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Avoid naming collision with default array element variable in autofix for no-for-loop rule #749

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merged 6 commits into from May 27, 2020
Merged

Avoid naming collision with default array element variable in autofix for no-for-loop rule #749

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f6ea659
fix: avoid naming collision with default array element variable in au…
bmish May 25, 2020
a1c5b30
More tests
fisker May 25, 2020
2740c62
Add more tests
fisker May 27, 2020
10772e7
Style
fisker May 27, 2020
00d4fb0
rename
fisker May 27, 2020
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style
fisker May 27, 2020
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10 changes: 9 additions & 1 deletion rules/no-for-loop.js
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Expand Up @@ -2,6 +2,7 @@
const getDocumentationUrl = require('./utils/get-documentation-url');
const isLiteralValue = require('./utils/is-literal-value');
const {flatten} = require('lodash');
const avoidCapture = require('./utils/avoid-capture');

const defaultElementName = 'element';
const isLiteralZero = node => isLiteralValue(node, 0);
Expand Down Expand Up @@ -261,6 +262,13 @@ const getReferencesInChildScopes = (scope, name) => {
];
};

const getChildScopesRecursive = scope => {
return [
scope,
...flatten(scope.childScopes.map(s => getChildScopesRecursive(s)))
];
};

const create = context => {
const sourceCode = context.getSourceCode();
const {scopeManager} = sourceCode;
Expand Down Expand Up @@ -335,7 +343,7 @@ const create = context => {
const shouldGenerateIndex = isIndexVariableUsedElsewhereInTheLoopBody(indexVariable, bodyScope, arrayIdentifierName);

const index = indexIdentifierName;
const element = elementIdentifierName || defaultElementName;
const element = elementIdentifierName || avoidCapture(defaultElementName, getChildScopesRecursive(bodyScope), context.parserOptions.ecmaVersion);
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@fisker fisker May 26, 2020 •
edited

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I think this is not right.

			for (let i = 0; i < arr.length; i += 1) {
				console.log(arr[1]);
				function foo(element) {
					console.log(element);
				}
			}

It should allow use variable element.

this foo function scope should not included, because it didn't use arr[1], this is why avoidCapture didn't recursive automaticlly.

We need collect scopes from references.

BTW: don't squash commits, this makes review harder.

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A few questions for you.

  1. By arr[1], do you mean arr[i]? The rule doesn't report a violation with arr[1].
  2. In your example, I see that we technically can use element as our new array variable name, but wouldn't that be unnecessarily confusing? The no-shadow rule suggests this is bad practice.

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  1. Yes, arr[1], sorry.
  2. Yes no-shadow suggest no variable shadowing, it's default to function, do you use all option? My example is about function scope, but there are other scopes.

This example

for (let i = 0; i < errors.length; i++) {
  console.log(errors[i]);

  try {
    doSomethingThrowError();
  } catch(error) {}
}

After #745 we will fix it to

for (const error_ of errors) {
  console.log(error_);

  try {
    doSomethingThrowError();
  } catch(error) {}
}

I don't want use error_, I can use error.

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Anyway, this is not very important, let's keep it this way now.

I'm going to check this PR again.

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Thanks for the explanation. I will follow-up with your recommendation if I have a chance.

const array = arrayIdentifierName;

let declarationElement = element;
Expand Down
128 changes: 128 additions & 0 deletions test/no-for-loop.js
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Expand Up @@ -482,6 +482,134 @@ ruleTester.run('no-for-loop', rule, {
const [ a, b ] = element;
console.log(a, b, element);
}
`),

// Avoid naming collision when using default element name.
testCase(outdent`
for (let i = 0; i < arr.length; i += 1) {
console.log(arr[i]);
const element = foo();
console.log(element);
}
`, outdent`
for (const element_ of arr) {
console.log(element_);
const element = foo();
console.log(element);
}
`),

// Avoid naming collision when using default element name (different scope).
testCase(outdent`
function element(element_) {
for (let i = 0; i < arr.length; i += 1) {
console.log(arr[i], element);
}
}
`, outdent`
function element(element_) {
for (const element__ of arr) {
console.log(element__, element);
}
}
`),
testCase(outdent`
for (let i = 0; i < arr.length; i += 1) {
function element__(element) {
console.log(arr[i], element);
}
}
`, outdent`
for (const element_ of arr) {
function element__(element) {
console.log(element_, element);
}
}
`),
bmish marked this conversation as resolved.
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testCase(outdent`
for (let i = 0; i < arr.length; i += 1) {
function element_(element) {
console.log(arr[i], element);
}
}
`, outdent`
for (const element__ of arr) {
function element_(element) {
console.log(element__, element);
}
}
`),
testCase(outdent`
for (let i = 0; i < arr.length; i += 1) {
function element() {
console.log(arr[i], element);
}
}
`, outdent`
for (const element_ of arr) {
function element() {
console.log(element_, element);
}
}
`),
testCase(outdent`
for (let i = 0; i < arr.length; i += 1) {
console.log(arr[i], element);
}
`, outdent`
for (const element_ of arr) {
console.log(element_, element);
}
`),
testCase(outdent`
for (let element = 0; element < arr.length; element += 1) {
console.log(element, arr[element]);
}
`, outdent`
for (const [element, element_] of arr.entries()) {
console.log(element, element_);
}
`),
testCase(outdent`
for (let element = 0; element < arr.length; element += 1) {
console.log(arr[element]);
}
`, outdent`
for (const element_ of arr) {
console.log(element_);
}
`),
testCase(outdent`
for (const element of arr) {
for (let j = 0; j < arr2.length; j += 1) {
console.log(element, arr2[j]);
}
}
`, outdent`
for (const element of arr) {
for (const element_ of arr2) {
console.log(element, element_);
}
}
`),

// Avoid naming collision when using default element name (multiple collisions).
testCase(outdent`
for (let i = 0; i < arr.length; i += 1) {
const element = foo();
console.log(arr[i]);
const element_ = foo();
console.log(element);
console.log(element_);
}
`, outdent`
for (const element__ of arr) {
const element = foo();
console.log(element__);
const element_ = foo();
console.log(element);
console.log(element_);
}
`)
]
});
Expand Down