Generate completions with `miniserve --print-completions <shell>`

This patch adds a `--print-completions` option to generate shell
completion files at runtime. This ensures the completions are always up
to date.

Fixes #377.

2 files changed, 18 insertions, 8 deletions

diff --git a/src/args.rs b/src/args.rs
index 909a88f..d6cfc69 100644
--- a/src/args.rs
+++ b/src/args.rs
@@ -21,7 +21,7 @@ const ROUTE_ALPHABET: [char; 16] = [
     about,
     global_settings = &[structopt::clap::AppSettings::ColoredHelp],
 )]
-struct CliArgs {
+pub struct CliArgs {
     /// Be verbose, includes emitting access logs
     #[structopt(short = "v", long = "verbose")]
     verbose: bool,
@@ -131,6 +131,10 @@ struct CliArgs {
     /// Hide version footer
     #[structopt(short = "F", long = "hide-version-footer")]
     hide_version_footer: bool,
+
+    /// Generate completion file for a shell
+    #[structopt(long = "print-completions", value_name = "shell")]
+    pub print_completions: Option<structopt::clap::Shell>,
 }
 
 /// Checks wether an interface is valid, i.e. it can be parsed into an IP address
@@ -205,9 +209,7 @@ pub fn parse_header(src: &str) -> Result<HeaderMap, httparse::Error> {
 }
 
 /// Parses the command line arguments
-pub fn parse_args() -> crate::MiniserveConfig {
-    let args = CliArgs::from_args();
-
+pub fn parse_args(args: CliArgs) -> crate::MiniserveConfig {
     let interfaces = if !args.interfaces.is_empty() {
         args.interfaces
     } else {
diff --git a/src/main.rs b/src/main.rs
index 17ab204..747a705 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -11,6 +11,7 @@ use std::net::{IpAddr, Ipv4Addr, SocketAddr};
 use std::thread;
 use std::time::Duration;
 use structopt::clap::crate_version;
+use structopt::StructOpt;
 use yansi::{Color, Paint};
 
 mod archive;
@@ -101,20 +102,27 @@ pub struct MiniserveConfig {
 }
 
 fn main() {
-    match run() {
+    let args = args::CliArgs::from_args();
+
+    if let Some(shell) = args.print_completions {
+        args::CliArgs::clap().gen_completions_to("miniserve", shell, &mut std::io::stdout());
+        return;
+    }
+
+    let miniserve_config = args::parse_args(args);
+
+    match run(miniserve_config) {
         Ok(()) => (),
         Err(e) => errors::log_error_chain(e.to_string()),
     }
 }
 
 #[actix_web::main(miniserve)]
-async fn run() -> Result<(), ContextualError> {
+async fn run(miniserve_config: MiniserveConfig) -> Result<(), ContextualError> {
     if cfg!(windows) && !Paint::enable_windows_ascii() {
         Paint::disable();
     }
 
-    let miniserve_config = args::parse_args();
-
     let log_level = if miniserve_config.verbose {
         simplelog::LevelFilter::Info
     } else {