refactoring custom command registration

To make it less error-prone

src/builtins.rs

@@ -3,38 +3,38 @@ use crate::{CmdEnv, CmdResult};
 use std::io::{Read, Write};
 
 pub(crate) fn builtin_echo(env: &mut CmdEnv) -> CmdResult {
-    let args = env.args();
-    let msg = if args.len() > 1 && args[1] == "-n" {
-        args[2..].join(" ")
+    let args = env.get_args();
+    let msg = if !args.is_empty() && args[0] == "-n" {
+        args[1..].join(" ")
     } else {
-        args[1..].join(" ") + "\n"
+        args.join(" ") + "\n"
     };
 
     write!(env.stdout(), "{}", msg)
 }
 
 pub(crate) fn builtin_error(env: &mut CmdEnv) -> CmdResult {
-    error!("{}", env.args()[1..].join(" "));
+    error!("{}", env.get_args().join(" "));
     Ok(())
 }
 
 pub(crate) fn builtin_warn(env: &mut CmdEnv) -> CmdResult {
-    warn!("{}", env.args()[1..].join(" "));
+    warn!("{}", env.get_args().join(" "));
     Ok(())
 }
 
 pub(crate) fn builtin_info(env: &mut CmdEnv) -> CmdResult {
-    info!("{}", env.args()[1..].join(" "));
+    info!("{}", env.get_args().join(" "));
     Ok(())
 }
 
 pub(crate) fn builtin_debug(env: &mut CmdEnv) -> CmdResult {
-    debug!("{}", env.args()[1..].join(" "));
+    debug!("{}", env.get_args().join(" "));
     Ok(())
 }
 
 pub(crate) fn builtin_trace(env: &mut CmdEnv) -> CmdResult {
-    trace!("{}", env.args()[1..].join(" "));
+    trace!("{}", env.get_args().join(" "));
     Ok(())
 }
 

src/lib.rs

@@ -297,7 +297,7 @@
 //! # use cmd_lib::*;
 //! # use std::io::Write;
 //! fn my_cmd(env: &mut CmdEnv) -> CmdResult {
-//!     let args = env.args();
+//!     let args = env.get_args();
 //!     let (res, stdout, stderr) = spawn_with_output! {
 //!         orig_cmd $[args]
 //!             --long-option xxx

src/process.rs

@@ -29,9 +29,14 @@ pub struct CmdEnv {
     current_dir: PathBuf,
 }
 impl CmdEnv {
+    /// Returns the name of this command.
+    pub fn get_cmd_name(&self) -> &str {
+        &self.args[0]
+    }
+
     /// Returns the arguments for this command.
-    pub fn args(&self) -> &[String] {
-        &self.args
+    pub fn get_args(&self) -> &[String] {
+        &self.args[1..]
     }
 
     /// Fetches the environment variable key for this command.

tests/test_macros.rs

@@ -189,13 +189,13 @@ fn test_proc_env() {
 fn test_export_cmd() {
     use std::io::Write;
     fn my_cmd(env: &mut CmdEnv) -> CmdResult {
-        let msg = format!("msg from foo(), args: {:?}", env.args());
+        let msg = format!("msg from foo(), args: {:?}", env.get_args());
         writeln!(env.stderr(), "{}", msg)?;
         writeln!(env.stdout(), "bar")
     }
 
     fn my_cmd2(env: &mut CmdEnv) -> CmdResult {
-        let msg = format!("msg from foo2(), args: {:?}", env.args());
+        let msg = format!("msg from foo2(), args: {:?}", env.get_args());
         writeln!(env.stderr(), "{}", msg)?;
         writeln!(env.stdout(), "bar2")
     }