ts-runtime-validation

Why?

Get bulletproof type validation based off typescript interfaces without any extra work. This package will ingest your existing types and generate the code for you.

How?

This is a code generator that is designed to run as a yarn / npm script. By default scans your source directory for files ending in the provided glob pattern. It will generate types based off exported type aliases and typescript interfaces. By default: *.jsonschema.{ts,tsx}. The output will create three files:

1. ./src/ts-runtime-validation/validation.schema.json - containing the jsonschema types
2. ./src/SchemaDefinition.ts - containing the typescript.
3. ./src/isValidSchema.ts - containing a type guard type inferring helper method (intended for consumption in your code base - examples below)
4. ./src/ValidationType.ts - containing an exported namespace containing every single exported validation type

Limitations

The schema generator does not allow multiple interfaces / types to share the same name.

Footnote

The helper file assumes you have ajv-validator peer dependency installed. Since this is only a code generation tool this package can be installed as a dev dependency.

Installation

# yarn
yarn add --dev ts-runtime-validation
# npm
npm install --dev ts-runtime-validation

CLI usage

Ensure your project files containing the schemas you want to validate end with the prefix .jsonschema.ts

Usage: ts-runtime-validation [options]

Options:
  --glob                         Glob file path of typescript files to generate ts-interface -> json-schema validations - default: *.jsonschema.{ts,tsx}
  --rootPath <rootFolder>        RootPath of source (default: "./src")
  --output <outputFolder>        Code generation output directory (relative to root path) (default: "./.ts-runtime-validation")
  --tsconfigPath <tsconfigPath>  Path to customt tsconfig (relative to root path) (default: "")
  --generate-helpers             Only generate JSON schema without typescript helper files (default: true)
  --additionalProperties         Allow additional properties to pass validation (default: false)
  -h, --help                     display help for command
Done in 0.44s.

npm script usage

The intended use for ts-runtime-validation is as a npm script. Here it can also be tweaked to watch (eg. using nodemon)

{
    "scripts": {
        "generate-types": "ts-runtime-validation"
    },
    "devDependencies": {
        "ts-runtime-validation": "^1.4.1"
    }
}

Example snippets

Type guard

import { isValidSchema } from "./.ts-runtime-validation/isValidSchema"; // this is autogenerated by the CLI as a helper file

if (isValidSchema(data, "#/definitions/ITypeA")) {
    // variable: data in this block will have typings for ITypeA
} else {
    // type is invalid and not known here
    throw new Error("Failed to validate payload");
}

Type assertion

import * as schema from "../runtime-validation/validation.schema.json";
import Ajv from "ajv";
import { ISchema, schemas } from "../runtime-validation/SchemaDefinition";

const validator = new Ajv({ allErrors: true });
validator.compile(schema);

export const assertValidSchema = <T extends keyof typeof schemas>(data: unknown, schemaKeyRef: T): data is ISchema[T] => {
    validator.validate(schemaKeyRef as string, data);
    if (validator.errors || Boolean(validator.errors)) {
        const error = { schemaKeyRef, errors: validator.errorsText(), data };
        if (process.env.ENVIRONMENT === "dev") {
            console.log(error);
        }
        throw new Error(JSON.stringify(error));
    }
    return true;
};

Contributing

Submit a PR

License

MIT