feat: Cross-platform microfrontends port command (#11098)

### Description

Adds a `turbo get-mfe-port` command so you can more easily assign the
ports to your microfrontends. The command fetches the port for the
microfrontend according to `microfrontends.json`, and forwards it into
the script.

### Testing Instructions

Hand-tested it and added some tests.

Author: anthonyshew

crates/turborepo-lib/src/cli/error.rs

@@ -9,7 +9,7 @@ use turborepo_telemetry::events::command::CommandEventBuilder;
 use turborepo_ui::{color, BOLD, GREY};
 
 use crate::{
-    commands::{bin, generate, link, login, ls, prune, CommandBase},
+    commands::{bin, generate, get_mfe_port, link, login, ls, prune, CommandBase},
     daemon::DaemonError,
     query,
     rewrite_json::RewriteError,
@@ -46,6 +46,8 @@ pub enum Error {
     #[error(transparent)]
     Generate(#[from] generate::Error),
     #[error(transparent)]
+    GetMfePort(#[from] get_mfe_port::Error),
+    #[error(transparent)]
     #[diagnostic(transparent)]
     Ls(#[from] ls::Error),
     #[error(transparent)]
@@ -125,3 +127,58 @@ pub async fn print_potential_tasks(
 
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_get_mfe_port_error_conversion() {
+        // Test NoPackageJson error
+        let err = get_mfe_port::Error::NoPackageJson;
+        let cli_err: Error = err.into();
+        assert!(matches!(cli_err, Error::GetMfePort(_)));
+        assert_eq!(
+            cli_err.to_string(),
+            "No package.json found in current directory"
+        );
+
+        // Test NoPackageName error
+        let err = get_mfe_port::Error::NoPackageName;
+        let cli_err: Error = err.into();
+        assert!(matches!(cli_err, Error::GetMfePort(_)));
+        assert_eq!(
+            cli_err.to_string(),
+            "package.json is missing the 'name' field"
+        );
+
+        // Test NoMicrofrontendsConfig error
+        let err = get_mfe_port::Error::NoMicrofrontendsConfig;
+        let cli_err: Error = err.into();
+        assert!(matches!(cli_err, Error::GetMfePort(_)));
+        assert_eq!(cli_err.to_string(), "No microfrontends configuration found");
+
+        // Test PackageNotInConfig error
+        let err = get_mfe_port::Error::PackageNotInConfig("my-app".to_string());
+        let cli_err: Error = err.into();
+        assert!(matches!(cli_err, Error::GetMfePort(_)));
+        assert_eq!(
+            cli_err.to_string(),
+            "Package 'my-app' not found in microfrontends configuration"
+        );
+    }
+
+    #[test]
+    fn test_get_mfe_port_error_source() {
+        // Test that error source chain works properly
+        let err = get_mfe_port::Error::NoPackageJson;
+        let cli_err: Error = err.into();
+
+        match cli_err {
+            Error::GetMfePort(inner) => {
+                assert!(matches!(inner, get_mfe_port::Error::NoPackageJson));
+            }
+            _ => panic!("Expected GetMfePort error variant"),
+        }
+    }
+}

crates/turborepo-lib/src/cli/mod.rs

@@ -28,8 +28,8 @@ use turborepo_ui::{ColorConfig, GREY};
 use crate::{
     cli::error::print_potential_tasks,
     commands::{
-        bin, boundaries, clone, config, daemon, generate, info, link, login, logout, ls, prune,
-        query, run, scan, telemetry, unlink, CommandBase,
+        bin, boundaries, clone, config, daemon, generate, get_mfe_port, info, link, login, logout,
+        ls, prune, query, run, scan, telemetry, unlink, CommandBase,
     },
     get_version,
     run::watch::WatchClient,
@@ -574,6 +574,9 @@ impl Args {
 pub enum Command {
     /// Get the path to the Turbo binary
     Bin,
+    /// Get the port assigned to the current microfrontend
+    #[clap(name = "get-mfe-port")]
+    GetMfePort,
     #[clap(hide = true)]
     Boundaries {
         #[clap(short = 'F', long, group = "scope-filter-group")]
@@ -1393,6 +1396,15 @@ pub async fn run(
 
             Ok(0)
         }
+        Command::GetMfePort => {
+            let event = CommandEventBuilder::new("get-mfe-port").with_parent(&root_telemetry);
+            event.track_call();
+
+            let base = CommandBase::new(cli_args.clone(), repo_root, version, color_config)?;
+            get_mfe_port::run(&base).await?;
+
+            Ok(0)
+        }
         Command::Boundaries { ignore, reason, .. } => {
             let event = CommandEventBuilder::new("boundaries").with_parent(&root_telemetry);
             let ignore = *ignore;