How can an extension use path variables in a settings string that specifies a path?

[rkeithhill]

• VSCode Version: 0.10.14-insider
• OS Version: Windows 10 1511

Steps to Reproduce:

1. Extension provides a setting which specifies a path to a tool configuration file that ships in the extension's install dir.
2. We want to allow the user to override this path in either a user setting or a workspace setting.
3. We would rather not require the user have to specify a hard-coded absolute path (C:\foo\bar...) when they override the setting at either the user level or the workspace level (.vscode\settings.json).
4. So how does an extension handle this situation? Using a naked relative path e.g. ./ScriptAnalyzerSettings.psd1 would be confusing because the meaning of . would likely change depending on which setting file is in effect (global, user or workspace).
5. I would prefer that our extension could ask VSCode to expand certain variables for us before sending the settings path to the extension (either during extension activation or when a user changes a settings file). I would like to see these variables available: ${workspaceRoot}, ${extensionRoot} and perhaps ${home}.
6. The primary scenario I want to see enabled is having a setting value like "${workspaceRoot}\custom-settings.psd1" get translated to an absolute path by VSCode and that absolute path is then provided to the extension e.g. "C:\work\PowerShell\MyNewModule\custom-settings.psd1".

cc @daviwil

[alexdima]

I think the configuration service could do this such that this knowledge doesn't leak through everywhere.

What do you think @bpasero @aeschli ?

[bpasero]

#2809

[alexdima]

@bpasero I don't think this is about environmental variables (which present a lot more challenges than VSCode built-in paths constants?)

[rkeithhill]

The environment variable approach could work but wouldn't be ideal. I see that our extension's language host exe inherits the following env vars from VSCode:

Now, if VSCode also defined VSCODE_WORKSPACEROOT and VSCODE_EXTENSIONROOT we could make this work. However we would have a user education/usability issue. In some cases (ie launch.json) we tell users to use ${workspaceRoot} to specify a path to a file in their workspace. But in settings.json we tell them that to specify a path to a "settings" file in their workspace they have to use %VSCODE_WORKSPACEROOT%. Seems a bit inconsistent.

[bpasero]

#2809 covers also variables we introduce.