Friendly microbundle-specific resolve errors (#687)

.changeset/angry-goats-knock.md

@@ -0,0 +1,5 @@
+---
+"microbundle": patch
+---
+
+Add friendly microbundle-specific errors when modules can't be resolved.

src/index.js

@@ -421,9 +421,26 @@ function createConfig(options, entry, format, writeMeta) {
 				}
 				return externalTest(id);
 			},
+
+			onwarn(warning, warn) {
+				// https://github.com/rollup/rollup/blob/0fa9758cb7b1976537ae0875d085669e3a21e918/src/utils/error.ts#L324
+				if (warning.code === 'UNRESOLVED_IMPORT') {
+					stdout(
+						`Failed to resolve the module ${warning.source} imported by ${warning.importer}` +
+							`\nIs the module installed? Note:` +
+							`\n ↳ to inline a module into your bundle, install it to "devDependencies".` +
+							`\n ↳ to depend on a module via import/require, install it to "dependencies".`,
+					);
+					return;
+				}
+
+				warn(warning);
+			},
+
 			treeshake: {
 				propertyReadSideEffects: false,
 			},
+
 			plugins: []
 				.concat(
 					postcss({