Attempted to fix priority metadata handling.

Now if it is not implied to be zero, it should be saved and applied like
non-zero values.

src/backend/generators.h

@@ -736,7 +736,7 @@ namespace YAML {
             out << BeginMap
                 << Key << "name" << Value << rhs.Name();
 
-            if (rhs.Priority() != 0)
+            if (rhs.IsPriorityExplicit())
                 out << Key << "priority" << Value << rhs.Priority();
 
             if (!rhs.Enabled())

src/backend/metadata.cpp

@@ -295,15 +295,15 @@ namespace boss {
         return _name;
     }
 
-    Plugin::Plugin() : enabled(true), priority(0), isMaster(false), crc(0), numOverrideRecords(0) {}
-    Plugin::Plugin(const std::string& n) : name(n), enabled(true), priority(0), isMaster(false), crc(0), numOverrideRecords(0) {
+    Plugin::Plugin() : enabled(true), priority(0), isMaster(false), crc(0), numOverrideRecords(0), _isPriorityExplicit(false) {}
+    Plugin::Plugin(const std::string& n) : name(n), enabled(true), priority(0), isMaster(false), crc(0), numOverrideRecords(0), _isPriorityExplicit(false) {
         //If the name passed ends in '.ghost', that should be trimmed.
         if (boost::iends_with(name, ".ghost"))
             name = name.substr(0, name.length() - 6);
     }
 
 	Plugin::Plugin(boss::Game& game, const std::string& n, const bool headerOnly)
-        : name(n), enabled(true), priority(0), isMaster(false), crc(0), numOverrideRecords(0) {
+        : name(n), enabled(true), priority(0), isMaster(false), crc(0), numOverrideRecords(0), _isPriorityExplicit(false) {
 
 		// Get data from file contents using libespm. Assumes libespm has already been initialised.
         BOOST_LOG_TRIVIAL(trace) << name << ": " << "Opening with libespm...";
@@ -403,10 +403,12 @@ namespace boss {
     void Plugin::MergeMetadata(const Plugin& plugin) {
         BOOST_LOG_TRIVIAL(trace) << "Merging metadata for: " << name;
 
-        //For 'enabled' and 'priority' metadata, use the given plugin's values, but if the 'priority' user value is zero, ignore it.
+        //For 'enabled' and 'priority' metadata, use the given plugin's values, but if the 'priority' user value is not explicit, ignore it.
         enabled = plugin.Enabled();
-        if (plugin.Priority() != 0)
+        if (plugin.IsPriorityExplicit()) {
             priority = plugin.Priority();
+            _isPriorityExplicit = true;
+        }
 
         //Merge the following. If any files in the source already exist in the destination, they will be skipped. Files have display strings and condition strings which aren't considered when comparing them, so will be lost if the plugin being merged in has additional data in these strings.
         std::set<File> files = plugin.LoadAfter();
@@ -437,10 +439,15 @@ namespace boss {
         Plugin p(*this);
 
         p.Enabled(plugin.Enabled());
-        if (priority != plugin.Priority())
+        if (priority != plugin.Priority()) {
             p.Priority(plugin.Priority());
-        else
+            p.SetPriorityExplicit(plugin.IsPriorityExplicit());
+        }
+        else {
             p.Priority(0);
+            p.SetPriorityExplicit(false);
+        }
+            
 
         //Compare this plugin against the given plugin.
         set<File> files = plugin.LoadAfter();
@@ -523,6 +530,10 @@ namespace boss {
         enabled = e;
     }
 
+    void Plugin::SetPriorityExplicit(bool state) {
+        _isPriorityExplicit = state;
+    }
+
     void Plugin::Priority(const int p) {
         priority = p;
     }
@@ -610,13 +621,17 @@ namespace boss {
     }
 
     bool Plugin::HasNameOnly() const {
-        return priority == 0 && enabled == true && loadAfter.empty() && requirements.empty() && incompatibilities.empty() && messages.empty() && tags.empty() && _dirtyInfo.empty();
+        return !IsPriorityExplicit() && enabled == true && loadAfter.empty() && requirements.empty() && incompatibilities.empty() && messages.empty() && tags.empty() && _dirtyInfo.empty();
     }
 
     bool Plugin::IsRegexPlugin() const {
         return boost::iends_with(name, "\\.esm") || boost::iends_with(name, "\\.esp");
     }
 
+    bool Plugin::IsPriorityExplicit() const {
+        return priority != 0 || _isPriorityExplicit;
+    }
+
     bool Plugin::operator == (const Plugin& rhs) const {
         return (boost::iequals(name, rhs.Name())
             || (IsRegexPlugin() && boost::regex_match(rhs.Name(), boost::regex(name, boost::regex::perl|boost::regex::icase)))

src/backend/metadata.h

@@ -185,6 +185,7 @@ namespace boss {
 
         void Name(const std::string& name);
         void Enabled(const bool enabled);
+        void SetPriorityExplicit(bool state);
         void Priority(const int priority);
         void LoadAfter(const std::set<File>& after);
         void Reqs(const std::set<File>& reqs);
@@ -197,6 +198,7 @@ namespace boss {
         bool HasNameOnly() const;
         bool IsRegexPlugin() const;
         bool LoadsBSA(const Game& game) const;
+        bool IsPriorityExplicit() const;
 
         //Compare name strings.
         bool operator == (const Plugin& rhs) const;
@@ -214,6 +216,7 @@ namespace boss {
     private:
         std::string name;
         bool enabled;  //Default to true.
+        bool _isPriorityExplicit;  //If false and priority is 0, then priority was not explicitly set as such.
         int priority;  //Default to 0 : >0 is lower down in load order, <0 is higher up.
         std::set<File> loadAfter;
         std::set<File> requirements;

src/backend/parsers.h

@@ -339,8 +339,10 @@ namespace YAML {
             if (node["enabled"])
                 rhs.Enabled(node["enabled"].as<bool>());
 
-            if (node["priority"])
+            if (node["priority"]) {
                 rhs.Priority(node["priority"].as<int>());
+                rhs.SetPriorityExplicit(true);
+            }
 
             if (node["after"])
                 rhs.LoadAfter(node["after"].as< std::set<boss::File> >());