Fix HTTP logging

[nickspoons]

As described in #1446, the HTTP version of OmniSharp-roslyn does not log any output.

I managed to find the commit where the logging stopped working, it was 4f9fb4d by @DustinCampbell. In that commit the HostHelpers.LogFilter() functionality was refactored into CompositionHostBuilder.CreateDefaultServiceProvider(), which has a configureLogging callback argument.

The problem here is that in the HTTP configureLogging callback, ExceptionHandlerMiddleware is included in a filter like this:

var exceptionHandlerMiddlewareName = typeof(ExceptionHandlerMiddleware).FullName;
builder.AddFilter(
    (category, logLevel) => category.Equals(exceptionHandlerMiddlewareName, StringComparison.OrdinalIgnoreCase));

This filter is applied on top of the filter already added in CompositionHostBuilder.CreateDefaultServiceProvider(), which looks like this:

var workspaceInformationServiceName = typeof(WorkspaceInformationService).FullName;
var projectEventForwarder = typeof(ProjectEventForwarder).FullName;

builder.AddFilter(
    (category, logLevel) =>
        environment.LogLevel <= logLevel &&
        category.StartsWith("OmniSharp", StringComparison.OrdinalIgnoreCase) &&
        !category.Equals(workspaceInformationServiceName, StringComparison.OrdinalIgnoreCase) &&
        !category.Equals(projectEventForwarder, StringComparison.OrdinalIgnoreCase));

The simplest way I have found to ensure that the HTTP filter doesn't clobber the CompositionHostBuilder filter is to duplicate the entire CompositionHostBuilder filter in the HTTP code:

var workspaceInformationServiceName = typeof(WorkspaceInformationService).FullName;
var projectEventForwarder = typeof(ProjectEventForwarder).FullName;
var exceptionHandlerMiddlewareName = typeof(ExceptionHandlerMiddleware).FullName;

builder.AddFilter(
    (category, logLevel) =>
        category.Equals(exceptionHandlerMiddlewareName, StringComparison.OrdinalIgnoreCase) ||
        (_environment.LogLevel <= logLevel &&
            category.StartsWith("OmniSharp", StringComparison.OrdinalIgnoreCase) &&
            !category.Equals(workspaceInformationServiceName, StringComparison.OrdinalIgnoreCase) &&
            !category.Equals(projectEventForwarder, StringComparison.OrdinalIgnoreCase)));

This is not a very clean solution so please let me know if there's a tidier way to do this.

Fixes #1446

[filipw]

Thanks - I tested it locally and indeed it works well. We can take it as-is to resolve the issue 👍