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fix(eslint-plugin): [prefer-return-this-type] check accessor properties with a function initializer #10794

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Merged
merged 2 commits into from
Feb 17, 2025
Merged

fix(eslint-plugin): [prefer-return-this-type] check accessor properties with a function initializer #10794

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b71a9fe
handle accessor property with prefer-return-this-type
ronami Feb 4, 2025
b463fe5
refactor and add missing tests
ronami Feb 6, 2025
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33 changes: 18 additions & 15 deletions packages/eslint-plugin/src/rules/prefer-return-this-type.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -148,24 +148,27 @@ export default createRule({
}
}

function checkProperty(
node: TSESTree.AccessorProperty | TSESTree.PropertyDefinition,
): void {
if (
!(
node.value?.type === AST_NODE_TYPES.FunctionExpression ||
node.value?.type === AST_NODE_TYPES.ArrowFunctionExpression
)
) {
return;
}

checkFunction(node.value, node.parent.parent);
}

return {
'ClassBody > AccessorProperty': checkProperty,
'ClassBody > MethodDefinition'(node: TSESTree.MethodDefinition): void {
checkFunction(node.value, node.parent.parent as ClassLikeDeclaration);
},
'ClassBody > PropertyDefinition'(
node: TSESTree.PropertyDefinition,
): void {
if (
!(
node.value?.type === AST_NODE_TYPES.FunctionExpression ||
node.value?.type === AST_NODE_TYPES.ArrowFunctionExpression
)
) {
return;
}

checkFunction(node.value, node.parent.parent as ClassLikeDeclaration);
checkFunction(node.value, node.parent.parent);
Comment on lines -167 to +169
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@ronami ronami Feb 6, 2025 •
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The type assertion seems unnecessary since #9560.

This is an unrelated change, but I decided to include it as it's a tiny change and on the same part of the code that the PR changes anyway.

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@ronami ronami Feb 6, 2025 •
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I wonder if this can be caught by no-unnecessary-type-assertion 🤔

Since ClassLikeDeclaration is a different type alias (and thus a different type), the comparison seems to fail (even though ClassLikeDeclaration is assigned the same type as the un-asserted type). Inlining the value of the type alias seem to cause no-unnecessary-type-assertion to report this.

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Yeah that would be nice. My hunch is it's some nuance about generic functions having type parameters inferred from types of arguments.

},
'ClassBody > PropertyDefinition': checkProperty,
};
},
});
84 changes: 84 additions & 0 deletions packages/eslint-plugin/tests/rules/prefer-return-this-type.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,25 @@ class Derived extends Base {
f(): Base {
return this;
}
}
`,
`
class Foo {
accessor f = () => {
return this;
};
}
`,
`
class Foo {
accessor f = (): this => {
return this;
};
}
`,
`
class Foo {
f?: string;
}
`,
Comment on lines +98 to 102
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@ronami ronami Feb 6, 2025 •
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This is a test addition that isn't related to the accessor changes, but was previously uncovered. This fails codecov (as the uncovered code has been moved to a function), and because it's such a tiny addition, I decided to include it in this PR.

],
Expand Down Expand Up @@ -108,6 +127,29 @@ class Foo {
},
{
code: `
class Foo {
f = function (): Foo {
return this;
};
}
`,
errors: [
{
column: 20,
line: 3,
messageId: 'useThisType',
},
],
output: `
class Foo {
f = function (): this {
return this;
};
}
`,
},
{
code: `
class Foo {
f(): Foo {
const self = this;
Expand Down Expand Up @@ -200,6 +242,48 @@ class Foo {
},
{
code: `
class Foo {
accessor f = (): Foo => {
return this;
};
}
`,
errors: [
{
column: 20,
line: 3,
messageId: 'useThisType',
},
],
output: `
class Foo {
accessor f = (): this => {
return this;
};
}
`,
},
{
code: `
class Foo {
accessor f = (): Foo => this;
}
`,
errors: [
{
column: 20,
line: 3,
messageId: 'useThisType',
},
],
output: `
class Foo {
accessor f = (): this => this;
}
`,
},
{
code: `
class Foo {
f1(): Foo | undefined {
return this;
Expand Down
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