ts-json-schema-generator

What is ts-json-schema-generator?

The ts-json-schema-generator package is a tool that generates JSON schemas from TypeScript types. It is useful for ensuring that your TypeScript types and JSON schemas stay in sync, which can be particularly helpful for validating JSON data against TypeScript interfaces or types.

What are ts-json-schema-generator's main functionalities?

Generate JSON Schema from TypeScript Interface

This feature allows you to generate a JSON schema from a TypeScript interface. You need to specify the path to your TypeScript file and the type you want to generate the schema for.

const { createGenerator } = require('ts-json-schema-generator');
const config = {
  path: 'path/to/your/file.ts',
  tsconfig: 'path/to/your/tsconfig.json',
  type: '*', // Or specify a particular type
};
const schema = createGenerator(config).createSchema(config.type);
console.log(JSON.stringify(schema, null, 2));

Generate JSON Schema for Specific Type

This feature allows you to generate a JSON schema for a specific TypeScript type. You need to specify the path to your TypeScript file and the type you want to generate the schema for.

const { createGenerator } = require('ts-json-schema-generator');
const config = {
  path: 'path/to/your/file.ts',
  tsconfig: 'path/to/your/tsconfig.json',
  type: 'MyType', // Specify the type you want to generate the schema for
};
const schema = createGenerator(config).createSchema(config.type);
console.log(JSON.stringify(schema, null, 2));

Generate JSON Schema with Custom Settings

This feature allows you to generate a JSON schema with custom settings. You can specify various options such as exposing all types, referencing the top-level schema, and using extended JSDoc annotations.

const { createGenerator } = require('ts-json-schema-generator');
const config = {
  path: 'path/to/your/file.ts',
  tsconfig: 'path/to/your/tsconfig.json',
  type: 'MyType',
  expose: 'all', // Expose all types
  topRef: true, // Reference the top-level schema
  jsDoc: 'extended', // Use extended JSDoc annotations
};
const schema = createGenerator(config).createSchema(config.type);
console.log(JSON.stringify(schema, null, 2));

Other packages similar to ts-json-schema-generator

typescript-json-schema

The typescript-json-schema package generates JSON schemas from TypeScript types. It is similar to ts-json-schema-generator but offers different configuration options and may have different performance characteristics.

json-schema-to-typescript

The json-schema-to-typescript package converts JSON schemas to TypeScript interfaces. While it performs the reverse operation of ts-json-schema-generator, it is often used in conjunction with it to ensure consistency between JSON schemas and TypeScript types.

ajv

The ajv package is a JSON schema validator that can be used to validate JSON data against JSON schemas. While it does not generate schemas from TypeScript types, it is often used alongside ts-json-schema-generator to validate data against the generated schemas.

README

ts-json-schema-generator

Extended version of https://github.com/xiag-ag/typescript-to-json-schema.

Inspired by YousefED/typescript-json-schema. Here's the differences list:

• this implementation avoids the use of typeChecker.getTypeAtLocation() (so probably it keeps correct type aliases)
• processing AST and formatting JSON schema have been split into two independent steps
• not exported types, interfaces, enums are not exposed in the definitions section in the JSON schema

Contributors

This project is made possible by a community of contributors. We welcome contributions of any kind (issues, code, documentation, examples, tests,...). Please read our code of conduct.

CLI Usage

Run the schema generator with npx:

npx ts-json-schema-generator --path 'my/project/**/*.ts' --type 'My.Type.Name'

Or install the package and then run it

npm install --save ts-json-schema-generator
./node_modules/.bin/ts-json-schema-generator --path 'my/project/**/*.ts' --type 'My.Type.Name'

Note that different platforms (e.g. Windows) may use different path separators so you may have to adjust the command above.

Also note that you need to quote paths with * as otherwise the shell will expand the paths and therefore only pass the first path to the generator.

