Version changing removes any existing version json.

gui/MCModInfoFrame.ui

@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>527</width>
-    <height>68</height>
+    <height>113</height>
    </rect>
   </property>
   <property name="sizePolicy">
@@ -28,12 +28,6 @@
   <layout class="QVBoxLayout" name="verticalLayout_2">
    <item>
     <widget class="QLabel" name="label_ModText">
-     <property name="sizePolicy">
-      <sizepolicy hsizetype="Expanding" vsizetype="Minimum">
-       <horstretch>0</horstretch>
-       <verstretch>0</verstretch>
-      </sizepolicy>
-     </property>
      <property name="text">
       <string>Select a mod to view title and authors...</string>
      </property>
@@ -53,12 +47,6 @@
    </item>
    <item>
     <widget class="QLabel" name="label_ModDescription">
-     <property name="sizePolicy">
-      <sizepolicy hsizetype="Preferred" vsizetype="Minimum">
-       <horstretch>0</horstretch>
-       <verstretch>0</verstretch>
-      </sizepolicy>
-     </property>
      <property name="text">
       <string>Select a mod to view description...</string>
      </property>

gui/mainwindow.cpp

@@ -606,6 +606,15 @@ void MainWindow::on_actionChangeInstMCVersion_triggered()
 	vselect.setFilter(1, "OneSix");
 	if (vselect.exec() && vselect.selectedVersion())
 	{
+		if (m_selectedInstance->versionIsCustom())
+		{
+			auto result = QMessageBox::warning(
+				this, tr("Are you sure?"),
+				tr("This will remove any library/version customization you did previously. "
+				   "This includes things like Forge install and similar."), QMessageBox::Ok, QMessageBox::Abort);
+			if(result != QMessageBox::Ok)
+				return;
+		}
 		m_selectedInstance->setIntendedVersionId(vselect.selectedVersion()->descriptor());
 	}
 }

logic/BaseInstance.h

@@ -44,15 +44,19 @@ class BaseInstance : public QObject
 	Q_OBJECT
 protected:
 	/// no-touchy!
-	BaseInstance(BaseInstancePrivate * d, const QString &rootDir, SettingsObject * settings, QObject *parent = 0);
+	BaseInstance(BaseInstancePrivate *d, const QString &rootDir, SettingsObject *settings,
+				 QObject *parent = 0);
+
 public:
 	/// virtual destructor to make sure the destruction is COMPLETE
 	virtual ~BaseInstance() {};
 
-	/// nuke thoroughly - deletes the instance contents, notifies the list/model which is responsible of cleaning up the husk
+	/// nuke thoroughly - deletes the instance contents, notifies the list/model which is
+	/// responsible of cleaning up the husk
 	void nuke();
 
-	/// The instance's ID. The ID SHALL be determined by MMC internally. The ID IS guaranteed to be unique.
+	/// The instance's ID. The ID SHALL be determined by MMC internally. The ID IS guaranteed to
+	/// be unique.
 	QString id() const;
 
 	/// get the type of this instance
@@ -77,10 +81,11 @@ public:
 	void setGroupInitial(QString val);
 	void setGroupPost(QString val);
 
-	
 	virtual QString intendedVersionId() const = 0;
 	virtual bool setIntendedVersionId(QString version) = 0;
 
+	virtual bool versionIsCustom() = 0;
+
 	/*!
 	 * The instance's current version.
 	 * This value represents the instance's current version. If this value is
@@ -96,7 +101,8 @@ public:
 	virtual bool shouldUpdate() const = 0;
 	virtual void setShouldUpdate(bool val) = 0;
 
-	/// Get the curent base jar of this instance. By default, it's the versions/$version/$version.jar
+	/// Get the curent base jar of this instance. By default, it's the
+	/// versions/$version/$version.jar
 	QString baseJar() const;
 
 	/// the default base jar of this instance
@@ -150,7 +156,8 @@ public:
 	/// returns a valid minecraft process, ready for launch
 	virtual MinecraftProcess *prepareForLaunch(LoginResponse response) = 0;
 
-	/// do any necessary cleanups after the instance finishes. also runs before 'prepareForLaunch'
+	/// do any necessary cleanups after the instance finishes. also runs before
+	/// 'prepareForLaunch'
 	virtual void cleanupAfterRun() = 0;
 
 	/// create a mod edit dialog for the instance
@@ -184,4 +191,3 @@ protected:
 
