Implement setSpreadProperties

packages/babel-core/src/config/validation/options.js

@@ -343,6 +343,7 @@ export const assumptionsNames = new Set<string>([
   "setClassMethods",
   "setComputedProperties",
   "setPublicClassFields",
+  "setSpreadProperties",
   "skipForOfIteratorClosing",
 ]);
 

packages/babel-plugin-proposal-object-rest-spread/src/index.js

@@ -17,17 +17,15 @@ const ZERO_REFS = (() => {
 export default declare((api, opts) => {
   api.assertVersion(7);
 
-  const { useBuiltIns = false, loose = false } = opts;
-
-  if (typeof loose !== "boolean") {
-    throw new Error(".loose must be a boolean, or undefined");
-  }
+  const { useBuiltIns = false } = opts;
 
   const ignoreFunctionLength =
     api.assumption("ignoreFunctionLength") ?? opts.loose;
   const objectRestNoSymbols =
     api.assumption("objectRestNoSymbols") ?? opts.loose;
   const pureGetters = api.assumption("pureGetters") ?? opts.loose;
+  const setSpreadProperties =
+    api.assumption("setSpreadProperties") ?? opts.loose;
 
   function getExtendsHelper(file) {
     return useBuiltIns
@@ -561,7 +559,7 @@ export default declare((api, opts) => {
         if (!hasSpread(path.node)) return;
 
         let helper;
-        if (loose) {
+        if (setSpreadProperties) {
           helper = getExtendsHelper(file);
         } else {
           try {

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties-with-useBuiltIns/assignment/input.js

@@ -0,0 +1,7 @@
+var x;
+var y;
+var z;
+
+z = { x, ...y };
+
+z = { x, w: { ...y } };

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties-with-useBuiltIns/assignment/output.js

@@ -0,0 +1,10 @@
+var x;
+var y;
+var z;
+z = Object.assign({
+  x
+}, y);
+z = {
+  x,
+  w: Object.assign({}, y)
+};

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties-with-useBuiltIns/expression/exec.js

@@ -0,0 +1,9 @@
+var log = [];
+
+var a = {
+  ...{ get foo() { log.push(1); } },
+  get bar() { log.push(2); }
+};
+
+// Loose mode uses regular Get, not GetOwnProperty.
+expect(log).toEqual([1, 2]);

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties-with-useBuiltIns/expression/input.js

@@ -0,0 +1,16 @@
+var a;
+var b;
+var c;
+var d;
+var x;
+var y;
+
+({ x, ...y, a, ...b, c });
+
+({ ...Object.prototype });
+
+({ ...{ foo: 'bar' } });
+
+({ ...{ foo: 'bar' }, ...{ bar: 'baz' } });
+
+({ ...{ get foo () { return 'foo' } } });

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties-with-useBuiltIns/expression/output.js

@@ -0,0 +1,28 @@
+var a;
+var b;
+var c;
+var d;
+var x;
+var y;
+Object.assign(Object.assign(Object.assign({
+  x
+}, y), {}, {
+  a
+}, b), {}, {
+  c
+});
+Object.assign({}, Object.prototype);
+Object.assign({}, {
+  foo: 'bar'
+});
+Object.assign(Object.assign({}, {
+  foo: 'bar'
+}), {
+  bar: 'baz'
+});
+Object.assign({}, {
+  get foo() {
+    return 'foo';
+  }
+
+});

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties-with-useBuiltIns/no-getOwnPropertyDescriptors/exec.js

@@ -0,0 +1,9 @@
+const oldGOPDs = Object.getOwnPropertyDescriptors;
+Object.getOwnPropertyDescriptors = null;
+
+try {
+  ({ ...{ a: 1 }, b: 1, ...{} });
+} finally {
+  Object.getOwnPropertyDescriptors = oldGOPDs;
+}
+

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties-with-useBuiltIns/no-object-assign-exec/exec.js

@@ -0,0 +1,43 @@
+"use strict";
+Object.defineProperty(Object.prototype, 'NOSET', {
+  get(value) {
+    // noop
+  },
+});
+
+Object.defineProperty(Object.prototype, 'NOWRITE', {
+  writable: false,
+  value: 'abc',
+});
+
+const obj = { 'NOSET': 123 };
+// this won't work as expected if transformed as Object.assign (or equivalent)
+// because those trigger object setters (spread don't)
+expect(() => {
+  const objSpread = { ...obj };
+}).toThrow();
+
+const obj2 = { 'NOWRITE': 456 };
+// this throws `TypeError: Cannot assign to read only property 'NOWRITE'`
+// if transformed as Object.assign (or equivalent) because those use *assignment* for creating properties
+// (spread defines them)
+expect(() => {
+  const obj2Spread = { ...obj2 };
+}).toThrow();
+
+const KEY = Symbol('key');
+const obj3Spread = { ...{ get foo () { return 'bar' } }, [KEY]: 'symbol' };
+expect(Object.getOwnPropertyDescriptor(obj3Spread, 'foo').value).toBe('bar');
+expect(Object.getOwnPropertyDescriptor(obj3Spread, KEY).value).toBe('symbol');
+
+const obj4Spread = { ...Object.prototype };
+expect(Object.getOwnPropertyDescriptor(obj4Spread, 'hasOwnProperty')).toBeUndefined();
+
+expect(() => ({ ...null, ...undefined })).not.toThrow();
+
+const o = Object.create(null);
+o.a = 'foo';
+o.__proto__ = [];
+const o2 = { ...o };
+// Loose will do o2.__proto__ = []
+expect(Array.isArray(Object.getPrototypeOf(o2))).toBe(true);

