Remove a lot of error code and error handling madness.

5 files changed, 196 insertions, 309 deletions

diff --git a/logic/MMCJson.cpp b/logic/MMCJson.cpp
new file mode 100644
index 00000000..14cde0c1
--- /dev/null
+++ b/logic/MMCJson.cpp
@@ -0,0 +1,53 @@
+#include "MMCJson.h"
+#include <QString>
+
+bool MMCJson::ensureBoolean(const QJsonValue val, const QString what)
+{
+	if (!val.isBool())
+		throw JSONValidationError(what + " is not boolean");
+	return val.isBool();
+}
+
+QJsonValue MMCJson::ensureExists(QJsonValue val, const QString what)
+{
+	if(val.isNull())
+		throw JSONValidationError(what + " does not exist");
+	return val;
+}
+
+QJsonArray MMCJson::ensureArray(const QJsonValue val, const QString what)
+{
+	if (!val.isArray())
+		throw JSONValidationError(what + " is not an array");
+	return val.toArray();
+}
+
+double MMCJson::ensureDouble(const QJsonValue val, const QString what)
+{
+	if (!val.isDouble())
+		throw JSONValidationError(what + " is not a number");
+	double ret = val.toDouble();
+}
+
+int MMCJson::ensureInteger(const QJsonValue val, const QString what)
+{
+	double ret = ensureDouble(val, what);
+	if (fmod(ret, 1) != 0)
+		throw JSONValidationError(what + " is not an integer");
+	return ret;
+}
+
+QJsonObject MMCJson::ensureObject(const QJsonValue val, const QString what)
+{
+	if (!val.isObject())
+		throw JSONValidationError(what + " is not an object");
+	return val.toObject();
+}
+
+QString MMCJson::ensureString(const QJsonValue val, const QString what)
+{
+	if (!val.isString())
+		throw JSONValidationError(what + " is not a string");
+	return val.toString();
+}
+
diff --git a/logic/MMCJson.h b/logic/MMCJson.h
new file mode 100644
index 00000000..3e7342b5
--- /dev/null
+++ b/logic/MMCJson.h
@@ -0,0 +1,46 @@
+/**
+ * Some de-bullshitting for Qt JSON failures.
+ *
+ * Simple exception-throwing
+ */
+
+#pragma once
+#include <QJsonValue>
+#include <QJsonObject>
+#include <QJsonArray>
+#include "MMCError.h"
+
+class JSONValidationError : public MMCError
+{
+public:
+	JSONValidationError(QString cause) : MMCError(cause) {};
+	virtual QString errorName()
+	{
+		return "JSONValidationError";
+	};
+	virtual ~JSONValidationError() {};
+};
+
+namespace MMCJson
+{
+/// make sure the value exists. throw otherwise.
+QJsonValue ensureExists(QJsonValue val, const QString what = "value");
+
+/// make sure the value is converted into an object. throw otherwise.
+QJsonObject ensureObject(const QJsonValue val, const QString what = "value");
+
+/// make sure the value is converted into an array. throw otherwise.
+QJsonArray ensureArray(const QJsonValue val, QString what = "value");
+
+/// make sure the value is converted into a string. throw otherwise.
+QString ensureString(const QJsonValue val, QString what = "value");
+
+/// make sure the value is converted into a boolean. throw otherwise.
+bool ensureBoolean(const QJsonValue val, QString what = "value");
+
+/// make sure the value is converted into an integer. throw otherwise.
+int ensureInteger(const QJsonValue val, QString what = "value");
+
+/// make sure the value is converted into a double precision floating number. throw otherwise.
+double ensureDouble(const QJsonValue val, QString what = "value");
+}
diff --git a/logic/OneSixVersionBuilder.cpp b/logic/OneSixVersionBuilder.cpp
index 98e4b54e..752f2d8f 100644
--- a/logic/OneSixVersionBuilder.cpp
+++ b/logic/OneSixVersionBuilder.cpp
@@ -73,10 +73,7 @@ bool OneSixVersionBuilder::buildInternal(const bool onlyVanilla, const QStringLi
 		file.fileId = "org.multimc.external." + file.name;
 		file.version = QString();
 		file.mcVersion = QString();
-		bool isError = false;
-		auto errorcode = file.applyTo(m_version);
-		if(errorcode != VersionFile::NoApplyError)
-			return false;
+		file.applyTo(m_version);
 	}
 	// else, if there's custom json, we just do that.
 	else if (QFile::exists(root.absoluteFilePath("custom.json")))
@@ -91,9 +88,7 @@ bool OneSixVersionBuilder::buildInternal(const bool onlyVanilla, const QStringLi
 		file.filename = "custom.json";
 		file.fileId = "org.multimc.custom.json";
 		file.version = QString();
-		auto errorcode = file.applyTo(m_version);
-		if(errorcode != VersionFile::NoApplyError)
-			return false;
+		file.applyTo(m_version);
 		// QObject::tr("The version descriptors of this instance are not compatible with the current version of MultiMC"));
 		// QObject::tr("Error while applying %1. Please check MultiMC-0.log for more info.")
 	}
@@ -111,18 +106,8 @@ bool OneSixVersionBuilder::buildInternal(const bool onlyVanilla, const QStringLi
 		file.fileId = "org.multimc.version.json";
 		file.version = m_instance->intendedVersionId();
 		file.mcVersion = m_instance->intendedVersionId();
-		auto error = file.applyTo(m_version);
-		if (error != VersionFile::NoApplyError)
-		{
-			/*
-			QMessageBox::critical(
-						m_widgetParent, QObject::tr("Error"),
-						QObject::tr(
-							"Error while applying %1. Please check MultiMC-0.log for more info.")
-						.arg(root.absoluteFilePath("version.json")));
-						*/
-			return false;
-		}
+		file.applyTo(m_version);
+		// QObject::tr("Error while applying %1. Please check MultiMC-0.log for more info.").arg(root.absoluteFilePath("version.json")));
 
