Allow extensions to specify custom tree view resoure type

[vbfox]

The FileKind was previously guessed from the collapsability of the item,
extensions now have the capability to set it manually.

Here the top level item come from vscode great icons theme for .fsproj files:

Fixes #43216

[msftclas]

All CLA requirements met.

[vbfox]

@sandy081 here is the PR I was speaking about in #43216 I think it's ready for review

[sandy081]

@vbfox Thanks for the PR. Why not using the trailing slash to determine if the resource is a directory or not?

[vbfox]

I preferred to be explicit as the extension often know what type of resource it is and also to avoid breaking extensions that would have started to depend on the current behavior.

But I can change it, It simplify the code a lot.

[sandy081]

I see your point, but we already have FileType in our proposed API here. Re-using that type might be right approach.

@bpasero May I know if we can reuse FileType here ?

[bpasero]

@sandy081 that is @jrieken area

[sandy081]

@vbfox I do not think using a new property which is file specific is good idea as the tree is generic. Another idea is, since this is related to icon, overload iconPath property to determine the resource type.

iconPath?: string | Uri | { light: string | Uri; dark: string | Uri } | 'file' | 'folder' ;

[sandy081]

Another idea is to define a ThemeIcon and use it for icon.

export namespace ThemeIcon {
	const file: ThemeIcon;
	const folder: ThemeIcon;
}

export class ThemeIcon {
         readonly id: string;
}

iconPath?: string | Uri | { light: string | Uri; dark: string | Uri } | ThemeIcon;

[vbfox]

I think I like the 'file' | 'folder' in iconPath solution the most, it's explicit simple and widely useful.

Especially if it also style as a file or folder without resource URI (In this case using the generic icons for file or folder)

I'll take a shoot at implementing that

[sandy081]

@vbfox Thanks for considering that.

I would prefer last solution of using ThemeIcon. This will be more explicit that given resource URI, icon for the tree item should be File theme icon or Folder them icon.

[vbfox]

@sandy081 I did the changes, choose the name ThemeIconCategory instead of ThemeIcon because I felt that a ThemeIcon would designate a single icon like a ThemeColor point to a single color and it's not what's happening here. But I can change it.

The multi process / saniziting was the most foreign thing for me so I hope I did it correctly:

• ThemeIconCategory is the type sent by the extension and is transformed to and IThemeIconCategory keeping only the id field
• The object matching IThemeIconCategory is passed to the main process and detected in customView.ts via it's id property

[sandy081]

@aeschli Would like to know your opinion on the name ThemeIconCategory?

[aeschli]

Should be ThemeIcon, like ThemeColor.
ThemeIconCategory doesn't fit.
The idea is to give our icons an identifier ('folder-icon', 'file-icon', 'refresh-button'...), and let icon themes provide a different icon

[sandy081]

Changes look good to me. There are some minor comments about the API documentation and little tweaks in passing theme icon. Since today is the code freeze, I will merge this PR and do the little tweaks myself. I hope you do not mind with that.

Thanks