@ts-to-json-schema/transform

This package is responsible for transforming TypeScript types into JSON Schema objects.

Installation

npm install @ts-to-json-schema/transform

or

yarn add @ts-to-json-schema/transform

Usage

This package is used internally by the @ts-to-json-schema/core package and should not be used directly.

Supported JSDoc Tags

The package supports the following JSDoc tags to add metadata to the JSON Schema:

@deprecated

Marks a field as deprecated.

interface Example {
  /**
   * @deprecated This field is deprecated and will be removed in the next version
   */
  field: string;
}

Result in JSON Schema:

{
  "type": "object",
  "properties": {
    "field": {
      "type": "string",
      "deprecated": true
    }
  },
  "required": ["field"]
}

@example

Provides example values for a field.

interface Example {
  /**
   * @example "example value"
   * @example 123
   */
  field: string;
}

Result in JSON Schema:

{
  "type": "object",
  "properties": {
    "field": {
      "type": "string",
      "examples": ["example value", "123"]
    }
  },
  "required": ["field"]
}

@see

Provides links to additional documentation.

interface Example {
  /**
   * @see https://example.com/docs
   */
  field: string;
}

Result in JSON Schema:

{
  "type": "object",
  "properties": {
    "field": {
      "type": "string",
      "see": "https://example.com/docs"
    }
  },
  "required": ["field"]
}

@since

Indicates the version in which a field was introduced.

interface Example {
  /**
   * @since 1.0.0
   */
  field: string;
}

Result in JSON Schema:

{
  "type": "object",
  "properties": {
    "field": {
      "type": "string",
      "since": "1.0.0"
    }
  },
  "required": ["field"]
}

@default

Provides a default value for a field.

interface Example {
  /**
   * @default "default value"
   */
  field: string;
}

Result in JSON Schema:

{
  "type": "object",
  "properties": {
    "field": {
      "type": "string",
      "default": "default value"
    }
  },
  "required": ["field"]
}

Numeric Validation Tags

@minimum and @maximum

Specify the minimum and maximum values for a numeric field.

interface Example {
  /**
   * @minimum 1
   * @maximum 100
   */
  field: number;
}

Result in JSON Schema:

{
  "type": "object",
  "properties": {
    "field": {
      "type": "number",
      "minimum": 1,
      "maximum": 100
    }
  },
  "required": ["field"]
}

String Validation Tags

@minLength and @maxLength

Specify the minimum and maximum lengths for a string field.

interface Example {
  /**
   * @minLength 3
   * @maxLength 100
   */
  field: string;
}

Result in JSON Schema:

{
  "type": "object",
  "properties": {
    "field": {
      "type": "string",
      "minLength": 3,
      "maxLength": 100
    }
  },
  "required": ["field"]
}

@format

Specifies the format of a field.

interface Example {
  /**
   * @format email
   */
  field: string;
}

Result in JSON Schema:

{
  "type": "object",
  "properties": {
    "field": {
      "type": "string",
      "format": "email"
    }
  },
  "required": ["field"]
}

Configuration

1. TypeScript Compiler API

import * as ts from 'typescript';
import transform from '@ts-to-json-schema/transform';

const program = ts.createProgram(['./index.ts'], compilerOptions);
const sourceFiles = program.getSourceFiles();
const compilerOptions = {
  lib: ["es2015"],
  strict: true,
};

for (const sourceFile of sourceFiles) {
  const transformedSourceFile = ts.transform(
    sourceFile,
    [transform(program)],
    compilerOptions
  );
  const result = ts.createPrinter().printNode(
    ts.EmitHint.Unspecified,
    transformedSourceFile.transformed[0],
    sourceFile
  );

  console.log(result);
}

2. Alternative Compiler

To apply the transformation to the TypeScript code using bundlers/runners (such as Webpack, ts-node, etc.), you must use an alternative compiler that supports plugins. Install one of the following compilers based on TypeScript version:

TypeScript Version	Compiler	Documentation
5.x or newer	ts-patch/compiler	link
3.x, 4.x	ttypescript	link

npm install --save-dev ts-patch

Follow the instructions in the documentation to configure @ts-to-json-schema/transform plugin. You need to enable strict mode too.

{
  "compilerOptions": {
    "strict": true,
    "plugins": [
      { "transform": "@ts-to-json-schema/transform", "type": "program" }
    ]
  }
}

Change TypeScript compiler (TSC) to Alternative compiler

If you just need compile/transform your TypeScript code into JavaScript code, you can use one of following commands instead of tsc:

• ttsc (for ttypescript)
• tspc (for ts-patch)

TS Node (ts-node)

Set the alternative compiler as ts-node compiler argument:

ts-node --compiler=ts-patch/compiler src/index.ts

Webpack + TS Loader

Set the alternative compiler in ts-loader options

module.exports = {
  // ...
  module: {
    rules: [
      {
        test: /\.ts$/,
        loader: 'ts-loader',
        exclude: /node_modules/,
        options: {
          compiler: 'ts-patch/compiler', // add here
        },
      },
    ],
  }
};

3. ESBuild

Follow the instructions in the ESBuild plugin documentation.