feat(cli): enhance help documentation and dynamic applet dispatch

README.md

@@ -134,8 +134,9 @@ warning_kind, message, event_wall_ns, client_send_wall_ns,
 client_receive_wall_ns
 ```
 
-Aliases are accepted for readability: `receive_delay` for `rd`, `send_delay`
-for `sd`, `server_processing` for `proc`, `server_received_count` for
+Aliases are accepted for readability: `receive_delay` and `receive_delay_us`
+for `rd` and `rd_us`, `send_delay` and `send_delay_us` for `sd` and `sd_us`,
+`server_processing` for `proc`, `server_received_count` for
 `server_received`, and `server_received_window` for `server_window`.
 
 The default table output favors readability with compact columns:

crates/irtt-cli/src/applet.rs

@@ -41,13 +41,15 @@ pub fn dispatch_from_argv(argv: Vec<OsString>) -> Result<AppletDispatch, String>
     let basename = applet_basename(argv0);
     if basename.starts_with("irtt-") && basename != "irtt-rs" {
         return Err(format!(
-            "unknown applet name '{basename}'. Known applet names: irtt-rs, irtt-cli, irtt-tui, irtt-server"
+            "unknown applet name '{basename}'. Known applet names: {}",
+            known_applet_binary_names()
         ));
     }
 
     let Some(command) = argv.get(1).and_then(|arg| arg.to_str()) else {
         return Err(format!(
-            "choose an applet: client, tui, or server\n\n{}",
+            "choose an applet: {}\n\n{}",
+            applet_command_names(),
             dispatcher_help()
         ));
     };
@@ -67,7 +69,8 @@ pub fn dispatch_from_argv(argv: Vec<OsString>) -> Result<AppletDispatch, String>
             argv: applet_argv("irtt-server", &argv[2..]),
         }),
         _ => Err(format!(
-            "unknown applet '{command}'. Choose one of: client, tui, server\n\n{}",
+            "unknown applet '{command}'. Choose one of: {}\n\n{}",
+            applet_command_names(),
             dispatcher_help()
         )),
     }
@@ -76,13 +79,47 @@ pub fn dispatch_from_argv(argv: Vec<OsString>) -> Result<AppletDispatch, String>
 pub fn dispatcher_help() -> String {
     let mut command = Command::new("irtt-rs")
         .about("IRTT-compatible multi-applet dispatcher")
-        .subcommand(Command::new("client").about("Run the stream client applet"))
-        .subcommand(Command::new("tui").about("Run the terminal UI applet"))
-        .subcommand(Command::new("server").about("Run the server applet"))
-        .after_help("Applet binary names: irtt-cli, irtt-tui, irtt-server");
+        .subcommand(Command::new("client").about(client_applet_about()))
+        .subcommand(Command::new("tui").about(tui_applet_about()))
+        .subcommand(Command::new("server").about("Server applet is not available in this build"))
+        .after_help(dispatcher_after_help());
     command.render_help().to_string()
 }
 
+fn client_applet_about() -> &'static str {
+    if cfg!(feature = "client") {
+        "Run the stream client applet"
+    } else {
+        "Stream client applet is not available in this build"
+    }
+}
+
+fn tui_applet_about() -> &'static str {
+    if cfg!(feature = "tui") {
+        "Run the terminal UI applet"
+    } else {
+        "Terminal UI applet is not available in this build"
+    }
+}
+
+fn known_applet_binary_names() -> &'static str {
+    "irtt-rs, irtt-cli, irtt-tui, irtt-server"
+}
+
+fn applet_command_names() -> &'static str {
+    "client, tui, or server"
+}
+
+fn dispatcher_after_help() -> &'static str {
+    if cfg!(feature = "tui") {
+        "Recognized applet binary names: irtt-cli, irtt-tui, irtt-server"
+    } else if cfg!(feature = "client") {
+        "Recognized applet binary names: irtt-cli, irtt-tui, irtt-server\nOptional applet: irtt-tui requires the tui feature"
+    } else {
+        "Recognized applet binary names: irtt-cli, irtt-tui, irtt-server\nOptional applets: irtt-cli requires the client feature; irtt-tui requires the tui feature"
+    }
+}
+
 fn applet_basename(argv0: &str) -> &str {
     Path::new(argv0)
         .file_name()
@@ -127,7 +164,11 @@ mod tests {
         };
         assert!(help.contains("IRTT-compatible multi-applet dispatcher"));
         assert!(help.contains("client"));
