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feat(eslint-plugin): [array-type] detect Readonly<string[]> case #8752

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feat(eslint-plugin): [array-type] detect Readonly<string[]> case #8752

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1864644
feat: add new type
developer-bandi Mar 20, 2024
18fff29
fix: test case
developer-bandi Mar 22, 2024
2471ff2
test: add test case
developer-bandi Mar 22, 2024
2ce7956
docs: add `ReadonlyArray<T>` description
developer-bandi Mar 22, 2024
76d9f36
test: add droped test case
developer-bandi Mar 23, 2024
dbcd788
fix: revert comment line and fix error position
developer-bandi Apr 7, 2024
8a361fe
fix: fix indent, docs description
developer-bandi Apr 28, 2024
1a59bd0
fix: revert indent
developer-bandi Apr 28, 2024
8fc0b82
fix: add exception and delete not related PR
developer-bandi May 3, 2024
7482f0d
Merge branch 'main' of https://github.com/developer-bandi/typescript-…
developer-bandi May 3, 2024
f3e3cff
docs: move no correct example to incorrect example
developer-bandi May 11, 2024
ae91e94
docs: fix example document
developer-bandi May 11, 2024
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5 changes: 4 additions & 1 deletion packages/eslint-plugin/docs/rules/array-type.mdx
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Original file line number Diff line number Diff line change
Expand Up @@ -42,14 +42,16 @@ const y: readonly string[] = ['a', 'b'];

### `"generic"`

Always use `Array<T>` or `ReadonlyArray<T>` for all array types.
Always use `Array<T>`, `ReadonlyArray<T>`, or `Readonly<Array<T>>` for all array types.
`readonly T[]` will be modified to `ReadonlyArray<T>` and `Readonly<T[]>` will be modified to `Readonly<Array<T>`.

<Tabs>
<TabItem value="❌ Incorrect">

```ts option='{ "default": "generic" }'
const x: string[] = ['a', 'b'];
const y: readonly string[] = ['a', 'b'];
const z: Readonly<string[]> = ['a', 'b'];
```

</TabItem>
Expand All @@ -58,6 +60,7 @@ const y: readonly string[] = ['a', 'b'];
```ts option='{ "default": "generic" }'
const x: Array<string> = ['a', 'b'];
const y: ReadonlyArray<string> = ['a', 'b'];
const z: Readonly<Array<string>> = ['a', 'b'];
```

</TabItem>
Expand Down
28 changes: 21 additions & 7 deletions packages/eslint-plugin/src/rules/array-type.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,8 @@ type MessageIds =
| 'errorStringArray'
| 'errorStringArraySimple'
| 'errorStringGeneric'
| 'errorStringGenericSimple';
| 'errorStringGenericSimple'
| 'errorStringArrayReadonly';

export default createRule<Options, MessageIds>({
name: 'array-type',
Expand All @@ -99,6 +100,8 @@ export default createRule<Options, MessageIds>({
"Array type using '{{readonlyPrefix}}{{type}}[]' is forbidden. Use '{{className}}<{{type}}>' instead.",
errorStringArray:
"Array type using '{{className}}<{{type}}>' is forbidden. Use '{{readonlyPrefix}}{{type}}[]' instead.",
errorStringArrayReadonly:
"Array type using '{{className}}<{{type}}>' is forbidden. Use '{{readonlyPrefix}}{{type}}' instead.",
errorStringArraySimple:
"Array type using '{{className}}<{{type}}>' is forbidden for simple types. Use '{{readonlyPrefix}}{{type}}[]' instead.",
errorStringGenericSimple:
Expand Down Expand Up @@ -199,13 +202,22 @@ export default createRule<Options, MessageIds>({
node.typeName.type !== AST_NODE_TYPES.Identifier ||
!(
node.typeName.name === 'Array' ||
node.typeName.name === 'ReadonlyArray'
)
node.typeName.name === 'ReadonlyArray' ||
node.typeName.name === 'Readonly'
) ||
(node.typeName.name === 'Readonly' &&
node.typeArguments?.params[0].type !== AST_NODE_TYPES.TSArrayType)
) {
return;
}

const isReadonlyArrayType = node.typeName.name === 'ReadonlyArray';
const isReadonlyWithGenericArrayType =
node.typeName.name === 'Readonly' &&
node.typeArguments?.params[0].type === AST_NODE_TYPES.TSArrayType;
Comment on lines +214 to +216
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[Bug] If the type name is Readonly and first type argument is not an array, we should return from the function. Because otherwise any Readonly<...> type will be reported.

const x: Readonly<string> = 'a'

playground

const isReadonlyArrayType =
node.typeName.name === 'ReadonlyArray' ||
isReadonlyWithGenericArrayType;

const currentOption = isReadonlyArrayType
? readonlyOption
: defaultOption;
Expand All @@ -218,7 +230,9 @@ export default createRule<Options, MessageIds>({
const typeParams = node.typeArguments?.params;
const messageId =
currentOption === 'array'
? 'errorStringArray'
? isReadonlyWithGenericArrayType
? 'errorStringArrayReadonly'
: 'errorStringArray'
: 'errorStringArraySimple';

if (!typeParams || typeParams.length === 0) {
Expand Down Expand Up @@ -256,13 +270,13 @@ export default createRule<Options, MessageIds>({
const start = `${parentParens ? '(' : ''}${readonlyPrefix}${
typeParens ? '(' : ''
}`;
const end = `${typeParens ? ')' : ''}[]${parentParens ? ')' : ''}`;
const end = `${typeParens ? ')' : ''}${isReadonlyWithGenericArrayType ? '' : `[]`}${parentParens ? ')' : ''}`;

context.report({
node,
messageId,
data: {
className: isReadonlyArrayType ? 'ReadonlyArray' : 'Array',
className: isReadonlyArrayType ? node.typeName.name : 'Array',
readonlyPrefix,
type: getMessageType(type),
},
Expand Down
23 changes: 23 additions & 0 deletions packages/eslint-plugin/tests/rules/array-type.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -397,6 +397,14 @@ function bazFunction(baz: Arr<ArrayClass<String>>) {
code: 'let a: readonly Array<number>[] = [[]];',
options: [{ default: 'generic', readonly: 'array' }],
},
{
code: 'let a: Readonly = [];',
options: [{ default: 'generic', readonly: 'array' }],
},
{
code: "const x: Readonly<string> = 'a';",
options: [{ default: 'array' }],
},
],
invalid: [
// Base cases from https://github.com/typescript-eslint/typescript-eslint/issues/2323#issuecomment-663977655
Expand Down Expand Up @@ -1918,6 +1926,21 @@ interface FooInterface {
},
],
},
{
code: "const x: Readonly<string[]> = ['a', 'b'];",
output: "const x: readonly string[] = ['a', 'b'];",
options: [{ default: 'array' }],
errors: [
{
messageId: 'errorStringArrayReadonly',
data: {
className: 'Readonly',
readonlyPrefix: 'readonly ',
type: 'string[]',
},
},
],
},
],
});

Expand Down