AliasStrings: no aliasing in template literals

Fixes a bug in which AliasStrings created an invalid AST, because it doesn't understand how to correctly modify template literals. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=175608155
google · Nov 14, 2017 · f7bae0d · f7bae0d
1 parent 488f3a3
commit f7bae0d
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Showing 2 changed files with 30 additions and 3 deletions.
diff --git a/src/com/google/javascript/jscomp/AliasStrings.java b/src/com/google/javascript/jscomp/AliasStrings.java
@@ -16,7 +16,6 @@
 
 package com.google.javascript.jscomp;
 
-import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
 import com.google.javascript.rhino.IR;
 import com.google.javascript.rhino.Node;
 import java.util.ArrayList;
@@ -47,8 +46,7 @@
  *       duplicate strings.
  *
  */
-class AliasStrings extends AbstractPostOrderCallback
-    implements CompilerPass {
+class AliasStrings implements CompilerPass, NodeTraversal.Callback {
 
   private static final Logger logger =
       Logger.getLogger(AliasStrings.class.getName());
@@ -131,6 +129,20 @@ public void process(Node externs, Node root) {
     }
   }
 
+  @Override
+  public boolean shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent) {
+    switch (n.getToken()) {
+      case TEMPLATELIT:
+      case TAGGED_TEMPLATELIT:
+      case TEMPLATELIT_SUB: // technically redundant, since it must be a child of the others
+        // TODO(bradfordcsmith): Consider replacing long and/or frequently occurring substrings
+        // within template literals with template substitutions.
+        return false;
+      default:
+        return true;
+    }
+  }
+
   @Override
   public void visit(NodeTraversal t, Node n, Node parent) {
     if (n.isString() && !parent.isGetProp() && !parent.isRegExp()) {

diff --git a/test/com/google/javascript/jscomp/AliasStringsTest.java b/test/com/google/javascript/jscomp/AliasStringsTest.java
@@ -45,6 +45,21 @@ protected CompilerPass getProcessor(Compiler compiler) {
     return pass;
   }
 
+  public void testTemplateLiteral() {
+    strings = ImmutableSet.of("aliasable string");
+    // TODO(bradfordcsmith): Maybe implement using aliases in template literals?
+    test(
+        lines(
+            "const A = 'aliasable string';",
+            "const B = 'aliasable string';",
+            "const AB = `${A}aliasable string${B}`;"),
+        lines(
+            "var $$S_aliasable$20string = 'aliasable string';",
+            "const A = $$S_aliasable$20string;",
+            "const B = $$S_aliasable$20string;",
+            "const AB = `${A}aliasable string${B}`"));
+  }
+
   public void testAssignment() {
     strings = ImmutableSet.of("none", "width", "overimaginative");