Re: Number of Japanese tests fails now

diff --git a/lib/languages b/lib/languages
index 00eba40919..494705637a 100644
--- a/lib/languages
+++ b/lib/languages
@@ -13,6 +13,7 @@
 #       BabelOptFormat     <format of option specification>
 #	PolyglossiaName    <polyglossianame>
 #	PolyglossiaOpts    "<language-specific options>"
+#	PreferTULangPack   <string>
 #	XindyName          <xindyname>
 #	ActiveChars        <activated characters>
 #	QuoteStyle         <british|danish|english|french|frenchin|
@@ -159,6 +160,9 @@
 #   requirement specified in "AltLangIfNot <requirement>" is not met.
 #   AltLanguage inherits the settings of the corresponding Language if the
 #   latter is defined first.
+# * PreferTULangPack might be used to define a language package that is used
+#   if this language is used alone and general language package setting is
+#   "auto", in TU encoding (i.e., with Xe- or LuaTeX).
 #
 ##########################################################################
 
@@ -1780,6 +1784,7 @@ Language japanese
 	BabelName        japanese
 	BabelOptFormat   \languageattribute{$lang$}{$opts$}
 	PolyglossiaName  japanese
+	PreferTULangPack none
 	Encoding         jis-platex
 	WordWrap         false
 	ImOffInMath      true
diff --git a/lib/lyx2lyx/lyx_2_6.py b/lib/lyx2lyx/lyx_2_6.py
index 507086648f..9aacfb75bf 100644
--- a/lib/lyx2lyx/lyx_2_6.py
+++ b/lib/lyx2lyx/lyx_2_6.py
@@ -886,6 +886,13 @@ def revert_shorthands2(document):
         i += 1
         continue
 
+
+def revert_lp_polyglossia(document):
+    """Revert language package polyglossia to auto"""
+    i = find_token(document.header, "\\language_package polyglossia", 0)
+    if i != -1:
+        document.header[i] = "\\language_package auto"
+
 ##
 # Conversion hub
 #
@@ -897,11 +904,13 @@ convert = [
     [646, []],
     [647, [convert_textbreaks]],
     [648, []],
-    [649, []]
+    [649, []],
+    [650, []]
 ]
 
 
 revert = [
+    [649, [revert_lp_polyglossia]],
     [648, [revert_shorthands2]],
     [647, [revert_hyphen_shorthands]],
     [646, [revert_textbreaks]],
diff --git a/src/BufferParams.cpp b/src/BufferParams.cpp
index bb862e90b2..8808d6a1f1 100644
--- a/src/BufferParams.cpp
+++ b/src/BufferParams.cpp
@@ -2351,19 +2351,23 @@ bool BufferParams::writeLaTeX(otexstream & os, LaTeXFeatures & features,
 		os << from_ascii(ams);
 
 	if (useNonTeXFonts) {
+		// We need fontspec if a non-default font or quotes are requested
+		bool const default_fonts = fontsRoman() == "default"
+				&& fontsSans() == "default"
+				&& fontsTypewriter() == "default";
+		bool const fontspec_features =
+				// these need fontspec features
+				features.isRequired("textquotesinglep")
+				|| features.isRequired("textquotedblp");
 		// Babel (as of 2017/11/03) loads fontspec itself
 		// However, it does so only if a non-default font is requested via \babelfont
 		// Thus load fontspec if this is not the case and we need fontspec features
 		bool const babel_needfontspec =
 				!features.isAvailableAtLeastFrom("babel", 2017, 11, 3)
-				|| (fontsRoman() == "default"
-				    && fontsSans() == "default"
-				    && fontsTypewriter() == "default"
-				    // these need fontspec features
-				    && (features.isRequired("textquotesinglep")
-					|| features.isRequired("textquotedblp")));
+				|| (default_fonts && fontspec_features);
 		if (!features.isProvided("fontspec")
-		    && (!features.useBabel() || babel_needfontspec))
+		    && (!features.useBabel() || babel_needfontspec)
+		    && (!features.usePrefTULangPack() || !default_fonts || fontspec_features))
 			os << "\\usepackage{fontspec}\n";
 		if (features.mustProvide("unicode-math")
 		    && features.isAvailable("unicode-math"))
diff --git a/src/Font.cpp b/src/Font.cpp
index bb5543d58c..1001bde4a1 100644
--- a/src/Font.cpp
+++ b/src/Font.cpp
@@ -822,8 +822,8 @@ void Font::validate(LaTeXFeatures & features) const
 
 	// FIXME: Do something for background and soul package?
 
