Support --allow-duplicate-declarations

src/com/google/common/css/JobDescription.java

@@ -47,6 +47,7 @@ public class JobDescription {
   public final boolean simplifyCss;
   public final boolean eliminateDeadStyles;
   public final boolean allowDefPropagation;
+  public final boolean allowDuplicateDeclarations;
   public final boolean allowUnrecognizedFunctions;
   public final Set<String> allowedNonStandardFunctions;
   public final boolean allowUnrecognizedProperties;
@@ -124,6 +125,7 @@ public enum SourceMapDetailLevel { ALL, DEFAULT }
       boolean useInternalBidiFlipper, boolean swapLtrRtlInUrl,
       boolean swapLeftRightInUrl, boolean simplifyCss,
       boolean eliminateDeadStyles, boolean allowDefPropagation,
+      boolean allowDuplicateDeclarations,
       boolean allowUnrecognizedFunctions,
       Set<String> allowedNonStandardFunctions,
       boolean allowUnrecognizedProperties,
@@ -162,6 +164,7 @@ public enum SourceMapDetailLevel { ALL, DEFAULT }
     this.simplifyCss = simplifyCss;
     this.eliminateDeadStyles = eliminateDeadStyles;
     this.allowDefPropagation = allowDefPropagation;
+    this.allowDuplicateDeclarations = allowDuplicateDeclarations;
     this.allowUnrecognizedFunctions = allowUnrecognizedFunctions;
     this.allowedNonStandardFunctions = ImmutableSet.copyOf(
         allowedNonStandardFunctions);

src/com/google/common/css/JobDescriptionBuilder.java

@@ -51,6 +51,7 @@ public class JobDescriptionBuilder {
   boolean simplifyCss;
   boolean eliminateDeadStyles;
   boolean allowDefPropagation;
+  boolean allowDuplicateDeclarations;
   boolean allowUnrecognizedFunctions;
   Set<String> allowedNonStandardFunctions;
   boolean allowUnrecognizedProperties;
@@ -88,6 +89,7 @@ public JobDescriptionBuilder() {
     this.simplifyCss = false;
     this.eliminateDeadStyles = false;
     this.allowDefPropagation = false;
+    this.allowDuplicateDeclarations = false;
     this.allowUnrecognizedFunctions = false;
     this.allowedNonStandardFunctions = Sets.newHashSet();
     this.allowUnrecognizedProperties = false;
@@ -411,6 +413,16 @@ public JobDescriptionBuilder allowDefPropagation() {
     return setAllowDefPropagation(true);
   }
 
+  public JobDescriptionBuilder setAllowDuplicateDeclarations(boolean allow) {
+    checkJobIsNotAlreadyCreated();
+    this.allowDuplicateDeclarations = allow;
+    return this;
+  }
+
+  public JobDescriptionBuilder allowDuplicateDeclarations() {
+    return setAllowDuplicateDeclarations(true);
+  }
+
   public JobDescriptionBuilder setAllowUndefinedConstants(boolean allow) {
     checkJobIsNotAlreadyCreated();
     this.allowUndefinedConstants = allow;
@@ -464,7 +476,7 @@ public JobDescription getJobDescription() {
         copyrightNotice, outputFormat, inputOrientation, outputOrientation,
         optimize, trueConditionNames, useInternalBidiFlipper, swapLtrRtlInUrl,
         swapLeftRightInUrl, simplifyCss, eliminateDeadStyles,
-        allowDefPropagation, allowUnrecognizedFunctions, allowedNonStandardFunctions,
+        allowDefPropagation, allowDuplicateDeclarations, allowUnrecognizedFunctions, allowedNonStandardFunctions,
         allowUnrecognizedProperties, allowedUnrecognizedProperties, allowUndefinedConstants,
         allowMozDocument, vendor,
         allowKeyframes, allowWebkitKeyframes, processDependencies,

src/com/google/common/css/compiler/commandline/ClosureCommandLineCompiler.java

@@ -149,6 +149,10 @@ static class Flags {
         + " from one file to propagate to other files.")
     private boolean allowDefPropagation = true;
 
+    @Option(name = "--allow-duplicate-declarations", usage = "Allow duplicate"
+      + " declarations without needing @alternate")
+    private boolean allowDuplicateDeclarations = false;
+
     @Option(name = "--allow-unrecognized-functions", usage =
         "Allow unrecognized functions.")
     private boolean allowUnrecognizedFunctions = false;
@@ -222,6 +226,7 @@ JobDescription createJobDescription() {
       builder.setCopyrightNotice(copyrightNotice);
       builder.setTrueConditionNames(trueConditions);
       builder.setAllowDefPropagation(allowDefPropagation);
+      builder.setAllowDuplicateDeclarations(allowDuplicateDeclarations);
       builder.setAllowUnrecognizedFunctions(allowUnrecognizedFunctions);
       builder.setAllowedNonStandardFunctions(allowedNonStandardFunctions);
       builder.setAllowedUnrecognizedProperties(allowedUnrecognizedProperties);

src/com/google/common/css/compiler/passes/PassRunner.java

@@ -144,9 +144,11 @@ public void runPasses(CssTree cssTree) {
           cssTree.getMutatingVisitController()).runPass();
     }
     if (job.eliminateDeadStyles) {
-      // Report errors for duplicate declarations
-      new DisallowDuplicateDeclarations(
-          cssTree.getVisitController(), errorManager).runPass();
+      if (!job.allowDuplicateDeclarations) {
+        // Report errors for duplicate declarations
+        new DisallowDuplicateDeclarations(
+                cssTree.getVisitController(), errorManager).runPass();
+      }
       // Split rules by selector and declaration.
       new SplitRulesetNodes(cssTree.getMutatingVisitController()).runPass();
       // Dead code elimination.

tests/com/google/common/css/compiler/commandline/ClosureCommandLineCompilerTest.java

@@ -68,6 +68,13 @@ public void testAllowDefPropagationDefaultsToTrue() throws Exception {
     assertTrue(jobDescription.allowDefPropagation);
   }
 
+  public void testAllowDuplicateDeclarationsDefaultsToFalse() throws Exception {
+    ClosureCommandLineCompiler.Flags flags =
+            ClosureCommandLineCompiler.parseArgs(new String[] {"/dev/null"}, EXIT_CODE_HANDLER);
+    JobDescription jobDescription = flags.createJobDescription();
+    assertFalse(jobDescription.allowDuplicateDeclarations);
+  }
+
 
   public void testEmptyImportBlocks() throws Exception {
     // See b/29995881