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Merged
merged 16 commits into from
Jan 17, 2022
Merged

fix(type-utils): isTypeReadonly now handles conditional types #4421

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974858a
fix(type-utils): make isTypeReadonly's options param optional
RebeccaStevens Jan 9, 2022
bb209f4
test(type-utils): add basic tests for isTypeReadonly
RebeccaStevens Jan 9, 2022
468ac17
test: add union tests for isTypeReadonly
RebeccaStevens Jan 9, 2022
dfd5a24
fix(type-utils): union types always being marked as readonly
RebeccaStevens Jan 9, 2022
1983d52
test(type-utils): add conditional type tests to isTypeReadonly
RebeccaStevens Jan 9, 2022
2b0e454
fix(type-utils): isTypeReadonly now handles conditional types
RebeccaStevens Jan 9, 2022
3a3832b
Merge branch 'main' into issue-4420
RebeccaStevens Jan 11, 2022
f2a8cf3
Merge branch 'main' into issue-4418
RebeccaStevens Jan 11, 2022
669be93
Merge branch 'main' into issue-4420
RebeccaStevens Jan 17, 2022
bce11f3
Merge branch 'main' into issue-4418
RebeccaStevens Jan 17, 2022
5b9a818
Merge branch 'main' into issue-4420
RebeccaStevens Jan 17, 2022
7b36d90
Merge branch 'main' into issue-4418
RebeccaStevens Jan 17, 2022
727d999
Merge branch 'main' into issue-4418
RebeccaStevens Jan 17, 2022
b3122ef
Merge branch 'issue-4418' into issue-4420
RebeccaStevens Jan 17, 2022
071c088
Merge branch 'main' into issue-4420
bradzacher Jan 17, 2022
2b275e8
Update isTypeReadonly.test.ts
bradzacher Jan 17, 2022
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15 changes: 15 additions & 0 deletions packages/type-utils/src/isTypeReadonly.ts
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
import { ESLintUtils } from '@typescript-eslint/utils';
import {
isConditionalType,
isObjectType,
isUnionType,
isUnionOrIntersectionType,
Expand Down Expand Up @@ -223,6 +224,20 @@ function isTypeReadonlyRecurser(
return readonlyness;
}

if (isConditionalType(type)) {
const result = [type.root.node.trueType, type.root.node.falseType]
.map(checker.getTypeFromTypeNode)
.every(
t =>
seenTypes.has(t) ||
isTypeReadonlyRecurser(checker, t, options, seenTypes) ===
Readonlyness.Readonly,
);

const readonlyness = result ? Readonlyness.Readonly : Readonlyness.Mutable;
return readonlyness;
}

// all non-object, non-intersection types are readonly.
// this should only be primitive types
if (!isObjectType(type) && !isUnionOrIntersectionType(type)) {
Expand Down
32 changes: 32 additions & 0 deletions packages/type-utils/tests/isTypeReadonly.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -164,6 +164,38 @@ describe('isTypeReadonly', () => {
])('handles a union of non fully readonly types', runTests);
});
});

describe('Conditional Types', () => {
describe('is readonly', () => {
const runTests = runTestIsReadonly;

it.each([
[
'type Test<T> = T extends readonly number[] ? readonly string[] : readonly number[];',
],
])('handles conditional type that are fully readonly', runTests);

it.each([
[
'type Test<T> = T extends number[] ? readonly string[] : readonly number[];',
],
])('should ignore mutable conditions', runTests);
});

describe('is not readonly', () => {
const runTests = runTestIsNotReadonly;

it.each([
['type Test<T> = T extends number[] ? string[] : number[];'],
[
'type Test<T> = T extends number[] ? string[] : readonly number[];',
],
[
'type Test<T> = T extends number[] ? readonly string[] : number[];',
],
])('handles non fully readonly conditional types', runTests);
});
});
});

describe('treatMethodsAsReadonly', () => {
Expand Down