 		if (onlyVanilla)
 			break;
@@ -155,17 +140,8 @@ bool OneSixVersionBuilder::buildInternal(const bool onlyVanilla, const QStringLi
 		{
 			QLOG_DEBUG() << "Applying file with order" << order;
 			auto filePair = files[order];
-			auto error = filePair.second.applyTo(m_version);
-			if (error != VersionFile::NoApplyError)
-			{
-				/*
-				QMessageBox::critical(
-							m_widgetParent, QObject::tr("Error"),
-							QObject::tr("Error while applying %1. Please check MultiMC-0.log "
-										"for more info.").arg(filePair.first));
-										*/
-				return false;
-			}
+			filePair.second.applyTo(m_version);
+			// QObject::tr("Error while applying %1. Please check MultiMC-0.log for more info.").arg(filePair.first));
 		}
 	} while(0);
 
@@ -203,37 +179,12 @@ bool OneSixVersionBuilder::readJsonAndApply(const QJsonObject &obj)
 {
 	m_version->clear();
 
-	bool isError = false;
-	VersionFile file = VersionFile::fromJson(QJsonDocument(obj), QString(), false, isError);
-	if (isError)
-	{
-		/*
-		QMessageBox::critical(
-			m_widgetParent, QObject::tr("Error"),
-			QObject::tr("Error while reading. Please check MultiMC-0.log for more info."));
-			*/
-		return false;
-	}
-	VersionFile::ApplyError error = file.applyTo(m_version);
-	if (error == VersionFile::OtherError)
-	{
-		/*
-		QMessageBox::critical(
-			m_widgetParent, QObject::tr("Error"),
-			QObject::tr("Error while applying. Please check MultiMC-0.log for more info."));
-			*/
-		return false;
-	}
-	else if (error == VersionFile::LauncherVersionError)
-	{
-		/*
-		QMessageBox::critical(
-					m_widgetParent, QObject::tr("Error"),
-					QObject::tr("The version descriptors of this instance are not compatible with the current version of MultiMC"));
-					*/
-		return false;
-	}
+	VersionFile file = VersionFile::fromJson(QJsonDocument(obj), QString(), false);
+	// QObject::tr("Error while reading. Please check MultiMC-0.log for more info."));
 
