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fix(eslint-plugin): [prefer-find] support ternary branches in prefer-find #8421

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merged 7 commits into from Mar 11, 2024
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fix(eslint-plugin): [prefer-find] support ternary branches in prefer-find #8421

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f372aba
8379: Support ternary branches in prefer-find
kirkwaiblinger Feb 5, 2024
0db4183
fix codecov
kirkwaiblinger Feb 9, 2024
2200f83
lintfix
kirkwaiblinger Feb 9, 2024
7fd8285
Update packages/eslint-plugin/tests/rules/prefer-find.test.ts
kirkwaiblinger Feb 23, 2024
9d1b79a
add some straightforward tests
kirkwaiblinger Feb 23, 2024
f397a3a
remove any
kirkwaiblinger Feb 24, 2024
9e599c0
tweak tests slightly
kirkwaiblinger Feb 24, 2024
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66 changes: 47 additions & 19 deletions packages/eslint-plugin/src/rules/prefer-find.ts
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Expand Up @@ -41,20 +41,41 @@ export default createRule({
filterNode: TSESTree.Node;
}

function parseIfArrayFilterExpression(
function parseArrayFilterExpressions(
expression: TSESTree.Expression,
): FilterExpressionData | undefined {
): FilterExpressionData[] {
if (expression.type === AST_NODE_TYPES.SequenceExpression) {
// Only the last expression in (a, b, [1, 2, 3].filter(condition))[0] matters
const lastExpression = nullThrows(
expression.expressions.at(-1),
'Expected to have more than zero expressions in a sequence expression',
);
return parseIfArrayFilterExpression(lastExpression);
return parseArrayFilterExpressions(lastExpression);
}

if (expression.type === AST_NODE_TYPES.ChainExpression) {
return parseIfArrayFilterExpression(expression.expression);
return parseArrayFilterExpressions(expression.expression);
}

// This is the only reason we're returning a list rather than a single value.
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if (expression.type === AST_NODE_TYPES.ConditionalExpression) {
// Both branches of the ternary _must_ return results.
const consequentResult = parseArrayFilterExpressions(
expression.consequent,
);
if (consequentResult.length === 0) {
return [];
}

const alternateResult = parseArrayFilterExpressions(
expression.alternate,
);
if (alternateResult.length === 0) {
return [];
}

// Accumulate the results from both sides and pass up the chain.
return [...consequentResult, ...alternateResult];
}

// Check if it looks like <<stuff>>(...), but not <<stuff>>?.(...)
Expand All @@ -78,16 +99,19 @@ export default createRule({
// As long as the object is a (possibly nullable) array,
// this is an Array.prototype.filter expression.
if (isArrayish(filteredObjectType)) {
return {
isBracketSyntaxForFilter,
filterNode,
};
return [
{
isBracketSyntaxForFilter,
filterNode,
},
];
}
}
}
}

return undefined;
// not a filter expression.
return [];
}

/**
Expand Down Expand Up @@ -223,8 +247,8 @@ export default createRule({
CallExpression(node): void {
const object = getObjectIfArrayAtZeroExpression(node);
if (object) {
const filterExpression = parseIfArrayFilterExpression(object);
if (filterExpression) {
const filterExpressions = parseArrayFilterExpressions(object);
if (filterExpressions.length !== 0) {
context.report({
node,
messageId: 'preferFind',
Expand All @@ -233,9 +257,11 @@ export default createRule({
messageId: 'preferFindSuggestion',
fix: (fixer): TSESLint.RuleFix[] => {
return [
generateFixToReplaceFilterWithFind(
fixer,
filterExpression,
...filterExpressions.map(filterExpression =>
generateFixToReplaceFilterWithFind(
fixer,
filterExpression,
),
),
// Get rid of the .at(0) or ['at'](0).
generateFixToRemoveArrayElementAccess(
Expand All @@ -261,8 +287,8 @@ export default createRule({
): void {
if (isMemberAccessOfZero(node)) {
const object = node.object;
const filterExpression = parseIfArrayFilterExpression(object);
if (filterExpression) {
const filterExpressions = parseArrayFilterExpressions(object);
if (filterExpressions.length !== 0) {
context.report({
node,
messageId: 'preferFind',
Expand All @@ -271,9 +297,11 @@ export default createRule({
messageId: 'preferFindSuggestion',
fix: (fixer): TSESLint.RuleFix[] => {
return [
generateFixToReplaceFilterWithFind(
fixer,
filterExpression,
...filterExpressions.map(filterExpression =>
generateFixToReplaceFilterWithFind(
fixer,
filterExpression,
),
),
// Get rid of the [0].
generateFixToRemoveArrayElementAccess(
Expand Down
143 changes: 143 additions & 0 deletions packages/eslint-plugin/tests/rules/prefer-find.test.ts
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Expand Up @@ -70,6 +70,12 @@ ruleTester.run('prefer-find', rule, {
`,
"[1, 2, 3].filter(x => x)[Symbol('0')];",
"[1, 2, 3].filter(x => x)[Symbol.for('0')];",
'(Math.random() < 0.5 ? [1, 2, 3].filter(x => true) : [1, 2, 3])[0];',
`
(Math.random() < 0.5
? [1, 2, 3].find(x => true)
: [1, 2, 3].filter(x => true))[0];
`,
],

