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feat(eslint-plugin): [prefer-nullish-coalescing] add support for assignment expressions#10152
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JoshuaKGoldberg merged 12 commits intotypescript-eslint:mainfromabrahamguo:prefer-nullish-coalescing-assignmentsOct 21, 2024
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1e3281a extract current LogicalExpression logic into function
abrahamguo3d6a209 pull in other changes to rule file without edits
abrahamguodf78ea3 pull over genericizations for checkAssignmentOrLogicalExpression
abrahamguoff5db69 lint autofix
abrahamguo2a705a3 port over test changes
abrahamguo4c3fb24 change all declare consts to declare lets
abrahamguo731cb4a Merge branch 'main' of github.com:abrahamguo/typescript-eslint into p…
abrahamguo52066e0 apply lint rule
abrahamguoda2aeb8 reduce the number of duplicate tests
abrahamguode4fb70 revert incorrect unrelated changes
abrahamguobc0786e Merge branch 'main'
JoshuaKGoldberg22841da fix lint complaints
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199 changes: 112 additions & 87 deletionspackages/eslint-plugin/src/rules/prefer-nullish-coalescing.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -56,10 +56,10 @@ export default createRule<Options, MessageIds>({ | ||
| noStrictNullCheck: | ||
| 'This rule requires the `strictNullChecks` compiler option to be turned on to function correctly.', | ||
| preferNullishOverOr: | ||
| 'Prefer using nullish coalescing operator (`??{{ equals }}`) instead of a logical{{ description }}(`||{{ equals }}`), as it is a safer operator.', | ||
| preferNullishOverTernary: | ||
| 'Prefer using nullish coalescing operator (`??{{ equals }}`) instead of a ternary expression, as it is simpler to read.', | ||
| suggestNullish: 'Fix to nullish coalescing operator (`??{{ equals }}`).', | ||
| }, | ||
| schema: [ | ||
| { | ||
| @@ -171,7 +171,107 @@ export default createRule<Options, MessageIds>({ | ||
| }); | ||
| } | ||
| // todo: rename to something more specific? | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others.Learn more.
What's the resolution here? FWIW I don't mind the name as-is. | ||
| function checkAssignmentOrLogicalExpression( | ||
| node: TSESTree.AssignmentExpression | TSESTree.LogicalExpression, | ||
| description: string, | ||
| equals: string, | ||
| ): void { | ||
| const tsNode = parserServices.esTreeNodeToTSNodeMap.get(node); | ||
| const type = checker.getTypeAtLocation(tsNode.left); | ||
| if (!isTypeFlagSet(type, ts.TypeFlags.Null | ts.TypeFlags.Undefined)) { | ||
| return; | ||
| } | ||
| if (ignoreConditionalTests === true && isConditionalTest(node)) { | ||
| return; | ||
| } | ||
| if ( | ||
| ignoreMixedLogicalExpressions === true && | ||
| isMixedLogicalExpression(node) | ||
| ) { | ||
| return; | ||
| } | ||
| // https://github.com/typescript-eslint/typescript-eslint/issues/5439 | ||
| /* eslint-disable @typescript-eslint/no-non-null-assertion */ | ||
| const ignorableFlags = [ | ||
| (ignorePrimitives === true || ignorePrimitives!.bigint) && | ||
| ts.TypeFlags.BigIntLike, | ||
| (ignorePrimitives === true || ignorePrimitives!.boolean) && | ||
| ts.TypeFlags.BooleanLike, | ||
| (ignorePrimitives === true || ignorePrimitives!.number) && | ||
| ts.TypeFlags.NumberLike, | ||
| (ignorePrimitives === true || ignorePrimitives!.string) && | ||
| ts.TypeFlags.StringLike, | ||
| ] | ||
| .filter((flag): flag is number => typeof flag === 'number') | ||
| .reduce((previous, flag) => previous | flag, 0); | ||
| if ( | ||
| type.flags !== ts.TypeFlags.Null && | ||
| type.flags !== ts.TypeFlags.Undefined && | ||
| (type as ts.UnionOrIntersectionType).types.some(t => | ||
| tsutils | ||
