Babel Config Validator

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.

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

bash

# 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)