All: Better handling of null values in settings

ReactNativeClient/android/app/build.gradle

@@ -90,8 +90,8 @@ android {
 		applicationId "net.cozic.joplin"
 		minSdkVersion 16
 		targetSdkVersion 22
-		versionCode 84
-		versionName "0.10.69"
+		versionCode 85
+		versionName "0.10.70"
 		ndk {
 			abiFilters "armeabi-v7a", "x86"
 		}

ReactNativeClient/lib/models/Setting.js

@@ -242,7 +242,9 @@ class Setting extends BaseModel {
 		if (md.type == Setting.TYPE_BOOL) return value ? '1' : '0';
 		if (md.type == Setting.TYPE_ARRAY) return value ? JSON.stringify(value) : '[]';
 		if (md.type == Setting.TYPE_OBJECT) return value ? JSON.stringify(value) : '{}';
-		return value;
+		if (md.type == Setting.TYPE_STRING) return value ? value + '' : '';
+
+		throw new Error('Unhandled value type: ' + md.type);	
 	}
 
 	static formatValue(key, value) {
@@ -274,7 +276,12 @@ class Setting extends BaseModel {
 			return {};
 		}
 
-		return value;
+		if (md.type === Setting.TYPE_STRING) {
+			if (!value) return '';
+			return value + '';
+		}
+
+		throw new Error('Unhandled value type: ' + md.type);
 	}
 
 	static value(key) {
@@ -283,6 +290,7 @@ class Setting extends BaseModel {
 		// and object and change a key, the objects will be detected as equal. By returning a copy
 		// we avoid this problem.
 		function copyIfNeeded(value) {
+			if (value === null || value === undefined) return value;
 			if (Array.isArray(value)) return value.slice();
 			if (typeof value === 'object') return Object.assign({}, value);
 			return value;

ReactNativeClient/lib/registry.js

@@ -80,7 +80,17 @@ reg.scheduleSync = async (delay = null) => {
 
 			const contextKey = 'sync.' + syncTargetId + '.context';
 			let context = Setting.value(contextKey);
+			try {
 				context = context ? JSON.parse(context) : {};
+			} catch (error) {
+				// Clearing the context is inefficient since it means all items are going to be re-downloaded
+				// however it won't result in duplicate items since the synchroniser is going to compare each
+				// item to the current state.
+				reg.logger().warn('Could not parse JSON sync context ' + contextKey + ':', context);
+				reg.logger().info('Clearing context and starting from scratch');
+				context = null;
+			}
+
 			try {
 				reg.logger().info('Starting scheduled sync');
 				let newContext = await sync.start({ context: context });

ReactNativeClient/lib/synchronizer.js

@@ -166,7 +166,6 @@ class Synchronizer {
 			let error = new Error(_('Synchronisation is already in progress. State: %s', this.state()));
 			error.code = 'alreadyStarted';
 			throw error;
-			return;
 		}
 
 		this.state_ = 'in_progress';