feat: support loading of new files automatically with --live (#94)

* add chokidar and debouncing depdendencies

* use chokidar to watch for changes and reload

this utilizes the chokidar watcher to watch all JS files
under the functions directory and for all items within the
assets directories.

this also uses the lodash debouncer to prevent multiple files
changing in quick succession (250ms) from causing too many
reloads.

* fix(server): adjust file watcher paths

* style(server): fix spacing of imports

Co-authored-by: Dominik Kundel <dkundel@twilio.com>

Author: imnotjames

package-lock.json

@@ -48,6 +48,7 @@
     "body-parser": "^1.18.3",
     "boxen": "^1.3.0",
     "chalk": "^2.4.2",
+    "chokidar": "^3.2.3",
     "columnify": "^1.5.4",
     "common-tags": "^1.8.0",
     "conf": "^5.0.0",
@@ -61,6 +62,7 @@
     "is-ci": "^2.0.0",
     "listr": "^0.14.3",
     "lodash.camelcase": "^4.3.0",
+    "lodash.debounce": "^4.0.8",
     "lodash.kebabcase": "^4.1.1",
     "lodash.startcase": "^4.4.0",
     "log-symbols": "^2.2.0",
@@ -88,6 +90,7 @@
     "@types/got": "^9.6.0",
     "@types/jest": "^24.0.15",
     "@types/listr": "^0.14.0",
+    "@types/lodash.debounce": "^4.0.6",
     "@types/lodash.kebabcase": "^4.1.6",
     "@types/lodash.startcase": "^4.4.6",
     "@types/prompts": "^2.0.1",

package.json

@@ -8,6 +8,10 @@ import express, {
 } from 'express';
 import userAgentMiddleware from 'express-useragent';
 import nocache from 'nocache';
+import { printRouteInfo } from '../printers/start';
+import chokidar from 'chokidar';
+import debounce from 'lodash.debounce';
+import path from 'path';
 import { StartCliConfig } from '../config/start';
 import { wrapErrorInHtml } from '../utils/error-html';
 import { getDebugFunction } from '../utils/logger';
@@ -18,6 +22,7 @@ import { constructGlobalScope, functionToRoute } from './route';
 
 const debug = getDebugFunction('twilio-run:server');
 const DEFAULT_PORT = process.env.PORT || 3000;
+const RELOAD_DEBOUNCE_MS = 250;
 const DEFAULT_BODY_SIZE_LAMBDA = '6mb';
 
 function requireUncached(module: string): any {
@@ -80,8 +85,43 @@ export async function createServer(
     });
   }
 
-  const routes = await getFunctionsAndAssets(config.baseDir);
-  const routeMap = setRoutes(routes);
+  let routes = await getFunctionsAndAssets(config.baseDir);
+  let routeMap = setRoutes(routes);
+
+  if (config.live) {
+    const watcher = chokidar.watch(
+      [
+        path.join(config.baseDir, '/(functions|src)/**/*.js'),
+        path.join(config.baseDir, '/(assets|static)/**/*'),
+      ],
+      {
+        ignoreInitial: true
+      }
+    );
+
+    const reloadRoutes = async () => {
+      routes = await getFunctionsAndAssets(config.baseDir);
+      routeMap = setRoutes(routes);
+
+      await printRouteInfo(config);
+    };
+
+    // Debounce so we don't needlessly reload when multiple files are changed
+    const debouncedReloadRoutes = debounce(reloadRoutes, RELOAD_DEBOUNCE_MS);
+
+    watcher
+      .on('add', path => {
+        debug(`Reloading Routes: add @ ${path}`);
+        debouncedReloadRoutes();
+      })
+      .on('unlink', path => {
+        debug(`Reloading Routes: unlink @ ${path}`);
+        debouncedReloadRoutes();
+      });
+
+    // Clean the watcher up when exiting.
+    process.on('exit', () => watcher.close());
+  }
 
   constructGlobalScope(config);