feat: allow no fs factory

.changeset/ten-apricots-buy.md

@@ -0,0 +1,5 @@
+---
+"rdf-transform-graph-imports": patch
+---
+
+Make the `FsUtilsFactory` optional. An exception wil be thrown when an enviornment does not provide that factory and a filesystem import is loaded

README.md

@@ -4,7 +4,7 @@ This package provides a stream transform which replaces import statements with c
 
 ## Installation
 
-Install the package itself and a RDF/JS environment which provides the factories [`NamespaceFactory`](https://github.com/rdfjs-base/namespace), [`FsUtilsFactory`](https://github.com/zazuko/rdf-utils-fs), and [`FetchFactory`](https://github.com/rdfjs-base/fetch-lite). If unsure, try [`@zazuko/env-node`](https://npm.im/@zazuko/env-node).
+Install the package itself and an RDF/JS environment which provides the factories [`NamespaceFactory`](https://github.com/rdfjs-base/namespace),  [`FetchFactory`](https://github.com/rdfjs-base/fetch-lite), and, optionally, [`FsUtilsFactory`](https://github.com/zazuko/rdf-utils-fs). If unsure, try [`@zazuko/env-node`](https://npm.im/@zazuko/env-node).
 
 ```bash
 npm install rdf-transform-graph-imports @zazuko/env-node

lib/env.ts

@@ -4,5 +4,5 @@ import type FsUtilsFactory from '@zazuko/rdf-utils-fs/Factory.js'
 import type { FetchFactory } from '@rdfjs/fetch-lite/Factory.js'
 import type ClownfaceFactory from 'clownface/Factory.js'
 
-type Environment = RdfjsEnvironment<NamespaceFactory | FsUtilsFactory | FetchFactory | ClownfaceFactory>
+type Environment = RdfjsEnvironment<NamespaceFactory | FsUtilsFactory | FetchFactory | ClownfaceFactory> | RdfjsEnvironment<NamespaceFactory | FetchFactory | ClownfaceFactory>
 export default Environment

lib/fetchImport.ts

@@ -3,6 +3,10 @@ import Environment from './env.js'
 
 export default async function (env: Environment, importTarget: string | URL) {
   if (typeof importTarget === 'string') {
+    if (!('fromFile' in env)) {
+      throw new Error('Importing from file is not supported')
+    }
+
     return env.fromFile(importTarget, { implicitBaseIRI: true })
   }