src/vs/workbench/api/common/extHostDebugService.ts/ExtHostDebugServiceBase/$substituteVariables
class ExtHostDebugServiceBase:	public async $substituteVariables(folderUri: UriComponents | undefined, config: IConfig): Promise<IConfig> {
		let ws: IWorkspaceFolder | undefined;
		const folder = await this.getFolder(folderUri);
		if (folder) {
			ws = {
				uri: folder.uri,
				name: folder.name,
				index: folder.index,
				toResource: () => {
					throw new Error('Not implemented');
				}
			};
		}
		const variableResolver = await this._variableResolver.getResolver();
		return variableResolver.resolveAnyAsync(ws, config);
	}