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feat(eslint-plugin): [no-misused-promises] warn when spreading promises (typescript-eslint#5053)
* feat(eslint-plugin): warn when spreading promises * feat(eslint-plugin): fix typo * feat(eslint-plugin): handle logical expressions * feat(eslint-plugin): test spreading promises in arrays Co-authored-by: Josh Goldberg <[email protected]>
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‎packages/eslint-plugin/docs/rules/no-misused-promises.md

Lines changed: 56 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -13,9 +13,9 @@ See [`no-floating-promises`](./no-floating-promises.md) for detecting unhandled
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## Rule Details
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This rule accepts a single option which is an object with `checksConditionals`
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and `checksVoidReturn` properties indicating which types of misuse to flag.
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Both are enabled by default.
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This rule accepts a single option which is an object with `checksConditionals`,
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`checksVoidReturn`, and `checksSpreads` properties indicating which types of
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misuse to flag. All are enabled by default.
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2020
## Options
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@@ -24,6 +24,7 @@ type Options = [
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{
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checksConditionals?: boolean;
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checksVoidReturn?: boolean | ChecksVoidReturnOptions;
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checksSpreads?: boolean;
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},
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];
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@@ -39,6 +40,7 @@ const defaultOptions: Options = [
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{
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checksConditionals: true,
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checksVoidReturn: true,
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checksSpreads: true,
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},
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];
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```
@@ -101,6 +103,21 @@ For example, if you don't mind that passing a `() => Promise<void>` to a `() =>
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}
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```
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### `"checksSpreads"`
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If you don't want to check object spreads, you can add this configuration:
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```json
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{
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"@typescript-eslint/no-misused-promises": [
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"error",
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{
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"checksSpreads": false
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}
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]
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}
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```
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### `checksConditionals: true`
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Examples of code for this rule with `checksConditionals: true`:
@@ -212,6 +229,42 @@ eventEmitter.on('some-event', () => {
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<!--/tabs-->
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### `checksSpreads: true`
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Examples of code for this rule with `checksSpreads: true`:
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<!--tabs-->
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#### ❌ Incorrect
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```ts
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const getData = () => someAsyncOperation({ myArg: 'foo' });
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return { foo: 42, ...getData() };
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const getData2 = async () => {
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await someAsyncOperation({ myArg: 'foo' });
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};
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return { foo: 42, ...getData2() };
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```
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#### ✅ Correct
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```ts
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const getData = () => someAsyncOperation({ myArg: 'foo' });
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return { foo: 42, ...(await getData()) };
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const getData2 = async () => {
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await someAsyncOperation({ myArg: 'foo' });
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};
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return { foo: 42, ...(await getData2()) };
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```
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<!--tabs-->
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## When Not To Use It
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If you do not use Promises in your codebase or are not concerned with possible

‎packages/eslint-plugin/src/rules/no-misused-promises.ts

Lines changed: 37 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,6 +8,7 @@ type Options = [
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{
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checksConditionals?: boolean;
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checksVoidReturn?: boolean | ChecksVoidReturnOptions;
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checksSpreads?: boolean;
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},
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];
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@@ -25,7 +26,8 @@ type MessageId =
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| 'voidReturnVariable'
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| 'voidReturnProperty'
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| 'voidReturnReturnValue'
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| 'voidReturnAttribute';
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| 'voidReturnAttribute'
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| 'spread';
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function parseChecksVoidReturn(
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checksVoidReturn: boolean | ChecksVoidReturnOptions | undefined,
@@ -75,6 +77,7 @@ export default util.createRule<Options, MessageId>({
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voidReturnAttribute:
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'Promise-returning function provided to attribute where a void return was expected.',
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conditional: 'Expected non-Promise value in a boolean conditional.',
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spread: 'Expected a non-Promise value to be spreaded in an object.',
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},
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schema: [
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{
@@ -99,6 +102,9 @@ export default util.createRule<Options, MessageId>({
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},
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],
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},
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checksSpreads: {
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type: 'boolean',
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},
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},
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},
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],
@@ -108,10 +114,11 @@ export default util.createRule<Options, MessageId>({
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{
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checksConditionals: true,
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checksVoidReturn: true,
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checksSpreads: true,
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},
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],
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create(context, [{ checksConditionals, checksVoidReturn }]) {
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create(context, [{ checksConditionals, checksVoidReturn, checksSpreads }]) {
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const parserServices = util.getParserServices(context);
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const checker = parserServices.program.getTypeChecker();
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@@ -153,6 +160,10 @@ export default util.createRule<Options, MessageId>({
153160
}
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: {};
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const spreadChecks: TSESLint.RuleListener = {
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SpreadElement: checkSpread,
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};
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function checkTestConditional(node: {
157168
test: TSESTree.Expression | null;
158169
}): void {
@@ -376,13 +387,37 @@ export default util.createRule<Options, MessageId>({
376387
}
377388
}
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390+
function checkSpread(node: TSESTree.SpreadElement): void {
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const tsNode = parserServices.esTreeNodeToTSNodeMap.get(node);
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if (isSometimesThenable(checker, tsNode.expression)) {
394+
context.report({
395+
messageId: 'spread',
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node: node.argument,
397+
});
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}
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}
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379401
return {
380402
...(checksConditionals ? conditionalChecks : {}),
381403
...(checksVoidReturn ? voidReturnChecks : {}),
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...(checksSpreads ? spreadChecks : {}),
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};
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},
384407
});
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function isSometimesThenable(checker: ts.TypeChecker, node: ts.Node): boolean {
410+
const type = checker.getTypeAtLocation(node);
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for (const subType of tsutils.unionTypeParts(checker.getApparentType(type))) {
413+
if (tsutils.isThenableType(checker, node, subType)) {
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return true;
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}
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}
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return false;
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}
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// Variation on the thenable check which requires all forms of the type (read:
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// alternates in a union) to be thenable. Otherwise, you might be trying to
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// check if something is defined or undefined and get caught because one of the

