文盘Rust -- 子命令提示，提高用户体验

notice"Rust is a trademark of the Mozilla Foundation in the US and other countries."

上次我们聊到 CLI 的领域交互模式。在领域交互模式中，可能存在多层次的子命令。在使用过程中如果全评记忆的话，命令少还好，多了真心记不住。频繁 --help 也是个很麻烦的事情。如果每次按 tab 键就可以提示或补齐命令是不是很方便呢。这一节我们就来说说 autocommplete 如何实现。我们还是以 interactcli-rs 中的实现来解说实现过程。

实现过程

其实，rustyline  已经为我们提供了基本的helper功能框架,其中包括了completer。我们来看代码，文件位置src/interact/cli.rs

#[derive(Helper)] struct MyHelper { completer: CommandCompleter, highlighter: MatchingBracketHighlighter, validator: MatchingBracketValidator, hinter: HistoryHinter, colored_prompt: String, } pub fn run() { let config = Config::builder() .history_ignore_space(true) .completion_type(CompletionType::List) .output_stream(OutputStreamType::Stdout) .build(); let h = MyHelper { completer: get_command_completer(), highlighter: MatchingBracketHighlighter::new(), hinter: HistoryHinter {}, colored_prompt: "".to_owned(), validator: MatchingBracketValidator::new(), }; let mut rl = Editor::with_config(config); // let mut rl = Editor::<()>::new(); rl.set_helper(Some(h)); ...... }

首先定义 MyHelper 结构体， 需要实现 Completer + Hinter + Highlighter + Validator trait。然后通过rustyline的set_helper函数加载我们定义好的helper。在MyHelper 结构体中，需要我们自己来实现completer的逻辑。

Sub command autocompleter实现详解

SubCmd 结构体

#[derive(Debug, Clone)] pub struct SubCmd { pub level: usize, pub command_name: String, pub subcommands: Vec<String>, }

SubCmd 结构体包含，命令级别，命令名称，以及该命令包含的子命令信息，以便在实现实现 autocomplete 时定位命令和子命令的范围

在程序启动时遍历所有的command，src/cmd/rootcmd.rs 中的all_subcommand函数负责收集所有命令并转换为Vec

pub fn all_subcommand(app: &clap_Command, beginlevel: usize, input: &mut Vec<SubCmd>) { let nextlevel = beginlevel + 1; let mut subcmds = vec![]; for iterm in app.get_subcommands() { subcmds.push(iterm.get_name().to_string()); if iterm.has_subcommands() { all_subcommand(iterm, nextlevel, input); } else { if beginlevel == 0 { all_subcommand(iterm, nextlevel, input); } } } let subcommand = SubCmd { level: beginlevel, command_name: app.get_name().to_string(), subcommands: subcmds, }; input.push(subcommand); }

CommandCompleter 子命令自动补充功能的核心部分

#[derive(Debug, Clone)] pub struct CommandCompleter { subcommands: Vec<SubCmd>, } impl CommandCompleter { pub fn new(subcmds: Vec<SubCmd>) -> Self { Self { subcommands: subcmds, } } //获取level下所有可能的子命令 pub fn level_possible_cmd(&self, level: usize) -> Vec<String> { let mut subcmds = vec![]; let cmds = self.subcommands.clone(); for iterm in cmds { if iterm.level == level { subcmds.push(iterm.command_name.clone()); } } return subcmds; } //获取level下某字符串开头的子命令 pub fn level_prefix_possible_cmd(&self, level: usize, prefix: &str) -> Vec<String> { let mut subcmds = vec![]; let cmds = self.subcommands.clone(); for iterm in cmds { if iterm.level == level && iterm.command_name. starts_with(prefix) { subcmds.push(iterm.command_name); } } return subcmds; } //获取某level 下某subcommand的所有子命令 pub fn level_cmd_possible_sub_cmd(&self, level: usize, cmd: String) -> Vec<String> { let mut subcmds = vec![]; let cmds = self.subcommands.clone(); for iterm in cmds { if iterm.level == level && iterm.command_name == cmd { subcmds = iterm.subcommands.clone(); } } return subcmds; } //获取某level 下某subcommand的所有prefix子命令 pub fn level_cmd_possible_prefix_sub_cmd( &self, level: usize, cmd: String, prefix: &str, ) -> Vec<String> { let mut subcmds = vec![]; let cmds = self.subcommands.clone(); for iterm in cmds { if iterm.level == level && iterm.command_name == cmd { for i in iterm.subcommands { if i.starts_with(prefix) { subcmds.push(i); } } } } return subcmds; } pub fn complete_cmd(&self, line: &str, pos: usize) -> Result<(usize, Vec<Pair>)> { let mut entries: Vec<Pair> = Vec::new(); let d: Vec<_> = line.split( ).collect(); if d.len() == 1 { if d.last() == Some(&"") { for str in self.level_possible_cmd(1) { let mut replace = str.clone(); replace.push_str(" "); entries.push(Pair { display: str.clone(), replacement: replace, }); } return Ok((pos, entries)); } if let Some(last) = d.last() { for str in self.level_prefix_possible_cmd (1, *last) { let mut replace = str.clone(); replace.push_str(" "); entries.push(Pair { display: str.clone(), replacement: replace, }); } return Ok((pos - last.len(), entries)); } } if d.last() == Some(&"") { for str in self .level_cmd_possible_sub_cmd(d.len() - 1, d.get(d.len() - 2).unwrap().to_string()) { let mut replace = str.clone(); replace.push_str(" "); entries.push(Pair { display: str.clone(), replacement: replace, }); } return Ok((pos, entries)); } if let Some(last) = d.last() { for str in self. level_cmd_possible_prefix_sub_cmd( d.len() - 1, d.get(d.len() - 2).unwrap().to_string(), *last, ) { let mut replace = str.clone(); replace.push_str(" "); entries.push(Pair { display: str.clone(), replacement: replace, }); } return Ok((pos - last.len(), entries)); } Ok((pos, entries)) } } impl Completer for CommandCompleter { type Candidate = Pair; fn complete(&self, line: &str, pos: usize, _ctx: & Context<_>) -> Result<(usize, Vec<Pair>)> { self.complete_cmd(line, pos) } }

CommandCompleter 的实现部分比较多，大致包括两个部分，前一部分包括：获取某一级别下所有可能的子命令、获取某级别下某字符串开头的子命令、获取某级别下某个命令的所有子命令，等基本功能。这部分代码中有注释就不一一累述。函数complete_cmd用来计算行中的位置以及在该位置的替换内容。输入项是命令行的内容以及光标所在位置，输出项为在该位置需要替换的内容。比如，我们在提示符下输入 "root cm" root 下包含 cmd1、cmd2 两个子命令，此时如果按 tab键，complete_cmd 函数就会返回 (7,[cmd1,cmd2])。

文盘Rust系列

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文盘Rust -- 领域交互模式如何实现

文盘Rust -- 子命令提示，提高用户体验