ESLint v10: Flat Config Completion and JSX Tracking
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ESLint's transition to flat config, important for JavaScript/TypeScript developer tooling.
ESLint v10 removes legacy eslintrc entirely, dropping APIs like defineParser and shouldUseFlatConfig, and shifts config resolution to per-file directories for monorepo clarity. Native JSX reference tracking eliminates no-unused-vars false positives, and RuleTester gains requireMessage/requireLocation assertions. Node.js support tightens to ^20.19.0 || ^22.13.0 || >=24, while community migration pains persist: eslint-plugin-react and eslint-config-next lack v10 peer dependency updates, and Rust-based alternatives Biome/Oxlint continue to gain adoption.
- Run `npx @eslint/migrate-config` to move from .eslintrc to flat config, verify all plugins declare ESLint v10 peer dependencies, and evaluate Rust-based linters like Biome for faster linting in new projects.
For platform engineers managing large monorepos and CI pipelines, this breaking change forces migration away from legacy eslintrc, and the JSX fix removes a long-standing pain point in React codebases, while the rise of Rust-based linters signals a potential shift in toolchain performance expectations.