LangiumDocumentFactory + update + empty filesystem

[cdietrich]

LangiumDocumentFactory.update tries to reparse files in "changed" state and therefore try to read from (in our case) empty file system.
so somehow manage to get into this state by calling build in parallel, same uri.

(did not figure out the exact classpath yet)

what would be your recommendation for such a situation

• custom/own file system?
• no use in parallel?
• other ideas?

import { describe, test } from "vitest";
import { createHelloWorldServices } from "../src/hello-world-module.js";
import { AstNode, EmptyFileSystem, URI } from "langium";
import { LangiumSharedServices } from "langium/lsp";

class Compiler {
    constructor(private services: LangiumSharedServices) {
        // Initialize compiler
    }

    public hasDocument(uri: URI): boolean {
    return this.services.workspace.LangiumDocuments.hasDocument(uri)
  }

    public async addDocuments(
    docs: {uri: URI, content: string}[],
    options: {
      validation: boolean
    } = { validation: false }
  ): Promise<void> {
    const documentBuilder = this.services.workspace.DocumentBuilder
    const langiumDocs = docs.map(({ uri, content }) => {
      const ld = this.services.workspace.LangiumDocumentFactory.fromString<AstNode>(content, uri)
      if (this.hasDocument(uri)) {
        this.services.workspace.LangiumDocuments.deleteDocument(uri)
      }
      this.services.workspace.LangiumDocuments.addDocument(ld)

      return ld
    })

    console.log(
      "xxxx",
      langiumDocs.map(d => d.state)
    )
    await documentBuilder.build(langiumDocs, {
      validation: options.validation
        ? options.validation
        : {
            categories: ["built-in"], // lexing, parsing, linking
          },
    })
  }
}

describe('Parsing tests', () => {
    test('sample', async () => {
        const services = createHelloWorldServices(EmptyFileSystem);
        const compiler = new Compiler(services.shared);

        const datax = new Array(4).fill({uri: URI.parse("sample/demo.hello"), content: 'person Christian'}).flat() as {
        uri: URI
        content: string
        }[]

        await Promise.all(
        datax.map(async d => {
            //if (!compiler.hasDocument(d.uri))
            await compiler.addDocuments([d], { validation: true })
        })
        )
        })
});

[msujew]

Hey @cdietrich,

no use in parallel?

Yes, Langium's document builder is not safe for multiple builds in parallel. You should run them in sequence or use the WorkspaceLock to ensure that only one build is executed at a time. It's not like you gain any performance from running them in parallel, since everything is still single-threaded.