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fix(eslint-plugin): [no-unnecessary-condition] allow nullish coalescing for naked type parameter #6910

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merged 2 commits into from Apr 17, 2023
+34 −2
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fix(eslint-plugin): [no-unnecessary-condition] allow nullish coalescing for naked type parameter #6910

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64cb69e
fix(eslint-plugin): [no-unnecessary-condition] allow nullish coalesci…
dora1998 Apr 15, 2023
a1c766c
add tests
dora1998 Apr 17, 2023
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10 changes: 8 additions & 2 deletions packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
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Expand Up @@ -263,8 +263,14 @@ export default createRule<Options, MessageId>({

function checkNodeForNullish(node: TSESTree.Expression): void {
const type = getNodeType(node);
// Conditional is always necessary if it involves `any` or `unknown`
if (isTypeAnyType(type) || isTypeUnknownType(type)) {

// Conditional is always necessary if it involves `any`, `unknown` or a naked type parameter
if (
isTypeFlagSet(
type,
ts.TypeFlags.Any | ts.TypeFlags.Unknown | ts.TypeFlags.TypeParameter,
)
) {
return;
}

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26 changes: 26 additions & 0 deletions packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
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Expand Up @@ -280,6 +280,16 @@ function test(a: string | null | undefined) {
`
function test(a: unknown) {
return a ?? 'default';
}
`,
`
function test<T>(a: T) {
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[Testing] The cases of T extends 'a' (always truthy) and T extends 'a' | null (still needing ??) seem to work, but aren't explicitly covered for ?? cases. Could you add in a couple more unit tests along those lines please?

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Oh sorry, I added them!
I also added a alwaysNullish case 😄

return a ?? 'default';
}
`,
`
function test<T extends string | null>(a: T) {
return a ?? 'default';
}
`,
// Indexing cases
Expand Down Expand Up @@ -827,6 +837,14 @@ function test(a: string) {
code: `
function test(a: string | false) {
return a ?? 'default';
}
`,
errors: [ruleError(3, 10, 'neverNullish')],
},
{
code: `
function test<T extends string>(a: T) {
return a ?? 'default';
}
`,
errors: [ruleError(3, 10, 'neverNullish')],
Expand Down Expand Up @@ -858,6 +876,14 @@ function test(a: null[]) {
},
{
code: `
function test<T extends null>(a: T) {
return a ?? 'default';
}
`,
errors: [ruleError(3, 10, 'alwaysNullish')],
},
{
code: `
function test(a: never) {
return a ?? 'default';
}
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