Programmatic Usage

// main.js

const tsj = require("ts-json-schema-generator");
const fs = require("fs");

/** @type {import('ts-json-schema-generator/dist/src/Config').Config} */
const config = {
    path: "path/to/source/file",
    tsconfig: "path/to/tsconfig.json",
    type: "*", // Or <type-name> if you want to generate schema for that one type only
};

const outputPath = "path/to/output/file";

const schema = tsj.createGenerator(config).createSchema(config.type);
const schemaString = JSON.stringify(schema, null, 2);
fs.writeFile(outputPath, schemaString, (err) => {
    if (err) throw err;
});

Run the schema generator via node main.js.

Custom formatting

Extending the built-in formatting is possible by creating a custom formatter and adding it to the main formatter:

1. First we create a formatter, in this case for formatting function types:

// my-function-formatter.ts
import { BaseType, Definition, FunctionType, SubTypeFormatter } from "ts-json-schema-generator";
import ts from "typescript";

export class MyFunctionTypeFormatter implements SubTypeFormatter {
    // You can skip this line if you don't need childTypeFormatter
    public constructor(private childTypeFormatter: TypeFormatter) {}

    public supportsType(type: FunctionType): boolean {
        return type instanceof FunctionType;
    }

    public getDefinition(type: FunctionType): Definition {
        // Return a custom schema for the function property.
        return {
            type: "object",
            properties: {
                isFunction: {
                    type: "boolean",
                    const: true,
                },
            },
        };
    }

    // If this type does NOT HAVE children, generally all you need is:
    public getChildren(type: FunctionType): BaseType[] {
        return [];
    }

    // However, if children ARE supported, you'll need something similar to
    // this (see src/TypeFormatter/{Array,Definition,etc}.ts for some examples):
    public getChildren(type: FunctionType): BaseType[] {
        return this.childTypeFormatter.getChildren(type.getType());
    }
}

1. Then we add the formatter as a child to the core formatter using the augmentation callback:

import { createProgram, createParser, SchemaGenerator, createFormatter } from "ts-json-schema-generator";
import { MyFunctionTypeFormatter } from "./my-function-formatter.ts";
import fs from "fs";

const config = {
    path: "path/to/source/file",
    tsconfig: "path/to/tsconfig.json",
    type: "*", // Or <type-name> if you want to generate schema for that one type only
};

// We configure the formatter an add our custom formatter to it.
const formatter = createFormatter(config, (fmt, circularReferenceTypeFormatter) => {
    // If your formatter DOES NOT support children, e.g. getChildren() { return [] }:
    fmt.addTypeFormatter(new MyFunctionTypeFormatter());
    // If your formatter DOES support children, you'll need this reference too:
    fmt.addTypeFormatter(new MyFunctionTypeFormatter(circularReferenceTypeFormatter));
});

const program = createProgram(config);
const parser = createParser(program, config);
const generator = new SchemaGenerator(program, parser, formatter, config);
const schema = generator.createSchema(config.type);
const outputPath = "path/to/output/file";

const schemaString = JSON.stringify(schema, null, 2);
fs.writeFile(outputPath, schemaString, (err) => {
    if (err) throw err;
});

Custom parsing

Similar to custom formatting, extending the built-in parsing works practically the same way:

1. First we create a parser, in this case for parsing construct types:

// my-constructor-parser.ts
import { Context, StringType, ReferenceType, BaseType, SubNodeParser } from "ts-json-schema-generator";
// use typescript exported by TJS to avoid version conflict
import ts from "ts-json-schema-generator";

export class MyConstructorParser implements SubNodeParser {
    supportsNode(node: ts.Node): boolean {
        return node.kind === ts.SyntaxKind.ConstructorType;
    }
    createType(node: ts.Node, context: Context, reference?: ReferenceType): BaseType | undefined {
        return new StringType(); // Treat constructors as strings in this example
    }
}

