[decorators] Correctly insert _initialize(this) after super(). (#8970)

* [decorators] Correctly insert `_initialize(this)` after `super()`.

This commit fixes to problem:
1) After `super();` statements, `_initialize(this)` was inserted without
   a trailing semicolon.
2) `(0, super())` causes an infinite recursion.

* Fix tests

* Add test

packages/babel-plugin-proposal-decorators/src/transformer.js

@@ -113,6 +113,10 @@ const bareSupersVisitor = {
   CallExpression(path, { initializeInstanceElements }) {
     if (path.get("callee").isSuper()) {
       path.insertAfter(t.cloneNode(initializeInstanceElements));
+
+      // Sometimes this path gets requeued (e.g. in (super(), foo)), and
+      // it leads to infinite recursion.
+      path.skip();
     }
   },
   Function(path) {

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initiailzer-after-super-bug-8808/input.js

@@ -0,0 +1,6 @@
+@decorator(parameter)
+class Sub extends Super {
+  constructor() {
+    super().method();
+  }
+}

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initiailzer-after-super-bug-8808/output.js

@@ -0,0 +1,17 @@
+let Sub = babelHelpers.decorate([decorator(parameter)], function (_initialize, _Super) {
+  "use strict";
+
+  class Sub extends _Super {
+    constructor() {
+      var _temp;
+
+      (_temp = super(), _initialize(this), _temp).method();
+    }
+
+  }
+
+  return {
+    F: Sub,
+    d: []
+  };
+}, Super);

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initialize-after-super-bug-8931/input.js

@@ -0,0 +1,7 @@
+@dec
+class B extends A {
+  constructor() {
+    super();
+    [];
+  }
+}

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initialize-after-super-bug-8931/output.js

@@ -0,0 +1,19 @@
+let B = babelHelpers.decorate([dec], function (_initialize, _A) {
+  "use strict";
+
+  class B extends _A {
+    constructor() {
+      super();
+
+      _initialize(this);
+
+      [];
+    }
+
+  }
+
+  return {
+    F: B,
+    d: []
+  };
+}, A);

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initialize-after-super-expression/input.js

@@ -0,0 +1,6 @@
+@dec
+class B extends A {
+  constructor() {
+    (0, super());
+  }
+}

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initialize-after-super-expression/output.js

@@ -0,0 +1,17 @@
+let B = babelHelpers.decorate([dec], function (_initialize, _A) {
+  "use strict";
+
+  class B extends _A {
+    constructor() {
+      var _temp;
+
+      0, (_temp = super(), _initialize(this), _temp);
+    }
+
+  }
+
+  return {
+    F: B,
+    d: []
+  };
+}, A);

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initialize-after-super-multiple/input.js

@@ -0,0 +1,14 @@
+@dec
+class B extends A {
+  constructor() {
+    const foo = () => { super(); };
+
+    if (a) { super(); }
+    else { foo(); }
+
+    while (0) { super(); }
+
+    super();
+  }
+}
+

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initialize-after-super-multiple/output.js

@@ -0,0 +1,37 @@
+let B = babelHelpers.decorate([dec], function (_initialize, _A) {
+  "use strict";
+
+  class B extends _A {
+    constructor() {
+      const foo = () => {
+        super();
+
+        _initialize(this);
+      };
+
+      if (a) {
+        super();
+
+        _initialize(this);
+      } else {
+        foo();
+      }
+
+      while (0) {
+        super();
+
+        _initialize(this);
+      }
+
+      super();
+
+      _initialize(this);
+    }
+
+  }
+
+  return {
+    F: B,
+    d: []
+  };
+}, A);

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initialize-after-super-statement/input.js

@@ -0,0 +1,6 @@
+@dec
+class B extends A {
+  constructor() {
+    super();
+  }
+}

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/initialize-after-super-statement/output.js

@@ -0,0 +1,17 @@
+let B = babelHelpers.decorate([dec], function (_initialize, _A) {
+  "use strict";
+
+  class B extends _A {
+    constructor() {
+      super();
+
+      _initialize(this);
+    }
+
+  }
+
+  return {
+    F: B,
+    d: []
+  };
+}, A);

packages/babel-traverse/src/path/modification.js

@@ -105,7 +105,17 @@ export function insertAfter(nodes) {
     parentPath.isExportNamedDeclaration() ||
     (parentPath.isExportDefaultDeclaration() && this.isDeclaration())
   ) {
-    return parentPath.insertAfter(nodes);
+    return parentPath.insertAfter(
+      nodes.map(node => {
+        // Usually after an expression we can safely insert another expression:
+        //   A.insertAfter(B)
+        //     foo = A;  -> foo = (A, B);
+        // If A is an expression statement, it isn't safe anymore so we need to
+        // convert B to an expression statement
+        //     A;        -> A; B // No semicolon! It could break if followed by [!
+        return t.isExpression(node) ? t.expressionStatement(node) : node;
+      }),
+    );
   } else if (
     (this.isNodeType("Expression") && !this.isJSXElement()) ||
     (parentPath.isForStatement() && this.key === "init")

packages/babel-traverse/test/modification.js

@@ -235,7 +235,9 @@ describe("modification", function() {
         fnPath.insertAfter(t.identifier("x"));
 
         expect(bodyPath.get("body")).toHaveLength(2);
-        expect(bodyPath.get("body.1").node).toEqual(t.identifier("x"));
+        expect(bodyPath.get("body.1").node).toEqual(
+          t.expressionStatement(t.identifier("x")),
+        );
       });
 
       it("the ExportDefaultDeclaration, if a declaration is exported", function() {
@@ -246,7 +248,9 @@ describe("modification", function() {
         fnPath.insertAfter(t.identifier("x"));
 
         expect(bodyPath.get("body")).toHaveLength(2);
-        expect(bodyPath.get("body.1").node).toEqual(t.identifier("x"));
+        expect(bodyPath.get("body.1").node).toEqual(
+          t.expressionStatement(t.identifier("x")),
+        );
       });
 
       it("the exported expression", function() {