Expose Apple Multi-architecture Split Transition to Skylark.

This omits validation for this transition, which will follow in a future change.

RELNOTES: None.
PiperOrigin-RevId: 174183651

4 files changed, 93 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkAttr.java b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkAttr.java
index dbbf27fd80..ad927c4801 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkAttr.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkAttr.java
@@ -25,6 +25,7 @@ import com.google.devtools.build.lib.packages.Attribute.AllowedValueSet;
 import com.google.devtools.build.lib.packages.Attribute.ConfigurationTransition;
 import com.google.devtools.build.lib.packages.Attribute.SkylarkComputedDefaultTemplate;
 import com.google.devtools.build.lib.packages.Attribute.SplitTransition;
+import com.google.devtools.build.lib.packages.Attribute.SplitTransitionProvider;
 import com.google.devtools.build.lib.packages.AttributeValueSource;
 import com.google.devtools.build.lib.packages.BuildType;
 import com.google.devtools.build.lib.packages.Provider;
@@ -291,6 +292,8 @@ public final class SkylarkAttr implements SkylarkValue {
         builder.cfg(ConfigurationTransition.HOST);
       } else if (trans instanceof SplitTransition<?>) {
         builder.cfg((SplitTransition<?>) trans);
+      } else if (trans instanceof SplitTransitionProvider) {
+        builder.cfg((SplitTransitionProvider) trans);
       } else if (!trans.equals("target")) {
         throw new EvalException(ast.getLocation(),
             "cfg must be either 'data', 'host', or 'target'.");
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/AppleSkylarkCommon.java b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleSkylarkCommon.java
index d61b803e60..f9c20db7d6 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/AppleSkylarkCommon.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleSkylarkCommon.java
@@ -21,6 +21,7 @@ import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
 import com.google.devtools.build.lib.collect.nestedset.Order;
+import com.google.devtools.build.lib.packages.Attribute.SplitTransitionProvider;
 import com.google.devtools.build.lib.packages.Info;
 import com.google.devtools.build.lib.packages.Provider;
 import com.google.devtools.build.lib.rules.apple.AppleConfiguration;
@@ -314,6 +315,31 @@ public class AppleSkylarkCommon {
         platform, xcodeConfig.getSdkVersionForPlatform(platform));
   }
 
+  @SkylarkCallable(
+      name = "multi_arch_split",
+      doc = "A configuration transition for rule attributes to build dependencies in one or"
+          + " more Apple platforms. "
+          + "<p>Use of this transition requires that the 'platform_type' and 'minimum_os_version'"
+          + " string attributes are defined and mandatory on the rule.</p>"
+          + "<p>The value of the platform_type attribute will dictate the target architectures "
+          + " for which dependencies along this configuration transition will be built.</p>"
+          + "<p>Options are:</p>"
+          + "<ul>"
+          + "<li><code>ios</code>: architectures gathered from <code>--ios_multi_cpus</code>.</li>"
+          + "<li><code>macos</code>: architectures gathered from <code>--macos_cpus</code>.</li>"
+          + "<li><code>tvos</code>: architectures gathered from <code>--tvos_cpus</code>.</li>"
+          + "<li><code>watchos</code>: architectures gathered from <code>--watchos_cpus</code>."
+          + "</li></ul>"
+          + "<p>minimum_os_version should be a dotted version string such as '7.3', and is used to"
+          + " set the minimum operating system on the configuration similarly based on platform"
+          + " type. For example, specifying platform_type 'ios' and minimum_os_version '8.0' will"
+          + " ensure that dependencies are built with minimum iOS version '8.0'.",
+      structField = true
+  )
+  public SplitTransitionProvider getMultiArchSplitProvider() {
+    return new MultiArchSplitTransitionProvider();
+  }
+
   @SkylarkSignature(
     name = "new_objc_provider",
     objectType = AppleSkylarkCommon.class,
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 7d0e9af46f..394c2202b7 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
@@ -35,6 +35,8 @@ import com.google.devtools.build.lib.rules.apple.ApplePlatform;
 import com.google.devtools.build.lib.rules.apple.ApplePlatform.PlatformType;
 import com.google.devtools.build.lib.rules.apple.DottedVersion;
 import com.google.devtools.build.lib.rules.objc.ObjcRuleClasses.PlatformRule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkPrinter;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import java.util.List;
 import java.util.stream.Collectors;
 