 // pointer for lazy people
 typedef std::shared_ptr<BaseInstance> InstancePtr;
-

logic/LegacyInstance.h

@@ -10,7 +10,8 @@ class LegacyInstance : public BaseInstance
 	Q_OBJECT
 public:
 
-	explicit LegacyInstance(const QString &rootDir, SettingsObject * settings, QObject *parent = 0);
+	explicit LegacyInstance(const QString &rootDir, SettingsObject *settings,
+							QObject *parent = 0);
 
 	/// Path to the instance's minecraft.jar
 	QString runnableJar() const;
@@ -52,6 +53,12 @@ public:
 
 	virtual QString intendedVersionId() const;
 	virtual bool setIntendedVersionId(QString version);
+	// the `version' of Legacy instances is defined by the launcher code.
+	// in contrast with OneSix, where `version' is described in a json file
+	virtual bool versionIsCustom() override
+	{
+		return false;
+	};
 
 	virtual bool shouldUpdate() const;
 	virtual void setShouldUpdate(bool val);
@@ -67,6 +74,7 @@ public:
 	bool menuActionEnabled(QString action_name) const;
 	virtual QString getStatusbarDescription();
 
-protected slots:
+protected
+slots:
 	virtual void jarModsChanged();
 };

logic/LegacyUpdate.cpp

@@ -57,7 +57,7 @@ void LegacyUpdate::lwjglStart()
 	auto worker = MMC->qnam();
 	QNetworkRequest req(realUrl);
 	req.setRawHeader("Host", hostname.toLatin1());
-	req.setHeader(QNetworkRequest::UserAgentHeader, "Wget/1.14 (linux-gnu)");
+	req.setHeader(QNetworkRequest::UserAgentHeader, "MultiMC/5.0 (Cached)");
 	QNetworkReply *rep = worker->get(req);
 
 	m_reply = std::shared_ptr<QNetworkReply>(rep);
@@ -100,7 +100,7 @@ void LegacyUpdate::lwjglFinished(QNetworkReply *reply)
 		QString hostname = realUrl.host();
 		QNetworkRequest req(redirectedTo);
 		req.setRawHeader("Host", hostname.toLatin1());
-		req.setHeader(QNetworkRequest::UserAgentHeader, "Wget/1.14 (linux-gnu)");
+		req.setHeader(QNetworkRequest::UserAgentHeader, "MultiMC/5.0 (Cached)");
 		QNetworkReply *rep = worker->get(req);
 		connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
 				SIGNAL(progress(qint64, qint64)));

logic/OneSixInstance.cpp

@@ -192,6 +192,11 @@ bool OneSixInstance::setIntendedVersionId(QString version)
 {
 	settings().set("IntendedVersion", version);
 	setShouldUpdate(true);
+	auto pathCustom = PathCombine(instanceRoot(), "custom.json");
+	auto pathOrig = PathCombine(instanceRoot(), "version.json");
+	QFile::remove(pathCustom);
+	QFile::remove(pathOrig);
+	reloadFullVersion();
 	return true;
 }
 
@@ -271,8 +276,12 @@ bool OneSixInstance::reloadFullVersion()
 		d->version = version;
 		return true;
 	}
+	else
+	{
+		d->version.reset();
 		return false;
 	}
+}
 
 std::shared_ptr<OneSixVersion> OneSixInstance::getFullVersion()
 {

logic/OneSixInstance.h

@@ -10,8 +10,8 @@ class OneSixInstance : public BaseInstance
 {
 	Q_OBJECT
 public:
-	explicit OneSixInstance(const QString &rootDir, SettingsObject * settings, QObject *parent = 0);
+	explicit OneSixInstance(const QString &rootDir, SettingsObject *settings,
-	
+							QObject *parent = 0);
 
 	//////  Mod Lists  //////
 	std::shared_ptr<ModList> loaderModList();
@@ -46,13 +46,14 @@ public:
 	/// customize the current base version
 	bool customizeVersion();
 	/// is the current version original, or custom?
-	bool versionIsCustom();
+	virtual bool versionIsCustom() override;
 
 	virtual QString defaultBaseJar() const;
 	virtual QString defaultCustomBaseJar() const;
 
 	virtual bool menuActionEnabled(QString action_name) const;
 	virtual QString getStatusbarDescription();
+
 private:
 	QStringList processMinecraftArgs(LoginResponse response);
 };