATFORM_TYPE_ATTR_NAME, STRING);
     try {
       return getPlatformType(attributeValue);
     } catch (IllegalArgumentException exception) {
-      throw ruleContext.throwWithAttributeError(MultiArchPlatformRule.PLATFORM_TYPE_ATTR_NAME,
+      throw ruleContext.throwWithAttributeError(
+          PlatformRule.PLATFORM_TYPE_ATTR_NAME,
           String.format(UNSUPPORTED_PLATFORM_TYPE_ERROR_FORMAT, attributeValue));
     }
   }
@@ -79,18 +80,19 @@ public class MultiArchSplitTransitionProvider implements SplitTransitionProvider
    *     an invalid value
    */
   public static void validateMinimumOs(RuleContext ruleContext) throws RuleErrorException {
-    String attributeValue =
-        ruleContext.attributes().get(MultiArchPlatformRule.MINIMUM_OS_VERSION, STRING);
+    String attributeValue = ruleContext.attributes().get(PlatformRule.MINIMUM_OS_VERSION, STRING);
     // TODO(b/37096178): This should be a mandatory attribute.
     if (!Strings.isNullOrEmpty(attributeValue)) {
       try {
         DottedVersion minimumOsVersion = DottedVersion.fromString(attributeValue);
         if (minimumOsVersion.hasAlphabeticCharacters() || minimumOsVersion.numComponents() > 2) {
-          throw ruleContext.throwWithAttributeError(MultiArchPlatformRule.MINIMUM_OS_VERSION,
+          throw ruleContext.throwWithAttributeError(
+              PlatformRule.MINIMUM_OS_VERSION,
               String.format(INVALID_VERSION_STRING_ERROR_FORMAT, attributeValue));
         }
       } catch (IllegalArgumentException exception) {
-        throw ruleContext.throwWithAttributeError(MultiArchPlatformRule.MINIMUM_OS_VERSION,
+        throw ruleContext.throwWithAttributeError(
+            PlatformRule.MINIMUM_OS_VERSION,
             String.format(INVALID_VERSION_STRING_ERROR_FORMAT, attributeValue));
       }
     }
@@ -116,10 +118,8 @@ public class MultiArchSplitTransitionProvider implements SplitTransitionProvider
   @Override
   public SplitTransition<?> apply(Rule fromRule) {
     NonconfigurableAttributeMapper attrMapper = NonconfigurableAttributeMapper.of(fromRule);
-    String platformTypeString = 
-        attrMapper.get(MultiArchPlatformRule.PLATFORM_TYPE_ATTR_NAME, STRING);
-    String minimumOsVersionString = 
-        attrMapper.get(MultiArchPlatformRule.MINIMUM_OS_VERSION, STRING);
+    String platformTypeString = attrMapper.get(PlatformRule.PLATFORM_TYPE_ATTR_NAME, STRING);
+    String minimumOsVersionString = attrMapper.get(PlatformRule.MINIMUM_OS_VERSION, STRING);
     PlatformType platformType;
     Optional<DottedVersion> minimumOsVersion;
     try {
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcRuleClasses.java b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcRuleClasses.java
index eef0a42b8c..163704f760 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcRuleClasses.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcRuleClasses.java
@@ -19,6 +19,7 @@ import static com.google.devtools.build.lib.packages.Attribute.ConfigurationTran
 import static com.google.devtools.build.lib.packages.Attribute.attr;
 import static com.google.devtools.build.lib.packages.BuildType.LABEL;
 import static com.google.devtools.build.lib.packages.BuildType.LABEL_LIST;
+import static com.google.devtools.build.lib.packages.ImplicitOutputsFunction.fromTemplates;
 import static com.google.devtools.build.lib.syntax.Type.BOOLEAN;
 import static com.google.devtools.build.lib.syntax.Type.STRING;
 import static com.google.devtools.build.lib.syntax.Type.STRING_LIST;
@@ -44,6 +45,7 @@ import com.google.devtools.build.lib.packages.Attribute;
 import com.google.devtools.build.lib.packages.Attribute.LateBoundLabel;
 import com.google.devtools.build.lib.packages.AttributeMap;
 import com.google.devtools.build.lib.packages.BuildType;
+import com.google.devtools.build.lib.packages.ImplicitOutputsFunction.SafeImplicitOutputsFunction;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.RuleClass.Builder;
@@ -830,6 +832,12 @@ public class ObjcRuleClasses {
   static final String PROTOBUF_WELL_KNOWN_TYPES = "$protobuf_well_known_types";
 
