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feat(eslint-plugin): [prefer-nullish-coalescing] add option ignoreBooleanCoercion (typescript-eslint#9924)
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‎packages/eslint-plugin/docs/rules/prefer-nullish-coalescing.mdx

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@@ -172,6 +172,28 @@ foo ?? 'a string';
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Also, if you would like to ignore all primitives types, you can set `ignorePrimitives: true`. It is equivalent to `ignorePrimitives: { string: true, number: true, bigint: true, boolean: true }`.
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### `ignoreBooleanCoercion`
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Whether to ignore expressions that coerce a value into a boolean: `Boolean(...)`.
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Incorrect code for `ignoreBooleanCoercion: false`, and correct code for `ignoreBooleanCoercion: true`:
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```ts option='{ "ignoreBooleanCoercion": true }' showPlaygroundButton
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let a: string | true | undefined;
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let b: string | boolean | undefined;
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const x = Boolean(a || b);
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```
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Correct code for `ignoreBooleanCoercion: false`:
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```ts option='{ "ignoreBooleanCoercion": false }' showPlaygroundButton
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let a: string | true | undefined;
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let b: string | boolean | undefined;
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const x = Boolean(a ?? b);
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```
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### `allowRuleToRunWithoutStrictNullChecksIKnowWhatIAmDoing`
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{/* insert option description */}

‎packages/eslint-plugin/src/rules/prefer-nullish-coalescing.ts

Lines changed: 92 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -21,6 +21,7 @@ import {
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export type Options = [
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{
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allowRuleToRunWithoutStrictNullChecksIKnowWhatIAmDoing?: boolean;
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ignoreBooleanCoercion?: boolean;
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ignoreConditionalTests?: boolean;
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ignoreMixedLogicalExpressions?: boolean;
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ignorePrimitives?:
@@ -71,6 +72,11 @@ export default createRule<Options, MessageIds>({
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description:
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'Unless this is set to `true`, the rule will error on every file whose `tsconfig.json` does _not_ have the `strictNullChecks` compiler option (or `strict`) set to `true`.',
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},
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ignoreBooleanCoercion: {
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type: 'boolean',
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description:
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'Whether to ignore arguments to the `Boolean` constructor',
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},
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ignoreConditionalTests: {
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type: 'boolean',
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description:
@@ -126,6 +132,7 @@ export default createRule<Options, MessageIds>({
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defaultOptions: [
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{
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allowRuleToRunWithoutStrictNullChecksIKnowWhatIAmDoing: false,
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ignoreBooleanCoercion: false,
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ignoreConditionalTests: true,
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ignoreMixedLogicalExpressions: false,
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ignorePrimitives: {
@@ -142,6 +149,7 @@ export default createRule<Options, MessageIds>({
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[
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{
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allowRuleToRunWithoutStrictNullChecksIKnowWhatIAmDoing,
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ignoreBooleanCoercion,
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ignoreConditionalTests,
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ignoreMixedLogicalExpressions,
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ignorePrimitives,
@@ -431,46 +439,102 @@ export default createRule<Options, MessageIds>({
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'LogicalExpression[operator = "||"]'(
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node: TSESTree.LogicalExpression,
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): void {
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if (
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ignoreBooleanCoercion === true &&
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isBooleanConstructorContext(node, context)
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) {
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return;
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}
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checkAssignmentOrLogicalExpression(node, 'or', '');
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},
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};
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},
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});
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function isConditionalTest(node: TSESTree.Node): boolean {
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const parents = new Set<TSESTree.Node | null>([node]);
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let current = node.parent;
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while (current) {
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parents.add(current);
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const parent = node.parent;
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if (parent == null) {
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return false;
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}
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if (
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(current.type === AST_NODE_TYPES.ConditionalExpression ||
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current.type === AST_NODE_TYPES.DoWhileStatement ||
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current.type === AST_NODE_TYPES.IfStatement ||
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current.type === AST_NODE_TYPES.ForStatement ||
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current.type === AST_NODE_TYPES.WhileStatement) &&
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parents.has(current.test)
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) {
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return true;
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}
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if (parent.type === AST_NODE_TYPES.LogicalExpression) {
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return isConditionalTest(parent);
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}
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if (
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[
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AST_NODE_TYPES.ArrowFunctionExpression,
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AST_NODE_TYPES.FunctionExpression,
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].includes(current.type)
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) {
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/**
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* This is a weird situation like:
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* `if (() => a || b) {}`
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* `if (function () { return a || b }) {}`
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*/
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return false;
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}
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if (
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parent.type === AST_NODE_TYPES.ConditionalExpression &&
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(parent.consequent === node || parent.alternate === node)
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) {
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return isConditionalTest(parent);
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}
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if (
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parent.type === AST_NODE_TYPES.SequenceExpression &&
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parent.expressions.at(-1) === node
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) {
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return isConditionalTest(parent);
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}
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current = current.parent;
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if (
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(parent.type === AST_NODE_TYPES.ConditionalExpression ||
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parent.type === AST_NODE_TYPES.DoWhileStatement ||
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parent.type === AST_NODE_TYPES.IfStatement ||
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parent.type === AST_NODE_TYPES.ForStatement ||
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parent.type === AST_NODE_TYPES.WhileStatement) &&
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parent.test === node
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) {
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return true;
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}
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return false;
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}
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function isBooleanConstructorContext(
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node: TSESTree.Node,
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context: Readonly<TSESLint.RuleContext<MessageIds, Options>>,
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): boolean {
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const parent = node.parent;
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if (parent == null) {
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return false;
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}
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if (parent.type === AST_NODE_TYPES.LogicalExpression) {
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return isBooleanConstructorContext(parent, context);
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}
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if (
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parent.type === AST_NODE_TYPES.ConditionalExpression &&
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(parent.consequent === node || parent.alternate === node)
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) {
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return isBooleanConstructorContext(parent, context);
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}
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if (
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parent.type === AST_NODE_TYPES.SequenceExpression &&
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parent.expressions.at(-1) === node
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) {
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return isBooleanConstructorContext(parent, context);
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}
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return isBuiltInBooleanCall(parent, context);
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}
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function isBuiltInBooleanCall(
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node: TSESTree.Node,
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context: Readonly<TSESLint.RuleContext<MessageIds, Options>>,
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): boolean {
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if (
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node.type === AST_NODE_TYPES.CallExpression &&
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node.callee.type === AST_NODE_TYPES.Identifier &&
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// eslint-disable-next-line @typescript-eslint/internal/prefer-ast-types-enum
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node.callee.name === 'Boolean' &&
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node.arguments[0]
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) {
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const scope = context.sourceCode.getScope(node);
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const variable = scope.set.get(AST_TOKEN_TYPES.Boolean);
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return variable == null || variable.defs.length === 0;
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}
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return false;
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}
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‎packages/eslint-plugin/tests/docs-eslint-output-snapshots/prefer-nullish-coalescing.shot

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