Omnisharp-vscode: Add option to make 'unnecessary using directive' diagnostics to appear

[cruz82]

Environment data

dotnet --info output:

.NET Command Line Tools (1.0.1)

Product Information:
Version: 1.0.1
Commit SHA-1 hash: 005db40cd1

Runtime Environment:
OS Name: fedora
OS Version: 25
OS Platform: Linux
RID: fedora.24-x64
Base Path: /opt/dotnet/sdk/1.0.1

VS Code version: 1.11.2
C# Extension version: 1.9.0

Steps to reproduce

Add an unnecessary using statement.

Expected behavior

A diagnostic info message about the unnecessary using statement.

Actual behavior

No diagnostic info message is shown and the using statement is not highlighted.

[Leopotam]

vscode 1.12.0, c# extension 7439ef476f038e927604fe3f9753c7132c2cf42d commit (after 1.9.0 release) - same behaviour.

[DustinCampbell]

This is by design. We suppressed this message in the PR to https://github.com/OmniSharp/omnisharp-vscode/issues/1231. Eventually, we hope to have faded code support in VS Code so we can provide this information a bit more unobtrusively (https://github.com/Microsoft/vscode/issues/20219 tracks this).

Note that the light bulb still appears and works if you move it to an unnecessary using, but we will no longer spam unnecessary using diagnostics.

[cateyes99]

At least __don't agree__ with removing the __wavy underline__ in the editor for those unnecessary using directives! without those signs in the editor so we __cannot__ spot them anymore, would u expect us to move the cursor __each line by line__ in __each .cs file__ to find out unnecessary using directives?! this change makes the Remove Unnecessary Usings __totally useless__.

[DustinCampbell]

I appreciate your passion @cateyes99! Unfortunately, VS Code doesn't make it possible to remove the item from the Problems list (which _many_ complained about) while keeping the squiggle in the editor.

If you like, you can file an issue (or submit a PR) to make this behavior optional. And, eventually, I hope we'll have the ability to fade code as I mentioned before to make this behave more like it does in Visual Studio (in VS, we fade unnecessary using directives but don't just the message in the Error List).

[cruz82]

@DustinCampbell pull request to make this configurable.

[DustinCampbell]

Nice! I've re-opened, assigned to you, and put in our 1.10 milestone. Thanks very much for the contribution!

[DustinCampbell]

Adding the same comment I put in the PR here:

I'm planning to release a new C# for VS Code beta later today or early tomorrow. That will have this setting in it.

[eamodio]

@DustinCampbell Probably don't want to go down this route, but this extension _could_ provide unused usings via decorations rather than diagnostics. The TypeLens extension currently does this: https://github.com/kisstkondoros/typelens/blob/master/src/extension.ts#L96