Make build error cause more clear by prepending with module name

Simplify the diagnosis of build failures by showing the module name
encountering the issue right before the error itself is printed.

Also apply the fix to warnings.

Fixes #15815

Signed-off-by: Mitchell Hentges <mhentges@spotify.com>

.changeset/eight-hotels-sparkle.md

@@ -0,0 +1,5 @@
+---
+'@backstage/cli': patch
+---
+
+Show module name causing error during build

packages/cli/src/lib/bundler/bundle.ts

@@ -32,6 +32,10 @@ import chalk from 'chalk';
 const WARN_AFTER_BUNDLE_GZIP_SIZE = 512 * 1024;
 const WARN_AFTER_CHUNK_GZIP_SIZE = 1024 * 1024;
 
+function applyContextToError(error: string, moduleName: string): string {
+  return `Failed to compile '${moduleName}':\n  ${error}`;
+}
+
 export async function buildBundle(options: BuildOptions) {
   const { statsJsonEnabled, schema: configSchema } = options;
 
@@ -127,15 +131,25 @@ async function build(config: webpack.Configuration, isCi: boolean) {
   if (errors.length) {
     // Only keep the first error. Others are often indicative
     // of the same problem, but confuse the reader with noise.
-    throw new Error(`Failed to compile.\n${errors[0]}`);
+    const errorWithContext = applyContextToError(
+      errors[0],
+      serializedStats.errors?.[0].moduleName || '',
+    );
+    throw new Error(errorWithContext);
   }
   if (isCi && warnings.length) {
+    const warningsWithContext = warnings.map((warning, i) => {
+      return applyContextToError(
+        warning,
+        serializedStats.warnings?.[i].moduleName || '',
+      );
+    });
     console.log(
       chalk.yellow(
         '\nTreating warnings as errors because process.env.CI = true.\n',
       ),
     );
-    throw new Error(`Failed to compile.\n${warnings.join('\n\n')}`);
+    throw new Error(warningsWithContext.join('\n\n'));
   }
 
   return { stats };