120 lines
3.2 KiB
JavaScript
120 lines
3.2 KiB
JavaScript
/**
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* Rule: no-nesting
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* Avoid nesting your promises.
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*/
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'use strict'
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const { getScope } = require('./lib/eslint-compat')
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const getDocsUrl = require('./lib/get-docs-url')
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const hasPromiseCallback = require('./lib/has-promise-callback')
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const isInsidePromise = require('./lib/is-inside-promise')
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module.exports = {
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meta: {
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type: 'suggestion',
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docs: {
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description: 'Disallow nested `then()` or `catch()` statements.',
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url: getDocsUrl('no-nesting'),
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},
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schema: [],
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},
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create(context) {
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/**
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* Array of callback function scopes.
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* Scopes are in order closest to the current node.
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* @type {import('eslint').Scope.Scope[]}
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*/
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const callbackScopes = []
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/**
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* @param {import('eslint').Scope.Scope} scope
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* @returns {Iterable<import('eslint').Scope.Reference>}
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*/
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function* iterateDefinedReferences(scope) {
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for (const variable of scope.variables) {
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for (const reference of variable.references) {
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yield reference
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}
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}
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}
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return {
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':function'(node) {
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if (isInsidePromise(node)) {
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callbackScopes.unshift(getScope(context, node))
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}
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},
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':function:exit'(node) {
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if (isInsidePromise(node)) {
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callbackScopes.shift()
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}
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},
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CallExpression(node) {
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if (!hasPromiseCallback(node)) return
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if (!callbackScopes.length) {
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// The node is not in the callback function.
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return
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}
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// Checks if the argument callback uses variables defined in the closest callback function scope.
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//
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// e.g.
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// ```
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// doThing()
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// .then(a => getB(a)
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// .then(b => getC(a, b))
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// )
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// ```
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//
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// In the above case, Since the variables it references are undef,
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// we cannot refactor the nesting like following:
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// ```
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// doThing()
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// .then(a => getB(a))
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// .then(b => getC(a, b))
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// ```
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//
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// However, `getD` can be refactored in the following:
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// ```
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// doThing()
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// .then(a => getB(a)
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// .then(b => getC(a, b)
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// .then(c => getD(a, c))
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// )
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// )
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// ```
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// ↓
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// ```
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// doThing()
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// .then(a => getB(a)
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// .then(b => getC(a, b))
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// .then(c => getD(a, c))
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// )
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// ```
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// This is why we only check the closest callback function scope.
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//
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const closestCallbackScope = callbackScopes[0]
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for (const reference of iterateDefinedReferences(
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closestCallbackScope
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)) {
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if (
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node.arguments.some(
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(arg) =>
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arg.range[0] <= reference.identifier.range[0] &&
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reference.identifier.range[1] <= arg.range[1]
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)
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) {
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// Argument callbacks refer to variables defined in the callback function.
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return
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}
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}
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context.report({
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node: node.callee.property,
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message: 'Avoid nesting promises.',
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})
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},
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}
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},
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}
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