add completion subcommands (#99)

* add completion subcommands

* improve error mgmt, add entry to readme

Co-authored-by: Clément DOUIN <soywod@users.noreply.github.com>

README.md

@@ -25,6 +25,7 @@ Minimalist CLI email client, written in Rust.
   * [Move a message](#move-a-message)
   * [Delete a message](#delete-a-message)
   * [Listen to new messages](#listen-to-new-messages)
+* [Completions](#completions)
 * [Interfaces](#interfaces)
   * [GUI](#gui)
   * [TUI](#tui)
@@ -237,6 +238,32 @@ systemctl --user enable himalaya.service
 systemctl --user start  himalaya.service
 ```
 
+## Completions
+
+```sh
+# For bash shells
+himalaya bash-completions
+
+# For zsh shells
+himalaya zsh-completions
+
+# For fish shells
+himalaya fish-completions
+```
+
+Those commands print the generated scripts to the stdout. You will have
+to manually save and source them. For example:
+
+```sh
+himalaya bash-completions > himalaya-completions.bash
+```
+
+```sh
+# ~/.bashrc
+
+source himalaya-completions.bash
+```
+
 ## Interfaces
 
 ### GUI

src/completion/cli.rs

@@ -0,0 +1,34 @@
+use clap::{self, App, ArgMatches, SubCommand};
+use error_chain::error_chain;
+use std::io;
+
+error_chain! {}
+
+pub fn completion_subcmds<'a>() -> Vec<App<'a, 'a>> {
+    vec![
+        SubCommand::with_name("bash-completions").about("Generates bash completions script"),
+        SubCommand::with_name("zsh-completions").about("Generates zsh completions script"),
+        SubCommand::with_name("fish-completions").about("Generates fish completions script"),
+    ]
+}
+
+pub fn completion_matches(mut app: App, matches: &ArgMatches) -> Result<bool> {
+    use clap::Shell::*;
+
+    if matches.is_present("bash-completions") {
+        app.gen_completions_to("himalaya", Bash, &mut io::stdout());
+        return Ok(true);
+    }
+
+    if matches.is_present("zsh-completions") {
+        app.gen_completions_to("himalaya", Zsh, &mut io::stdout());
+        return Ok(true);
+    }
+
+    if matches.is_present("fish-completions") {
+        app.gen_completions_to("himalaya", Fish, &mut io::stdout());
+        return Ok(true);
+    }
+
+    Ok(false)
+}

src/main.rs

@@ -27,13 +27,17 @@ mod mbox {
     pub(crate) mod cli;
     pub(crate) mod model;
 }
+mod completion {
+    pub(crate) mod cli;
+}
 
-use clap;
+use clap::{self, App};
 use error_chain::error_chain;
 use log::{debug, error};
 use std::env;
 
 use crate::{
+    completion::cli::{completion_matches, completion_subcmds},
     config::cli::account_arg,
     flag::cli::{flag_matches, flag_subcmds},
     imap::cli::{imap_matches, imap_subcmds},
@@ -52,12 +56,13 @@ error_chain! {
         ImapCli(crate::imap::cli::Error, crate::imap::cli::ErrorKind);
         MboxCli(crate::mbox::cli::Error, crate::mbox::cli::ErrorKind);
         MsgCli(crate::msg::cli::Error, crate::msg::cli::ErrorKind);
+        CompletionCli(crate::completion::cli::Error, crate::completion::cli::ErrorKind);
         OutputLog(crate::output::log::Error, crate::output::log::ErrorKind);
     }
 }
 
-fn run() -> Result<()> {
-    let matches = clap::App::new(env!("CARGO_PKG_NAME"))
+fn build_cli() -> App<'static, 'static> {
+    clap::App::new(env!("CARGO_PKG_NAME"))
         .version(env!("CARGO_PKG_VERSION"))
         .about(env!("CARGO_PKG_DESCRIPTION"))
         .author(env!("CARGO_PKG_AUTHORS"))
@@ -68,7 +73,11 @@ fn run() -> Result<()> {
         .subcommands(imap_subcmds())
         .subcommands(mbox_subcmds())
         .subcommands(msg_subcmds())
-        .get_matches();
+        .subcommands(completion_subcmds())
+}
+
+fn run() -> Result<()> {
+    let matches = build_cli().get_matches();
 
     let output_fmt: OutputFmt = matches.value_of("output").unwrap().into();
     let log_level: LogLevel = matches.value_of("log").unwrap().into();
@@ -91,6 +100,10 @@ fn run() -> Result<()> {
             break;
         }
 
+        if completion_matches(build_cli(), &matches)? {
+            break;
+        }
+
         msg_matches(&matches)?;
         break;
     }