lupdate: Do not touch a translated file without target language

[ChangeLog][lupdate] lupdate will now generate an error if it is asked
to update a .ts file with translations, but without a target language.
This is to ensure that plural translations are not destroyed.

Fixes: QTBUG-53775
Change-Id: I646c1f2ec42a32dbc1a4676ad784887613607b78
Reviewed-by: Kai Koehne <kai.koehne@qt.io>

3 files changed, 25 insertions, 0 deletions

diff --git a/src/linguist/lupdate/main.cpp b/src/linguist/lupdate/main.cpp
index 134eab336..ba1126aa7 100644
--- a/src/linguist/lupdate/main.cpp
+++ b/src/linguist/lupdate/main.cpp
@@ -310,6 +310,19 @@ static void updateTsFiles(const Translator &fetchedTor, const QStringList &tsFil
                 printErr(LU::tr("lupdate warning: Specified source language '%1' disagrees with"
                                 " existing file's language '%2'. Ignoring.\n")
                          .arg(sourceLanguage, tor.sourceLanguageCode()));
+            // If there is translation in the file, the language should be recognized
+            // (when the language is not recognized, plural translations are lost)
+            if (tor.translationsExist()) {
+                QLocale::Language l;
+                QLocale::Country c;
+                tor.languageAndCountry(tor.languageCode(), &l, &c);
+                QStringList forms;
+                if (!getNumerusInfo(l, c, 0, &forms, 0)) {
+                    printErr(LU::tr("File %1 won't be updated: it contains translation but the"
+                    " target language is not recognized\n").arg(fileName));
+                    continue;
+                }
+            }
         } else {
             if (!targetLanguage.isEmpty())
                 tor.setLanguageCode(targetLanguage);
diff --git a/src/linguist/shared/translator.cpp b/src/linguist/shared/translator.cpp
index af669e235..db28ea396 100644
--- a/src/linguist/shared/translator.cpp
+++ b/src/linguist/shared/translator.cpp
@@ -433,6 +433,17 @@ void Translator::stripUntranslatedMessages()
     m_indexOk = false;
 }
 
+bool Translator::translationsExist()
+{
+    for (TMM::Iterator it = m_messages.begin(); it != m_messages.end(); ) {
+        if (it->isTranslated())
+            return true;
+        else
+            ++it;
+    }
+    return false;
+}
+
 void Translator::stripEmptyContexts()
 {
     for (TMM::Iterator it = m_messages.begin(); it != m_messages.end();)
diff --git a/src/linguist/shared/translator.h b/src/linguist/shared/translator.h
index 8919a13df..5b5d12250 100644
--- a/src/linguist/shared/translator.h
+++ b/src/linguist/shared/translator.h
@@ -135,6 +135,7 @@ public:
     void dropTranslations();
     void dropUiLines();
     void makeFileNamesAbsolute(const QDir &originalPath);
+    bool translationsExist();
 
     struct Duplicates { QSet<int> byId, byContents; };
     Duplicates resolveDuplicates();