-	if (((features.usePolyglossia() && lang_->polyglossia() != doc_language->polyglossia())
-	     || (features.useBabel() && lang_->babel() != doc_language->babel())
+	if (((features.usePolyglossia(true) && lang_->polyglossia() != doc_language->polyglossia())
+	     || (features.useBabel(true) && lang_->babel() != doc_language->babel())
 	     || (doc_language->encoding()->package() == Encoding::CJK && lang_ != doc_language))
 	    && lang_ != ignore_language
 	    && lang_ != latex_language)
diff --git a/src/LaTeXFeatures.cpp b/src/LaTeXFeatures.cpp
index 69341eaf9c..308951bd7d 100644
--- a/src/LaTeXFeatures.cpp
+++ b/src/LaTeXFeatures.cpp
@@ -577,14 +577,31 @@ LaTeXFeatures::LaTeXFeatures(Buffer const & b, BufferParams const & p,
 {}
 
 
-LaTeXFeatures::LangPackage LaTeXFeatures::langPackage() const
+bool LaTeXFeatures::usePrefTULangPack() const
 {
-	string const local_lp = bufferParams().lang_package;
+	return (bufferParams().lang_package == "auto"
+		|| (bufferParams().lang_package == "default"
+		    && lyxrc.language_package_selection == "auto"))
+		&& !hasLanguages()
+		&& !params_.language->preferTULangPack().empty();
+}
+
+
+LaTeXFeatures::LangPackage LaTeXFeatures::langPackage(bool const ignore_prefs) const
+{
+	// monolingual documents with PreferTULangPack use that if the local
+	// or global setting is "auto"
+	string const local_lp = !ignore_prefs
+				&& params_.useNonTeXFonts
+				&& usePrefTULangPack()
+			? params_.language->preferTULangPack()
+			: bufferParams().lang_package;
 
 	// Locally, custom is just stored as a string
 	// in bufferParams().lang_package.
 	if (local_lp != "auto"
 	    && local_lp != "babel"
+	    && local_lp != "polyglossia"
 	    && local_lp != "default"
 	    && local_lp != "none")
 		 return LANG_PACK_CUSTOM;
@@ -592,7 +609,7 @@ LaTeXFeatures::LangPackage LaTeXFeatures::langPackage() const
 	if (local_lp == "none")
 		return LANG_PACK_NONE;
 
-	/* If "auto" is selected, we load polyglossia with non-TeX fonts,
+	/* If "auto" or "polyglossia" is selected, we load polyglossia with non-TeX fonts,
 	 * else we select babel.
 	 * If babel is selected (either directly or via the "auto"
 	 * mechanism), we really do only require it if we have
@@ -607,7 +624,7 @@ LaTeXFeatures::LangPackage LaTeXFeatures::langPackage() const
 		!bufferParams().language->babel().empty()
 		|| !this->getBabelLanguages().empty();
 
-	if (local_lp == "auto") {
+	if (local_lp == "auto" || local_lp == "polyglossia") {
 		// polyglossia requirement has priority over babel
 		if (polyglossia_required)
 			return LANG_PACK_POLYGLOSSIA;
@@ -621,7 +638,8 @@ LaTeXFeatures::LangPackage LaTeXFeatures::langPackage() const
 	}
 
