feat: allow returning a Response or Promise<Response> from locateFile

Author: birtles

.changeset/proud-beers-win.md

@@ -0,0 +1,5 @@
+---
+"@birchill/nice-sqlite-wasm": minor
+---
+
+Allow returning a `Response` or `Promise<Response>` from `locateFile`

README.md

@@ -85,6 +85,7 @@ Then update the table below.
 | ---------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------- |
 | `0001-locatefile-nullish-coalesce.patch` | Allow a user-provided `locateFile` function to be used (rather than clobbered).                                                             |
 | `0002-hardcode-locatefile-path.patch`    | Hardcodes the path used in the default `locateFile` implementation so that bundlers don't complain about dependencies based on expressions. |
+| `0003-locatefile-with-response.patch`    | Allows a user-provided `locateFile` function to return a `Response` or a `Promise<Response>`.                                               |
 
 ### Building the WASM module
 

patches/0003-locatefile-with-response.patch

@@ -0,0 +1,28 @@
+diff --git a/ext/wasm/api/pre-js.c-pp.js b/ext/wasm/api/pre-js.c-pp.js
+index da399df..9ec48b3 100644
+--- a/ext/wasm/api/pre-js.c-pp.js
++++ b/ext/wasm/api/pre-js.c-pp.js
+@@ -101,7 +101,9 @@
+           ? "" : scriptDirectory)
+     );
+     sims.debugModule("instantiateWasm() uri =", uri, "sIMS =",this);
+-    const wfetch = ()=>fetch(uri, {credentials: 'same-origin'});
++    const response = uri instanceof Response || uri instanceof Promise
++      ? uri
++      : fetch(uri, { credentials: 'same-origin' });
+     const finalThen = (arg)=>{
+       arg.imports = imports;
+       sims.instantiateWasm = arg /* used by sqlite3-api-prologue.c-pp.js */;
+@@ -110,10 +112,10 @@
+     const loadWasm = WebAssembly.instantiateStreaming
+           ? async ()=>
+           WebAssembly
+-          .instantiateStreaming(wfetch(), imports)
++          .instantiateStreaming(response, imports)
+           .then(finalThen)
+           : async ()=>// Safari < v15
+-          wfetch()
++          Promise.resolve(response)
+           .then(response => response.arrayBuffer())
+           .then(bytes => WebAssembly.instantiate(bytes, imports))
+           .then(finalThen)

src/sqlite3.d.ts

@@ -2241,7 +2241,10 @@ declare type Sqlite3Static = {
 };
 
 declare type InitOptions = {
-  locateFile?: (path: string, prefix: string) => string;
+  locateFile?: (
+    path: string,
+    prefix: string,
+  ) => string | Response | Promise<Response>;
   print?: (msg: string) => void;
   printErr?: (msg: string) => void;
 };