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feat(eslint-plugin): [no-unnecessary-parameter-property-assignment] add new rule #8903
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feat(eslint-plugin): [no-unnecessary-property-assignment] add new rule
yeonjuan 8ec7665
Merge branch 'main' into new-rule/7045
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Merge branch 'main' into new-rule/7045
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42 changes: 42 additions & 0 deletions
42
packages/eslint-plugin/docs/rules/no-unnecessary-parameter-property-assignment.mdx
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,42 @@ | ||
| --- | ||
| description: 'Disallow unnecessary assignment of constructor property parameter.' | ||
| --- | ||
|
|
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| import Tabs from '@theme/Tabs'; | ||
| import TabItem from '@theme/TabItem'; | ||
|
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| > 🛑 This file is source code, not the primary documentation location! 🛑 | ||
| > | ||
| > See **https://typescript-eslint.io/rules/no-unnecessary-parameter-property-assignment** for documentation. | ||
|
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| [TypeScript's parameter properties](https://www.typescriptlang.org/docs/handbook/2/classes.html#parameter-properties) allow creating and initializing a member in one place. | ||
| Therefore, in most cases, it is not necessary to assign parameter properties of the same name to members within a constructor. | ||
|
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| ## Examples | ||
|
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| <Tabs> | ||
| <TabItem value="❌ Incorrect"> | ||
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| ```ts | ||
| class Foo { | ||
| constructor(public bar: string) { | ||
| this.bar = bar; | ||
| } | ||
| } | ||
| ``` | ||
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| </TabItem> | ||
| <TabItem value="✅ Correct"> | ||
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| ```ts | ||
| class Foo { | ||
| constructor(public bar: string) {} | ||
| } | ||
| ``` | ||
|
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| </TabItem> | ||
| </Tabs> | ||
|
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| ## When Not To Use It | ||
|
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| If you don't use parameter properties, you can ignore this rule. |
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233 changes: 233 additions & 0 deletions
233
packages/eslint-plugin/src/rules/no-unnecessary-parameter-property-assignment.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,233 @@ | ||
| import { DefinitionType } from '@typescript-eslint/scope-manager'; | ||
| import type { TSESTree } from '@typescript-eslint/utils'; | ||
| import { AST_NODE_TYPES, ASTUtils } from '@typescript-eslint/utils'; | ||
|
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| import { createRule, getStaticStringValue, nullThrows } from '../util'; | ||
|
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| const UNNECESSARY_OPERATORS = new Set(['=', '&&=', '||=', '??=']); | ||
|
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| export default createRule({ | ||
| name: 'no-unnecessary-parameter-property-assignment', | ||
| meta: { | ||
| docs: { | ||
| description: | ||
| 'Disallow unnecessary assignment of constructor property parameter', | ||
| }, | ||
| fixable: 'code', | ||
| messages: { | ||
| unnecessaryAssign: | ||
| 'This assignment is unnecessary since it is already assigned by a parameter property.', | ||
| }, | ||
| schema: [], | ||
| type: 'suggestion', | ||
| }, | ||
| defaultOptions: [], | ||
| create(context) { | ||
| const reportInfoStack: { | ||
| assignedBeforeUnnecessary: Set<string>; | ||
| assignedBeforeConstructor: Set<string>; | ||
| unnecessaryAssignments: { | ||
| name: string; | ||
| node: TSESTree.AssignmentExpression; | ||
| }[]; | ||
| }[] = []; | ||
|
|
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| function isThisMemberExpression( | ||
| node: TSESTree.Node, | ||
| ): node is TSESTree.MemberExpression { | ||
| return ( | ||
| node.type === AST_NODE_TYPES.MemberExpression && | ||
| node.object.type === AST_NODE_TYPES.ThisExpression | ||
| ); | ||
| } | ||
|
|
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| function getPropertyName(node: TSESTree.Node): string | null { | ||
| if (!isThisMemberExpression(node)) { | ||
| return null; | ||
| } | ||
|
|
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| if (node.property.type === AST_NODE_TYPES.Identifier) { | ||
| return node.property.name; | ||
| } | ||
| if (node.computed) { | ||
| return getStaticStringValue(node.property); | ||
| } | ||
| return null; | ||
| } | ||
|
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| function findParentFunction( | ||
| node: TSESTree.Node | undefined, | ||
| ): | ||
| | TSESTree.FunctionExpression | ||
| | TSESTree.FunctionDeclaration | ||
| | TSESTree.ArrowFunctionExpression | ||
| | undefined { | ||
| if ( | ||
| !node || | ||
| node.type === AST_NODE_TYPES.FunctionDeclaration || | ||
| node.type === AST_NODE_TYPES.FunctionExpression || | ||
| node.type === AST_NODE_TYPES.ArrowFunctionExpression | ||
| ) { | ||
| return node; | ||
| } | ||
| return findParentFunction(node.parent); | ||
| } | ||
|
|
||
| function findParentPropertyDefinition( | ||
| node: TSESTree.Node | undefined, | ||
| ): TSESTree.PropertyDefinition | undefined { | ||
| if (!node || node.type === AST_NODE_TYPES.PropertyDefinition) { | ||
| return node; | ||
| } | ||
| return findParentPropertyDefinition(node.parent); | ||