+	file.applyTo(m_version);
+	// QObject::tr("Error while applying. Please check MultiMC-0.log for more info."));
+	// QObject::tr("The version descriptors of this instance are not compatible with the current version of MultiMC"));
 	return true;
 }
 
@@ -242,11 +193,7 @@ bool OneSixVersionBuilder::parseJsonFile(const QFileInfo& fileInfo, const bool r
 	QFile file(fileInfo.absoluteFilePath());
 	if (!file.open(QFile::ReadOnly))
 	{
-		/*
-		QMessageBox::critical(
-			m_widgetParent, QObject::tr("Error"),
-			QObject::tr("Unable to open %1: %2").arg(file.fileName(), file.errorString()));
-			*/
+		// QObject::tr("Unable to open %1: %2").arg(file.fileName(), file.errorString());
 		return false;
 	}
 	QJsonParseError error;
@@ -261,17 +208,8 @@ bool OneSixVersionBuilder::parseJsonFile(const QFileInfo& fileInfo, const bool r
 								  */
 		return false;
 	}
-	bool isError = false;
-	*out = VersionFile::fromJson(doc, file.fileName(), requireOrder, isError, isFTB);
-	if (isError)
-	{
-		/*
-		QMessageBox::critical(
-			m_widgetParent, QObject::tr("Error"),
-			QObject::tr("Error while reading %1. Please check MultiMC-0.log for more info.")
-				.arg(file.fileName()));
-				*/
-	}
+	*out = VersionFile::fromJson(doc, file.fileName(), requireOrder, isFTB);
+	// QObject::tr("Error while reading %1. Please check MultiMC-0.log for more info.").arg(file.fileName());
 	return true;
 }
 
diff --git a/logic/VersionFile.cpp b/logic/VersionFile.cpp
index 76cf9279..4423e733 100644
--- a/logic/VersionFile.cpp
+++ b/logic/VersionFile.cpp
@@ -7,19 +7,20 @@
 #include "logic/VersionFile.h"
 #include "logic/OneSixLibrary.h"
 #include "logic/VersionFinal.h"
+#include "MMCJson.h"
 
+using namespace MMCJson;
 
 #define CURRENT_MINIMUM_LAUNCHER_VERSION 14
 
 VersionFile::Library VersionFile::Library::fromJson(const QJsonObject &libObj,
-													const QString &filename, bool &isError)
+													const QString &filename)
 {
-	isError = true;
 	Library out;
 	if (!libObj.contains("name"))
 	{
-		QLOG_ERROR() << filename << "contains a library that doesn't have a 'name' field";
-		return out;
+		throw JSONValidationError(filename +
+								  "contains a library that doesn't have a 'name' field");
 	}
 	out.name = libObj.value("name").toString();
 
@@ -45,44 +46,17 @@ VersionFile::Library VersionFile::Library::fromJson(const QJsonObject &libObj,
 	readString("MMC-absoluteUrl", out.absoluteUrl);
 	if (libObj.contains("extract"))
 	{
-		if (!libObj.value("extract").isObject())
-		{
-			QLOG_ERROR() << filename
-						 << "contains a library with an 'extract' field that's not an object";
-			return out;
-		}
-		QJsonObject extractObj = libObj.value("extract").toObject();
-		if (!extractObj.contains("exclude") || !extractObj.value("exclude").isArray())
-		{
-			QLOG_ERROR() << filename << "contains a library with an invalid 'extract' field";
-			return out;
-		}
 		out.applyExcludes = true;
-		QJsonArray excludeArray = extractObj.value("exclude").toArray();
-		for (auto excludeVal : excludeArray)
+		auto extractObj = ensureObject(libObj.value("extract"));
+		for (auto excludeVal : ensureArray(extractObj.value("exclude")))
 		{
-			if (!excludeVal.isString())
-			{
-				QLOG_WARN() << filename << "contains a library that contains an 'extract' "
-										   "field that contains an invalid 'exclude' entry "
-										   "(skipping)";
-			}
-			else
-			{
-				out.excludes.append(excludeVal.toString());
-			}
+			out.excludes.append(ensureString(excludeVal));
 		}
 	}
 	if (libObj.contains("natives"))
 	{
-		if (!libObj.value("natives").isObject())
-		{
-			QLOG_ERROR() << filename
-						 << "contains a library with a 'natives' field that's not an object";
-			return out;
-		}
 		out.applyNatives = true;
-		QJsonObject nativesObj = libObj.value("natives").toObject();
+		QJsonObject nativesObj = ensureObject(libObj.value("natives"));
 		for (auto it = nativesObj.begin(); it != nativesObj.end(); ++it)
 		{
 			if (!it.value().isString())
@@ -101,24 +75,19 @@ VersionFile::Library VersionFile::Library::fromJson(const QJsonObject &libObj,
 		out.applyRules = true;
 		out.rules = rulesFromJsonV4(libObj);
 	}
-	isError = false;
 	return out;
 }
 
-VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filename,
-								  const bool requireOrder, bool &isError, const bool isFTB)
+VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filename, const bool requireOrder, const bool isFTB)
 {
 	VersionFile out;
-	isError = true;
 	if (doc.isEmpty() || doc.isNull())
 	{
-		QLOG_ERROR() << filename << "is empty or null";
-		return out;
+		throw JSONValidationError(filename + " is empty or null");
 	}
 	if (!doc.isObject())
 	{
-		QLOG_ERROR() << "The root of" << filename << "is not an object";
-		return out;
+		throw JSONValidationError("The root of " + filename + " is not an object");
 	}
 
 	QJsonObject root = doc.object();
@@ -127,18 +96,11 @@ VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filen
 	{
 		if (root.contains("order"))
 		{
-			if (root.value("order").isDouble())
-			{
-				out.order = root.value("order").toDouble();
-			}
-			else
-			{
-				QLOG_ERROR() << "'order' field contains an invalid value in" << filename;
-				return out;
-			}
+			out.order = ensureInteger(root.value("order"));
 		}
 		else
 		{
+			// FIXME: evaluate if we don't want to throw exceptions here instead
 			QLOG_ERROR() << filename << "doesn't contain an order field";
 		}
 	}
@@ -153,19 +115,11 @@ VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filen
 	{
 		if (root.contains(key))
 		{
-			QJsonValue val = root.value(key);
-			if (!val.isString())
-			{
-				QLOG_WARN() << key << "is not a string in" << filename << "(skipping)";
-			}
-			else
-			{
-				variable = val.toString();
-			}
+			variable = ensureString(root.value(key));
 		}
 	};
 
-	// FTB id attribute is completely bogus. We ignore it.
+	// FIXME: This should be ignored when applying.
 	if (!isFTB)
 	{
 		readString("id", out.id);
@@ -180,108 +134,47 @@ VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filen
 	readString("releaseTime", out.releaseTime);
 	readString("time", out.time);
 	readString("assets", out.assets);
+
 	if (root.contains("minimumLauncherVersion"))
 	{
-		QJsonValue val = root.value("minimumLauncherVersion");
-		if (!val.isDouble())
-		{
-			QLOG_WARN() << "minimumLauncherVersion is not an int in" << filename
-						<< "(skipping)";
-		}
-		else
-		{
-			out.minimumLauncherVersion = val.toDouble();
-		}
+		out.minimumLauncherVersion = ensureInteger(root.value("minimumLauncherVersion"));
 	}
 
