wasm: fix qtloader.js preRun usage

Emscripten documents that preRun should be an array
of functions, but also accepts setting it to a single
function.

qtloader.js was accidentally using this feature, which
works as long as qtloader is the single user, but breaks
if other code expects an array. A typical error in this
case is:

   "Module.preRun.push is not a function"

Fix this by creating and maintaining preRun as an array.

Pick-to: 6.6 6.7
Change-Id: Ie1382695f3f25839cb971ab4adc81984fc8c53ca
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

1 files changed, 8 insertions, 7 deletions

diff --git a/src/plugins/platforms/wasm/qtloader.js b/src/plugins/platforms/wasm/qtloader.js
index 1b76d4ecc1..c0bb3652cf 100644
--- a/src/plugins/platforms/wasm/qtloader.js
+++ b/src/plugins/platforms/wasm/qtloader.js
@@ -116,15 +116,13 @@ async function qtLoad(config)
         }
     }
 
-    const originalPreRun = config.preRun;
-    config.preRun = instance =>
-    {
-        originalPreRun?.();
-
+    const qtPreRun = (instance) => {
+        // Copy qt.environment to instance.ENV
         throwIfEnvUsedButNotExported(instance, config);
         for (const [name, value] of Object.entries(config.qt.environment ?? {}))
             instance.ENV[name] = value;
 
+        // Copy self.preloadData to MEMFS
         const makeDirs = (FS, filePath) => {
             const parts = filePath.split("/");
             let path = "/";
@@ -142,13 +140,16 @@ async function qtLoad(config)
                 }
             }
         }
-
         throwIfFsUsedButNotExported(instance, config);
         for ({destination, data} of self.preloadData) {
             makeDirs(instance.FS, destination);
             instance.FS.writeFile(destination, new Uint8Array(data));
         }
-    };
+    }
+
+    if (!config.preRun)
+        config.preRun = [];
+    config.preRun.push(qtPreRun);
 
     config.onRuntimeInitialized = () => config.qt.onLoaded?.();