vscode插件快餐教程(6) - LSP协议的初始化参数

学习了lsp的代码补全之后，我们可以尝试搭建一套可以运行的lsp的系统。
在此之前，我们再将一些细节夯实一下。

我们在第4节曾经介绍过LSP的初始化的握手过程。
我们可以在connection的onInitialize函数中来接收客户端的初始化参数，比如客户端的能力。

connection.onInitialize((params: InitializeParams) => {
    let capabilities = params.capabilities;

    return {
        capabilities: {
            textDocumentSync: documents.syncKind,
            // Tell the client that the server supports code completion
            completionProvider: {
                resolveProvider: true
            }
        }
    };
})

我们先用一张图来看一下lsp初始化参数所包含的内容：

下面我们看下这些定义：

interface InitializeParams {
    /**
     * The process Id of the parent process that started
     * the server. Is null if the process has not been started by another process.
     * If the parent process is not alive then the server should exit (see exit notification) its process.
     */
    processId: number | null;

    /**
     * The rootPath of the workspace. Is null
     * if no folder is open.
     *
     * @deprecated in favour of rootUri.
     */
    rootPath?: string | null;

    /**
     * The rootUri of the workspace. Is null if no
     * folder is open. If both `rootPath` and `rootUri` are set
     * `rootUri` wins.
     */
    rootUri: DocumentUri | null;

    /**
     * User provided initialization options.
     */
    initializationOptions?: any;

    /**
     * The capabilities provided by the client (editor or tool)
     */
    capabilities: ClientCapabilities;

    /**
     * The initial trace setting. If omitted trace is disabled ('off').
     */
    trace?: 'off' | 'messages' | 'verbose';

    /**
     * The workspace folders configured in the client when the server starts.
     * This property is only available if the client supports workspace folders.
     * It can be `null` if the client supports workspace folders but none are
     * configured.
     *
     * Since 3.6.0
     */
    workspaceFolders?: WorkspaceFolder[] | null;
}

我们将上面的信息分下类，如下图所示：

主要有三种信息：

• 一是运行环境相关的信息，如路径相关信息和进程相关信息。
• 二是能力信息。
• 三是一些辅助信息，包括trace设置和用户自定义信息。

路径信息是只有在插件运行的vscode中已经打开了一个目录时才可以获取到。
假设我打开的目录是：/Users/ziyingliuziying/working/gitlab/cafmode/server，那么rootPath返回的结果是：/Users/ziyingliuziying/working/gitlab/cafmode/server。而rootUri返回的结果是：file:///Users/ziyingliuziying/working/gitlab/cafmode/server。
workspaceFolders是一个由WorkspaceFolder组成的数组。每一个WorkspaceFolder是由name和uri组成的对象。以上面的例子为例：name为server, uri是file:///Users/ziyingliuziying/working/gitlab/cafmode/server