From 83cc8dd7b88c4a4c5e0a7ffe35b27c6b85aa48fa Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 7 Feb 2026 22:49:42 +0000
Subject: [PATCH] Implement Portuguese language variant fallback for Auto
 Detect

Co-authored-by: pierotofy <1951843+pierotofy@users.noreply.github.com>
---
 libretranslate/app.py      | 12 ++++++------
 libretranslate/language.py | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/libretranslate/app.py b/libretranslate/app.py
index d20104c..d2a9415 100644
--- a/libretranslate/app.py
+++ b/libretranslate/app.py
@@ -23,7 +23,7 @@ from werkzeug.http import http_date
 from werkzeug.utils import secure_filename
 
 from libretranslate import flood, remove_translated_files, scheduler, secret, security, storage, cache
-from libretranslate.language import model2iso, iso2model, detect_languages, improve_translation_formatting
+from libretranslate.language import model2iso, iso2model, detect_languages, improve_translation_formatting, get_language_with_fallback
 from libretranslate.locales import (
     _,
     _lazy,
@@ -794,12 +794,12 @@ def create_app(args):
         else:
           detected_src_lang = {"confidence": 0.0, "language": "en"}
 
-        src_lang = next(iter([l for l in languages if l.code == detected_src_lang["language"]]), None)
+        src_lang = get_language_with_fallback(detected_src_lang["language"], languages)
 
         if src_lang is None:
             abort(400, description=_("%(lang)s is not supported", lang=source_lang))
 
-        tgt_lang = next(iter([l for l in languages if l.code == target_lang]), None)
+        tgt_lang = get_language_with_fallback(target_lang, languages)
 
         if tgt_lang is None:
             abort(400, description=_("%(lang)s is not supported",lang=target_lang))
@@ -977,12 +977,12 @@ def create_app(args):
         if os.path.splitext(file.filename)[1] not in frontend_argos_supported_files_format:
             abort(400, description=_("Invalid request: file format not supported"))
 
-        src_lang = next(iter([l for l in languages if l.code == source_lang]), None)
+        src_lang = get_language_with_fallback(source_lang, languages)
 
         if src_lang is None and source_lang != "auto":
             abort(400, description=_("%(lang)s is not supported", lang=source_lang))
 
-        tgt_lang = next(iter([l for l in languages if l.code == target_lang]), None)
+        tgt_lang = get_language_with_fallback(target_lang, languages)
 
         if tgt_lang is None:
             abort(400, description=_("%(lang)s is not supported", lang=target_lang))
@@ -1005,7 +1005,7 @@ def create_app(args):
                 src_texts = argostranslatefiles.get_texts(filepath)
                 candidate_langs = detect_languages(src_texts)
                 detected_src_lang = candidate_langs[0]
-                src_lang = next(iter([l for l in languages if l.code == detected_src_lang["language"]]), None)
+                src_lang = get_language_with_fallback(detected_src_lang["language"], languages)
                 if src_lang is None:
                     abort(400, description=_("%(lang)s is not supported", lang=detected_src_lang["language"]))
 
diff --git a/libretranslate/language.py b/libretranslate/language.py
index 42f8866..1284634 100644
--- a/libretranslate/language.py
+++ b/libretranslate/language.py
@@ -47,6 +47,24 @@ def load_lang_codes():
     languages = load_languages()
     return tuple(l.code for l in languages)
 
+def get_language_with_fallback(lang_code, languages):
+    lang = next(iter([l for l in languages if l.code == lang_code]), None)
+    if lang is not None:
+        return lang
+    
+    language_variants = {
+        'pt': ['pb'],
+        'pb': ['pt']
+    }
+    
+    fallbacks = language_variants.get(lang_code, [])
+    for fallback_code in fallbacks:
+        fallback_lang = next(iter([l for l in languages if l.code == fallback_code]), None)
+        if fallback_lang is not None:
+            return fallback_lang
+    
+    return None
+
 def detect_languages(text):
     # detect batch processing
     if isinstance(text, list):