Reintroduce WASMFS+OPFS support, albeit as a separate (less portable) WASM build.

FossilOrigin-Name: 7e4c594e9591101f6b727212c99f561498444e86d3d059e5864a717c614f903a

1 files changed, 15 insertions, 29 deletions

diff --git a/ext/wasm/api/sqlite3-api-prologue.js b/ext/wasm/api/sqlite3-api-prologue.js
index 77739db57..f3d0a7c40 100644
--- a/ext/wasm/api/sqlite3-api-prologue.js
+++ b/ext/wasm/api/sqlite3-api-prologue.js
@@ -92,8 +92,8 @@
      currently work due to incompatible Emscripten-side changes made
      in the WASMFS+OPFS combination. This option is currently ignored.
 
-   [^1] = This property may optionally be a function, in which case this
-          function re-assigns calls that function to fetch the value,
+   [^1] = This property may optionally be a function, in which case
+          this function calls that function to fetch the value,
           enabling delayed evaluation.
 
    The returned object is the top-level sqlite3 namespace object.
@@ -149,11 +149,6 @@ globalThis.sqlite3ApiBootstrap = function sqlite3ApiBootstrap(
       config[k] = config[k]();
     }
   });
-  config.wasmOpfsDir =
-    /* 2022-12-17: WASMFS+OPFS can no longer be activated from the
-       main thread (aborts via a failed assert() if it's attempted),
-       which eliminates any(?) benefit to supporting it. */  false;
-
   /**
       The main sqlite3 binding API gets installed into this object,
       mimicking the C API as closely as we can. The numerous members
@@ -1177,31 +1172,31 @@ globalThis.sqlite3ApiBootstrap = function sqlite3ApiBootstrap(
   /** State for sqlite3_wasmfs_opfs_dir(). */
   let __wasmfsOpfsDir = undefined;
   /**
-     2022-12-17: incompatible WASMFS changes have made WASMFS+OPFS
-     unavailable from the main thread, which eliminates the most
-     significant benefit of supporting WASMFS. This function is now a
-     no-op which always returns a falsy value. Before that change,
-     this function behaved as documented below (and how it will again
-     if we can find a compelling reason to support it).
-
      If the wasm environment has a WASMFS/OPFS-backed persistent
      storage directory, its path is returned by this function. If it
      does not then it returns "" (noting that "" is a falsy value).
 
      The first time this is called, this function inspects the current
      environment to determine whether persistence support is available
-     and, if it is, enables it (if needed).
+     and, if it is, enables it (if needed). After the first call it
+     always returns the cached result.
+
+     If the returned string is not empty, any files stored under the
+     given path (recursively) are housed in OPFS storage. If the
+     returned string is empty, this particular persistent storage
+     option is not available on the client.
+
+     Though the mount point name returned by this function is intended
+     to remain stable, clients should not hard-coded it anywhere. Always call this function to get the path.
 
-     This function currently only recognizes the WASMFS/OPFS storage
-     combination and its path refers to storage rooted in the
-     Emscripten-managed virtual filesystem.
+     Note that this function is a no-op in must builds of this
+     library, as the WASMFS capability requires a custom
+     build.
   */
   capi.sqlite3_wasmfs_opfs_dir = function(){
     if(undefined !== __wasmfsOpfsDir) return __wasmfsOpfsDir;
     // If we have no OPFS, there is no persistent dir
     const pdir = config.wasmfsOpfsDir;
-    console.error("sqlite3_wasmfs_opfs_dir() can no longer work due "+
-                  "to incompatible WASMFS changes. It will be removed.");
     if(!pdir
        || !globalThis.FileSystemHandle
        || !globalThis.FileSystemDirectoryHandle
@@ -1223,8 +1218,6 @@ globalThis.sqlite3ApiBootstrap = function sqlite3ApiBootstrap(
   };
 
   /**
-     Experimental and subject to change or removal.
-
      Returns true if sqlite3.capi.sqlite3_wasmfs_opfs_dir() is a
      non-empty string and the given name starts with (that string +
      '/'), else returns false.
@@ -1234,13 +1227,6 @@ globalThis.sqlite3ApiBootstrap = function sqlite3ApiBootstrap(
     return (p && name) ? name.startsWith(p+'/') : false;
   };
 
-  // This bit is highly arguable and is incompatible with the fiddle shell.
-  if(false && 0===wasm.exports.sqlite3_vfs_find(0)){
-    /* Assume that sqlite3_initialize() has not yet been called.
-       This will be the case in an SQLITE_OS_KV build. */
-    wasm.exports.sqlite3_initialize();
-  }
-
   /**
      Given an `sqlite3*`, an sqlite3_vfs name, and an optional db name
      (defaulting to "main"), returns a truthy value (see below) if