c5t-current-schema-ts

C5T/Current schema common type definitions and validators for TypeScript.

The library provides compile-time (in TypeScript) and runtime (in io-ts) type definitions for the common primitive and collection types used by the schema definitions generated by the C5T/Current schema export as TypeScript.

Usage

If C5T/Current TypeScript schemas are used, this library is required to be installed as a peer dependency because it is required from the schema files, along with the io-ts library which provides low-level primitives for TypeScript compile-time and runtime type definitions used in the schema files.

npm install --save c5t-current-schema-ts io-ts

NOTE: The schema files specify the recommended versions of c5t-current-schema-ts and io-ts at the top, for example:

// peerDependencies: io-ts@^0.6.1 c5t-current-schema-ts@^0.2.1

The generated TypeScript schema files export two items per CURRENT_STRUCT:

• a const with a runtime type object created via io-ts interface or union,
• a compile-time TypeScript type representing that runtime type.

Examples

Type definitions

Given the following C5T/Current type definitions:

CURRENT_STRUCT(Primitives) {
  CURRENT_FIELD(a, uint8_t);
  CURRENT_FIELD_DESCRIPTION(a, "It's the \"order\" of fields that matters.");
  CURRENT_FIELD(b, uint16_t);
  CURRENT_FIELD_DESCRIPTION(b, "Field descriptions can be set in any order.");
  CURRENT_FIELD(c, uint32_t);
  CURRENT_FIELD(d, uint64_t);
  CURRENT_FIELD(e, int8_t);
  CURRENT_FIELD(f, int16_t);
  CURRENT_FIELD(g, int32_t);
  CURRENT_FIELD(h, int64_t);
  CURRENT_FIELD(i, char);
  CURRENT_FIELD(j, std::string);
  CURRENT_FIELD(k, float);
  CURRENT_FIELD(l, double);
  CURRENT_FIELD(m, bool);
  CURRENT_FIELD_DESCRIPTION(m, "Multiline\ndescriptions\ncan be used.");
  CURRENT_FIELD(n, std::chrono::microseconds);
  CURRENT_FIELD(o, std::chrono::milliseconds);
};

CURRENT_VARIANT(MyFreakingVariant, A, X, Y);

The following TypeScript type definitions are generated:

import * as iots from 'io-ts';
import * as C5TCurrent from 'c5t-current-schema-ts';

export const Primitives_IO = iots.interface({
  // It's the "order" of fields that matters.
  a: C5TCurrent.UInt8_IO,

  // Field descriptions can be set in any order.
  b: C5TCurrent.UInt16_IO,
  c: C5TCurrent.UInt32_IO,
  d: C5TCurrent.UInt64_IO,
  e: C5TCurrent.Int8_IO,
  f: C5TCurrent.Int16_IO,
  g: C5TCurrent.Int32_IO,
  h: C5TCurrent.Int64_IO,
  i: C5TCurrent.Char_IO,
  j: C5TCurrent.String_IO,
  k: C5TCurrent.Float_IO,
  l: C5TCurrent.Double_IO,

  // Multiline
  // descriptions
  // can be used.
  m: C5TCurrent.Bool_IO,
  n: C5TCurrent.Microseconds_IO,
  o: C5TCurrent.Milliseconds_IO,
}, 'Primitives');
export type Primitives = iots.TypeOf<typeof Primitives_IO>;

export const MyFreakingVariant_IO = iots.union([
  MyFreakingVariant_VariantCase_A_IO,
  MyFreakingVariant_VariantCase_X_IO,
  MyFreakingVariant_VariantCase_Y_IO,
  iots.null,
], 'MyFreakingVariant');
export type MyFreakingVariant = iots.TypeOf<typeof MyFreakingVariant_IO>;

Type validation

The validate function from io-ts returns a value of the Either type which can be either Right that contains the validated object or Left that contains the error. This Either type and the isRight function to tell Right from Left are defined in the fp-ts module at fp-ts/lib/Either.

WARNING Due to the out-of-memory issues with TypeScript processing fp-ts, as of 2017-08-23 fp-ts is not recommended to be used directly. Use io-ts/lib/PathReporter or io-ts/lib/ThrowReporter with try..catch around it if required.

import * as fs from 'fs';
import * as iots from 'io-ts';
import { PathReporter } from 'io-ts/lib/PathReporter';
import { ThrowReporter } from 'io-ts/lib/ThrowReporter';

import * as generated_schema_ts from './generated_schema_ts';

const generated_schema_serialized: generated_schema_ts.FullTest = JSON.parse(String(fs.readFileSync('./generated_schema_serialized.json')));
const validation_result = iots.validate(generated_schema_serialized, generated_schema_ts.Primitives_IO);

const error_report: string[] = PathReporter.report(validation_result);
// `PathReporter.report` on a succeeded validation returns `[ 'No errors!' ]`.
// `PathReporter.report` on a failed validation returns an array of error messages.

try {
  ThrowReporter.report(validation_result);
  // `ThrowReporter.report` on a succeeded validation is a no-op.
  // `ThrowReporter.report` on a failed validation throws an `Error`.
}
catch (validation_error) {
  //
}

Contribution

Please see C5T/Current guidelines for contribution.