| .intersectionTypeParts(t) | ||
| .some(t => tsutils.isTypeFlagSet(t, ignorableFlags)), | ||
| ) | ||
| ) { | ||
| return; | ||
| } | ||
| /* eslint-enable @typescript-eslint/no-non-null-assertion */ | ||
| const barBarOperator = nullThrows( | ||
| context.sourceCode.getTokenAfter( | ||
| node.left, | ||
| token => | ||
| token.type === AST_TOKEN_TYPES.Punctuator && | ||
| token.value === node.operator, | ||
| ), | ||
| NullThrowsReasons.MissingToken('operator', node.type), | ||
| ); | ||
| function* fix( | ||
| fixer: TSESLint.RuleFixer, | ||
| ): IterableIterator<TSESLint.RuleFix> { | ||
| if (isLogicalOrOperator(node.parent)) { | ||
| // '&&' and '??' operations cannot be mixed without parentheses (e.g. a && b ?? c) | ||
| if ( | ||
| node.left.type === AST_NODE_TYPES.LogicalExpression && | ||
| !isLogicalOrOperator(node.left.left) | ||
| ) { | ||
| yield fixer.insertTextBefore(node.left.right, '('); | ||
| } else { | ||
| yield fixer.insertTextBefore(node.left, '('); | ||
| } | ||
| yield fixer.insertTextAfter(node.right, ')'); | ||
| } | ||
| yield fixer.replaceText( | ||
| barBarOperator, | ||
| node.operator.replace('||', '??'), | ||
| ); | ||
| } | ||
| context.report({ | ||
| node: barBarOperator, | ||
| messageId: 'preferNullishOverOr', | ||
| data: { description, equals }, | ||
| suggest: [ | ||
| { | ||
| messageId: 'suggestNullish', | ||
| data: { equals }, | ||
| fix, | ||
| }, | ||
| ], | ||
| }); | ||
| } | ||
| return { | ||
| 'AssignmentExpression[operator = "||="]'( | ||
| node: TSESTree.AssignmentExpression, | ||
| ): void { | ||
| checkAssignmentOrLogicalExpression(node, 'assignment', '='); | ||
| }, | ||
| ConditionalExpression(node: TSESTree.ConditionalExpression): void { | ||
| if (ignoreTernaryTests) { | ||
| return; | ||
| @@ -200,7 +300,7 @@ export default createRule<Options, MessageIds>({ | ||
| node.test.right.left, | ||
| node.test.right.right, | ||
| ]; | ||
| if (['||','||='].includes(node.test.operator)) { | ||
| if ( | ||
| node.test.left.operator === '===' && | ||
| node.test.right.operator === '===' | ||
| @@ -304,9 +404,12 @@ export default createRule<Options, MessageIds>({ | ||
| context.report({ | ||
| node, | ||
| messageId: 'preferNullishOverTernary', | ||
| // TODO: also account for = in the ternary clause | ||
| data: { equals: '' }, | ||
| suggest: [ | ||
| { | ||
| messageId: 'suggestNullish', | ||
| data: { equals: '' }, | ||
| fix(fixer: TSESLint.RuleFixer): TSESLint.RuleFix { | ||
| const [left, right] = | ||
| operator === '===' || operator === '==' | ||
| @@ -325,90 +428,10 @@ export default createRule<Options, MessageIds>({ | ||
| }); | ||
| } | ||
| }, | ||
| 'LogicalExpression[operator = "||"]'( | ||
| node: TSESTree.LogicalExpression, | ||
| ): void { | ||
| checkAssignmentOrLogicalExpression(node, 'or', ''); | ||
| }, | ||
| }; | ||
| }, | ||
| @@ -451,7 +474,9 @@ function isConditionalTest(node: TSESTree.Node): boolean { | ||
| return false; | ||
| } | ||
| function isMixedLogicalExpression( | ||
| node: TSESTree.AssignmentExpression | TSESTree.LogicalExpression, | ||
| ): boolean { | ||
| const seen = new Set<TSESTree.Node | undefined>(); | ||
| const queue = [node.parent, node.left, node.right]; | ||
| for (const current of queue) { | ||
| @@ -463,7 +488,7 @@ function isMixedLogicalExpression(node: TSESTree.LogicalExpression): boolean { | ||
| if (current.type === AST_NODE_TYPES.LogicalExpression) { | ||
| if (current.operator === '&&') { | ||
| return true; | ||
| } else if (['||','||='].includes(current.operator)) { | ||
| // check the pieces of the node to catch cases like `a || b || c && d` | ||
| queue.push(current.parent, current.left, current.right); | ||
| } | ||
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