Improve error when opening C# project on an Apple Silicon M1 machine without Rosetta

Issue Description

During the start of the OmniSharp server a call using the built-in mono command returns a Bad CPU type in executable error.

Steps to Reproduce

On a new Apple Silicon M1 machine:

1. Download and install the Mac Universal version of Visual Studio Code
2. Download and install the preview version of .NET 6 (6.0.100-preview.4.21255.9)
3. Create a new C# console project dotnet new console -n ConsoleApp
4. Open ConsoleApp folder in Visual Studio Code

Expected Behavior

Project loads and C# language features (e.g. code completion) are available.

Actual Behavior

An error is returned in the OmniSharp log and C# features are unavailable.

Logs

OmniSharp log

Starting OmniSharp server at 6/11/2021, 7:28:11 AM Target: /Users/miguellira/Developer/ConsoleApp

OmniSharp server started. Path: /Users/miguellira/.vscode/extensions/ms-dotnettools.csharp-1.23.12/.omnisharp/1.37.10/run PID: 10636

/Users/miguellira/.vscode/extensions/ms-dotnettools.csharp-1.23.12/.omnisharp/1.37.10/run: line 27: /Users/miguellira/.vscode/extensions/ms-dotnettools.csharp-1.23.12/.omnisharp/1.37.10/bin/mono: Bad CPU type in executable [ERROR] Error: OmniSharp server load timed out. Use the ‘omnisharp.projectLoadTimeout’ setting to override the default delay (one minute).

C# log

Installing C# dependencies... Platform: darwin, arm64

Downloading package ‘OmniSharp for OSX’ (37658 KB)… Done! Validating download… Integrity Check succeeded. Installing package ‘OmniSharp for OSX’

Downloading package ‘.NET Core Debugger (macOS / x64)’ (45875 KB)… Done! Validating download… Integrity Check succeeded. Installing package ‘.NET Core Debugger (macOS / x64)’

Downloading package ‘.NET Core Debugger (macOS / arm64)’ (47834 KB)… Done! Validating download… Integrity Check succeeded. Installing package ‘.NET Core Debugger (macOS / arm64)’

Downloading package ‘Razor Language Server (macOS / x64)’ (60206 KB)… Done! Installing package ‘Razor Language Server (macOS / x64)’

Finished

[WARNING]: arm64 macOS is not officially supported by the .NET Core debugger. You may experience unexpected issues when running in this configuration.

Environment information

VSCode version: 1.57.0 C# Extension: 1.23.12

Mono Information

OmniSharp using built-in mono

Dotnet Information

.NET SDK (reflecting any global.json): Version: 6.0.100-preview.4.21255.9 Commit: 950e4949a7

Runtime Environment: OS Name: Mac OS X OS Version: 11.4 OS Platform: Darwin RID: osx.11.0-arm64 Base Path: /usr/local/share/dotnet/sdk/6.0.100-preview.4.21255.9/

Host (useful for support): Version: 6.0.0-preview.4.21253.7 Commit: bfd6048a60

.NET SDKs installed: 6.0.100-preview.4.21255.9 [/usr/local/share/dotnet/sdk]

.NET runtimes installed: Microsoft.AspNetCore.App 6.0.0-preview.4.21253.5 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.NETCore.App 6.0.0-preview.4.21253.7 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs: https://aka.ms/dotnet-download

Visual Studio Code Extensions

Extension	Author	Version
csharp	ms-dotnettools	1.23.12

[filipw]

There is a native prerelease already here https://github.com/OmniSharp/omnisharp-vscode/releases/tag/v1.24.0-beta1 You need to install it and set omnisharp.useModernNet to true

[filipw]

This is interesting, I have been using OmniSharp on an M1 mac since December without any issues. There is no ARM64 built of Omnisharp but it works fine with Rosetta. Looks like for some reason Rosetta does not kick in here.

Do you have Rosetta installed?

softwareupdate --install-rosetta