 	if (local_lp == "default") {
-		if (lyxrc.language_package_selection == "auto") {
+		if (lyxrc.language_package_selection == "auto"
+		    || lyxrc.language_package_selection == "polyglossia") {
 			// polyglossia requirement has priority over babel
 			if (polyglossia_required)
 				return LANG_PACK_POLYGLOSSIA;
diff --git a/src/LaTeXFeatures.h b/src/LaTeXFeatures.h
index acbfaba62c..ccba1cdfae 100644
--- a/src/LaTeXFeatures.h
+++ b/src/LaTeXFeatures.h
@@ -182,14 +182,16 @@ public:
 	void setBuffer(Buffer const &);
 	///
 	BufferParams const & bufferParams() const;
+	///
+	bool usePrefTULangPack() const;
 	/** Which language package do we require? \p englishbabel determines
 	 *  if we require babel even if English is the only language.
 	 */
-	LangPackage langPackage() const;
+	LangPackage langPackage(bool const ignore_prefs = false) const;
 	/// Convenience function to test if we use babel
-	bool useBabel() const { return langPackage() == LANG_PACK_BABEL; }
+	bool useBabel(bool const ignore_prefs = false) const { return langPackage(ignore_prefs) == LANG_PACK_BABEL; }
 	/// Convenience function to test if we use polyglossia
-	bool usePolyglossia() const { return langPackage() == LANG_PACK_POLYGLOSSIA; }
+	bool usePolyglossia(bool const ignore_prefs = false) const { return langPackage(ignore_prefs) == LANG_PACK_POLYGLOSSIA; }
 	/// are we in a float?
 	bool inFloat() const { return in_float_; }
 	/// are we in a float?
diff --git a/src/Language.cpp b/src/Language.cpp
index 718031218b..748ddd92b0 100644
--- a/src/Language.cpp
+++ b/src/Language.cpp
@@ -157,6 +157,7 @@ bool Language::readLanguage(Lexer & lex)
 		LA_LANG_VARIETY,
 		LA_POLYGLOSSIANAME,
 		LA_POLYGLOSSIAOPTS,
+		LA_PREFERTULANGPACK,
 		LA_XINDYNAME,
 		LA_POSTBABELPREAMBLE,
 		LA_PREBABELPREAMBLE,
@@ -195,6 +196,7 @@ bool Language::readLanguage(Lexer & lex)
 		{ "polyglossiaopts",      LA_POLYGLOSSIAOPTS },
 		{ "postbabelpreamble",    LA_POSTBABELPREAMBLE },
 		{ "prebabelpreamble",     LA_PREBABELPREAMBLE },
+		{ "prefertulangpack",     LA_PREFERTULANGPACK },
 		{ "provides",             LA_PROVIDES },
 		{ "quotestyle",           LA_QUOTESTYLE },
 		{ "requires",             LA_REQUIRES },
@@ -246,6 +248,9 @@ bool Language::readLanguage(Lexer & lex)
 		case LA_POLYGLOSSIAOPTS:
 			lex >> polyglossia_opts_;
 			break;
+		case LA_PREFERTULANGPACK:
+			lex >> prefer_TU_lang_pack_;
+			break;
 		case LA_XINDYNAME:
 			lex >> xindy_;
 			break;
diff --git a/src/Language.h b/src/Language.h
index 80f56198db..2e1ac3a235 100644
--- a/src/Language.h
+++ b/src/Language.h
@@ -59,6 +59,8 @@ public:
 	/// polyglossia language options
 	std::string const polyglossiaOpts() const { return polyglossia_opts_; }
 	/// polyglossia language options
+	std::string const preferTULangPack() const { return prefer_TU_lang_pack_; }
+	/// polyglossia language options
 	std::string const xindy() const { return xindy_; }
 	/// Is this language only supported by polyglossia?
 	bool isPolyglossiaExclusive() const;
@@ -149,6 +151,8 @@ private:
 	///
 	trivstring polyglossia_opts_;
 	///
+	trivstring prefer_TU_lang_pack_;
+	///
 	trivstring xindy_;
 	///
 	trivstring quote_style_;
diff --git a/src/frontends/qt/GuiDocument.cpp b/src/frontends/qt/GuiDocument.cpp
index c4dcc782e2..ea19171bf3 100644
--- a/src/frontends/qt/GuiDocument.cpp
+++ b/src/frontends/qt/GuiDocument.cpp
@@ -1107,6 +1107,8 @@ GuiDocument::GuiDocument(GuiView & lv)
 		qt_("Automatic"), toqstr("auto"));
 	langModule->languagePackageCO->addItem(
 		qt_("Always Babel"), toqstr("babel"));
+	langModule->languagePackageCO->addItem(
+		qt_("Polyglossia if Possible"), toqstr("polyglossia"));
 	langModule->languagePackageCO->addItem(
 		qt_("Custom"), toqstr("custom"));
 	langModule->languagePackageCO->addItem(
@@ -4352,7 +4354,7 @@ void GuiDocument::paramsToDialog()
 	if (extern_babel)
 		p = langModule->languagePackageCO->findData(toqstr("babel"));
 	else if (extern_polyglossia)
-		p = langModule->languagePackageCO->findData(toqstr("auto"));
+		p = langModule->languagePackageCO->findData(toqstr("polyglossia"));
 	else
 		p = langModule->languagePackageCO->findData(toqstr(bp_.lang_package));
 
diff --git a/src/frontends/qt/GuiPrefs.cpp b/src/frontends/qt/GuiPrefs.cpp
index f3dbcb827e..1290556215 100644
--- a/src/frontends/qt/GuiPrefs.cpp
+++ b/src/frontends/qt/GuiPrefs.cpp
@@ -3274,6 +3274,8 @@ PrefLanguage::PrefLanguage(GuiPreferences * form)
 		qt_("Automatic"), toqstr("auto"));
 	languagePackageCO->addItem(
 		qt_("Always Babel"), toqstr("babel"));
+	languagePackageCO->addItem(
+		qt_("Polyglossia if Possible"), toqstr("polyglossia"));
 	languagePackageCO->addItem(
 		qt_("Custom"), toqstr("custom"));
 	languagePackageCO->addItem(
diff --git a/src/version.h b/src/version.h
index a97dda20e0..1c0ba33986 100644
--- a/src/version.h
+++ b/src/version.h
@@ -32,8 +32,8 @@ extern char const * const lyx_version_info;
 
 // Do not remove the comment below, so we get merge conflict in
 // independent branches. Instead add your own.
-#define LYX_FORMAT_LYX 649 // spitz: more shorthands
-#define LYX_FORMAT_TEX2LYX 649
+#define LYX_FORMAT_LYX 650 // spitz: language package polyglossia
+#define LYX_FORMAT_TEX2LYX 650
 
 #if LYX_FORMAT_TEX2LYX != LYX_FORMAT_LYX
 #ifndef _MSC_VER