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Fix: Fix false positives/negatives in require-meta-fixable rule #158

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merged 1 commit into from
Jul 11, 2021
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Fix: Fix false positives/negatives in require-meta-fixable rule #158

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25 changes: 4 additions & 21 deletions docs/rules/require-meta-fixable.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2,19 +2,19 @@

✔️ The `"extends": "plugin:eslint-plugin/recommended"` property in a configuration file enables this rule.

A fixable ESLint rule must have a valid `meta.fixable` property. A rule reports a problem with a `fix()` function but does not export a `meta.fixable` property is likely to cause an unexpected error.
ESLint requires fixable rules to specify a valid `meta.fixable` property (with value `code` or `whitespace`).

## Rule Details

This rule aims to require ESLint rules to have a `meta.fixable` property if necessary.
This rule aims to require fixable ESLint rules to have a valid `meta.fixable` property.

Examples of **incorrect** code for this rule:

```js
/* eslint eslint-plugin/require-meta-fixable: "error" */

module.exports = {
meta: {},
meta: {}, // missing `fixable` property
create (context) {
context.report({
node,
Expand Down Expand Up @@ -44,20 +44,6 @@ module.exports = {
};
```

```js
/* eslint eslint-plugin/require-meta-fixable: "error" */

module.exports = { create (context) {
context.report({
node,
message: 'foo',
fix (fixer) {
return fixer.remove(node);
},
});
} };
```

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why removing the example? it seems a good example to have.

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@bmish bmish Jul 11, 2021 •
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This example shows the rule without any meta object. I would consider this to be a rare edge case, and I would argue that including too many unimportant edge cases can distract from the primary examples and make the documentation too long and difficult to understand. The key point we're trying to get across is that "fixable being missing" is in invalid case, and that's already covered by the test case above this one.

If you still prefer, I can add it back, but just wanted to make my case against it.

Examples of **correct** code for this rule:

```js
Expand Down Expand Up @@ -91,10 +77,7 @@ module.exports = {
};
```

## When Not To Use It

If you do not plan to implement autofixable rules, you can turn off this rule.

## Further Reading

* [ESLint's autofix API](http://eslint.org/docs/developer-guide/working-with-rules#applying-fixes)
* [ESLint's rule basics mentioning `meta.fixable`](https://eslint.org/docs/developer-guide/working-with-rules#rule-basics)
33 changes: 22 additions & 11 deletions lib/rules/require-meta-fixable.js
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Expand Up @@ -5,6 +5,7 @@

'use strict';

const { getStaticValue } = require('eslint-utils');
const utils = require('../utils');

// ------------------------------------------------------------------------------
Expand All @@ -20,6 +21,10 @@ module.exports = {
recommended: true,
},
schema: [],
messages: {
invalid: '`meta.fixable` must be either `code`, `whitespace` or `null`.',
missing: 'Fixable rules must export a `meta.fixable` property.',
},
},

create (context) {
Expand Down Expand Up @@ -62,19 +67,25 @@ module.exports = {
ruleInfo.meta.properties.find(prop => utils.getKeyName(prop) === 'fixable');

if (metaFixableProp) {
const VALID_VALUES = new Set(['code', 'whitespace', null, undefined]);
const valueIsValid = metaFixableProp.value.type === 'Literal'
? VALID_VALUES.has(metaFixableProp.value.value)
// eslint-disable-next-line unicorn/no-nested-ternary
: metaFixableProp.value.type === 'TemplateLiteral' && metaFixableProp.value.quasis.length === 1
? VALID_VALUES.has(metaFixableProp.value.quasis[0].value.cooked)
: metaFixableProp.value.type === 'Identifier' && metaFixableProp.value.name === 'undefined';
const staticValue = getStaticValue(metaFixableProp.value, context.getScope());
if (!staticValue) {
// Ignore non-static values since we can't determine what they look like.
return;
}

if (!['code', 'whitespace', null, undefined].includes(staticValue.value)) {
// `fixable` property has an invalid value.
context.report({ node: metaFixableProp.value, messageId: 'invalid' });
return;
}

