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feat(eslint-plugin): [explicit-function-return-type] add allowIIFEs option #6237

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Merged
merged 16 commits into from
Feb 12, 2023
Merged

feat(eslint-plugin): [explicit-function-return-type] add allowIIFEs option #6237

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dd7e799
feat(eslint-plugin): [explicit-function-return-type] add allowIIFEs o…
yeonjuan Dec 17, 2022
3f8a981
remove useless code
yeonjuan Dec 17, 2022
a242fb7
fix tests
yeonjuan Dec 17, 2022
75a520d
apply reviews
yeonjuan Dec 18, 2022
28f2a6a
remove useless lint
yeonjuan Dec 18, 2022
0739ae5
add tc
yeonjuan Dec 18, 2022
d3e168c
fix
yeonjuan Dec 18, 2022
47cf0c5
Merge branch 'main' into fix/#6115
yeonjuan Dec 23, 2022
a6fba09
add test cases
yeonjuan Dec 26, 2022
9c7da1b
Merge branch 'fix/#6115-temp' into fix/#6115
yeonjuan Dec 26, 2022
10f64e0
Merge branch 'main' into fix/#6115
yeonjuan Feb 12, 2023
7affa5b
fix
yeonjuan Feb 12, 2023
2657eb6
fix
yeonjuan Feb 12, 2023
0af3c21
add test cases
yeonjuan Feb 12, 2023
1c702dc
add test case
yeonjuan Feb 12, 2023
f18a367
Update packages/eslint-plugin/tests/rules/explicit-function-return-ty…
JoshuaKGoldberg Feb 12, 2023
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20 changes: 20 additions & 0 deletions packages/eslint-plugin/docs/rules/explicit-function-return-type.md
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Original file line number Diff line number Diff line change
Expand Up @@ -257,6 +257,26 @@ You may pass function/method names you would like this rule to ignore, like so:
}
```

### `allowIIFE`

Examples of code for this rule with `{ allowIIFE: true }`:

#### ❌ Incorrect

```ts
var func = () => 'foo';
```

#### ✅ Correct

```ts
var foo = (() => 'foo')();

