Add PGlite version to VFS file

Related to electric-sql#369

packages/pglite/src/pglite.ts

@@ -424,6 +424,9 @@ export class PGlite
     for (const initFn of extensionInitFns) {
       await initFn()
     }
+
+    // Write the PGlite version to a file
+    await this.writePGliteVersionFile()
   }
 
   /**
@@ -763,4 +766,14 @@ export class PGlite
   _runExclusiveTransaction<T>(fn: () => Promise<T>): Promise<T> {
     return this.#transactionMutex.runExclusive(fn)
   }
+
+  /**
+   * Write the PGlite version to a file
+   */
+  async writePGliteVersionFile() {
+    const version = await this.query<{ version: string }>('SELECT version()')
+    const versionString = `Created by: ${version.rows[0].version}`
+    const filePath = `${PGDATA}/PGLITE_VERSION`
+    this.mod!.FS.writeFile(filePath, versionString)
+  }
 }

packages/pglite/src/postgresMod.ts

@@ -34,4 +34,19 @@ type PostgresFactory<T extends PostgresMod = PostgresMod> = (
   moduleOverrides?: Partial<T>,
 ) => Promise<T>
 
-export default PostgresModFactory as PostgresFactory<PostgresMod>
+const PGLITE_VERSION = 'v0.2.11'
+
+const PostgresModFactoryWithVersion: PostgresFactory<PostgresMod> = async (
+  moduleOverrides = {},
+) => {
+  const mod = await PostgresModFactory(moduleOverrides)
+  mod.preRun.push((mod) => {
+    mod.FS.writeFile(
+      '/confdefs.h',
+      `#define PG_VERSION_STR "PostgreSQL $PG_VERSION (PGlite ${PGLITE_VERSION}) on $host, compiled by $cc_string, \`expr $ac_cv_sizeof_void_p * 8\`-bit"`
+    )
+  })
+  return mod
+}
+
+export default PostgresModFactoryWithVersion

packages/pglite/tests/version.test.ts

@@ -0,0 +1,28 @@
+import { PGlite } from '../src/pglite';
+import { describe, it, expect } from 'vitest';
+import { promises as fs } from 'fs';
+
+describe('PGlite version reporting', () => {
+  let pg: PGlite;
+
+  beforeAll(async () => {
+    pg = await PGlite.create({ dataDir: 'memory://test' });
+  });
+
+  afterAll(async () => {
+    await pg.close();
+  });
+
+  it('should create PGLITE_VERSION file with correct content', async () => {
+    const versionFilePath = '/tmp/pglite/base/PGLITE_VERSION';
+    const versionFileContent = await fs.readFile(versionFilePath, 'utf8');
+    const version = await pg.query<{ version: string }>('SELECT version()');
+    const expectedContent = `Created by: ${version.rows[0].version}`;
+    expect(versionFileContent).toBe(expectedContent);
+  });
+
+  it('should report correct version with SELECT VERSION()', async () => {
+    const result = await pg.query<{ version: string }>('SELECT version()');
+    expect(result.rows[0].version).toContain('PGlite');
+  });
+});