   /**
+   * Template for the fat binary output (using Apple's "lipo" tool to combine binaries of multiple
+   * architectures).
+   */
+  static final SafeImplicitOutputsFunction LIPOBIN_OUTPUT = fromTemplates("%{name}_lipobin");
+
+  /**
    * Common attributes for {@code objc_*} rules that link sources and dependencies.
    */
   public static class LinkingRule implements RuleDefinition {
@@ -884,16 +892,16 @@ public class ObjcRuleClasses {
   }
 
   /**
-   * Common attributes for apple rules that build multi-architecture outputs for a given platform
-   * type (such as ios or watchos).
+   * Common attributes for apple rules that produce outputs for a given platform type (such as ios
+   * or watchos).
    */
-  public static class MultiArchPlatformRule implements RuleDefinition {
+  public static class PlatformRule implements RuleDefinition {
 
     /**
      * Attribute name for apple platform type (e.g. ios or watchos).
      */
     static final String PLATFORM_TYPE_ATTR_NAME = "platform_type";
-    
+
     /**
      * Attribute name for the minimum OS version (e.g. "7.3").
      */
@@ -901,16 +909,8 @@ public class ObjcRuleClasses {
 
     @Override
     public RuleClass build(Builder builder, RuleDefinitionEnvironment env) {
-      MultiArchSplitTransitionProvider splitTransitionProvider =
-          new MultiArchSplitTransitionProvider();
       return builder
-          // This is currently a hack to obtain all child configurations regardless of the attribute
-          // values of this rule -- this rule does not currently use the actual info provided by
-          // this attribute.
-          .add(attr(CHILD_CONFIG_ATTR, LABEL)
-              .cfg(splitTransitionProvider)
-              .value(ObjcRuleClasses.APPLE_TOOLCHAIN))
-          /* <!-- #BLAZE_RULE($apple_multiarch_rule).ATTRIBUTE(platform_type) -->
+          /* <!-- #BLAZE_RULE($apple_platform_rule).ATTRIBUTE(platform_type) -->
           The type of platform for which to create artifacts in this rule.
 
           This dictates which Apple platform SDK is used for compilation/linking and which flag is
@@ -935,13 +935,14 @@ public class ObjcRuleClasses {
           </ul>
           <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
           // TODO(b/37635370): Remove the "ios" default and make this mandatory.
-          .add(attr(PLATFORM_TYPE_ATTR_NAME, STRING)
-              .value(PlatformType.IOS.toString())
-              .nonconfigurable("Determines the configuration transition on deps"))
-          /* <!-- #BLAZE_RULE($apple_multiarch_rule).ATTRIBUTE(minimum_os) -->
+          .add(
+              attr(PLATFORM_TYPE_ATTR_NAME, STRING)
+                  .value(PlatformType.IOS.toString())
+                  .nonconfigurable("Determines the configuration transition on deps"))
+          /* <!-- #BLAZE_RULE($apple_platform_rule).ATTRIBUTE(minimum_os) -->
           The minimum OS version that this target and its dependencies should be built for.
 
-          This should be a dotted version string such as "7.3". 
+          This should be a dotted version string such as "7.3".
           <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
           // TODO(b/37096178): This should be a mandatory attribute.
           .add(
@@ -953,9 +954,39 @@ public class ObjcRuleClasses {
     @Override
     public Metadata getMetadata() {
       return RuleDefinition.Metadata.builder()
+          .name("$apple_platform_rule")
+          .type(RuleClassType.ABSTRACT)
+          .build();
+    }
+  }
+
+  /**
+   * Common attributes for apple rules that build multi-architecture outputs for a given platform
+   * type (such as ios or watchos).
+   */
+  public static class MultiArchPlatformRule implements RuleDefinition {
+
+    @Override
+    public RuleClass build(Builder builder, RuleDefinitionEnvironment env) {
+      MultiArchSplitTransitionProvider splitTransitionProvider =
+          new MultiArchSplitTransitionProvider();
+      return builder
+          // This is currently a hack to obtain all child configurations regardless of the attribute
+          // values of this rule -- this rule does not currently use the actual info provided by
+          // this attribute.
+          .add(
+              attr(CHILD_CONFIG_ATTR, LABEL)
+                  .cfg(splitTransitionProvider)
+                  .value(ObjcRuleClasses.APPLE_TOOLCHAIN))
+          .build();
+    }
+
+    @Override
+    public Metadata getMetadata() {
+      return RuleDefinition.Metadata.builder()
           .name("$apple_multiarch_rule")
           .type(RuleClassType.ABSTRACT)
-          .ancestors(CrosstoolRule.class)
+          .ancestors(PlatformRule.class, CrosstoolRule.class)
           .build();
     }
   }