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fix(eslint-plugin): [no-unnecessary-condition] don't report on unnecessary optional array index access when noUncheckedIndexedAccess is enabled #10961

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Merged
merged 3 commits into from
Mar 24, 2025
Merged

fix(eslint-plugin): [no-unnecessary-condition] don't report on unnecessary optional array index access when noUncheckedIndexedAccess is enabled #10961

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06db97e
initial implementation
ronami Mar 16, 2025
a03ba8e
add tests
ronami Mar 16, 2025
e3a479c
cover missing edge cases
ronami Mar 23, 2025
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20 changes: 12 additions & 8 deletions packages/eslint-plugin/src/rules/no-unnecessary-condition.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -357,7 +357,7 @@ export default createRule<Options, MessageId>({
// Since typescript array index signature types don't represent the
// possibility of out-of-bounds access, if we're indexing into an array
// just skip the check, to avoid false positives
if (isArrayIndexExpression(expression)) {
if (!isNoUncheckedIndexedAccess && isArrayIndexExpression(expression)) {
return;
}

Expand Down Expand Up @@ -424,12 +424,13 @@ export default createRule<Options, MessageId>({
// possibility of out-of-bounds access, if we're indexing into an array
// just skip the check, to avoid false positives
if (
!isArrayIndexExpression(node) &&
!(
node.type === AST_NODE_TYPES.ChainExpression &&
node.expression.type !== AST_NODE_TYPES.TSNonNullExpression &&
optionChainContainsOptionArrayIndex(node.expression)
)
isNoUncheckedIndexedAccess ||
(!isArrayIndexExpression(node) &&
!(
node.type === AST_NODE_TYPES.ChainExpression &&
node.expression.type !== AST_NODE_TYPES.TSNonNullExpression &&
optionChainContainsOptionArrayIndex(node.expression)
))
) {
messageId = 'neverNullish';
}
Expand Down Expand Up @@ -835,7 +836,10 @@ export default createRule<Options, MessageId>({
// Since typescript array index signature types don't represent the
// possibility of out-of-bounds access, if we're indexing into an array
// just skip the check, to avoid false positives
if (optionChainContainsOptionArrayIndex(node)) {
if (
!isNoUncheckedIndexedAccess &&
optionChainContainsOptionArrayIndex(node)
) {
return;
}

Expand Down
146 changes: 146 additions & 0 deletions packages/eslint-plugin/tests/rules/no-unnecessary-condition.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -399,6 +399,21 @@ const tuple = ['foo'] as const;
declare const n: number;
tuple[n]?.toUpperCase();
`,
{
code: `
declare const arr: Array<{ value: string } & (() => void)>;
if (arr[42]?.value) {
}
arr[41]?.();
`,
languageOptions: {
parserOptions: {
project: './tsconfig.noUncheckedIndexedAccess.json',
projectService: false,
tsconfigRootDir: getFixturesRootDir(),
},
},
},
`
if (arr?.[42]) {
}
Expand All @@ -417,6 +432,23 @@ declare const foo: TupleA | TupleB;
declare const index: number;
foo[index]?.toString();
`,
{
code: `
type TupleA = [string, number];
type TupleB = [string, number];

declare const foo: TupleA | TupleB;
declare const index: number;
foo[index]?.toString();
`,
languageOptions: {
parserOptions: {
project: './tsconfig.noUncheckedIndexedAccess.json',
projectService: false,
tsconfigRootDir: getFixturesRootDir(),
},
},
},
`
declare const returnsArr: undefined | (() => string[]);
if (returnsArr?.()[42]) {
Expand Down Expand Up @@ -3272,5 +3304,119 @@ declare const t: T;
t.a.a.a.value;
`,
},
{
code: `
declare const test: Array<{ a?: string }>;

if (test[0]?.a) {
test[0]?.a;
}
`,
errors: [
{
column: 10,
endColumn: 12,
endLine: 5,
line: 5,
messageId: 'neverOptionalChain',
},
],
languageOptions: {
parserOptions: {
project: './tsconfig.noUncheckedIndexedAccess.json',
projectService: false,
tsconfigRootDir: getFixturesRootDir(),
},
},
output: `
declare const test: Array<{ a?: string }>;

if (test[0]?.a) {
test[0].a;
}
`,
},
{
code: `
declare const arr2: Array<{ x: { y: { z: object } } }>;
arr2[42]?.x?.y?.z;
`,
errors: [
{
column: 12,
endColumn: 14,
endLine: 3,
line: 3,
messageId: 'neverOptionalChain',
},
{
column: 15,
endColumn: 17,
endLine: 3,
line: 3,
messageId: 'neverOptionalChain',
},
],
languageOptions: {
parserOptions: {
project: './tsconfig.noUncheckedIndexedAccess.json',
projectService: false,
tsconfigRootDir: getFixturesRootDir(),
},
},
output: `
declare const arr2: Array<{ x: { y: { z: object } } }>;
arr2[42]?.x.y.z;
`,
},
{
code: `
declare const arr: string[];

if (arr[0]) {
arr[0] ?? 'foo';
}
`,
errors: [
{
column: 3,
endColumn: 9,
endLine: 5,
line: 5,
messageId: 'neverNullish',
},
],
languageOptions: {
parserOptions: {
project: './tsconfig.noUncheckedIndexedAccess.json',
projectService: false,
tsconfigRootDir: getFixturesRootDir(),
},
},
},
{
code: `
declare const arr: object[];

if (arr[42] && arr[42]) {
}
`,
errors: [
{
column: 16,
endColumn: 23,
endLine: 4,
line: 4,
messageId: 'alwaysTruthy',
},
],
languageOptions: {
parserOptions: {
project: './tsconfig.noUncheckedIndexedAccess.json',
projectService: false,
tsconfigRootDir: getFixturesRootDir(),
},
},
},
],
});
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