External subcommands is the key;

subcommand/Cargo.lock

@@ -27,11 +27,26 @@ checksum = "2148adefda54e14492fb9bddcc600b4344c5d1a3123bd666dcb939c6f0e0e57e"
 dependencies = [
  "atty",
  "bitflags",
+ "clap_derive",
  "clap_lex",
+ "once_cell",
  "strsim",
  "termcolor",
 ]
 
+[[package]]
+name = "clap_derive"
+version = "4.0.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0177313f9f02afc995627906bbd8967e2be069f5261954222dac78290c2b9014"
+dependencies = [
+ "heck",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "clap_lex"
 version = "0.3.0"
@@ -41,6 +56,12 @@ dependencies = [
  "os_str_bytes",
 ]
 
+[[package]]
+name = "heck"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2540771e65fc8cb83cd6e8a237f70c319bd5c29f78ed1084ba5d50eeac86f7f9"
+
 [[package]]
 name = "hermit-abi"
 version = "0.1.19"
@@ -56,12 +77,60 @@ version = "0.2.137"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fc7fcc620a3bff7cdd7a365be3376c97191aeaccc2a603e600951e452615bf89"
 
+[[package]]
+name = "once_cell"
+version = "1.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "86f0b0d4bf799edbc74508c1e8bf170ff5f41238e5f8225603ca7caaae2b7860"
+
 [[package]]
 name = "os_str_bytes"
 version = "6.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7b5bf27447411e9ee3ff51186bf7a08e16c341efdde93f4d823e8844429bed7e"
 
+[[package]]
+name = "proc-macro-error"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
+dependencies = [
+ "proc-macro-error-attr",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.47"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ea3d908b0e36316caf9e9e2c4625cdde190a7e6f440d794667ed17a1855e725"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbe448f377a7d6961e30f5955f9b8d106c3f5e449d493ee1b125c1d43c2b5179"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "strsim"
 version = "0.10.0"
@@ -75,6 +144,17 @@ dependencies = [
  "clap",
 ]
 
+[[package]]
+name = "syn"
+version = "1.0.103"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a864042229133ada95abf3b54fdc62ef5ccabe9515b64717bcb9a1919e59445d"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
 [[package]]
 name = "termcolor"
 version = "1.1.3"
@@ -84,6 +164,18 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "unicode-ident"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ceab39d59e4c9499d4e5a8ee0e2735b891bb7308ac83dfb4e80cad195c9f6f3"
+
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
 [[package]]
 name = "winapi"
 version = "0.3.9"

subcommand/Cargo.toml

@@ -6,4 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-clap = "4.0.26"
+clap = { version = "4.0.26", features = ["derive"] }

subcommand/src/main.rs

@@ -1,8 +1,12 @@
+// This doesnt works:
+
 use clap::Arg;
 use clap::Command;
 
 fn main() {
     let command = Command::new("example")
+        .subcommand_required(true)
+        .allow_external_subcommands(true)
         .arg(
             Arg::new("working_directory")
                 .short('w')
@@ -18,8 +22,38 @@ fn main() {
 
     match matches.subcommand() {
         Some(("run", _sub_matches)) => println!("It's run"),
+        Some((ext, _sub_matches)) => println!("Finding if we have a \"{ext}\" command"),
         _ => {
             println!("Finding out if it an external command...")
         }
     }
 }
+
+// This doesn't work
+
+// use std::path::{Path, PathBuf};
+
+// use clap::{Parser, Subcommand};
+
+// #[derive(Parser)]
+// #[command(version)]
+// struct Cli {
+//     #[arg(short, long)]
+//     working_directory: Option<PathBuf>,
+
+//     #[command(subcommand)]
+//     command: Command,
+// }
+
+// #[derive(Subcommand)]
+// enum Command {
+//     Run { cases: Option<Vec<String>> },
+// }
+
+// fn main() {
+//     let cli = Cli::parse();
+//     match &cli.command {
+//         Command::Run { cases } => println!("Running cases: {:?}", cases),
+//         _ => println!("External"),
+//     }
+// }