[pve-devel] [PATCH installer 1/5] common: introduce simple cli subcommand parser based on pico-args

[Christoph Heiss]

This is a very slight abstraction on top of pico-args, to reduce
boilerplate code a bit for CLI subcommand handling.

No functional changes.

Signed-off-by: Christoph Heiss <c.heiss at proxmox.com>
---
 Cargo.toml                          |  1 +
 debian/control                      |  1 +
 proxmox-installer-common/Cargo.toml |  4 ++
 proxmox-installer-common/src/cli.rs | 62 +++++++++++++++++++++++++++++
 proxmox-installer-common/src/lib.rs |  3 ++
 5 files changed, 71 insertions(+)
 create mode 100644 proxmox-installer-common/src/cli.rs

diff --git a/Cargo.toml b/Cargo.toml
index bfec8f7..4165b96 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,6 +17,7 @@ edition = "2024"
 [workspace.dependencies]
 anyhow = "1.0"
 log = "0.4.20"
+pico-args = "0.5"
 regex = "1.7"
 serde = "1.0"
 serde_json = "1.0"
diff --git a/debian/control b/debian/control
index dec07ed..51c45a4 100644
--- a/debian/control
+++ b/debian/control
@@ -15,6 +15,7 @@ Build-Depends: cargo:native,
                librust-glob-0.3-dev,
                librust-hex-0.4-dev,
                librust-native-tls-dev,
+               librust-pico-args-0.5-dev,
                librust-pretty-assertions-1.4-dev,
                librust-regex-1+default-dev (>= 1.7~~),
                librust-rustls-0.21+dangerous-configuration-dev,
diff --git a/proxmox-installer-common/Cargo.toml b/proxmox-installer-common/Cargo.toml
index 4bdb2b0..8a6fb5c 100644
--- a/proxmox-installer-common/Cargo.toml
+++ b/proxmox-installer-common/Cargo.toml
@@ -22,6 +22,9 @@ rustls-native-certs = { version = "0.6", optional = true }
 sha2 = { version = "0.10", optional = true }
 ureq = { version = "2.6", features = [ "native-certs", "native-tls" ], optional = true }
 
+# `cli` feature
+pico-args = { workspace = true, optional = true }
+
 [features]
 http = [
     "dep:hex",
@@ -31,6 +34,7 @@ http = [
     "dep:sha2",
     "dep:ureq"
 ]
+cli = [ "dep:pico-args" ]
 
 [dev-dependencies]
 pretty_assertions = "1.4"
diff --git a/proxmox-installer-common/src/cli.rs b/proxmox-installer-common/src/cli.rs
new file mode 100644
index 0000000..1539001
--- /dev/null
+++ b/proxmox-installer-common/src/cli.rs
@@ -0,0 +1,62 @@
+//! Provides a simple command line parsing interface, with special support for
+//! (one-level deep) subcommands.
+
+use std::process;
+
+use anyhow::Result;
+
+pub use pico_args::Arguments;
+
+pub trait Subcommand {
+    /// Parses the arguments for this command from an [`pico_args::Arguments`].
+    fn parse(args: &mut Arguments) -> Result<Self>
+    where
+        Self: Sized;
+
+    /// Print command usage to stderr.
+    fn print_usage()
+    where
+        Self: Sized;
+
+    /// Runs the commands action.
+    fn run(&self) -> Result<()>;
+}
+
+pub struct AppInfo<'a> {
+    pub global_help: &'a str,
+    pub on_command: fn(Option<&str>, &mut Arguments) -> Result<()>,
+}
+
+pub fn run(info: AppInfo) -> process::ExitCode {
+    if let Err(err) = parse_args(&info) {
+        eprintln!("Error: {err:#}\n\n{}", info.global_help);
+        process::ExitCode::FAILURE
+    } else {
+        process::ExitCode::SUCCESS
+    }
+}
+
+fn parse_args(info: &AppInfo) -> Result<()> {
+    let mut args = pico_args::Arguments::from_env();
+    let subcommand = args.subcommand()?;
+
+    if subcommand.is_none() && args.contains(["-h", "--help"]) {
+        eprintln!("{}", info.global_help);
+        Ok(())
+    } else if args.contains(["-V", "--version"]) {
+        eprintln!("{} v{}", env!("CARGO_PKG_NAME"), env!("CARGO_PKG_VERSION"));
+        Ok(())
+    } else {
+        (info.on_command)(subcommand.as_deref(), &mut args)
+    }
+}
+
+pub fn handle_command<T: Subcommand>(args: &mut pico_args::Arguments) -> Result<()> {
+    if args.contains(["-h", "--help"]) {
+        T::print_usage();
+    } else if let Err(err) = T::parse(args).and_then(|cmd| cmd.run()) {
+        eprint!("Error: {err:#}");
+    }
+
+    Ok(())
+}
diff --git a/proxmox-installer-common/src/lib.rs b/proxmox-installer-common/src/lib.rs
index 3dc3bfb..ea907a0 100644
--- a/proxmox-installer-common/src/lib.rs
+++ b/proxmox-installer-common/src/lib.rs
@@ -7,6 +7,9 @@ pub mod utils;
 #[cfg(feature = "http")]
 pub mod http;
 
+#[cfg(feature = "cli")]
+pub mod cli;
+
 pub const RUNTIME_DIR: &str = "/run/proxmox-installer";
 
 /// Default placeholder value for the administrator email address.
-- 
2.49.0