 	if (root.contains("tweakers"))
 	{
-		QJsonValue tweakersVal = root.value("tweakers");
-		if (!tweakersVal.isArray())
-		{
-			QLOG_ERROR() << filename << "contains a 'tweakers' field, but it's not an array";
-			return out;
-		}
 		out.shouldOverwriteTweakers = true;
-		QJsonArray tweakers = root.value("tweakers").toArray();
-		for (auto tweakerVal : tweakers)
+		for (auto tweakerVal : ensureArray(root.value("tweakers")))
 		{
-			if (!tweakerVal.isString())
-			{
-				QLOG_ERROR() << filename
-							 << "contains a 'tweakers' field entry that's not a string";
-				return out;
-			}
-			out.overwriteTweakers.append(tweakerVal.toString());
+			out.overwriteTweakers.append(ensureString(tweakerVal));
 		}
 	}
+
 	if (root.contains("+tweakers"))
 	{
-		QJsonValue tweakersVal = root.value("+tweakers");
-		if (!tweakersVal.isArray())
-		{
-			QLOG_ERROR() << filename << "contains a '+tweakers' field, but it's not an array";
-			return out;
-		}
-		QJsonArray tweakers = root.value("+tweakers").toArray();
-		for (auto tweakerVal : tweakers)
+		for (auto tweakerVal : ensureArray(root.value("+tweakers")))
 		{
-			if (!tweakerVal.isString())
-			{
-				QLOG_ERROR() << filename
-							 << "contains a '+tweakers' field entry that's not a string";
-				return out;
-			}
-			out.addTweakers.append(tweakerVal.toString());
+			out.addTweakers.append(ensureString(tweakerVal));
 		}
 	}
+
 	if (root.contains("-tweakers"))
 	{
-		QJsonValue tweakersVal = root.value("-tweakers");
-		if (!tweakersVal.isArray())
-		{
-			QLOG_ERROR() << filename << "contains a '-tweakers' field, but it's not an array";
-			return out;
-		}
-		out.shouldOverwriteTweakers = true;
-		QJsonArray tweakers = root.value("-tweakers").toArray();
-		for (auto tweakerVal : tweakers)
+		for (auto tweakerVal : ensureArray(root.value("-tweakers")))
 		{
-			if (!tweakerVal.isString())
-			{
-				QLOG_ERROR() << filename
-							 << "contains a '-tweakers' field entry that's not a string";
-				return out;
-			}
-			out.removeTweakers.append(tweakerVal.toString());
+			out.removeTweakers.append(ensureString(tweakerVal));
 		}
 	}
 
