fix(new-compiler): improve translation error logging (#1991)

Co-authored-by: cherkanov_art <45258907+cherkanovart@users.noreply.github.com>

Author: AndreyHirsa

.changeset/yellow-cows-hear.md

@@ -0,0 +1,5 @@
+---
+"@lingo.dev/compiler": patch
+---
+
+Improve translation error logging by writing detailed errors to .lingo/translation-server.log

packages/new-compiler/src/translation-server/translation-server.ts

@@ -331,7 +331,7 @@ export class TranslationServer {
    */
   async translateAll(locale: LocaleCode): Promise<{
     translations: Record<string, string>;
-    errors: Array<{ hash: string; error: string }>;
+    errors: Array<{ hash: string; sourceText: string; error: string }>;
   }> {
     if (!this.translationService) {
       throw new Error("Translation server not initialized");
@@ -368,6 +368,27 @@ export class TranslationServer {
       allHashes,
     );
 
+    // Log detailed error information to server log file
+    if (result.errors.length > 0) {
+      this.logger.error(
+        `${result.errors.length} translation error(s) for ${locale}:`,
+      );
+      for (const err of result.errors) {
+        const prefix = `  [${locale}]`;
+        if (err.hash === "all") {
+          this.logger.error(`${prefix} ${err.error}`);
+          continue;
+        }
+        const source =
+          err.sourceText.length > 200
+            ? err.sourceText.slice(0, 200) + "..."
+            : err.sourceText;
+        this.logger.error(
+          `${prefix} hash=${err.hash} source="${source}" error="${err.error}"`,
+        );
+      }
+    }
+
     // Broadcast batch complete event
     const duration = Date.now() - startTime;
     this.broadcast(

packages/new-compiler/src/translators/translation-service.ts

@@ -259,7 +259,14 @@ Set the required API keys for real translations.`);
         // Merge translated texts with overridden translations
         newTranslations = { ...overriddenTranslations, ...translatedTexts };
       } catch (error) {
-        this.logger.error(`Translation failed:`, error);
+        const errorMessage =
+          error instanceof Error ? error.message : String(error);
+        this.logger.error(
+          `Translation failed for locale "${locale}": ${errorMessage}`,
+        );
+        if (error instanceof Error && error.stack) {
+          this.logger.debug(`Stack trace: ${error.stack}`);
+        }
 
         return {
           translations: this.pickTranslations(
@@ -270,10 +277,7 @@ Set the required API keys for real translations.`);
             {
               hash: "all",
               sourceText: "all",
-              error:
-                error instanceof Error
-                  ? error.message
-                  : "Unknown translation error",
+              error: errorMessage,
             },
           ],
           stats: {