prefer-array-flat: Fix incorrect fix, check `Array.prototype.concat…

….call` (#1317)

docs/rules/prefer-array-flat.md

@@ -7,49 +7,61 @@ This rule is fixable.
 ## Fail
 
 ```js
-const foo = bar.flatMap(x => x);
+const foo = array.flatMap(x => x);
 ```
 
 ```js
-const foo = bar.reduce((a, b) => a.concat(b), []);
+const foo = array.reduce((a, b) => a.concat(b), []);
 ```
 
 ```js
-const foo = bar.reduce((a, b) => [...a, ...b], []);
+const foo = array.reduce((a, b) => [...a, ...b], []);
 ```
 
 ```js
-const foo = [].concat(bar);
+const foo = [].concat(maybeArray);
 ```
 
 ```js
-const foo = [].concat(...bar);
+const foo = [].concat(...array);
 ```
 
 ```js
-const foo = [].concat.apply([], bar);
+const foo = [].concat.apply([], array);
 ```
 
 ```js
-const foo = Array.prototype.concat.apply([], bar);
+const foo = Array.prototype.concat.apply([], array);
 ```
 
 ```js
-const foo = _.flatten(bar);
+const foo = Array.prototype.concat.call([], maybeArray);
 ```
 
 ```js
-const foo = lodash.flatten(bar);
+const foo = Array.prototype.concat.call([], ...array);
 ```
 
 ```js
-const foo = underscore.flatten(bar);
+const foo = _.flatten(array);
+```
+
+```js
+const foo = lodash.flatten(array);
+```
+
+```js
+const foo = underscore.flatten(array);
 ```
 
 ## Pass
 
 ```js
-const foo = bar.flat();
+const foo = array.flat();
+```
+
+```js
+const foo = [maybeArray].flat();
 ```
 
 ## Options

rules/prefer-array-flat.js

@@ -9,6 +9,7 @@ const {
 const needsSemicolon = require('./utils/needs-semicolon');
 const shouldAddParenthesesToMemberExpressionObject = require('./utils/should-add-parentheses-to-member-expression-object');
 const {isNodeMatches, isNodeMatchesNameOrPath} = require('./utils/is-node-matches');
+const {getParenthesizedText, isParenthesized} = require('./utils/parentheses');
 
 const MESSAGE_ID = 'prefer-array-flat';
 const messages = {
@@ -89,7 +90,7 @@ const arrayReduce2 = {
  description: 'Array#reduce()'
 };
 
-// `[].concat(array)` and `[].concat(...array)`
+// `[].concat(maybeArray)` and `[].concat(...array)`
 const emptyArrayConcat = {
  selector: [
  methodCallSelector({
@@ -103,24 +104,33 @@ const emptyArrayConcat = {
  const argumentNode = node.arguments[0];
  return argumentNode.type === 'SpreadElement' ? argumentNode.argument : argumentNode;
  },
- description: '[].concat()'
+ description: '[].concat()',
+ shouldSwitchToArray: node => node.arguments[0].type !== 'SpreadElement'
 };
 
-// `[].concat.apply([], array)` and `Array.prototype.concat.apply([], array)`
+// - `[].concat.apply([], array)` and `Array.prototype.concat.apply([], array)`
+// - `[].concat.call([], maybeArray)` and `Array.prototype.concat.call([], maybeArray)`
+// - `[].concat.call([], ...array)` and `Array.prototype.concat.call([], ...array)`
 const arrayPrototypeConcat = {
  selector: [
  methodCallSelector({
- name: 'apply',
- length: 2
+ names: ['apply', 'call'],
+ length: 2,
+ allowSpreadElement: true
  }),
  emptyArraySelector('arguments.0'),
  arrayPrototypeMethodSelector({
  path: 'callee.object',
  name: 'concat'
  })
  ].join(''),
- getArrayNode: node => node.arguments[1],
- description: 'Array.prototype.concat()'
+ testFunction: node => node.arguments[1].type !== 'SpreadElement' || node.callee.property.name === 'call',
+ getArrayNode: node => {
+ const argumentNode = node.arguments[1];
+ return argumentNode.type === 'SpreadElement' ? argumentNode.argument : argumentNode;
+ },
+ description: 'Array.prototype.concat()',
+ shouldSwitchToArray: node => node.arguments[1].type !== 'SpreadElement' && node.callee.property.name === 'call'
 };
 
 const lodashFlattenFunctions = [
@@ -133,10 +143,21 @@ const anyCall = {
  getArrayNode: node => node.arguments[0]
 };
 
-function fix(node, array, sourceCode) {
+function fix(node, array, sourceCode, shouldSwitchToArray) {
+ if (typeof shouldSwitchToArray === 'function') {
+ shouldSwitchToArray = shouldSwitchToArray(node);
+ }
+
  return fixer => {
- let fixed = sourceCode.getText(array);
- if (shouldAddParenthesesToMemberExpressionObject(array, sourceCode)) {
+ let fixed = getParenthesizedText(array, sourceCode);
+ if (shouldSwitchToArray) {
+ // `array` is an argument, when it changes to `array[]`, we don't need add extra parentheses
+ fixed = `[${fixed}]`;
+ // And we don't need to add parentheses to the new array to call `.flat()`
+ } else if (
+ !isParenthesized(array, sourceCode) &&
+ shouldAddParenthesesToMemberExpressionObject(array, sourceCode)
+ ) {
  fixed = `(${fixed})`;
  }
 
@@ -173,7 +194,7 @@ function create(context) {
  }
  ];
 
