Improve esbuild watch mode (#160)

scripts/cmd/build.js

@@ -1,7 +1,7 @@
 import esbuild from 'esbuild';
 import del from 'del';
 import { promises as fs } from 'fs';
-import { resolve } from 'path';
+import { dim, green, red, yellow } from 'kleur/colors';
 import glob from 'tiny-glob';
 
 /** @type {import('esbuild').BuildOptions} */
@@ -11,13 +11,13 @@ const config = {
   sourcemap: 'inline',
   format: 'esm',
   platform: 'node',
-    target: 'node14'
-}
+  target: 'node14',
+};
 
 export default async function build(pattern, ...args) {
   const isDev = args.pop() === 'IS_DEV';
   const entryPoints = await glob(pattern, { filesOnly: true, absolute: true });
-    const { type = 'module', dependencies = {} } = await fs.readFile('./package.json').then(res => JSON.parse(res.toString()));
+  const { type = 'module', dependencies = {} } = await fs.readFile('./package.json').then((res) => JSON.parse(res.toString()));
   const format = type === 'module' ? 'esm' : 'cjs';
   const external = Object.keys(dependencies);
   const outdir = 'dist';
@@ -29,24 +29,35 @@ export default async function build(pattern, ...args) {
       entryPoints,
       outdir,
       external,
-            format
+      format,
     });
     return;
   }
 
   const builder = await esbuild.build({
     ...config,
-        watch: true,
+    watch: {
+      onRebuild(error, result) {
+        const date = new Date().toISOString();
+        if (error || (result && result.errors.length)) {
+          console.error(dim(`[${date}] `) + red(error || result.errors.join('\n')));
+        } else {
+          if (result.warnings.length) {
+            console.log(dim(`[${date}] `) + yellow('⚠ updated with warnings:\n' + result.warnings.join('\n')));
+          }
+          console.log(dim(`[${date}] `) + green('✔ updated'));
+        }
+      },
+    },
     entryPoints,
     outdir,
     external,
-        format
+    format,
   });
 
   process.on('beforeExit', () => {
     builder.stop?.();
-    })
-    
+  });
 }
 
 async function clean(outdir) {