‎packages/eslint-plugin/tests/rules/no-misused-promises.test.ts

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Original file line numberDiff line numberDiff line change
@@ -316,6 +316,63 @@ const _ = <Component onEvent={async () => {}} />;
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`,
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filename: 'react.tsx',
318318
},
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`
320+
console.log({ ...(await Promise.resolve({ key: 42 })) });
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`,
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`
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const getData = Promise.resolve({ key: 42 });
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console.log({
326+
someData: 42,
327+
...(await getData()),
328+
});
329+
`,
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`
331+
declare const condition: boolean;
332+
333+
console.log({ ...(condition && (await Promise.resolve({ key: 42 }))) });
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console.log({ ...(condition || (await Promise.resolve({ key: 42 }))) });
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console.log({ ...(condition ? {} : await Promise.resolve({ key: 42 })) });
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console.log({ ...(condition ? await Promise.resolve({ key: 42 }) : {}) });
337+
`,
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`
339+
console.log([...(await Promise.resolve(42))]);
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`,
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{
342+
code: `
343+
console.log({ ...Promise.resolve({ key: 42 }) });
344+
`,
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options: [{ checksSpreads: false }],
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},
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{
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code: `
349+
const getData = Promise.resolve({ key: 42 });
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console.log({
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someData: 42,
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...getData(),
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});
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`,
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options: [{ checksSpreads: false }],
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},
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{
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code: `
360+
declare const condition: boolean;
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console.log({ ...(condition && Promise.resolve({ key: 42 })) });
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console.log({ ...(condition || Promise.resolve({ key: 42 })) });
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console.log({ ...(condition ? {} : Promise.resolve({ key: 42 })) });
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console.log({ ...(condition ? Promise.resolve({ key: 42 }) : {}) });
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`,
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options: [{ checksSpreads: false }],
368+
},
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{
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code: `
371+
// This is invalid Typescript, but it shouldn't trigger this linter specifically
372+
console.log([...Promise.resolve(42)]);
373+
`,
374+
options: [{ checksSpreads: false }],
375+
},
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],
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321378
invalid: [
@@ -870,5 +927,48 @@ it('', async () => {});
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},
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],
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},
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{
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code: `
932+
console.log({ ...Promise.resolve({ key: 42 }) });
933+
`,
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errors: [
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{
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line: 2,
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messageId: 'spread',
938+
},
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],
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},
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{
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code: `
943+
const getData = () => Promise.resolve({ key: 42 });
944+
945+
console.log({
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someData: 42,
947+
...getData(),
948+
});
949+
`,
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errors: [
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{
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line: 6,
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messageId: 'spread',
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},
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],
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},
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{
958+
code: `
959+
declare const condition: boolean;
960+
961+
console.log({ ...(condition && Promise.resolve({ key: 42 })) });
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console.log({ ...(condition || Promise.resolve({ key: 42 })) });
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console.log({ ...(condition ? {} : Promise.resolve({ key: 42 })) });
964+
console.log({ ...(condition ? Promise.resolve({ key: 42 }) : {}) });
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`,
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errors: [
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{ line: 4, messageId: 'spread' },
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{ line: 5, messageId: 'spread' },
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{ line: 6, messageId: 'spread' },
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{ line: 7, messageId: 'spread' },
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],
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},
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],
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});

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