A pre-commit hook is the last line of defense before code enters the repository. It runs automatically when a developer runs git commit, and if it fails, the commit is aborted. The combination of Husky and lint-staged is the standard mechanism for this in JavaScript projects. Husky installs the Git hooks and manages their execution;…
ESLint’s output is not a fixed log. It is a formatter function that receives the lint results and returns a string. The default formatter is stylish, which produces the human-readable, colorized output that most developers recognize: a list of files, the rule violations under each file, and a summary line. The json formatter produces the…
ESLint’s default exit code behavior creates a blind spot in CI pipelines. Errors cause a non-zero exit code and fail the build, but warnings do not. A codebase can accumulate hundreds of warnings without the pipeline ever turning red, and the warnings become background noise that no one reads. The –max-warnings flag exists to close…
The –fix-dry-run flag is the preview counterpart to –fix. It runs the same multi-pass correction pipeline, computes the same fixes, and produces the same corrected code—but it does not write the result to disk. The flag was added in ESLint v4.9.0 specifically with editor plugins in mind: in some cases an integration can only communicate…
The –fix flag is ESLint’s mechanism for applying safe corrections to code without manual intervention. When a rule provides a fix, it is marked with a wrench icon (🔧) in the rules documentation, and ESLint can apply that fix automatically during a lint run . The flag does not fix everything. It fixes only the…
prettier.getFileInfo() answers a question that is different from resolveConfig() and different from format(). It does not return formatting options, and it does not format anything. It returns a description of the file: whether it is ignored by .prettierignore or node_modules, and which parser Prettier would infer from the filename or an installed plugin. The return…
prettier.resolveConfig() is the function that answers a deceptively simple question: given a file path, which configuration options apply? The answer is not simply “the contents of .prettierrc” because Prettier supports multiple configuration file formats, overrides for specific file patterns, and EditorConfig integration. The function searches from the file’s directory upward, finds the first applicable configuration,…
The JavaScript API is the programmatic interface to Prettier. It does not spawn a CLI process, does not read from stdin, and does not format every file in a directory. It takes a string, a set of options, and returns a result. The two functions that matter for most integrations are prettier.format(), which returns the…
eslint-plugin-prettier inverts the relationship between the two tools. Instead of Prettier running as a separate command and ESLint running separately, the plugin runs Prettier inside ESLint and reports formatting differences as individual ESLint issues . The prettier/prettier rule becomes the mechanism: when a file does not match Prettier’s output, ESLint reports an error on the…
Prettier and ESLint answer different questions. Prettier asks “how should this code look?” and reformats it. ESLint asks “is this code correct?” and reports problems. The two questions are independent, but the tools overlap: ESLint ships with formatting rules like indent, quotes, and semi that duplicate what Prettier does, and when both tools run, they…