RegExp literal fixes

packages/babel-plugin-transform-regexp-constructors/__tests__/transform-regexp-constructors-test.js

@@ -10,12 +10,30 @@ function transform(code) {
 }
 
 describe("transform-regexp-constructors-plugin", () => {
+  it("should not duplicate forward-slash escapes", () => {
+    const source = String.raw`var x = new RegExp('\\/');`;
+    const expected = String.raw`var x = /\//;`;
+    expect(transform(source)).toBe(expected);
+  });
+
+  it("should transform newlines fine", () => {
+    const source = String.raw`var x = new RegExp('\\n');`;
+    const expected = String.raw`var x = /\n/;`;
+    expect(transform(source)).toBe(expected);
+  });
+
   it("should transform RegExp constructors with string literals", () => {
     const source = "var x = new RegExp('ab+c');";
     const expected = "var x = /ab+c/;";
     expect(transform(source)).toBe(expected);
   });
 
+  it("should transform RegExp calls with string literals", () => {
+    const source = "var x = RegExp('ab+c');";
+    const expected = "var x = /ab+c/;";
+    expect(transform(source)).toBe(expected);
+  });
+
   it("should transform RegExp constructors with flags", () => {
     const source = "var x = new RegExp('ab+c', 'gimuy');";
     const expected = "var x = /ab+c/gimuy;";
@@ -60,9 +78,15 @@ const ret = /ab+c\\wd/g;`;
     expect(transform(source)).toBe(expected);
   });
 
-  it("should escape invalid chars", () => {
-    const source = "var x = new RegExp('\\r\\n\\n/x/')";
-    const expected = "var x = /\\r\\n\\n\\/x\\//;";
+  it("should prettify special whitespaces", () => {
+    const source = String.raw`var x = new RegExp('\b\f\v\t\r\n\n');`;
+    const expected = String.raw`var x = /[\b]\f\v\t\r\n\n/;`;
+    expect(transform(source)).toBe(expected);
+  });
+
+  it("should escape forward slashes", () => {
+    const source = String.raw`var x = new RegExp('/x/');`;
+    const expected = String.raw`var x = /\/x\//;`;
     expect(transform(source)).toBe(expected);
   });
 });

packages/babel-plugin-transform-regexp-constructors/src/index.js

@@ -1,34 +1,53 @@
 "use strict";
 
+function createRegExpLiteral(args, t) {
+  const evaluatedArgs = args.map((a) => a.evaluate());
+  if (!evaluatedArgs.every((a) => a.confident === true &&
+      typeof a.value === "string")) {
+    return;
+  }
+  let pattern = (evaluatedArgs.length >= 1 &&
+                    evaluatedArgs[0].value !== "") ?
+                  evaluatedArgs[0].value :
+                  "(?:)";
+  const flags = evaluatedArgs.length >= 2 ?
+                evaluatedArgs[1].value :
+                "";
+
+  pattern = new RegExp(pattern).source;
+  // This step is for prettification -- technically we can insert whitespace
+  // literals into a regExpLiteral just fine.
+  // e.g. '\t'.replace(/	/, '') === '\t'.replace(/\t/, '') === ''.
+  pattern = pattern.replace(/\n/g, "\\n")
+                   .replace(/\t/g, "\\t")
+                   .replace(/[\b]/g, "[\\b]")
+                   .replace(/\v/g, "\\v")
+                   .replace(/\f/g, "\\f")
+                   .replace(/\r/g, "\\r");
+  return t.regExpLiteral(pattern, flags);
+}
+
+function maybeReplaceWithRegExpLiteral(path, t) {
+  if (!t.isIdentifier(path.node.callee, {name: "RegExp"})) {
+    return;
+  }
+  const regExpLiteral = createRegExpLiteral(path.get("arguments"), t);
+  if (regExpLiteral) {
+    path.replaceWith(regExpLiteral);
+  }
+}
+
 module.exports = function({ types: t }) {
   return {
     name: "transform-regexp-constructors",
     visitor: {
       NewExpression(path) {
-        if (!t.isIdentifier(path.node.callee, {name: "RegExp"})) {
-          return;
-        }
-        const evaluatedArgs = path.get("arguments")
-                                  .map((a) => a.evaluate());
-        if (!evaluatedArgs.every((a) => a.confident === true &&
-            typeof a.value === "string")) {
-          return;
-        }
-        let pattern = (evaluatedArgs.length >= 1 &&
-                          evaluatedArgs[0].value !== "") ?
-                        evaluatedArgs[0].value :
-                        "(?:)";
-        const flags = evaluatedArgs.length >= 2 ?
-                      evaluatedArgs[1].value :
-                      "";
-
-        pattern = pattern
-          .replace(/\n/g, "\\n")
-          .replace(/\r/g, "\\r")
-          .replace(/\//g, "\\/");
-
-        path.replaceWith(t.regExpLiteral(pattern, flags));
-      }
+        maybeReplaceWithRegExpLiteral(path, t);
+      },
+      CallExpression(path) {
+        // equivalent to `new RegExp()` according to §21.2.3
+        maybeReplaceWithRegExpLiteral(path, t);
+      },
     },
   };
 };