Adding Brotli pre-compressed files as response body in ASP .NET Core 3.1

Question

I have a static pre-compressed JS file with Brotli in ASP .NET Core 3.1. I want when a request for that file arrives ending with .js, to return the content of the pre-compressed version which is with the same name, ending with .js.br.

I tried adding some middleware code:

app.UseSpaStaticFiles(new StaticFileOptions
{
    OnPrepareResponse = async (staticFilesContext) =>
    {
        IHeaderDictionary headers = staticFilesContext.Context.Response.Headers;
        var httpContext = staticFilesContext.Context;
        string contentType = headers["Content-Type"];

        if (contentType == "application/javascript" && staticFilesContext.File.Name.EndsWith("somehash.chunk.js"))
        {
            var compressed = @$"ClientApp\build\static\js\{staticFilesContext.File.Name}";

            var compressedBytes = await File.ReadAllBytesAsync(compressed);
            httpContext.Response.Headers.Add("Content-Encoding", "br");
            await httpContext.Response.Body.WriteAsync(compressedBytes);
        }
    }
});

I tried 2 npm libraries for the pre-compression:

brotli - with that one I got decoding error in Chrome console
brotli-max - the one I'm currently with, for which I receive the below error.

With that code, I get net::ERR_HTTP2_PROTOCOL_ERROR response in Chrome. Sometimes I get exception in Visual Studio 2019 for content length:

Response Content-Length mismatch: too many bytes written

How to properly write such a pre-compressed file as response? I'm doing pre-compression, because I'm using level 11 of Brotli which is the slowest, so dynamic compression is not an option for me.

Adding Brotli pre-compressed files as response body in ASP .NET Core 3.1

0 Answers0