- for (const {selector, testFunction, description, getArrayNode} of cases) {
+ for (const {selector, testFunction, description, getArrayNode, shouldSwitchToArray} of cases) {
  listeners[selector] = function (node) {
  if (testFunction && !testFunction(node)) {
  return;
@@ -196,7 +217,7 @@ function create(context) {
  sourceCode.getCommentsInside(node).length ===
  sourceCode.getCommentsInside(array).length
  ) {
- problem.fix = fix(node, array, sourceCode);
+ problem.fix = fix(node, array, sourceCode, shouldSwitchToArray);
  }
 
  context.report(problem);

rules/utils/should-add-parentheses-to-member-expression-object.js

@@ -20,6 +20,7 @@ function shouldAddParenthesesToMemberExpressionObject(node, sourceCode) {
  case 'ChainExpression':
  case 'TemplateLiteral':
  case 'ThisExpression':
+ case 'ArrayExpression':
  return false;
  case 'NewExpression':
  return !isNewExpressionWithParentheses(node, sourceCode);

test/prefer-array-flat.mjs

@@ -97,7 +97,11 @@ test.snapshot({
  '[].concat?.(array)'
  ],
  invalid: [
- '[].concat(array)'
+ '[].concat(maybeArray)',
+ '[].concat( ((0, maybeArray)) )',
+ '[].concat( ((maybeArray)) )',
+ '[].concat( [foo] )',
+ '[].concat( [[foo]] )'
  ]
 });
 
@@ -115,11 +119,16 @@ test.snapshot({
  '[].concat?.(...array)'
  ],
  invalid: [
- '[].concat(...array)'
+ '[].concat(...array)',
+ '[].concat(...(( array )))',
+ '[].concat(...(( [foo] )))',
+ '[].concat(...(( [[foo]] )))'
  ]
 });
 
-// `[].concat.apply([], array)`
+// - `[].concat.apply([], array)`
+// - `[].concat.call([], maybeArray)`
+// - `[].concat.call([], ...array)`
 test.snapshot({
  valid: [
  'new [].concat.apply([], array)',
@@ -139,11 +148,29 @@ test.snapshot({
  '[]?.concat.apply([], array)'
  ],
  invalid: [
- '[].concat.apply([], array)'
+ '[].concat.apply([], array)',
+ '[].concat.apply([], ((0, array)))',
+ '[].concat.apply([], ((array)))',
+ '[].concat.apply([], [foo])',
+ '[].concat.apply([], [[foo]])',
+
+ '[].concat.call([], maybeArray)',
+ '[].concat.call([], ((0, maybeArray)))',
+ '[].concat.call([], ((maybeArray)))',
+ '[].concat.call([], [foo])',
+ '[].concat.call([], [[foo]])',
+
+ '[].concat.call([], ...array)',
+ '[].concat.call([], ...((0, array)))',
+ '[].concat.call([], ...((array)))',
+ '[].concat.call([], ...[foo])',
+ '[].concat.call([], ...[[foo]])'
  ]
 });
 
-// `Array.prototype.concat.apply([], array)`
+// - `Array.prototype.concat.apply([], array)`
+// - `Array.prototype.concat.call([], maybeArray)`
+// - `Array.prototype.concat.call([], ...array)`
 test.snapshot({
  valid: [
  'new Array.prototype.concat.apply([], array)',
@@ -167,7 +194,23 @@ test.snapshot({
  'object.Array.prototype.concat.apply([], array)'
  ],
  invalid: [
- 'Array.prototype.concat.apply([], array)'
+ 'Array.prototype.concat.apply([], array)',
+ 'Array.prototype.concat.apply([], ((0, array)))',
+ 'Array.prototype.concat.apply([], ((array)))',
+ 'Array.prototype.concat.apply([], [foo])',
+ 'Array.prototype.concat.apply([], [[foo]])',
+
+ 'Array.prototype.concat.call([], maybeArray)',
+ 'Array.prototype.concat.call([], ((0, maybeArray)))',
+ 'Array.prototype.concat.call([], ((maybeArray)))',
+ 'Array.prototype.concat.call([], [foo])',
+ 'Array.prototype.concat.call([], [[foo]])',
+
+ 'Array.prototype.concat.call([], ...array)',
+ 'Array.prototype.concat.call([], ...((0, array)))',
+ 'Array.prototype.concat.call([], ...((array)))',
+ 'Array.prototype.concat.call([], ...[foo])',
+ 'Array.prototype.concat.call([], ...[[foo]])'
  ]
 });
 
@@ -294,9 +337,53 @@ test.snapshot({
  before()
  Array.prototype.concat.apply([], [array].concat(array))
  `,
+ outdent`
+ before()
+ Array.prototype.concat.apply([], +1)
+ `,
+ outdent`
+ before()
+ Array.prototype.concat.call([], +1)
+ `,
  // Parentheses
  'Array.prototype.concat.apply([], (0, array))',
+ 'Array.prototype.concat.call([], (0, array))',
  'async function a() { return [].concat(await getArray()); }',
+ '_.flatten((0, array))',
+ 'async function a() { return _.flatten(await getArray()); }',
+ 'async function a() { return _.flatten((await getArray())); }',
+ outdent`
+ before()
+ Array.prototype.concat.apply([], 1)
+ `,
+ outdent`
+ before()
+ Array.prototype.concat.call([], 1)
+ `,
+ outdent`
+ before()
+ Array.prototype.concat.apply([], 1.)
+ `,
+ outdent`
+ before()
+ Array.prototype.concat.call([], 1.)
+ `,
+ outdent`
+ before()
+ Array.prototype.concat.apply([], .1)
+ `,
+ outdent`
+ before()
+ Array.prototype.concat.call([], .1)
+ `,
+ outdent`
+ before()
+ Array.prototype.concat.apply([], 1.0)
+ `,
+ outdent`
+ before()
+ Array.prototype.concat.call([], 1.0)
+ `,
  // Comment
  '[].concat(some./**/array)',
  '[/**/].concat(some./**/array)',