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fix(eslint-plugin): [switch-exhaustive-check] handle infinite types #6922

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fix(eslint-plugin): [switch-exhaustive-check] handle infinite types #6922

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500c7e9
Sequence expression check and tests
cparros Mar 10, 2023
d526e42
Merge branch 'typescript-eslint:main' into main
cparros Apr 16, 2023
3e67893
swiatch-exhaustive-check update
cparros Apr 17, 2023
2be58d3
Merge branch 'typescript-eslint:main' into main
cparros May 6, 2023
df1f256
Merge branch 'main' into invalid-fix-for-union
cparros May 6, 2023
a3bea78
update
cparros May 6, 2023
de3669b
variable rename
cparros May 6, 2023
968bf95
update
cparros Jun 12, 2023
98df95a
Merge branch 'typescript-eslint:main' into main
cparros Jun 13, 2023
b42ccc9
type check for test cases
cparros Jun 18, 2023
7235f13
remove console log
cparros Jun 28, 2023
5a82e80
Merge branch 'typescript-eslint:main' into main
cparros Jun 28, 2023
634096e
Merge branch 'main' into invalid-fix-for-union
cparros Jun 28, 2023
a9c2a77
finite type check
cparros Jul 11, 2023
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26 changes: 25 additions & 1 deletion packages/eslint-plugin/src/rules/switch-exhaustiveness-check.ts
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Open in desktop
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
import type { TSESLint, TSESTree } from '@typescript-eslint/utils';
import { isTypeFlagSet, unionTypeParts } from 'tsutils';
import { isLiteralType, isTypeFlagSet, unionTypeParts } from 'tsutils';
import * as ts from 'typescript';

import {
Expand Down Expand Up @@ -113,13 +113,30 @@ export default createRule({
);
}

function isTypeFinite(type: ts.Type): boolean {
return (
// Check literal or unique symbol
isTypeFlagSet(
type,
ts.TypeFlags.Literal | ts.TypeFlags.UniqueESSymbol,
) &&
// Cannot be a general primitive
!isTypeFlagSet(
type,
ts.TypeFlags.Boolean | ts.TypeFlags.Number | ts.TypeFlags.String,
)
);
}

function checkSwitchExhaustive(node: TSESTree.SwitchStatement): void {
const discriminantType = getNodeType(node.discriminant);
const symbolName = discriminantType.getSymbol()?.escapedName;

if (discriminantType.isUnion()) {
const unionTypes = unionTypeParts(discriminantType);

const caseTypes: Set<ts.Type> = new Set();

for (const switchCase of node.cases) {
if (switchCase.test == null) {
// Switch has 'default' branch - do nothing.
Expand All @@ -129,6 +146,13 @@ export default createRule({
caseTypes.add(getNodeType(switchCase.test));
}

const isFinite = unionTypes.every(isTypeFinite);

if (!isFinite) {
// Union type is not finite - do nothing.
return;
}

const missingBranchTypes = unionTypes.filter(
unionType => !caseTypes.has(unionType),
);
Expand Down
62 changes: 36 additions & 26 deletions packages/eslint-plugin/tests/rules/switch-exhaustiveness-check.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -207,6 +207,42 @@ function test(value: ObjectUnion): number {
case 1:
return 1;
}
}
`,
`
declare const a: 'a' | 'b' | number;
switch (a) {
case 'a':
break;
case 'b':
break;
}
`,
`
declare const a: number | string;
switch (a) {
case 2:
break;
}
`,
`
declare const a: 'a' | (string & {});
switch (a) {
case 'a':
break;
}
`,
`
type FooBar = (string & { foo: void }) | 'bar';

const foobar = 'bar' as FooBar;
let result = 0;

switch (foobar) {
case 'bar': {
result = 42;
break;
}
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Just posting here so it doesn't get lost - tests should end up including bigints, booleans, symbols, unique symbols, and other fun wacky combinations/things just to be safe.

}
`,
],
Expand Down Expand Up @@ -373,32 +409,6 @@ switch (day) {
},
],
},
{
// Still complains with union intersection part
code: `
type FooBar = (string & { foo: void }) | 'bar';

const foobar = 'bar' as FooBar;
let result = 0;

switch (foobar) {
case 'bar': {
result = 42;
break;
}
}
`,
errors: [
{
messageId: 'switchIsNotExhaustive',
line: 7,
column: 9,
data: {
missingBranches: 'string & { foo: void; }',
},
},
],
},
{
code: `
const a = Symbol('a');
Expand Down