 	if (root.contains("libraries"))
 	{
+		// FIXME: This should be done when applying.
 		out.shouldOverwriteLibs = !isFTB;
-		QJsonValue librariesVal = root.value("libraries");
-		if (!librariesVal.isArray())
-		{
-			QLOG_ERROR() << filename << "contains a 'libraries' field, but its not an array";
-			return out;
-		}
-		QJsonArray librariesArray = librariesVal.toArray();
-		for (auto libVal : librariesArray)
+		for (auto libVal : ensureArray(root.value("libraries")))
 		{
-			if (!libVal.isObject())
-			{
-				QLOG_ERROR() << filename << "contains a library that's not an object";
-				return out;
-			}
-			QJsonObject libObj = libVal.toObject();
-			bool error;
-			Library lib = Library::fromJson(libObj, filename, error);
-			if (error)
-			{
-				QLOG_ERROR() << "Error while reading a library entry in" << filename;
-				return out;
-			}
+			auto libObj = ensureObject(libVal);
+
+			Library lib = Library::fromJson(libObj, filename);
+			// FIXME: This should be done when applying.
 			if (isFTB)
 			{
 				lib.hint = "local";
@@ -294,36 +187,18 @@ VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filen
 			}
 		}
 	}
+
 	if (root.contains("+libraries"))
 	{
-		QJsonValue librariesVal = root.value("+libraries");
-		if (!librariesVal.isArray())
-		{
-			QLOG_ERROR() << filename << "contains a '+libraries' field, but its not an array";
-			return out;
-		}
-		QJsonArray librariesArray = librariesVal.toArray();
-		for (auto libVal : librariesArray)
+		for (auto libVal : ensureArray(root.value("+libraries")))
 		{
-			if (!libVal.isObject())
-			{
-				QLOG_ERROR() << filename << "contains a library that's not an object";
-				return out;
-			}
-			QJsonObject libObj = libVal.toObject();
-			bool error;
-			Library lib = Library::fromJson(libObj, filename, error);
-			if (error)
-			{
-				QLOG_ERROR() << "Error while reading a library entry in" << filename;
-				return out;
-			}
-			if (!libObj.contains("insert"))
-			{
-				QLOG_ERROR() << "Missing 'insert' field in '+libraries' field in" << filename;
-				return out;
-			}
-			QJsonValue insertVal = libObj.value("insert");
+			QJsonObject libObj = ensureObject(libVal);
+			QJsonValue insertVal = ensureExists(libObj.value("insert"));
+
+			// parse the library
+			Library lib = Library::fromJson(libObj, filename);
+
+			// TODO: utility functions for handling this case. templates?
 			QString insertString;
 			{
 				if (insertVal.isString())
@@ -335,8 +210,8 @@ VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filen
 					QJsonObject insertObj = insertVal.toObject();
 					if (insertObj.isEmpty())
 					{
-						QLOG_ERROR() << "One library has an empty insert object in" << filename;
-						return out;
+						throw JSONValidationError("One library has an empty insert object in " +
+												  filename);
 					}
 					insertString = insertObj.keys().first();
 					lib.insertData = insertObj.value(insertString).toString();
@@ -360,13 +235,12 @@ VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filen
 			}
 			else
 			{
-				QLOG_ERROR() << "A '+' library in" << filename
-							 << "contains an invalid insert type";
-				return out;
+				throw JSONValidationError("A '+' library in " + filename +
+										  " contains an invalid insert type");
 			}
-			if (libObj.contains("MMC-depend") && libObj.value("MMC-depend").isString())
+			if (libObj.contains("MMC-depend"))
 			{
-				const QString dependString = libObj.value("MMC-depend").toString();
+				const QString dependString = ensureString(libObj.value("MMC-depend"));
 				if (dependString == "hard")
 				{
 					lib.dependType = Library::Hard;
@@ -377,9 +251,8 @@ VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filen
 				}
 				else
 				{
-					QLOG_ERROR() << "A '+' library in" << filename
-								 << "contains an invalid depend type";
-					return out;
+					throw JSONValidationError("A '+' library in " + filename +
+											  " contains an invalid depend type");
 				}
 			}
 			out.addLibs.append(lib);
@@ -387,36 +260,12 @@ VersionFile VersionFile::fromJson(const QJsonDocument &doc, const QString &filen
 	}
 	if (root.contains("-libraries"))
 	{
-		QJsonValue librariesVal = root.value("-libraries");
-		if (!librariesVal.isArray())
-		{
-			QLOG_ERROR() << filename << "contains a '-libraries' field, but its not an array";
-			return out;
-		}
-		QJsonArray librariesArray = librariesVal.toArray();
-		for (auto libVal : librariesArray)
+		for (auto libVal : ensureArray(root.value("-libraries")))
 		{
-			if (!libVal.isObject())
-			{
-				QLOG_ERROR() << filename << "contains a library that's not an object";
-				return out;
-			}
-			QJsonObject libObj = libVal.toObject();
-			if (!libObj.contains("name"))
-			{
-				QLOG_ERROR() << filename << "contains a library without a name";
-				return out;
-			}
-			if (!libObj.value("name").isString())
-			{
-				QLOG_ERROR() << filename << "contains a library without a valid 'name' field";
-				return out;
-			}
-			out.removeLibs.append(libObj.value("name").toString());
+			auto libObj = ensureObject(libVal);
+			out.removeLibs.append(ensureString(libObj.value("name")));
 		}
 	}
-
-	isError = false;
 	return out;
 }
 
@@ -457,16 +306,15 @@ int VersionFile::findLibrary(QList<std::shared_ptr<OneSixLibrary>> haystack,
 	return -1;
 }
 
-VersionFile::ApplyError VersionFile::applyTo(VersionFinal *version)
+void VersionFile::applyTo(VersionFinal *version)
 {
 	if (minimumLauncherVersion != -1)
 	{
 		if (minimumLauncherVersion > CURRENT_MINIMUM_LAUNCHER_VERSION)
 		{
-			QLOG_ERROR() << filename << "is for a different launcher version ("
-						 << minimumLauncherVersion << "), current supported is"
-						 << CURRENT_MINIMUM_LAUNCHER_VERSION;
-			return LauncherVersionError;
+			throw VersionBuildError(
+				QString("%1 is for a different launcher version (%2), current supported is %3")
+					.arg(filename, minimumLauncherVersion, CURRENT_MINIMUM_LAUNCHER_VERSION));
 		}
 	}
 
