Babel Config Validator

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name: babel-config-validator description: Validate Babel config files (babel.config.json, .babelrc, .babelrc.json, package.json#babel) for deprecated presets, plugin conflicts, ordering issues, and best practices. Use when validating Babel transpiler configs, auditing build setups, migrating Babel versions, or linting babel config files.

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Babel Config Validator

Validate babel.config.json, .babelrc, .babelrc.json, and package.json#babel for deprecated presets/plugins, conflicting transforms, ordering issues, and best practices. Supports text, JSON, and summary output formats with CI-friendly exit codes.

Commands

# Full validation (all 24+ rules)
python3 scripts/babel_config_validator.py validate babel.config.json
Quick syntax-only check (structure rules only)
python3 scripts/babel_config_validator.py check .babelrc
Explain config in human-readable form
python3 scripts/babel_config_validator.py explain babel.config.json
Suggest improvements
python3 scripts/babel_config_validator.py suggest package.json
JSON output (CI-friendly)
python3 scripts/babel_config_validator.py validate .babelrc --format json
Summary only (pass/fail + counts)
python3 scripts/babel_config_validator.py validate .babelrc --format summary
Strict mode (warnings become errors)
python3 scripts/babel_config_validator.py validate .babelrc --strict

Rules (24+)

| # | Category | Severity | Rule | |---|----------|----------|------| | S1 | Structure | Error | File not found or unreadable | | S2 | Structure | Error | Empty config or no content | | S3 | Structure | Warning | Both babel.config and .babelrc present (conflict) | | S4 | Structure | Warning | Unknown top-level config keys | | S5 | Structure | Error | Invalid JSON syntax | | P1 | Presets | Error | Deprecated preset (es2015, es2016, es2017, latest, stage-*) | | P2 | Presets | Warning | Preset ordering matters (@babel/preset-typescript before @babel/preset-env) | | P3 | Presets | Warning | Duplicate presets | | P4 | Presets | Error | Unknown/misspelled preset name | | P5 | Presets | Warning | Missing @babel/preset-env (most configs need it) | | L1 | Plugins | Error | Deprecated plugin (@babel/plugin-proposal-* → built-in) | | L2 | Plugins | Warning | Duplicate plugins | | L3 | Plugins | Warning | Plugin ordering conflict (decorators before class-properties) | | L4 | Plugins | Warning | Conflicting plugins (transform-runtime + external-helpers) | | L5 | Plugins | Warning | Plugin without @babel/ scope (may be community or typo) | | M1 | Modules | Warning | modules: false in preset-env without bundler context | | M2 | Modules | Warning | sourceType mismatch with modules setting | | M3 | Modules | Warning | Conflicting module transforms | | E1 | Env/Overrides | Warning | Empty env config section | | E2 | Env/Overrides | Warning | Override without test pattern | | E3 | Env/Overrides | Warning | Unknown env name (not development/production/test) | | B1 | Best Practices | Warning | loose mode inconsistency across plugins | | B2 | Best Practices | Warning | Missing targets/browserslist (unoptimized output) | | B3 | Best Practices | Warning | useBuiltIns without corejs version | | B4 | Best Practices | Warning | corejs version outdated (< 3) |

Output Formats

text (default): Human-readable with colors and severity icons

json: Machine-parseable JSON array of findings

summary: Pass/fail with error/warning counts

Exit Codes

0: No errors (warnings only or clean)

1: One or more errors found

2: File not found or invalid input

Requirements

Python 3.8+

No external dependencies (pure stdlib)