Added ability to whitelist specific property/function names to use loose mode when transforming destructuring

Author: lvl99

packages/babel-plugin-transform-destructuring/src/index.js

@@ -1,15 +1,43 @@
 import { declare } from "@babel/helper-plugin-utils";
 import { types as t } from "@babel/core";
+import escapeRegExp from "lodash/escapeRegExp";
+
+function checkNameMatchesSelectiveLoose(name, selectiveLoose) {
+  for (let i = 0; i < selectiveLoose.length; i++) {
+    if (selectiveLoose[i].test(name)) {
+      return true;
+    }
+  }
+  return false;
+}
 
 export default declare((api, options) => {
   api.assertVersion(7);
 
-  const { loose = false, useBuiltIns = false } = options;
+  const {
+    loose = false,
+    useBuiltIns = false,
+    selectiveLoose = false,
+  } = options;
 
   if (typeof loose !== "boolean") {
     throw new Error(`.loose must be a boolean or undefined`);
   }
 
+  // Format selectiveLoose entries to RegExp expressions that can
+  // match generated babel names, i.e. `_x`, `_x2`, `_x3`, etc.
+  if (selectiveLoose) {
+    if (selectiveLoose instanceof Array) {
+      for (let i = 0; i < selectiveLoose.length; i++) {
+        selectiveLoose[i] = new RegExp(
+          `^_${escapeRegExp(selectiveLoose[i])}\\d*$`,
+        );
+      }
+    } else {
+      throw new Error(`.selectiveLoose must be an array or undefined`);
+    }
+  }
+
   const arrayOnlySpread = loose;
 
   function getExtendsHelper(file) {
@@ -73,6 +101,7 @@ export default declare((api, options) => {
       this.kind = opts.kind;
       this.arrayOnlySpread = opts.arrayOnlySpread;
       this.addHelper = opts.addHelper;
+      this.selectiveLoose = opts.selectiveLoose;
     }
 
     buildVariableAssignment(id, init) {
@@ -210,8 +239,12 @@ export default declare((api, options) => {
           );
         }
 
+        const isLoose =
+          (this.selectiveLoose &&
+            checkNameMatchesSelectiveLoose(objRef.name, this.selectiveLoose)) ||
+          loose;
         value = t.callExpression(
-          this.addHelper(`objectWithoutProperties${loose ? "Loose" : ""}`),
+          this.addHelper(`objectWithoutProperties${isLoose ? "Loose" : ""}`),
           [t.cloneNode(objRef), keyExpression],
         );
       }
@@ -479,6 +512,7 @@ export default declare((api, options) => {
           scope: scope,
           nodes: nodes,
           arrayOnlySpread,
+          selectiveLoose,
           addHelper: name => this.addHelper(name),
         });
 
@@ -504,6 +538,7 @@ export default declare((api, options) => {
           scope: scope,
           nodes: nodes,
           arrayOnlySpread,
+          selectiveLoose,
           addHelper: name => this.addHelper(name),
         });
         destructuring.init(pattern, ref);
@@ -522,6 +557,7 @@ export default declare((api, options) => {
           scope: scope,
           nodes: nodes,
           arrayOnlySpread,
+          selectiveLoose,
           addHelper: name => this.addHelper(name),
         });
 
@@ -579,6 +615,7 @@ export default declare((api, options) => {
             scope: scope,
             kind: node.kind,
             arrayOnlySpread,
+            selectiveLoose,
             addHelper: name => this.addHelper(name),
           });
 

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/es7-object-rest-selective-loose/exec.js

@@ -0,0 +1,6 @@
+const useState = () => (["state", "dispatch"]);
+
+var [state, dispatch] = useState();
+
+expect(state).toBe("state");
+expect(dispatch).toBe("dispatch");

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/es7-object-rest-selective-loose/input.js

@@ -0,0 +1,9 @@
+var z = {};
+var { ...x } = z;
+var { x, ...y } = z;
+var { [x]: x, ...y } = z;
+(function({ x, ...y }) { });
+
+({ x, y, ...z } = o);
+
+var [state, dispatch] = useState();

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/es7-object-rest-selective-loose/options.json

@@ -0,0 +1,7 @@
+{
+  "plugins": [
+    ["transform-destructuring", { "selectiveLoose": ["z", "useState"] }],
+    "proposal-object-rest-spread",
+    ["external-helpers", { "helperVersion": "7.1.5" }]
+  ]
+}

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/es7-object-rest-selective-loose/output.js

@@ -0,0 +1,24 @@
+var z = {};
+var _z = z,
+    x = babelHelpers.extends({}, _z);
+var _z2 = z,
+    x = _z2.x,
+    y = babelHelpers.objectWithoutPropertiesLoose(_z2, ["x"]);
+var _z3 = z,
+    x = _z3[x],
+    y = babelHelpers.objectWithoutPropertiesLoose(_z3, [x].map(babelHelpers.toPropertyKey));
+
+(function (_ref) {
+  let x = _ref.x,
+      y = babelHelpers.objectWithoutProperties(_ref, ["x"]);
+});
+
+var _o = o;
+x = _o.x;
+y = _o.y;
+z = babelHelpers.objectWithoutProperties(_o, ["x", "y"]);
+
+var _useState = useState(),
+    _useState2 = babelHelpers.slicedToArray(_useState, 2),
+    state = _useState2[0],
+    dispatch = _useState2[1];