Add vite plugin

Author: nojaf

templates/rescript-template-vite/README.md

@@ -11,13 +11,7 @@ This is a Vite-based template with following setup:
 
 ## Development
 
-Run ReScript in dev mode:
-
-```sh
-npm run res:dev
-```
-
-In another tab, run the Vite dev server:
+Run the Vite dev server and ReScript in dev mode:
 
 ```sh
 npm run dev

templates/rescript-template-vite/vite.config.js

@@ -1,11 +1,78 @@
+import { spawn, execSync } from "child_process";
 import { defineConfig } from "vite";
 import react from "@vitejs/plugin-react";
 
+/**
+ * Helper plugin to start and stop the ReScript compiler in the Vite pipeline.
+ * @returns Vite plugin
+ */
+function rescript() {
+  let rescriptProcressRef = null;
+  let logger = { info: console.log, warn: console.warn, error: console.error };
+  let command = "build";
+
+  return {
+    name: "rescript",
+    enforce: "pre",
+    // Don't watch *.res files with Vite, ReScript will take care of these.
+    config: function (config) {
+      if (!config.server) {
+        config.server = {};
+      }
+
+      if (!config.server.watch) {
+        config.server.watch = {};
+      }
+
+      if (Array.isArray(config.server.watch.ignored)) {
+        config.server.watch.ignored.push("**/*.res");
+      } else {
+        config.server.watch.ignored = ["**/*.res"];
+      }
+    },
+    configResolved: async function (resolvedConfig) {
+      logger = resolvedConfig.logger;
+      command = resolvedConfig.command;
+    },
+    buildStart: async function () {
+      if (command === "build") {
+        logger.info(execSync("npx rescript").toString().trim());
+      } else {
+        rescriptProcressRef = spawn("npx", ["rescript", "-w"]);
+        logger.info(`Spawned rescript -w`);
+
+        // Process standard output
+        rescriptProcressRef.stdout.on("data", (data) => {
+          logger.info(data.toString().trim());
+        });
+
+        // Process standard error
+        rescriptProcressRef.stderr.on("data", (data) => {
+          logger.error(data.toString().trim());
+        });
+
+        // Handle process exit
+        rescriptProcressRef.on("close", (code) => {
+          console.log(`ReScript process exited with code ${code || 0}`);
+        });
+      }
+    },
+    buildEnd: async function () {
+      if (rescriptProcressRef && !rescriptProcressRef.killed) {
+        const pid = rescriptProcressRef.pid;
+        rescriptProcressRef.kill("SIGKILL"); // Default signal is SIGTERM
+        logger.info(`ReScript process with PID: ${pid} has been killed`);
+      }
+    },
+  };
+}
+
 // https://vitejs.dev/config/
 export default defineConfig({
   plugins: [
     react({
       include: ["**/*.res.mjs"],
     }),
+    rescript()
   ],
 });