Add fce repl command (#15)

tools/cli/src/args.rs

@@ -63,3 +63,11 @@ pub fn show_wit<'a, 'b>() -> App<'a, 'b> {
             .short("i")
             .help("path to the Wasm file")])
 }
+
+pub fn repl<'a, 'b>() -> App<'a, 'b> {
+    SubCommand::with_name("repl")
+        .about("Start Fluence application service REPL")
+        .setting(clap::AppSettings::TrailingVarArg)
+        .setting(clap::AppSettings::AllowLeadingHyphen)
+        .arg(Arg::from_usage("[optional]... 'fluence repl arguments'").multiple(true))
+}

tools/cli/src/main.rs

@@ -38,7 +38,8 @@ pub fn main() -> std::result::Result<(), anyhow::Error> {
         .setting(clap::AppSettings::ArgRequiredElseHelp)
         .subcommand(args::build())
         .subcommand(args::embed_wit())
-        .subcommand(args::show_wit());
+        .subcommand(args::show_wit())
+        .subcommand(args::repl());
     let arg_matches = app.get_matches();
 
     match arg_matches.subcommand() {
@@ -76,6 +77,25 @@ pub fn main() -> std::result::Result<(), anyhow::Error> {
 
             Ok(())
         }
+        ("repl", Some(args)) => {
+            use std::process::Command;
+            // use UNIX-specific API for replacing process image
+            use std::os::unix::process::CommandExt;
+
+            let trailing_args: Vec<&str> = args.values_of("optional").unwrap_or_default().collect();
+
+            let mut repl = Command::new("fce-repl");
+            repl.args(trailing_args);
+            let error = repl.exec();
+            if error.kind() == std::io::ErrorKind::NotFound {
+                println!("fce-repl not found, run `cargo +nightly install frepl` to install it");
+            } else {
+                // this branch should be executed if exec was successful, so just else if fine here
+                println!("error occurred: {:?}", error);
+            }
+
+            Ok(())
+        }
         c => Err(crate::errors::CLIError::NoSuchCommand(c.0.to_string()).into()),
     }
 }