Blazor/OpenCv js : Error: MONO_WASM: Module.ready couldn't be redefined

Question

I am currently working on a Blazor component that requires opencv. I've added opencv.js (4.8.0) in wwwroot.

Here is my html file:

<script async src="_content/MyComponent/opencv.js"></script>
<script src="_framework/blazor.webassembly.js"></script>

I keep getting the following error :

Failed to start platform. Reason: Error: MONO_WASM: Module.ready couldn't be redefined.
    at Vt (blazor.webassembly.js:1:62226)

I am very new to Blazor/Js and since I don't really understand how wasm works under the hood, it's hard for me to even understand the error.

Any documentation or explanation would be greatly appreciated.

Answer 1

Here is how I fixed my issue:

1. Open 'opencv.js' and replace the laste 4 lines as follows

  if (typeof Module === 'undefined')
    Module = {};
  return cv(Module);
}));

replace with

  if (typeof OpenCvModule === 'undefined')
    OpenCvModule = {};
  return cv(OpenCvModule);
}));

Module variable is apparently conflicting between Blazor's wasm and opencv.

Side note: to make sure that your script gets reloaded in your browser, rename it (do not forget the html file). Blazor's cache handling could be really annoying.