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties-with-useBuiltIns/options.json

@@ -0,0 +1,9 @@
+{
+  "plugins": [
+    ["external-helpers", { "helperVersion": "7.100.0"}],
+    ["proposal-object-rest-spread", { "useBuiltIns": true }]
+  ],
+  "assumptions": {
+    "setSpreadProperties": true
+  }
+}

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties/assignment/input.js

@@ -0,0 +1,7 @@
+var x;
+var y;
+var z;
+
+z = { x, ...y };
+
+z = { x, w: { ...y } };

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties/assignment/output.js

@@ -0,0 +1,10 @@
+var x;
+var y;
+var z;
+z = babelHelpers.extends({
+  x
+}, y);
+z = {
+  x,
+  w: babelHelpers.extends({}, y)
+};

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties/expression/exec.js

@@ -0,0 +1,9 @@
+var log = [];
+
+var a = {
+  ...{ get foo() { log.push(1); } },
+  get bar() { log.push(2); }
+};
+
+// Loose mode uses regular Get, not GetOwnProperty.
+expect(log).toEqual([1, 2]);

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties/expression/input.js

@@ -0,0 +1,16 @@
+var a;
+var b;
+var c;
+var d;
+var x;
+var y;
+
+({ x, ...y, a, ...b, c });
+
+({ ...Object.prototype });
+
+({ ...{ foo: 'bar' } });
+
+({ ...{ foo: 'bar' }, ...{ bar: 'baz' } });
+
+({ ...{ get foo () { return 'foo' } } });

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties/expression/output.js

@@ -0,0 +1,28 @@
+var a;
+var b;
+var c;
+var d;
+var x;
+var y;
+babelHelpers.extends(babelHelpers.extends(babelHelpers.extends({
+  x
+}, y), {}, {
+  a
+}, b), {}, {
+  c
+});
+babelHelpers.extends({}, Object.prototype);
+babelHelpers.extends({}, {
+  foo: 'bar'
+});
+babelHelpers.extends(babelHelpers.extends({}, {
+  foo: 'bar'
+}), {
+  bar: 'baz'
+});
+babelHelpers.extends({}, {
+  get foo() {
+    return 'foo';
+  }
+
+});

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties/no-getOwnPropertyDescriptors/exec.js

@@ -0,0 +1,9 @@
+const oldGOPDs = Object.getOwnPropertyDescriptors;
+Object.getOwnPropertyDescriptors = null;
+
+try {
+  ({ ...{ a: 1 }, b: 1, ...{} });
+} finally {
+  Object.getOwnPropertyDescriptors = oldGOPDs;
+}
+

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties/no-object-assign-exec/exec.js

@@ -0,0 +1,43 @@
+"use strict";
+Object.defineProperty(Object.prototype, 'NOSET', {
+  get(value) {
+    // noop
+  },
+});
+
+Object.defineProperty(Object.prototype, 'NOWRITE', {
+  writable: false,
+  value: 'abc',
+});
+
+const obj = { 'NOSET': 123 };
+// this won't work as expected if transformed as Object.assign (or equivalent)
+// because those trigger object setters (spread don't)
+expect(() => {
+  const objSpread = { ...obj };
+}).toThrow();
+
+const obj2 = { 'NOWRITE': 456 };
+// this throws `TypeError: Cannot assign to read only property 'NOWRITE'`
+// if transformed as Object.assign (or equivalent) because those use *assignment* for creating properties
+// (spread defines them)
+expect(() => {
+  const obj2Spread = { ...obj2 };
+}).toThrow();
+
+const KEY = Symbol('key');
+const obj3Spread = { ...{ get foo () { return 'bar' } }, [KEY]: 'symbol' };
+expect(Object.getOwnPropertyDescriptor(obj3Spread, 'foo').value).toBe('bar');
+expect(Object.getOwnPropertyDescriptor(obj3Spread, KEY).value).toBe('symbol');
+
+const obj4Spread = { ...Object.prototype };
+expect(Object.getOwnPropertyDescriptor(obj4Spread, 'hasOwnProperty')).toBeUndefined();
+
+expect(() => ({ ...null, ...undefined })).not.toThrow();
+
+const o = Object.create(null);
+o.a = 'foo';
+o.__proto__ = [];
+const o2 = { ...o };
+// Loose will do o2.__proto__ = []
+expect(Array.isArray(Object.getPrototypeOf(o2))).toBe(true);

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/assumption-setSpreadProperties/options.json

@@ -0,0 +1,9 @@
+{
+  "plugins": [
+    ["external-helpers", { "helperVersion": "7.100.0"}],
+    "proposal-object-rest-spread"
+  ],
+  "assumptions": {
+    "setSpreadProperties": true
+  }
+}