fix(next-codemod): handle CommonJS legacy ESLint configs in next-lint…#95710
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Alexoswin wants to merge 1 commit into
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fix(next-codemod): handle CommonJS legacy ESLint configs in next-lint…#95710Alexoswin wants to merge 1 commit into
Alexoswin wants to merge 1 commit into
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…-to-eslint-cli The next-lint-to-eslint-cli codemod assumed @eslint/migrate-config always generates eslint.config.mjs. The migration tool actually keeps the extension of JS legacy configs (.eslintrc.js -> eslint.config.js, .eslintrc.cjs -> eslint.config.cjs), so the codemod crashed with "Failed to find the expected output file" for those formats. Detect the generated flat config instead of hardcoding the .mjs name, and emit require() declarations instead of ESM import statements when updating a CommonJS flat config so the result stays loadable. Fixes vercel#85679
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What?
The
next-lint-to-eslint-clicodemod assumed that@eslint/migrate-configalways generateseslint.config.mjs. In practice, the migration tool preserves the module format of JavaScript-based legacy configs:.eslintrc.js→eslint.config.js.eslintrc.cjs→eslint.config.cjsBecause of this assumption, the codemod failed with:
when migrating projects using CommonJS ESLint configs.
This change detects whichever flat config file was actually generated instead of hardcoding
eslint.config.mjs. It also preserves the module system when updating CommonJS configs by generatingrequire()declarations instead of ESMimportstatements.Why?
next linthas been removed in Next.js 16, making this codemod the recommended migration path. Projects using.eslintrc.jsor.eslintrc.cjscurrently cannot complete the migration because the codemod crashes before finishing.Additionally, even if the generated file were found, the previous implementation would have inserted ESM imports into a CommonJS config, resulting in an invalid ESLint configuration.
How?
.mjs,.js, or.cjs) instead of assuming a fixed filename.require()declarations for CommonJS configs while preserving the existing ESM behavior for.mjsconfigs..eslintrc.cjsconfiguration.Testing
.eslintrc.cjsmigration.next-codemodtest suite successfully.eslint.config.cjsworks with ESLint 9 in a real sample project.Fixes #85679