if (!valueIsValid) {
context.report({ node: metaFixableProp, message: '`meta.fixable` must be either `code`, `whitespace` or `null`.' });
if (usesFixFunctions && !['code', 'whitespace'].includes(staticValue.value)) {
// Rule is fixable but `fixable` property does not have a fixable value.
context.report({ node: metaFixableProp.value, messageId: 'missing' });
}
} else if (usesFixFunctions) {
context.report({ node: ruleInfo.create, message: 'Fixable rules must export a `meta.fixable` property.' });
} else if (!metaFixableProp && usesFixFunctions) {
// Rule is fixable but is missing the `fixable` property.
context.report({ node: ruleInfo.meta || ruleInfo.create, messageId: 'missing' });
}
},
};
Expand Down
59 changes: 50 additions & 9 deletions tests/lib/rules/require-meta-fixable.js
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Original file line number Diff line number Diff line change
Expand Up @@ -12,9 +12,6 @@
const rule = require('../../../lib/rules/require-meta-fixable');
const RuleTester = require('eslint').RuleTester;

const MISSING_ERROR = { message: 'Fixable rules must export a `meta.fixable` property.', type: 'FunctionExpression' };
const INVALID_ERROR = { message: '`meta.fixable` must be either `code`, `whitespace` or `null`.', type: 'Property' };

// ------------------------------------------------------------------------------
// Tests
// ------------------------------------------------------------------------------
Expand All @@ -37,6 +34,16 @@ ruleTester.run('require-meta-fixable', rule, {
}
};
`,
// Value in variable.
`
const fixable = 'code';
module.exports = {
meta: { fixable },
create(context) {
context.report({node, message, fix: foo});
}
};
`,
`
module.exports = {
meta: { fixable: 'whitespace' },
Expand Down Expand Up @@ -93,6 +100,13 @@ ruleTester.run('require-meta-fixable', rule, {
}
};
`,
// `fixable` uses variable but no static value available.
`
module.exports = {
meta: { fixable: foo },
create(context) { context.report({node, message, fix: foo}); }
};
`,
`
module.exports = {
meta: {},
Expand Down Expand Up @@ -128,7 +142,15 @@ ruleTester.run('require-meta-fixable', rule, {
create(context) { context.report({node, message, fix: foo}); }
};
`,
errors: [MISSING_ERROR],
errors: [{ messageId: 'missing', type: 'ObjectExpression' }],
},
{
code: `
module.exports = {
create(context) { context.report({node, message, fix: foo}); }
};
`,
errors: [{ messageId: 'missing', type: 'FunctionExpression' }],
},
{
code: `
Expand All @@ -137,7 +159,7 @@ ruleTester.run('require-meta-fixable', rule, {
create(context) { context.report(node, loc, message, data, fix); }
};
`,
errors: [MISSING_ERROR],
errors: [{ messageId: 'missing', type: 'ObjectExpression' }],
},
{
code: `
Expand All @@ -146,7 +168,7 @@ ruleTester.run('require-meta-fixable', rule, {
create(context) { context.report({node, message}); }
};
`,
errors: [INVALID_ERROR],
errors: [{ messageId: 'invalid', type: 'Literal' }],
},
{
code: `
Expand All @@ -155,16 +177,35 @@ ruleTester.run('require-meta-fixable', rule, {
create(context) { context.report({node, message, fix: foo}); }
};
`,
errors: [INVALID_ERROR],
errors: [{ messageId: 'invalid', type: 'Literal' }],
},
{
code: `
const fixable = 'invalid';
module.exports = {
meta: { fixable },
create(context) { context.report({node, message, fix: foo}); }
};
`,
errors: [{ messageId: 'invalid', type: 'Identifier' }],
},
{
code: `
module.exports = {
meta: { fixable: null },
create(context) { context.report({node, message, fix: foo}); }
};
`,
errors: [{ messageId: 'missing', type: 'Literal' }],
},
{
code: `
module.exports = {
meta: { fixable: foo },
meta: { fixable: undefined },
create(context) { context.report({node, message, fix: foo}); }
};
`,
errors: [INVALID_ERROR],
errors: [{ messageId: 'missing', type: 'Identifier' }],
},
],
});