Workspace folder picker command (for #32936)

[bpasero]

fixes #32936

Introduces a simple new command vscode.pickWorkspace to pick a WorkspaceFolder via quick pick.

[bpasero]

@jrieken

What does this return? It must be triple-equal to the things we have in workspace.workspaceFolders. Also, why not have this as real API? Having the logic in the core shouldn't mean we cannot have a function for this

good point about the return type and identity, that is addressed in this change.

I rethought about having real API for this because I somewhat assume that this is a corner case where people might need it. If we want to go away from introducing more commands, I can also restore the proper API again and call into the command.

[jrieken]

that this is a corner case where people might need it.

Fair enough, I let @dbaeumer decide if a command is OK for him

[jrieken]

Oh, the test actually doesn't pass: https://travis-ci.org/Microsoft/vscode/jobs/277395186#L4159

[dbaeumer]

I always prefer explicit API over commands. The reason is:

• easier to discover
• I have code complete
• one place of documentation
• easier to keep compatible since we have compilers that check signatures.

But that might be me :-)

[bpasero]

@jrieken @dbaeumer fair enough, I provide this API now (while still using the command internally):

/**
 * Shows a selection list of [workspace folders](#workspace.workspaceFolders) to pick from.
 * Returns `undefined` if no folder is open.
 *
 * @param options Configures the behavior of the workspace folder list.
 * @return A promise that resolves to the workspace folder or `undefined`.
 */
export function showWorkspaceFolderPick(options?: WorkspaceFolderPickOptions): Thenable<WorkspaceFolder | undefined>;

/**
 * Options to configure the behaviour of the [workspace folder](#WorkspaceFolder) pick UI.
 */
export interface WorkspaceFolderPickOptions {

	/**
	 * An optional string to show as place holder in the input box to guide the user what to pick on.
	 */
	placeHolder?: string;

	/**
	 * Set to `true` to keep the picker open when focus moves to another part of the editor or to another window.
	 */
	ignoreFocusOut?: boolean;
}

[jrieken]

Don't define types inside a namespace but globally

[bpasero]

@jrieken isn't that globally? It is outside the window namespace.

[jrieken]

Oh, sorry. Didn't see that closing-curly