Move the OPFS VFS bits back into api/sqlite3-api-opfs.js. Refactor the OPFS VFS init process to use a Promise-returning function which the client must call, as that eliminates any uncertainty about when the VFS (necessarily activated asynchronously) actually becomes available to the client. Rename x-sync-async.* to test-opfs-vfs.* Milestone: first successful test of OPFS without WASMFS.

FossilOrigin-Name: b2abf60dbfa6648f671a3932cb65feb28d05a0d5b7f792351d14f9c13d9798c5

ext/wasm/test-opfs-vfs.js

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+/*
+  2022-09-17
+
+  The author disclaims copyright to this source code.  In place of a
+  legal notice, here is a blessing:
+
+  *   May you do good and not evil.
+  *   May you find forgiveness for yourself and forgive others.
+  *   May you share freely, never taking more than you give.
+
+  ***********************************************************************
+
+  A testing ground for the OPFS VFS.
+
+  Summary of how this works:
+
+  This file uses the sqlite3.StructBinder-created struct wrappers for
+  sqlite3_vfs, sqlite3_io_methods, ans sqlite3_file to set up a
+  conventional sqlite3_vfs (except that it's implemented in JS). The
+  methods which require OPFS APIs use a separate worker (hereafter called the
+  OPFS worker) to access that functionality. This worker and that one
+  use SharedArrayBuffer.
+*/
+'use strict';
+const tryOpfsVfs = function(sqlite3){
+  const toss = function(...args){throw new Error(args.join(' '))};
+  const logPrefix = "OPFS tester:";
+  const log = (...args)=>console.log(logPrefix,...args);
+  const warn =  (...args)=>console.warn(logPrefix,...args);
+  const error =  (...args)=>console.error(logPrefix,...args);
+  log("tryOpfsVfs()");
+  const capi = sqlite3.capi;
+  const pVfs = capi.sqlite3_vfs_find("opfs") || toss("Unexpectedly missing 'opfs' VFS.");
+  const oVfs = capi.sqlite3_vfs.instanceForPointer(pVfs) || toss("Unexpected instanceForPointer() result.");;
+  log("OPFS VFS:",pVfs, oVfs);
+
+  const dbFile = "my-persistent.db";
+  const db = new sqlite3.oo1.DB(dbFile, "c", "opfs");
+  log("db file:",db.filename);
+  try{
+    let n = db.selectValue("select count(*) from sqlite_schema");
+    if(n){
+      log("Persistent data found. sqlite_schema entry count =",n);
+    }
+    db.transaction((db)=>{
+      db.exec({
+        sql:[
+          "create table if not exists t(a);",
+          "insert into t(a) values(?),(?),(?);",
+        ],
+        bind: [performance.now() | 0,
+               (performance.now() |0) / 2,
+               (performance.now() |0) / 4]
+      });
+    });
+    log("count(*) from t =",db.selectValue("select count(*) from t"));
+  }finally{
+    db.close();
+  }
+
+  log("Done!");
+}/*tryOpfsVfs()*/;
+
+importScripts('sqlite3.js');
+self.sqlite3InitModule().then((EmscriptenModule)=>{
+  EmscriptenModule.sqlite3.installOpfsVfs()
+    .then((sqlite3)=>tryOpfsVfs(sqlite3))
+    .catch((e)=>{
+      console.error("Error initializing OPFS VFS:",e);
+    });
+});