-        assert!(help.contains("tui"));
+        if cfg!(feature = "tui") {
+            assert!(help.contains("Run the terminal UI applet"));
+        } else {
+            assert!(help.contains("Terminal UI applet is not available in this build"));
+        }
         assert!(help.contains("server"));
     }
 
@@ -136,7 +177,9 @@ mod tests {
         let err = dispatch_from_argv(vec!["irtt-rs".into()]).unwrap_err();
         assert!(err.contains("choose an applet"));
         assert!(err.contains("client"));
-        assert!(err.contains("tui"));
+        if cfg!(feature = "tui") {
+            assert!(err.contains("tui"));
+        }
         assert!(err.contains("server"));
     }
 
@@ -171,7 +214,9 @@ mod tests {
         let err = dispatch_from_argv(vec!["/usr/bin/irtt-typo".into()]).unwrap_err();
         assert!(err.contains("unknown applet name 'irtt-typo'"));
         assert!(err.contains("irtt-cli"));
-        assert!(err.contains("irtt-tui"));
+        if cfg!(feature = "tui") {
+            assert!(err.contains("irtt-tui"));
+        }
         assert!(err.contains("irtt-server"));
     }
 }

crates/irtt-cli/src/cmd/client/args.rs

@@ -26,20 +26,38 @@ pub struct ClientArgs {
     #[command(flatten)]
     pub common: CommonClientArgs,
 
-    /// Event row renderer format.
-    #[arg(long, value_enum, default_value_t = OutputFormat::Table)]
+    /// Event row output format.
+    #[arg(
+        long,
+        value_enum,
+        default_value_t = OutputFormat::Table,
+        long_help = "Event row output format.\n\nTable is the default interactive format. CSV, TSV, and JSON Lines default to all columns for structured export."
+    )]
     pub format: OutputFormat,
 
-    /// Comma-separated event row columns.
-    #[arg(short = 'c', long, value_name = "COLUMNS")]
+    /// Comma-separated event row columns, or default/all.
+    #[arg(
+        short = 'c',
+        long,
+        value_name = "COLUMNS",
+        long_help = "Comma-separated event row columns, or default/all.\n\nThe default table columns are compact and hide echo_sent rows. Custom table columns include all event rows. Run --list-columns to see valid names."
+    )]
     pub columns: Option<String>,
 
-    /// Print available event row columns and exit.
-    #[arg(long)]
+    /// List available event row columns and aliases, then exit.
+    #[arg(
+        long,
+        long_help = "List available event row columns and aliases, then exit.\n\nA server argument is not required when listing columns."
+    )]
     pub list_columns: bool,
 
     /// Header policy for table, CSV, and TSV output.
-    #[arg(long, value_enum, default_value_t = HeaderMode::Auto)]
+    #[arg(
+        long,
+        value_enum,
+        default_value_t = HeaderMode::Auto,
+        long_help = "Header policy for table, CSV, and TSV output.\n\nJSON Lines never prints a header."
+    )]
     pub header: HeaderMode,
 
     /// Include extra fields in table output and final summaries.

crates/irtt-cli/src/cmd/client/output.rs

@@ -129,17 +129,19 @@ impl OutputConfig {
             writeln!(out, "  {:<24} {}", column.name(), column.description()).unwrap();
         }
         writeln!(out).unwrap();
+        writeln!(out, "Aliases:").unwrap();
+        writeln!(out, "  receive_delay, receive_delay_us").unwrap();
+        writeln!(out, "  send_delay, send_delay_us").unwrap();
+        writeln!(out, "  server_processing").unwrap();
+        writeln!(out, "  server_received_count, server_received_window").unwrap();
+        writeln!(out).unwrap();
+        writeln!(out, "Special column sets:").unwrap();
         writeln!(
             out,
-            "Aliases: rd=receive_delay, sd=send_delay, proc=server_processing, \
-             server_received=server_received_count, server_window=server_received_window."
-        )
-        .unwrap();
-        writeln!(
-            out,
-            "Use --columns default for the format default, or --columns all for every column."
+            "  default  format default; compact for table, all columns for csv/tsv/jsonl"
         )
         .unwrap();
+        writeln!(out, "  all      every column").unwrap();
         out
     }
 }