| } | ||
|
|
||
| function isConstructorFunctionExpression( | ||
| node: TSESTree.Node | undefined, | ||
| ): node is TSESTree.FunctionExpression { | ||
| return ( | ||
| node?.type === AST_NODE_TYPES.FunctionExpression && | ||
| ASTUtils.isConstructor(node.parent) | ||
| ); | ||
| } | ||
|
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| function isReferenceFromParameter(node: TSESTree.Identifier): boolean { | ||
| const scope = context.sourceCode.getScope(node); | ||
|
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| const rightRef = scope.references.find( | ||
| ref => ref.identifier.name === node.name, | ||
| ); | ||
| return rightRef?.resolved?.defs.at(0)?.type === DefinitionType.Parameter; | ||
| } | ||
|
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| function isParameterPropertyWithName( | ||
| node: TSESTree.Parameter, | ||
| name: string, | ||
| ): boolean { | ||
| return ( | ||
| node.type === AST_NODE_TYPES.TSParameterProperty && | ||
| ((node.parameter.type === AST_NODE_TYPES.Identifier && // constructor (public foo) {} | ||
| node.parameter.name === name) || | ||
| (node.parameter.type === AST_NODE_TYPES.AssignmentPattern && // constructor (public foo = 1) {} | ||
| node.parameter.left.type === AST_NODE_TYPES.Identifier && | ||
| node.parameter.left.name === name)) | ||
| ); | ||
| } | ||
|
|
||
| function getIdentifier(node: TSESTree.Node): TSESTree.Identifier | null { | ||
| if (node.type === AST_NODE_TYPES.Identifier) { | ||
| return node; | ||
| } | ||
| if ( | ||
| node.type === AST_NODE_TYPES.TSAsExpression || | ||
| node.type === AST_NODE_TYPES.TSNonNullExpression | ||
| ) { | ||
| return getIdentifier(node.expression); | ||
| } | ||
| return null; | ||
| } | ||
|
|
||
| function isArrowIIFE(node: TSESTree.Node): boolean { | ||
| return ( | ||
| node.type === AST_NODE_TYPES.ArrowFunctionExpression && | ||
| node.parent.type === AST_NODE_TYPES.CallExpression | ||
| ); | ||
| } | ||
|
|
||
| return { | ||
| ClassBody(): void { | ||
| reportInfoStack.push({ | ||
| unnecessaryAssignments: [], | ||
| assignedBeforeUnnecessary: new Set(), | ||
| assignedBeforeConstructor: new Set(), | ||
| }); | ||
| }, | ||
| 'ClassBody:exit'(): void { | ||
| const { unnecessaryAssignments, assignedBeforeConstructor } = | ||
| nullThrows(reportInfoStack.pop(), 'The top stack should exist'); | ||
| unnecessaryAssignments.forEach(({ name, node }) => { | ||
| if (assignedBeforeConstructor.has(name)) { | ||
| return; | ||
| } | ||
| context.report({ | ||
| node, | ||
| messageId: 'unnecessaryAssign', | ||
| }); | ||
| }); | ||
| }, | ||
| 'PropertyDefinition AssignmentExpression'( | ||
| node: TSESTree.AssignmentExpression, | ||
| ): void { | ||
| const name = getPropertyName(node.left); | ||
|
|
||
| if (!name) { | ||
| return; | ||
| } | ||
|
|
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| const functionNode = findParentFunction(node); | ||
| if (functionNode) { | ||
| if ( | ||
| !( | ||
| isArrowIIFE(functionNode) && | ||
| findParentPropertyDefinition(node)?.value === functionNode.parent | ||
| ) | ||
| ) { | ||
| return; | ||
| } | ||
| } | ||
|
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| const { assignedBeforeConstructor } = nullThrows( | ||
| reportInfoStack.at(-1), | ||
| 'The top stack should exist', | ||
| ); | ||
| assignedBeforeConstructor.add(name); | ||
| }, | ||
| "MethodDefinition[kind='constructor'] > FunctionExpression AssignmentExpression"( | ||
| node: TSESTree.AssignmentExpression, | ||
| ): void { | ||
| const leftName = getPropertyName(node.left); | ||
|
|
||
| if (!leftName) { | ||
| return; | ||
| } | ||
|
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| let functionNode = findParentFunction(node); | ||
| if (functionNode && isArrowIIFE(functionNode)) { | ||
| functionNode = findParentFunction(functionNode.parent); | ||
| } | ||
|
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| if (!isConstructorFunctionExpression(functionNode)) { | ||
| return; | ||
| } | ||
|
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| const { assignedBeforeUnnecessary, unnecessaryAssignments } = | ||
| nullThrows( | ||
| reportInfoStack.at(reportInfoStack.length - 1), | ||
| 'The top of stack should exist', | ||
| ); | ||
|
|
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| if (!UNNECESSARY_OPERATORS.has(node.operator)) { | ||
| assignedBeforeUnnecessary.add(leftName); | ||
| return; | ||
| } | ||
|
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| const rightId = getIdentifier(node.right); | ||
|
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| if (leftName !== rightId?.name || !isReferenceFromParameter(rightId)) { | ||
| return; | ||
| } | ||
|
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| const hasParameterProperty = functionNode.params.some(param => | ||
| isParameterPropertyWithName(param, rightId.name), | ||
| ); | ||
|
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| if (hasParameterProperty && !assignedBeforeUnnecessary.has(leftName)) { | ||
| unnecessaryAssignments.push({ | ||
| name: leftName, | ||
| node, | ||
| }); | ||
| } | ||
| }, | ||
| }; | ||
| }, | ||
| }); |
22 changes: 22 additions & 0 deletions
22
...ugin/tests/docs-eslint-output-snapshots/no-unnecessary-parameter-property-assignment.shot
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Is this true? I'm not able to get it to fix my code, and I don't see where a fixer is passed to
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Aha! You're right - this was an oversight. eslint/eslint#18008 would have caught it.
Are you up for filing an issue and/or sending a PR @dasa? It'd be a great contribution 😁