Prettierrc Validator

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name: prettierrc-validator description: Validate and lint Prettier configuration files (.prettierrc, .prettierrc.json, .prettierrc.yaml, .prettierrc.toml, package.json#prettier) for structure, invalid options, deprecated fields, override conflicts, and best practices. 22 rules across 5 categories.

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Prettier Config Validator

Validate .prettierrc config files for correctness, deprecated options, conflicting overrides, and best practices. Supports JSON, YAML, TOML, and package.json#prettier field. JS configs are detected but not statically validated.

Commands

# Full lint (all rules)
python3 scripts/prettierrc_validator.py lint .prettierrc.json
Check enum values, ranges, type conflicts only
python3 scripts/prettierrc_validator.py options .prettierrc.json
Check deprecated/removed options only
python3 scripts/prettierrc_validator.py deprecated .prettierrc.json
Validate 'overrides' array only
python3 scripts/prettierrc_validator.py overrides .prettierrc.json
Validate structure/syntax only
python3 scripts/prettierrc_validator.py validate .prettierrc.json
JSON output (for CI / tooling)
python3 scripts/prettierrc_validator.py lint .prettierrc.json --format json
Summary line only
python3 scripts/prettierrc_validator.py lint .prettierrc.json --format summary

Supported files

.prettierrc (JSON or YAML auto-detected)

.prettierrc.json / .prettierrc.json5

.prettierrc.yaml / .prettierrc.yml

.prettierrc.toml

package.json — validates the "prettier" field

.prettierrc.js / prettier.config.js — detected but not validated statically

Rules (22)

Structure (5)

Invalid JSON / YAML / TOML syntax

Unknown top-level options

Wrong type for option (boolean, int, string, array expected)

Empty config file

package.json with missing or invalid prettier field

Options (7)

Invalid enum value (quoteProps, trailingComma, arrowParens, proseWrap, htmlWhitespaceSensitivity, endOfLine, embeddedLanguageFormatting)

printWidth out of reasonable range (< 20 or > 320)

tabWidth invalid (0 or negative, > 16 warning)

parser name not a known built-in parser

requirePragma + insertPragma both true (conflict)

rangeStart > rangeEnd (inverted range)

Unknown parser name (plugin-assumed)

Deprecated (2)

jsxBracketSameLine → use bracketSameLine (Prettier 2.4+)

Removed options (useFlowParser, tabs) with replacement guidance

Overrides (5)

Override missing files field

files empty array or wrong type

Override missing options (no effect)

Unknown option inside override

Duplicate glob pattern across overrides (precedence bug)

Best Practices (3)

Missing endOfLine setting (cross-platform advice)

Missing trailingComma (default changed in Prettier v3)

printWidth very short (< 40) — may cause awkward line breaks

useTabs: true without explicit tabWidth

Invalid / empty plugin entries

Output Formats

text (default): human-readable with severity icons

json: machine-readable list of issues (file, path, rule, severity, message, category)

summary: single line of counts

Exit Codes

0: No errors (warnings/info allowed)

1: Errors found

2: Invalid input (file not found, unparseable, unsupported format)

Requirements

Python 3.8+

Optional: PyYAML (better YAML parsing — falls back to a minimal parser for simple configs)

Optional: tomli (only for Python 3.10 and below; Python 3.11+ has tomllib built in)

Examples

Broken config

{ "printWidth": "100", "trailingComma": "some", "jsxBracketSameLine": true }

✗ ERROR   wrong-type          [printWidth] must be an integer
✗ ERROR   invalid-enum-value  [trailingComma] invalid value 'some' (valid: all, es5, none)
⚠ WARNING deprecated-option   [jsxBracketSameLine] use 'bracketSameLine'

Good CI gate

python3 scripts/prettierrc_validator.py lint .prettierrc.json --format summary
exit 1 on any error — fails the CI step

Broken config

{ "printWidth": "100", "trailingComma": "some", "jsxBracketSameLine": true }

✗ ERROR   wrong-type          [printWidth] must be an integer
✗ ERROR   invalid-enum-value  [trailingComma] invalid value 'some' (valid: all, es5, none)
⚠ WARNING deprecated-option   [jsxBracketSameLine] use 'bracketSameLine'

Good CI gate

python3 scripts/prettierrc_validator.py lint .prettierrc.json --format summary
exit 1 on any error — fails the CI step