@@ -42,7 +44,7 @@ import java.util.stream.Collectors;
  * {@link SplitTransitionProvider} implementation for multi-architecture apple rules which can
  * accept different apple platform types (such as ios or watchos).
  */
-public class MultiArchSplitTransitionProvider implements SplitTransitionProvider {
+public class MultiArchSplitTransitionProvider implements SplitTransitionProvider, SkylarkValue {
 
   @VisibleForTesting
   static final String UNSUPPORTED_PLATFORM_TYPE_ERROR_FORMAT =
@@ -147,6 +149,16 @@ public class MultiArchSplitTransitionProvider implements SplitTransitionProvider
     return new AppleBinaryTransition(platformType, minimumOsVersion);
   }
 
+  @Override
+  public boolean isImmutable() {
+    return true;
+  }
+
+  @Override
+  public void repr(SkylarkPrinter printer) {
+    printer.append("apple_common.multi_arch_split");
+  }
+
   /**
    * Transition that results in one configured target per architecture specified in the
    * platform-specific cpu flag for a particular platform type (for example, --watchos_cpus
diff --git a/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcSkylarkTest.java b/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcSkylarkTest.java
index 25c53ac660..2859878b69 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcSkylarkTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcSkylarkTest.java
@@ -20,10 +20,12 @@ import static com.google.devtools.build.lib.rules.objc.BundleableFile.BUNDLE_PAT
 import static org.junit.Assert.fail;
 
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Iterables;
 import com.google.common.collect.ObjectArrays;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.packages.SkylarkInfo;
 import com.google.devtools.build.lib.rules.apple.AppleToolchain;
 import com.google.devtools.build.lib.rules.apple.DottedVersion;
 import com.google.devtools.build.lib.rules.objc.ObjcCommandLineOptions.ObjcCrosstoolMode;
@@ -1257,6 +1259,55 @@ public class ObjcSkylarkTest extends ObjcRuleTestCase {
     assertThat(skylarkTarget.get(ObjcProvider.SKYLARK_CONSTRUCTOR)).isNotNull();
   }
 
+  @Test
+  public void testMultiArchSplitTransition() throws Exception {
+    scratch.file("examples/rule/BUILD");
+    scratch.file(
+        "examples/rule/apple_rules.bzl",
+        "def my_rule_impl(ctx):",
+        "   return_kwargs = {}",
+        "   for cpu_value in ctx.split_attr.deps:",
+        "     for child_target in ctx.split_attr.deps[cpu_value]:",
+        "       return_kwargs[cpu_value] = struct(objc=child_target.objc)",
+        "   return struct(**return_kwargs)",
+        "my_rule = rule(implementation = my_rule_impl,",
+        "   attrs = {",
+        "       'deps': attr.label_list(cfg=apple_common.multi_arch_split, providers=[['objc']]),",
+        "       'platform_type': attr.string(mandatory=True),",
+        "       'minimum_os_version': attr.string(mandatory=True)},",
+        "   fragments = ['apple'],",
+        ")");
+    scratch.file("examples/apple_skylark/a.cc");
+    scratch.file(
+        "examples/apple_skylark/BUILD",
+        "package(default_visibility = ['//visibility:public'])",
+        "load('/examples/rule/apple_rules', 'my_rule')",
+        "my_rule(",
+        "    name = 'my_target',",
+        "    deps = [':lib'],",
+        "    platform_type = 'ios',",
+        "    minimum_os_version='2.2'",
+        ")",
+        "objc_library(",
+        "    name = 'lib',",
+        "    srcs = ['a.m'],",
+        "    hdrs = ['a.h']",
+        ")");
+
+    useConfiguration("--ios_multi_cpus=armv7,arm64");
+    ConfiguredTarget skylarkTarget = getConfiguredTarget("//examples/apple_skylark:my_target");
+    ObjcProvider armv7Objc = ((SkylarkInfo) skylarkTarget.get("ios_armv7"))
+        .getValue("objc", ObjcProvider.class);
+    ObjcProvider arm64Objc = ((SkylarkInfo) skylarkTarget.get("ios_arm64"))
+        .getValue("objc", ObjcProvider.class);
+    assertThat(armv7Objc).isNotNull();
+    assertThat(arm64Objc).isNotNull();
+    assertThat(Iterables.getOnlyElement(armv7Objc.getObjcLibraries()).getExecPathString())
+        .contains("ios_armv7");
+    assertThat(Iterables.getOnlyElement(arm64Objc.getObjcLibraries()).getExecPathString())
+        .contains("ios_arm64");
+  }
+
   private void checkSkylarkRunMemleaksWithExpectedValue(boolean expectedValue) throws Exception {
     scratch.file("examples/rule/BUILD");
     scratch.file(