Remove undef from seqExpr - (Fix #373)

babel · Jan 23, 2017 · d228fc6 · d228fc6
1 parent 2b98b98
commit d228fc6
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diff --git a/...ugin-transform-remove-undefined/__tests__/babel-plugin-transform-remove-undefined-test.js b/...ugin-transform-remove-undefined/__tests__/babel-plugin-transform-remove-undefined-test.js
@@ -171,4 +171,36 @@ describe("transform-remove-undefined-plugin", () => {
       }`);
     expect(transform(source)).toBe(source);
   });
+
+  it("should remove from sequence expressions", () => {
+    const source = unpad(`
+      a = b, void 0, b = c, d.e.f(), void 0, hello.world();
+    `);
+    const expected = unpad(`
+      a = b, b = c, d.e.f(), hello.world();
+    `);
+    expect(transform(source)).toBe(expected);
+  });
+
+  it("should NOT remove last undefined from sequence expressions", () => {
+    const source = unpad(`
+      if (foo.bar(), void 0) {
+        foo.baz();
+      }
+      function bar() {
+        return a.b(), void 0;
+      }
+    `);
+    expect(transform(source)).toBe(source);
+  });
+
+  it("should remove last undefined from sequence expressions if safe", () => {
+    const source = unpad(`
+      a = b, void 0, b = c, d.e.f(), void 0, hello.world(), void 0;
+    `);
+    const expected = unpad(`
+      a = b, b = c, d.e.f(), hello.world();
+    `);
+    expect(transform(source)).toBe(expected);
+  });
 });
diff --git a/packages/babel-plugin-transform-remove-undefined/src/index.js b/packages/babel-plugin-transform-remove-undefined/src/index.js
@@ -80,6 +80,24 @@ module.exports = function() {
   return {
     name: "transform-remove-undefined",
     visitor: {
+      SequenceExpression(path) {
+        const expressions = path.get("expressions");
+
+        for (let i = 0; i < expressions.length; i++) {
+          const expr = expressions[i];
+          if (!isPureAndUndefined(expr)) continue;
+
+          // last value
+          if (i === expressions.length - 1) {
+            if (path.parentPath.isExpressionStatement()) {
+              expr.remove();
+            }
+          } else {
+            expr.remove();
+          }
+        }
+      },
+
       ReturnStatement(path) {
         if (path.node.argument !== null) {
           if (isPureAndUndefined(path.get("argument"))) {