var bar = (function () {
return 'bar';
})();
```

## When Not To Use It

If you don't wish to prevent calling code from using function return values in unexpected ways, then
Expand Down
21 changes: 21 additions & 0 deletions packages/eslint-plugin/src/rules/explicit-function-return-type.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ type Options = [
allowConciseArrowFunctionExpressionsStartingWithVoid?: boolean;
allowFunctionsWithoutTypeParameters?: boolean;
allowedNames?: string[];
allowIIFEs?: boolean;
},
];
type MessageIds = 'missingReturnType';
Expand Down Expand Up @@ -75,6 +76,11 @@ export default util.createRule<Options, MessageIds>({
},
type: 'array',
},
allowIIFEs: {
description:
'Whether to ignore immediately invoked function expressions (IIFEs).',
type: 'boolean',
},
},
additionalProperties: false,
},
Expand All @@ -88,6 +94,7 @@ export default util.createRule<Options, MessageIds>({
allowDirectConstAssertionInArrowFunctions: true,
allowConciseArrowFunctionExpressionsStartingWithVoid: false,
allowedNames: [],
allowIIFEs: false,
},
],
create(context, [options]) {
Expand All @@ -102,6 +109,10 @@ export default util.createRule<Options, MessageIds>({
return true;
}

if (options.allowIIFEs && isIIFE(node)) {
return true;
}

if (!options.allowedNames?.length) {
return false;
}
Expand Down Expand Up @@ -149,6 +160,16 @@ export default util.createRule<Options, MessageIds>({
}
return false;
}

function isIIFE(
node:
| TSESTree.ArrowFunctionExpression
| TSESTree.FunctionExpression
| TSESTree.FunctionDeclaration,
): boolean {
return node.parent!.type === AST_NODE_TYPES.CallExpression;
}

return {
'ArrowFunctionExpression, FunctionExpression'(
node: TSESTree.ArrowFunctionExpression | TSESTree.FunctionExpression,
Expand Down
214 changes: 214 additions & 0 deletions packages/eslint-plugin/tests/rules/explicit-function-return-type.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -595,6 +595,132 @@ const x: Bar<Foo> = arg1 => arg2 => arg1 + arg2;
},
],
},
{
filename: 'test.ts',
code: `
let foo = function (): number {
return 1;
};
`,
options: [
{
allowIIFEs: true,
},
],
},
{
filename: 'test.ts',
code: `
const foo = (function () {
return 1;
})();
`,
options: [
{
allowIIFEs: true,
},
],
},
{
filename: 'test.ts',
code: `
const foo = (() => {
return 1;
})();
`,
options: [
{
allowIIFEs: true,
},
],
},
{
filename: 'test.ts',
code: `
const foo = ((arg: number): number => {
return arg;
})(0);
`,
options: [
{
allowIIFEs: true,
},
],
},
{
filename: 'test.ts',
code: `
const foo = (() => (() => 'foo')())();
`,
options: [
{
allowIIFEs: true,
},
],
},
{
filename: 'test.ts',
code: `
let foo = (() => (): string => {
return 'foo';
})()();
`,
options: [
{
allowIIFEs: true,
},
],
},
{
filename: 'test.ts',
code: `
let foo = (() => (): string => {
return 'foo';
})();
`,
options: [
{
allowIIFEs: true,
allowHigherOrderFunctions: false,
},
],
},
{
filename: 'test.ts',
code: `
let foo = (() => (): string => {
return 'foo';
})()();
`,
options: [
{
allowIIFEs: true,
allowHigherOrderFunctions: true,
},
],
},
{
filename: 'test.ts',
code: `
let foo = (() => (): void => {})()();
`,
options: [
{
allowIIFEs: true,
},
],
},
{
filename: 'test.ts',
code: `
let foo = (() => (() => {})())();
`,
options: [
{
allowIIFEs: true,
},
],
},
],
invalid: [
{
Expand Down Expand Up @@ -1477,5 +1603,93 @@ class Foo {
},
],
},
{
filename: 'test.ts',
code: `
const foo = (function () {
return 'foo';
})();
`,
options: [
{
allowIIFEs: false,
},
],
errors: [
{
messageId: 'missingReturnType',
line: 2,
endLine: 2,
column: 14,
endColumn: 25,
},
],
},
{
filename: 'test.ts',
code: `
const foo = (function () {
return () => {
return 1;
};
})();
`,
options: [
{
allowIIFEs: true,
},
],
errors: [
{
messageId: 'missingReturnType',
line: 3,
endLine: 3,
column: 10,
endColumn: 15,
},
],
},
{
filename: 'test.ts',
code: `
let foo = function () {
return 'foo';
};
`,
options: [
{
allowIIFEs: true,
},
],
errors: [
{
messageId: 'missingReturnType',
line: 2,
endLine: 2,
column: 11,
endColumn: 22,
},
],
},
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Let's add a bit more test coverage:

  • IIFEs with return types
  • Multiple levels of IIFEs (e.g. (() => () => {})()())
  • Arguments & parameters

{
filename: 'test.ts',
code: `
let foo = (() => () => {})()();
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@JoshuaKGoldberg
How should we handle multiple levels of IIFEs? For now, it allows only if the function is called directly.

const foo = (() => () => "foo")()(); // error

const bar = (() => (() => "foo")())(); // pass

Should both cases be passed when the allowIIFEs option is true?

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@yeonjuan The first one IMO is not an "IIFE" by definition—(() => () => "foo")() is an expression that happens to evaluate to a function, not a function expression itself. It's fine if we don't handle it.

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I would agree with that assessment.
The inner function is not an IIFE, just the outer function.

`,
options: [
{
allowIIFEs: true,
},
],
errors: [
{
messageId: 'missingReturnType',
line: 2,
endLine: 2,
column: 18,
endColumn: 23,
},
],
},
],
});