[libcalamares] Test the translated string with real translations

- introduce a bogus translation context, load translations,
  and check that the context-enabled translator does its job.

src/libcalamares/CMakeLists.txt

@@ -215,10 +215,29 @@ calamares_add_test(
         ${geoip_src}
 )
 
+# Build up translations for this one test
+set( trans_file "localetest" )
+set( trans_infile ${CMAKE_CURRENT_BINARY_DIR}/${trans_file}.qrc )
+set( trans_outfile ${CMAKE_CURRENT_BINARY_DIR}/qrc_${trans_file}.cxx )
+set( calamares_i18n_qrc_content "<file>localetest_nl.qm</file>" )
+configure_file( ${CMAKE_SOURCE_DIR}/lang/calamares_i18n.qrc.in ${trans_infile} @ONLY )
+
+qt5_add_translation(QM_FILES "${CMAKE_CURRENT_SOURCE_DIR}/testdata/localetest_nl.ts")
+
+# Run the resource compiler (rcc_options should already be set)
+add_custom_command(
+    OUTPUT ${trans_outfile}
+    COMMAND "${Qt5Core_RCC_EXECUTABLE}"
+    ARGS ${rcc_options} --format-version 1 -name ${trans_file} -o ${trans_outfile} ${trans_infile}
+    MAIN_DEPENDENCY ${trans_infile}
+    DEPENDS ${QM_FILES}
+)
+
 calamares_add_test(
     libcalamareslocaletest
     SOURCES
         locale/Tests.cpp
+        ${trans_outfile}
 )
 
 calamares_add_test(

src/libcalamares/locale/Tests.cpp

@@ -16,6 +16,7 @@
 #include "CalamaresVersion.h"
 #include "GlobalStorage.h"
 #include "utils/Logger.h"
+#include "utils/Retranslator.h"
 
 #include <QtTest/QtTest>
 
@@ -33,6 +34,7 @@ private Q_SLOTS:
     void testTranslatableLanguages();
     void testTranslatableConfig1();
     void testTranslatableConfig2();
+    void testTranslatableConfigContext();
     void testLanguageScripts();
 
     void testEsperanto();
@@ -246,6 +248,32 @@ LocaleTests::testTranslatableConfig2()
     QCOMPARE( ts3.count(), 1 );  // The empty string
 }
 
+void
+LocaleTests::testTranslatableConfigContext()
+{
+    using TS = CalamaresUtils::Locale::TranslatedString;
+
+    const QString original( "Quit" );
+    TS quitUntranslated( original );
+    TS quitTranslated( original, metaObject()->className() );
+
+    QCOMPARE( quitUntranslated.get(), original );
+    QCOMPARE( quitTranslated.get(), original );
+
+    // Load translation data from QRC
+    QVERIFY( QFile::exists( ":/lang/localetest_nl.qm" ) );
+    QTranslator t;
+    QVERIFY( t.load( QString( ":/lang/localetest_nl" ) ) );
+    QCoreApplication::installTranslator( &t );
+
+    // Translation doesn't affect the one without context
+    QCOMPARE( quitUntranslated.get(), original );
+    // But the translation **does** affect this class' context
+    QCOMPARE( quitTranslated.get(), QStringLiteral( "Ophouden" ) );
+    QCOMPARE( tr( "Quit" ), QStringLiteral( "Ophouden" ) );
+}
+
+
 void
 LocaleTests::testRegions()
 {

src/libcalamares/testdata/localetest_nl.ts

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- SPDX-FileCopyrightText: no
+     SPDX-License-Identifier: CC0-1.0
+-->
+<!DOCTYPE TS>
+<TS language="nl" version="2.1">
+  <context>
+    <name>LocaleTests</name>
+    <message>
+      <location filename="Tests.cpp" line="22"/>
+      <source>Quit</source>
+      <translation>Ophouden</translation>
+    </message>
+  </context>
+</TS>