Add support of empty target to LateBoundAlias.

RELNOTES:none
PiperOrigin-RevId: 197132230

1 files changed, 20 insertions, 6 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/LateBoundAlias.java b/src/main/java/com/google/devtools/build/lib/rules/LateBoundAlias.java
index 3e309c338b..176411b7f6 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/LateBoundAlias.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/LateBoundAlias.java
@@ -18,13 +18,17 @@ import static com.google.devtools.build.lib.packages.BuildType.LABEL;
 
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.actions.MutableActionGraph.ActionConflictException;
 import com.google.devtools.build.lib.analysis.AliasProvider;
 import com.google.devtools.build.lib.analysis.BaseRuleClasses;
 import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
 import com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
+import com.google.devtools.build.lib.analysis.Runfiles;
+import com.google.devtools.build.lib.analysis.RunfilesProvider;
 import com.google.devtools.build.lib.analysis.VisibilityProvider;
 import com.google.devtools.build.lib.analysis.VisibilityProviderImpl;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
@@ -36,14 +40,19 @@ import com.google.devtools.build.lib.packages.RuleClass;
 import java.util.function.Function;
 
 /** Implements template for creating custom alias rules. */
-public class LateBoundAlias implements RuleConfiguredTargetFactory {
+public final class LateBoundAlias implements RuleConfiguredTargetFactory {
 
   private static final String ATTRIBUTE_NAME = ":alias";
 
   @Override
-  public ConfiguredTarget create(RuleContext ruleContext) {
+  public ConfiguredTarget create(RuleContext ruleContext)
+      throws ActionConflictException {
     ConfiguredTarget actual =
         (ConfiguredTarget) ruleContext.getPrerequisite(ATTRIBUTE_NAME, Mode.TARGET);
+    if (actual == null) {
+      return createEmptyConfiguredTarget(ruleContext);
+    }
+
     return new AliasConfiguredTarget(
         ruleContext,
         actual,
@@ -54,10 +63,15 @@ public class LateBoundAlias implements RuleConfiguredTargetFactory {
             new VisibilityProviderImpl(ruleContext.getVisibility())));
   }
 
-  /**
-   *  Rule definition for custom alias rules"
-   */
-  public static class CommonAliasRule implements RuleDefinition {
+  private ConfiguredTarget createEmptyConfiguredTarget(RuleContext ruleContext)
+      throws ActionConflictException {
+    return new RuleConfiguredTargetBuilder(ruleContext)
+        .addProvider(RunfilesProvider.class, RunfilesProvider.simple(Runfiles.EMPTY))
+        .build();
+  }
+
+  /** Rule definition for custom alias rules */
+  public abstract static class CommonAliasRule implements RuleDefinition {
 
     private static final String ATTRIBUTE_NAME = ":alias";