feat(2688): --watch for changes

Cargo.toml

@@ -165,6 +165,7 @@ num = "0.4.3"
 indenter = "0.3.3"
 derive_more = { workspace = true }
 strum = "0.26.2"
+notify = "6.1.1"
 
 [dev-dependencies]
 datatest-stable = "0.2.9"

src/cli/command.rs

@@ -26,6 +26,9 @@
         /// separated by spaces if more than one
         #[arg(required = true)]
         file_paths: Vec<String>,
+        /// Watch for file changes
+        #[arg(short, long)]
+        watch: bool,
     },
 
     /// Validate a composition spec

src/cli/server/http_server.rs

@@ -1,7 +1,9 @@
 use std::ops::Deref;
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 
 use anyhow::Result;
+use lazy_static::lazy_static;
+use tokio::runtime::Runtime;
 use tokio::sync::oneshot::{self};
 
 use super::http_1::start_http_1;
@@ -12,6 +14,10 @@
 use crate::core::config::ConfigModule;
 use crate::core::Errata;
 
+lazy_static! {
+    pub static ref RUNTIME: Arc<Mutex<Option<Runtime>>> = Arc::new(Mutex::new(None));
+}
+
 pub struct Server {
     config_module: ConfigModule,
     server_up_sender: Option<oneshot::Sender<()>>,
@@ -47,15 +53,19 @@
     }
 
     /// Starts the server in its own multithreaded Runtime
-    pub async fn fork_start(self) -> Result<()> {
+    pub async fn fork_start(self, watch: bool) -> Result<()> {
         let runtime = tokio::runtime::Builder::new_multi_thread()
             .worker_threads(self.config_module.deref().server.get_workers())
             .enable_all()
             .build()?;
-
-        let result = runtime.spawn(async { self.start().await }).await?;
-        runtime.shutdown_background();
-
-        result
+        if watch {
+            let handle = runtime.spawn(async { self.start().await });
+            RUNTIME.lock().unwrap().get_or_insert(runtime);
+            handle.await?
+        } else {
+            let result = runtime.spawn(async { self.start().await }).await?;
+            runtime.shutdown_background();
+            result
+        }
     }
 }

src/cli/tc/mod.rs

@@ -3,4 +3,4 @@ mod gen;
 mod helpers;
 mod init;
 pub mod run;
-mod start;
+pub mod start;

src/cli/tc/run.rs

@@ -35,8 +35,8 @@
 
 async fn run_command(cli: Cli, config_reader: ConfigReader, runtime: TargetRuntime) -> Result<()> {
     match cli.command {
-        Command::Start { file_paths } => {
-            start::start_command(file_paths, &config_reader).await?;
+        Command::Start { file_paths, watch } => {
+            start::start_command(file_paths, watch, config_reader).await?;
         }
         Command::Check { file_paths, n_plus_one_queries, schema, format } => {
             check::check_command(