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fix(eslint-plugin): [no-useless-template-literals] report Infinity & NaN #8295

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Jan 29, 2024
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fix(eslint-plugin): [no-useless-template-literals] report Infinity & NaN #8295

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3158dad
fix(eslint-plugin): [no-useless-template-literals] report Infinity & NaN
StyleShit Jan 23, 2024
b0bc73d
remove unnecessary tests
StyleShit Jan 25, 2024
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28 changes: 24 additions & 4 deletions packages/eslint-plugin/src/rules/no-useless-template-literals.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,24 @@ export default createRule<[], MessageId>({
return isString(type);
}

function isLiteral(expression: TSESTree.Expression): boolean {
return expression.type === AST_NODE_TYPES.Literal;
}

function isInfinityIdentifier(expression: TSESTree.Expression): boolean {
return (
expression.type === AST_NODE_TYPES.Identifier &&
expression.name === 'Infinity'
);
}

function isNaNIdentifier(expression: TSESTree.Expression): boolean {
return (
expression.type === AST_NODE_TYPES.Identifier &&
expression.name === 'NaN'
);
}
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[Style] Nit: both of these functions check expression.type === AST_NODE_TYPES.Identifier. I think it'd be just a bit cleaner code to avoid the duplicate check and instead have a single function for both. WDYT?

This is a super nitpicky nit and definitely not a blocker 😄.

A good potential followup might be to look into writing a general catch-all function for this. Searching expression.type === AST_NODE_TYPES.Identifier shows a few dozen results. Maybe half or more of them or so are similar calls.

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Yeah, so I basically took inspiration from this:

typescript-eslint/packages/eslint-plugin/src/rules/no-inferrable-types.ts

Lines 73 to 80 in 8622286

function isIdentifier(
init: TSESTree.Expression,
...names: string[]
): boolean {
return (
init.type === AST_NODE_TYPES.Identifier && names.includes(init.name)
);
}

And thought about extracting it to a util, WDYT?

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Probably useful to have that as a util yeah. I'm not super picky here to be honest.


return {
TemplateLiteral(node: TSESTree.TemplateLiteral): void {
if (node.parent.type === AST_NODE_TYPES.TaggedTemplateExpression) {
Expand Down Expand Up @@ -91,13 +109,15 @@ export default createRule<[], MessageId>({
return;
}

const literalsOrUndefinedExpressions = node.expressions.filter(
const fixableExpressions = node.expressions.filter(
(expression): expression is TSESTree.Literal | TSESTree.Identifier =>
expression.type === AST_NODE_TYPES.Literal ||
isUndefinedIdentifier(expression),
isLiteral(expression) ||
isUndefinedIdentifier(expression) ||
isInfinityIdentifier(expression) ||
isNaNIdentifier(expression),
);

literalsOrUndefinedExpressions.forEach(expression => {
fixableExpressions.forEach(expression => {
context.report({
node: expression,
messageId: 'noUselessTemplateLiteral',
Expand Down
26 changes: 26 additions & 0 deletions packages/eslint-plugin/tests/rules/no-useless-template-literals.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -280,6 +280,32 @@ ruleTester.run('no-useless-template-literals', rule, {
],
},

{
code: '`${Infinity}`;',
output: '`Infinity`;',
errors: [
{
messageId: 'noUselessTemplateLiteral',
line: 1,
column: 4,
endColumn: 12,
},
],
},

{
code: '`${NaN}`;',
output: '`NaN`;',
errors: [
{
messageId: 'noUselessTemplateLiteral',
line: 1,
column: 4,
endColumn: 7,
},
],
},

{
code: "`${'a'} ${'b'}`;",
output: '`a b`;',
Expand Down