[vscode][plugin] Respect when condition for vscode plugins

[vinokurig]

Description

Some vscode extensions have when condition provided in hair pacage.json file, e.g. the vscode github-pull-request extension has such condition in the view contribution: https://github.com/microsoft/vscode-pull-request-github/blob/d91e778705cd5af0785c5a05184ebc550334b409/package.json#L182
Since #5855 was applied the plugin view is unavailable.

Reproduction Steps

1. Remove git from theia/examples/browser/package.json.
2. Download vscode git extension.
3. Create plugins folder in Theia's root and paste the plugin to it.
4. Clone the vscode github extension and compile it.
5. Start the github plugin as a Hosted Plugin.
6. Click the GitHub icon.

WRONG: The view is unavailable:

OS and Theia version:

Diagnostics:

[akosyakov]

@vinokurig I believe it is already supported: https://github.com/theia-ide/theia/blob/5339bef84b447d457b15432f2b6a08368f95765f/packages/plugin-ext/src/main/browser/view/plugin-view-registry.ts#L112-L121

[vinokurig]

@akosyakov

@vinokurig I believe it is already supported: https://github.com/theia-ide/theia/blob/5339bef84b447d457b15432f2b6a08368f95765f/packages/plugin-ext/src/main/browser/view/plugin-view-registry.ts#L112-L121

It is, but it doesn't respect condition from the GitHub plugin: "when": "!config.githubPullRequests.showInSCM && config.git.enabled"
https://github.com/microsoft/vscode-pull-request-github/blob/d91e778705cd5af0785c5a05184ebc550334b409/package.json#L182
I'll rename the issue title

[akosyakov]

All preferences contributed by VS Code extensions should be already supported in when closure. These preferences are contributed by git and git pull request extensions, not by Theia. Are you sure that you have VS Code git extension installed?

[vinokurig]

@akosyakov

Are you sure that you have VS Code git extension installed?

yes, I can see contributed git preferences:

But they are not registered in the ContextKeyService

[akosyakov]

Sound like bug, they should be resolved from here: https://github.com/theia-ide/theia/blob/566ebda6b9ede33984ff0d06044e889b2191c9d7/packages/monaco/src/browser/monaco-frontend-module.ts#L140-L151 You can try to debug it.