invalid: [
Expand Down Expand Up @@ -584,5 +590,142 @@ arr.find(f, thisArg);
},
],
},
{
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[Testing] Just to be through, could you also add a test for a desired report with and within a ternary? Like the valid case above, but either with two .filters or with the [0] on the other side of the last )?

(Math.random() < 0.5
  ? [1, 2, 3].filter(x => false)
  : [1, 2, 3].filter(x => true))[0];
(Math.random() < 0.5
  ? [1, 2, 3].find(x => true)
  : [1, 2, 3].filter(x => true)[0]);

The cases lower down are a bit more complex. It's nice to have more straightforward ones to use as a reference too.

code: `
(Math.random() < 0.5
? [1, 2, 3].filter(x => false)
: [1, 2, 3].filter(x => true))[0];
`,
errors: [
{
line: 2,
messageId: 'preferFind',
suggestions: [
{
messageId: 'preferFindSuggestion',
output: `
(Math.random() < 0.5
? [1, 2, 3].find(x => false)
: [1, 2, 3].find(x => true));
`,
},
],
},
],
},
{
code: `
Math.random() < 0.5
? [1, 2, 3].find(x => true)
: [1, 2, 3].filter(x => true)[0];
`,
errors: [
{
line: 4,
messageId: 'preferFind',
suggestions: [
{
messageId: 'preferFindSuggestion',
output: `
Math.random() < 0.5
? [1, 2, 3].find(x => true)
: [1, 2, 3].find(x => true);
`,
},
],
},
],
},
{
code: `
declare const f: (arg0: unknown, arg1: number, arg2: Array<unknown>) => boolean,
g: (arg0: unknown) => boolean;
const nestedTernaries = (
Math.random() < 0.5
? Math.random() < 0.5
? [1, 2, 3].filter(f)
: []?.filter(x => 'shrug')
: [2, 3, 4]['filter'](g)
).at(0.2);
`,
errors: [
{
line: 4,
messageId: 'preferFind',
suggestions: [
{
messageId: 'preferFindSuggestion',
output: `
declare const f: (arg0: unknown, arg1: number, arg2: Array<unknown>) => boolean,
g: (arg0: unknown) => boolean;
const nestedTernaries = (
Math.random() < 0.5
? Math.random() < 0.5
? [1, 2, 3].find(f)
: []?.find(x => 'shrug')
: [2, 3, 4]["find"](g)
);
`,
},
],
},
],
},

{
code: `
declare const f: (arg0: unknown) => boolean, g: (arg0: unknown) => boolean;
const nestedTernariesWithSequenceExpression = (
Math.random() < 0.5
? ('sequence',
'expression',
Math.random() < 0.5 ? [1, 2, 3].filter(f) : []?.filter(x => 'shrug'))
: [2, 3, 4]['filter'](g)
).at(0.2);
`,
errors: [
{
line: 3,
messageId: 'preferFind',
suggestions: [
{
messageId: 'preferFindSuggestion',
output: `
declare const f: (arg0: unknown) => boolean, g: (arg0: unknown) => boolean;
const nestedTernariesWithSequenceExpression = (
Math.random() < 0.5
? ('sequence',
'expression',
Math.random() < 0.5 ? [1, 2, 3].find(f) : []?.find(x => 'shrug'))
: [2, 3, 4]["find"](g)
);
`,
},
],
},
],
},

{
code: `
declare const spreadArgs: [(x: unknown) => boolean];
[1, 2, 3].filter(...spreadArgs).at(0);
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`,
errors: [
{
line: 3,
messageId: 'preferFind',
suggestions: [
{
messageId: 'preferFindSuggestion',
output: `
declare const spreadArgs: [(x: unknown) => boolean];
[1, 2, 3].find(...spreadArgs);
`,
},
],
},
],
},
],
});