1. Then we add the parser as a child to the core parser using the augmentation callback:

import { createProgram, createParser, SchemaGenerator, createFormatter } from "ts-json-schema-generator";
import { MyConstructorParser } from "./my-constructor-parser.ts";
import fs from "fs";

const config = {
    path: "path/to/source/file",
    tsconfig: "path/to/tsconfig.json",
    type: "*", // Or <type-name> if you want to generate schema for that one type only
};

const program = createProgram(config);

// We configure the parser an add our custom parser to it.
const parser = createParser(program, config, (prs) => {
    prs.addNodeParser(new MyConstructorParser());
});

const formatter = createFormatter(config);
const generator = new SchemaGenerator(program, parser, formatter, config);
const schema = generator.createSchema(config.type);
const outputPath = "path/to/output/file";

const schemaString = JSON.stringify(schema, null, 2);
fs.writeFile(outputPath, schemaString, (err) => {
    if (err) throw err;
});

Options

-p, --path 'index.ts'
    The path to the TypeScript source file. If this is not provided, the type will be searched in the project specified in the `.tsconfig`.

-t, --type 'My.Type.Name'
    The type the generated schema will represent. If omitted, the generated schema will contain all
    types found in the files matching path. The same is true if '*' is specified.

-i, --id 'generatedSchemaId'
    The `$id` of the generated schema. If omitted, there will be no `$id`.

-e, --expose <all|none|export>
    all: Create shared $ref definitions for all types.
    none: Do not create shared $ref definitions.
    export (default): Create shared $ref definitions only for exported types (not tagged as `@internal`).

-f, --tsconfig 'my/project/tsconfig.json'
    Use a custom tsconfig file for processing typescript (see https://www.typescriptlang.org/docs/handbook/tsconfig-json.html) instead of the default:
    {
        "compilerOptions": {
            "noEmit": true,
            "emitDecoratorMetadata": true,
            "experimentalDecorators": true,
            "target": "ES5",
            "module": "CommonJS",
            "strictNullChecks": false,
        }
    }

-j, --jsDoc <extended|none|basic>
    none: Do not use JsDoc annotations.
    basic: Read JsDoc annotations to provide schema properties.
    extended (default): Also read @nullable, and @asType annotations.

--unstable
    Do not sort properties.

--strict-tuples
    Do not allow additional items on tuples.

--no-top-ref
    Do not create a top-level $ref definition.

--no-type-check
    Skip type checks for better performance.

--no-ref-encode
    Do not encode references. According to the standard, references must be valid URIs but some tools do not support encoded references.

--validation-keywords
    Provide additional validation keywords to include.

-o, --out
    Specify the output file path. Without this option, the generator logs the response in the console.

--additional-properties <true|false>
    Controls whether or not to allow additional properties for objects that have no index signature.

    true: Additional properties are allowed
    false (default): Additional properties are not allowed

--minify
    Minify generated schema (default: false)

Current state

• interface types
• enum types
• union, tuple, type[] types
• Date, RegExp, URL types
• string, boolean, number types
• "value", 123, true, false, null, undefined literals
• type aliases
• generics
• typeof
• keyof
• conditional types

Run locally

yarn --silent run run --path 'test/valid-data/type-mapped-array/*.ts' --type 'MyObject'

Debug

yarn --silent run debug --path 'test/valid-data/type-mapped-array/*.ts' --type 'MyObject'

And connect via the debugger protocol.

AST Explorer is amazing for developers of this tool!

Publish

Publishing is handled by a 2-branch pre-release process, configured in publish-auto.yml. All changes should be based off the default next branch, and are published automatically.

• PRs made into the default branch are auto-deployed to the next pre-release tag on NPM. The result can be installed with npm install ts-json-schema-generator@next
  • When merging into next, please use the squash and merge strategy.
• To release a new stable version, open a PR from next into stable using this compare link.
  • When merging from next into stable, please use the create a merge commit strategy.