Bug: (flat config) ESLint crashes when merging a null value in a config #17820
Closed
Description
Environment
Node version: v18.16.1
npm version: v9.5.0
Local ESLint version: v8.55.0 (Currently used)
Global ESLint version: Not found
Operating System: darwin 23.1.0
What parser are you using?
Default (Espree)
What did you do?
module.exports = [
{
languageOptions: {
parserOptions: {
foo: {},
}
},
},
{
languageOptions: {
parserOptions: {
foo: null,
}
},
},
]What did you expect to happen?
The second parserOptions.foo should override the first - which is the way it used to work with .eslintrc configs.
What actually happened?
Oops! Something went wrong! :(
ESLint: 8.55.0
TypeError: Cannot convert undefined or null to object
at Function.keys (<anonymous>)
at deepMerge (<root>/node_modules/eslint/lib/config/flat-config-schema.js:91:30)
at deepMerge (<root>/node_modules/eslint/lib/config/flat-config-schema.js:105:27)
at ObjectSchema.merge (<root>/node_modules/eslint/lib/config/flat-config-schema.js:271:16)
at <root>/node_modules/@humanwhocodes/object-schema/src/object-schema.js:244:54
at Array.reduce (<anonymous>)
at ObjectSchema.merge (<root>/node_modules/@humanwhocodes/object-schema/src/object-schema.js:237:24)
at ObjectSchema.merge (<root>/node_modules/@humanwhocodes/object-schema/src/object-schema.js:176:39)
at <root>/node_modules/@humanwhocodes/object-schema/src/object-schema.js:244:54
at Array.reduce (<anonymous>)
Link to Minimal Reproducible Example
https://github.com/bradzacher/eslint-flat-config-bugs/tree/main/null-merge-crash
Participation
- I am willing to submit a pull request for this issue.
Additional comments
In typescript-eslint we have a convenience config which can be used to disable type-aware linting on files i.e. someone can use { files: ["*.js"], extends: ['plugin:@typescript-eslint/disable-type-checked'] } to override their base config and disable type-aware linting.
In eslintrc files this works as expected. In flat configs this crashes.