Fold "String#replaceAll" when all the values involved are literals.

PiperOrigin-RevId: 383518491

Author: concavelenz

src/com/google/javascript/jscomp/PeepholeReplaceKnownMethods.java

@@ -275,6 +275,8 @@ private Node tryFoldKnownStringMethods(Node subtree, Node callTarget) {
               return tryFoldStringCharAt(subtree, stringNode, firstArg);
             case "charCodeAt":
               return tryFoldStringCharCodeAt(subtree, stringNode, firstArg);
+            case "replaceAll":
+              return tryFoldStringReplaceAll(subtree, stringNode, firstArg);
             default: // fall out
           }
         }
@@ -859,6 +861,39 @@ private Node tryFoldStringCharAt(Node n, Node stringNode, Node arg1) {
     return resultNode;
   }
 
+  /** Try to fold .charAt() calls on strings */
+  private Node tryFoldStringReplaceAll(Node n, Node stringNode, Node arg1) {
+    checkArgument(n.isCall());
+    checkArgument(stringNode.isStringLit());
+
+    Node arg2 = arg1.getNext();
+    if (arg2 == null || arg2.getNext() != null) {
+      // too few or too many parameters
+      return n;
+    }
+
+    if (!arg1.isStringLit() || !arg2.isStringLit()) {
+      // only string literals are supported for folding.
+      return n;
+    }
+
+    String replacementPattern = arg2.getString();
+    if (replacementPattern.contains("$")) {
+      // 'special' replacements aren't supported yet.
+      return n;
+    }
+
+    // Java "replace" acts like JavaScript's "replaceAll" and replaces all occurrences.
+    String original = stringNode.getString();
+    String newString = original.replace(arg1.getString(), arg2.getString());
+
+    Node resultNode = IR.string(newString).srcref(stringNode);
+    Node parent = n.getParent();
+    n.replaceWith(resultNode);
+    reportChangeToEnclosingScope(parent);
+    return resultNode;
+  }
+
   /**
    * Try to fold .charCodeAt() calls on strings
    */

test/com/google/javascript/jscomp/PeepholeReplaceKnownMethodsTest.java

@@ -37,10 +37,11 @@ public PeepholeReplaceKnownMethodsTest() {
     super(
         MINIMAL_EXTERNS
             + lines(
-                // NOTE: these are defined as variadic to avoid wrong-argument-count warnings in
-                // NTI,
+                // NOTE: these are defined as variadic to avoid wrong-argument-count warnings,
                 // which enables testing that the pass does not touch calls with wrong argument
                 // count.
+                "/** @type {function(this: string, ...*): string} */ String.prototype.replaceAll;",
+                "/** @type {function(this: string, ...*): string} */ String.prototype.replace;",
                 "/** @type {function(this: string, ...*): string} */ String.prototype.substring;",
                 "/** @type {function(this: string, ...*): string} */ String.prototype.substr;",
                 "/** @type {function(this: string, ...*): string} */ String.prototype.slice;",
@@ -205,6 +206,41 @@ public void testFoldStringSubstr() {
     foldSame("x = `abc ${xyz} def`.substr(0,2)");
   }
 
+  @Test
+  public void testFoldStringReplace() {
+    // TODO(johnlenz): support folding this case
+    foldSame("x = 'acaca'.replace('c','x')");
+
+    // not a literal
+    foldSame("x.replace('x','c')");
+
+    foldSame("'Xyz'.replace('Xyz', '$$')"); // would fold to '$'
+    foldSame("'PreXyzPost'.replace('Xyz', '$&')"); // would fold to 'PreXyzPost'
+    foldSame("'PreXyzPost'.replace('Xyz', '$`')"); // would fold to 'PrePrePost'
+    foldSame("'PreXyzPost'.replace('Xyz', '$\\'')"); // would fold to  'PrePostPost'
+    foldSame("'PreXyzPostXyz'.replace('Xyz', '$\\'')"); // would fold to 'PrePostXyzPost'
+    foldSame("'123'.replace('2', '$`')"); // would fold to '113'
+  }
+
+  @Test
+  public void testFoldStringReplaceAll() {
+    fold("x = 'abcde'.replaceAll('bcd','c')", "x = 'ace'");
+    fold("x = 'abcde'.replaceAll('c','xxx')", "x = 'abxxxde'");
+    fold("x = 'abcde'.replaceAll('xxx','c')", "x = 'abcde'");
+
+    fold("x = 'c_c_c'.replaceAll('c','x')", "x = 'x_x_x'");
+
+    // not a literal
+    foldSame("x.replaceAll('x','c')");
+
+    foldSame("'Xyz'.replaceAll('Xyz', '$$')"); // would fold to '$'
+    foldSame("'PreXyzPost'.replaceAll('Xyz', '$&')"); // would fold to 'PreXyzPost'
+    foldSame("'PreXyzPost'.replaceAll('Xyz', '$`')"); // would fold to 'PrePrePost'
+    foldSame("'PreXyzPost'.replaceAll('Xyz', '$\\'')"); // would fold to  'PrePostPost'
+    foldSame("'PreXyzPostXyz'.replaceAll('Xyz', '$\\'')"); // would fold to 'PrePostXyzPost'
+    foldSame("'123'.replaceAll('2', '$`')"); // would fold to '113'
+  }
+
   @Test
   public void testFoldStringSubstring() {
     fold("x = 'abcde'.substring(0,2)", "x = 'ab'");