@@ -475,8 +323,8 @@ VersionFile::ApplyError VersionFile::applyTo(VersionFinal *version)
 		if (QRegExp(mcVersion, Qt::CaseInsensitive, QRegExp::Wildcard).indexIn(version->id) ==
 			-1)
 		{
-			QLOG_ERROR() << filename << "is for a different version of Minecraft";
-			return OtherError;
+			throw VersionBuildError(
+				QString("%1 is for a different version of Minecraft").arg(filename));
 		}
 	}
 
@@ -587,7 +435,7 @@ VersionFile::ApplyError VersionFile::applyTo(VersionFinal *version)
 			}
 			else
 			{
-				QLOG_WARN() << "Couldn't find" << lib.insertData << "(skipping)";
+				QLOG_WARN() << "Couldn't find" << lib.name << "(skipping)";
 			}
 			break;
 		}
@@ -623,10 +471,10 @@ VersionFile::ApplyError VersionFile::applyTo(VersionFinal *version)
 					if (ourVersion > otherVersion ||
 						(lib.dependType == Library::Hard && ourVersion != otherVersion))
 					{
-						QLOG_ERROR() << "Error resolving library dependencies between"
-									 << otherLib->rawName() << "and" << lib.name << "in"
-									 << filename;
-						return OtherError;
+						throw VersionBuildError(
+							QString(
+								"Error resolving library dependencies between %1 and %2 in %3.")
+								.arg(otherLib->rawName(), lib.name, filename));
 					}
 					else
 					{
@@ -651,10 +499,10 @@ VersionFile::ApplyError VersionFile::applyTo(VersionFinal *version)
 						// it: fail
 						if (lib.dependType == Library::Hard)
 						{
-							QLOG_ERROR() << "Error resolving library dependencies between"
-										 << otherLib->rawName() << "and" << lib.name << "in"
-										 << filename;
-							return OtherError;
+							throw VersionBuildError(QString(
+								"Error resolving library dependencies between %1 and %2 in %3.")
+														.arg(otherLib->rawName(), lib.name,
+															 filename));
 						}
 					}
 				}
@@ -697,6 +545,4 @@ VersionFile::ApplyError VersionFile::applyTo(VersionFinal *version)
 	versionFile.filename = filename;
 	versionFile.order = order;
 	version->versionFiles.append(versionFile);
-
-	return NoApplyError;
 }
diff --git a/logic/VersionFile.h b/logic/VersionFile.h
index 04694999..37c8c415 100644
--- a/logic/VersionFile.h
+++ b/logic/VersionFile.h
@@ -5,8 +5,21 @@
 #include <memory>
 #include "logic/OpSys.h"
 #include "logic/OneSixRule.h"
+#include "MMCError.h"
+
 class VersionFinal;
 
+class VersionBuildError : public MMCError
+{
+public:
+	VersionBuildError(QString cause) : MMCError(cause) {};
+	virtual QString errorName()
+	{
+		return "VersionBuildError";
+	};
+	virtual ~VersionBuildError() {};
+};
+
 struct VersionFile
 {
 	int order;
@@ -65,26 +78,17 @@ struct VersionFile
 		};
 		DependType dependType = Soft;
 
-		static Library fromJson(const QJsonObject &libObj, const QString &filename,
-								bool &isError);
+		static Library fromJson(const QJsonObject &libObj, const QString &filename);
 	};
 	bool shouldOverwriteLibs = false;
 	QList<Library> overwriteLibs;
 	QList<Library> addLibs;
 	QList<QString> removeLibs;
 
-	enum ApplyError
-	{
-		LauncherVersionError,
-		OtherError,
-		NoApplyError
-	};
-
 	static VersionFile fromJson(const QJsonDocument &doc, const QString &filename,
-								const bool requireOrder, bool &isError,
-								const bool isFTB = false);
+								const bool requireOrder, const bool isFTB = false);
 
 	static std::shared_ptr<OneSixLibrary> createLibrary(const Library &lib);
 	int findLibrary(QList<std::shared_ptr<OneSixLibrary>> haystack, const QString &needle);
-	ApplyError applyTo(VersionFinal *version);
+	void applyTo(VersionFinal *version);
 };
\ No newline at end of file