UseSpa() returns index.html from API instead of 404

Question

By default .UseSpa() in startup.cs catches every request that arrives to its point of the pipeline, and tries to handle it as a request to the SPA main page

I want to keep 404 for for my API calls at route /api/* just in case when typo in api url is made it my logger would log 404 and and not like "Error Code: 200 Message: Http failure during parsing for https://localhost:5001/api/non-existing-api-should-give-404" (because it got index.html in response)

Already spend over day on this and I can't find solution :( UseSpa() seems to overwrite any not matched endpoint. Any ideas how to solve it?

Here is basic configure from Startup.cs, problem is in Production Environment.

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.UseHttpsRedirection();
            if (!env.IsDevelopment())
            {
                app.UseSpaStaticFiles();
            }

            app.UseRouting();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });

            app.UseSpa(spa =>
            {
                if (env.IsDevelopment())
                {
                    spa.UseProxyToSpaDevelopmentServer("http://127.0.0.1:4200");
                }
            });
        }

user_11398810 · Answer

The UseSpa middlware is a catch-all, and any request that gets to that point will always have the default SPA page returned. This means any request to a route that hasn't yet found a controller will always return the default SPA page, and not throw a 404.

What you will want to do it only call UseSpa() if the route is not prefixed with /api. Which essentially lets any requests that start with/api skip past that point.

Change:

app.UseSpa(spa =>
{
    //...
});

To:

app.MapWhen(x => !x.Request.Path.Value.StartsWith("/api"), builder =>
{
    builder.UseSpa(spa =>
    {
        //...
    });
});

This will let any request that starts with /api past that point, and if no other middleware or routes are matched, a 404 will be returned.

UseSpa() returns index.html from API instead of 404

1 Answers