schemagen

Generate TypeScript, Python, and Go types from JSON Schema. One binary, zero dependencies.

Install

Homebrew (macOS/Linux)

brew tap mirpo/homebrew-tools
brew install schemagen

Go

go install github.com/mirpo/schemagen@latest

Binary

Download from GitHub Releases.

Usage

# Generate TypeScript
schemagen generate schemas/ --out-ts ./types

# Generate Python (Pydantic v2)
schemagen generate schemas/ --out-py ./models

# Generate Go
schemagen generate schemas/ --out-go ./models

# All three at once
schemagen generate schemas/ --out-ts ./types --out-py ./models --out-go ./models

Commands

Global Flags

These flags are available for all commands:

• -v, --verbose - Enable verbose/debug logging
• --json - Output logs in JSON format

generate

Generate code from JSON Schema files.

schemagen generate <input> [flags]

Flags:

Output directories:

• --out-ts <dir> - TypeScript output directory
• --out-py <dir> - Python output directory
• --out-go <dir> - Go output directory

General:

• --extract-inline - Extract inline enums and nested objects to top-level types
• --output-strategy <strategy> - Output strategy: bundle, multifile, or bundledeps (default: multifile)
• --disable-headers - Remove generated file headers
• --disable-timestamp - Remove timestamp from headers

TypeScript-specific:

• --ts-unknown-any - Use unknown instead of any for untyped schemas
• --ts-additional-properties - Add index signatures for additionalProperties

Python-specific:

• --py-snake-case-field - Convert field names to snake_case with JSON alias
• --py-additional-properties - Add model_config = ConfigDict(extra='allow') for schemas with additionalProperties

Go-specific:

• --go-package <name> - Package name for generated files (default: models)
• --go-pointers - Use pointers for optional fields (default: true)
• --go-omit-empty - Add omitempty to optional JSON tags (default: true)
• --go-module-path <path> - Go module path for absolute imports (e.g., github.com/org/project)

validate

Check if schemas are valid JSON Schema.

schemagen validate schemas/

Flags:

• --format <format> - Output format: text or json (default: text)

verify

Check if generated code matches schemas. Returns exit code 2 if drift detected. Useful for CI.

schemagen verify schemas/ --out-ts ./types

Flags:

• --quiet - Suppress output (only exit codes)

diff

Show what would change if you regenerated.

schemagen diff schemas/ --out-ts ./types

What it generates

TypeScript

• Interfaces with JSDoc comments
• @format annotations (uuid, email, etc.)
• Union types for enums
• Auto-generated barrel exports (index.ts)

Python

• Pydantic v2 BaseModel classes
• Field constraints (min, max, pattern)
• Format types (EmailStr, UUID, datetime)
• Enum classes
• Optional: model_config = ConfigDict(extra='allow') for additionalProperties (use --py-additional-properties)
• Auto-generated barrel exports (__init__.py)

Go

• Structs with JSON tags
• Go validator tags (min, max, email, uuid, etc.)
• Embedded structs for allOf composition
• UUID and time.Time format types
• Configurable pointer usage and package naming

Validation Libraries

TypeScript with Zod

Generate Zod schemas alongside TypeScript interfaces:

# Interfaces + Zod schemas
schemagen generate schema.json --out-ts ./types --ts-zod

# Only Zod schemas (with z.infer<> types)
schemagen generate schema.json --out-ts ./types --ts-zod-only

# Additional options
--ts-zod-strict        # Add .strict() to object schemas
--ts-zod-coerce-dates  # Use z.coerce.date() for date-time

Python with Pydantic v2

Python output uses Pydantic v2 BaseModel with built-in validation:

• Field constraints: min_length, max_length, pattern, ge, le
• Format types: EmailStr, UUID, datetime
• Enums with string/int values

License

MIT