extensions/typescript-language-features/src/languageFeatures/fileConfigurationManager.ts/FileConfigurationManager/constructor
class FileConfigurationManager:	public constructor(
		private readonly client: ITypeScriptServiceClient,
		onCaseInsensitiveFileSystem: boolean
	) {
		super();
		this.formatOptions = new ResourceMap(undefined, { onCaseInsensitiveFileSystem });
		vscode.workspace.onDidCloseTextDocument(textDocument => {
			// When a document gets closed delete the cached formatting options.
			// This is necessary since the tsserver now closed a project when its
			// last file in it closes which drops the stored formatting options
			// as well.
			this.formatOptions.delete(textDocument.uri);
		}, undefined, this._disposables);
	}