Metano Runtime

1.0.3 verified Fri May 01 auth: no javascript

Runtime support library for code generated by the Metano C# → TypeScript transpiler (v1.0.3, updated April 2026). Provides C#-compatible primitives such as HashCode (xxHash32), HashSet with structural equality, a full LINQ API via Enumerable, a branded UUID type for System.Guid mapping, runtime type guards (isInt32, isString, etc.), and JSON serialization (system/json). Release cadence is active (multiple versions per month). Key differentiator: automatically added by Metano to generated projects; side-effect-free for tree-shaking. Requires @typescript/native-preview (peer dep). Only relevant for Metano users; not designed for general-purpose use.

Common errors

error Error: Cannot find module 'metano-runtime' ↓

cause metano-runtime is not installed; Metano should add it automatically but missing npm install step.

fix

Run 'npm install' after code generation, or manually add 'metano-runtime' to dependencies.

error TypeError: Class extends value undefined is not a constructor or null ↓

cause Missing peer dependency @typescript/native-preview v7, required for generic type utilities.

fix

Run 'npm install @typescript/native-preview@^7'.

error Cannot find module 'metano-runtime/system/json' ↓

cause Subpath imports may not be supported by older bundlers or Node.js versions (<12).

fix

Update Node.js to >=14 or use a bundler that supports the 'exports' field in package.json.

Warnings

gotcha This library is auto-installed by the Metano transpiler; manual use is discouraged. The public API is unstable across Metano versions. ↓

fix Only consume via generated code; do not depend on it directly.

deprecated The 'Erasable' annotation was renamed to 'NoContainer' in v1.0.0. ↓

fix Use [NoContainer] attribute instead of [Erasable] in generated code.

breaking Peer dependency @typescript/native-preview ^7 required since v1.0.0. Older versions did not require it. ↓

fix Add @typescript/native-preview@^7 as a dependency or devDependency.

Install

npm install metano-runtime

yarn add metano-runtime

pnpm add metano-runtime

Imports

HashCode

wrong

import HashCode from 'metano-runtime'

correct

import { HashCode } from 'metano-runtime'

Named export, not default. ESM-only (no CJS). Types included.

HashSet
wrong
```
const { HashSet } = require('metano-runtime')
```
correct
```
import { HashSet } from 'metano-runtime'
```
Named export. Not available via default import. Requires peer dep @typescript/native-preview for generics.
Enumerable
wrong
```
import { Enumerable } from 'metano-runtime/enumerable'
```
correct
```
import { Enumerable } from 'metano-runtime'
```
Export is from top-level package, not subpath. Provides .NET-like LINQ operations.

UUID

wrong

import { Uuid } from 'metano-runtime'

correct

import { UUID } from 'metano-runtime'

Case-sensitive: 'UUID' in all caps. Branded string type.

JsonSerializer

wrong

import { JsonSerializer } from 'metano-runtime'

correct

import { JsonSerializer } from 'metano-runtime/system/json'

Located under 'system/json' subpath; not exported from main entry point.

Quickstart

Demonstrates core runtime features: HashCode, HashSet, Enumerable, UUID, and int32 type guard.

import { HashCode, HashSet, Enumerable, UUID, isInt32 } from 'metano-runtime';
// HashCode usage
const hc = new HashCode();
hc.add('hello');
hc.add(42);
const hash = hc.toHashCode(); // number
// HashSet with structural equality
class Point {
  constructor(readonly x: number, readonly y: number) {}
  equals(other: Point) { return this.x === other.x && this.y === other.y; }
  hashCode() {
    const hc = new HashCode();
    hc.add(this.x);
    hc.add(this.y);
    return hc.toHashCode();
  }
}
const set = new HashSet<Point>();
set.add(new Point(1, 2));
console.log(set.has(new Point(1, 2))); // true
// Enumerable (LINQ)
const result = Enumerable.from([1, 2, 3, 4, 5])
  .where(x => x > 1)
  .select(x => x * 2)
  .toArray(); // [4, 6, 8, 10]
// UUID
const id = UUID.newUuid();
console.log(id); // "550e8400-e29b-41d4-a716-446655440000"
if (UUID.isUuid(id)) { console.log('valid UUID'); }
// Type guard
console.log(isInt32(123)); // true
console.log(isInt32(1.5)); // false