Disable and hide autoupdate functionality if can't write ckan.exe

Cmdline/Action/Upgrade.cs

@@ -29,11 +29,14 @@ public int RunCommand(CKAN.KSP ksp, object raw_options)
                 // What? No files specified?
                 User.RaiseMessage("Usage: ckan upgrade Mod [Mod2, ...]");
                 User.RaiseMessage("  or   ckan upgrade --all");
-                User.RaiseMessage("  or   ckan upgrade ckan");
+                if (AutoUpdate.CanUpdate)
+                {
+                    User.RaiseMessage("  or   ckan upgrade ckan");
+                }
                 return Exit.BADOPT;
             }
 
-            if (!options.upgrade_all && options.modules[0] == "ckan")
+            if (!options.upgrade_all && options.modules[0] == "ckan" && AutoUpdate.CanUpdate)
             {
                 User.RaiseMessage("Querying the latest CKAN version");
                 AutoUpdate.Instance.FetchLatestReleaseInfo();

Core/Net/AutoUpdate.cs

@@ -1,4 +1,5 @@
-using System;
+using System;
+using System.IO;
 using System.Diagnostics;
 using System.Net;
 using System.Reflection;
@@ -17,42 +18,44 @@ namespace CKAN
     public class AutoUpdate
     {
 
-        private readonly ILog log = LogManager.GetLogger(typeof(AutoUpdate));
+        private static readonly ILog log = LogManager.GetLogger(typeof(AutoUpdate));
 
-        private readonly Uri latestCKANReleaseApiUrl = new Uri("https://api.github.com/repos/KSP-CKAN/CKAN/releases/latest");
+        private static readonly Uri latestCKANReleaseApiUrl = new Uri("https://api.github.com/repos/KSP-CKAN/CKAN/releases/latest");
 
-        private readonly Uri latestUpdaterReleaseApiUrl = new Uri(
+        private static readonly Uri latestUpdaterReleaseApiUrl = new Uri(
             "https://api.github.com/repos/KSP-CKAN/CKAN-autoupdate/releases/latest");
 
         private Tuple<Uri, long> fetchedUpdaterUrl;
         private Tuple<Uri, long> fetchedCkanUrl;
 
         public Version LatestVersion { get; private set; }
-        public string ReleaseNotes { get; private set; }
+        public string  ReleaseNotes  { get; private set; }
 
-        private static AutoUpdate instance;
-
-        public static AutoUpdate Instance
-        {
-            get
-            {
-                if (instance == null)
-                {
-                    instance = new AutoUpdate();
-                }
-                return instance;
-            }
-            private set { }
-        }
+        public static readonly AutoUpdate Instance = new AutoUpdate();
 
         // This is private so we can enforce our class being a singleton.
         private AutoUpdate() { }
 
-        public static void ClearCache()
+        private static bool CanWrite(string path)
         {
-            instance = new AutoUpdate();
+            try {
+                // Try to open the file for writing.
+                // We won't actually write, but we expect the OS to stop us if we don't have permissions.
+                using (FileStream fs = new FileStream(exePath, FileMode.Open, FileAccess.ReadWrite)) { }
+                return true;
+            } catch {
+                return false;
+            }
         }
 
+        private static readonly string exePath = Assembly.GetEntryAssembly().Location;
+
+        /// <summary>
+        /// Report whether it's possible to run the auto-updater.
+        /// Checks whether we can overwrite the running ckan.exe.
+        /// </summary>
+        public static readonly bool CanUpdate = CanWrite(exePath);
+
         /// <summary>
         /// Our metadata is considered fetched if we have a latest version, release notes,
         /// and download URLs for the ckan executable and helper.
@@ -82,9 +85,7 @@ public void FetchLatestReleaseInfo()
                 return;
             }
 
-            string body = response.body.ToString();
-
-            ReleaseNotes = ExtractReleaseNotes(body);
+            ReleaseNotes  = ExtractReleaseNotes(response.body.ToString());
             LatestVersion = new CKANVersion(response.tag_name.ToString(), response.name.ToString());
         }
 
@@ -97,15 +98,9 @@ public void FetchLatestReleaseInfo()
         public string ExtractReleaseNotes(string releaseBody)
         {
             string divider = "\r\n---\r\n";
-            string[] notesArray = releaseBody.Split(new string[] { divider }, StringSplitOptions.None);
-
-            if (notesArray.Length > 1)
-            {
-                // Return everything after the first divider, re-joining if necessary.
-                return string.Join(divider, notesArray.Skip(1));
-            }
-
-            return notesArray[0];
+            // Get at most two pieces, the first is the image, the second is the release notes
+            string[] notesArray = releaseBody.Split(new string[] { divider }, 2, StringSplitOptions.None);
+            return notesArray.Length > 1 ? notesArray[1] : null;
         }
 
         /// <summary>
@@ -132,12 +127,11 @@ public void StartUpdateProcess(bool launchCKANAfterUpdate, IUser user = null)
 
             // run updater
             SetExecutable(updaterFilename);
-            var path = Assembly.GetEntryAssembly().Location;
             Process.Start(new ProcessStartInfo
             {
-                Verb = "runas",
-                FileName = updaterFilename,
-                Arguments = String.Format(@"{0} ""{1}"" ""{2}"" {3}", pid, path, ckanFilename, launchCKANAfterUpdate ? "launch" : "nolaunch"),
+                Verb      = "runas",
+                FileName  = updaterFilename,
+                Arguments = String.Format(@"{0} ""{1}"" ""{2}"" {3}", pid, exePath, ckanFilename, launchCKANAfterUpdate ? "launch" : "nolaunch"),
                 UseShellExecute = false
             });
 
@@ -151,7 +145,7 @@ public void StartUpdateProcess(bool launchCKANAfterUpdate, IUser user = null)
         /// </summary>
         /// <returns>The URL to the downloadable asset.</returns>
         internal Tuple<Uri, long> RetrieveUrl(dynamic response)
-        { 
+        {
             if (response.assets.Count == 0)
             {
                 throw new Kraken("The latest release isn't uploaded yet.");
@@ -164,7 +158,7 @@ internal Tuple<Uri, long> RetrieveUrl(dynamic response)
         /// <summary>
         /// Fetches the URL provided, and de-serialises the returned JSON
         /// data structure into a dynamic object.
-        /// 
+        ///
         /// May throw an exception (especially a WebExeption) on failure.
         /// </summary>
         /// <returns>A dynamic object representing the JSON we fetched.</returns>

GUI/Main.cs

@@ -286,7 +286,7 @@ protected override void OnLoad(EventArgs e)
             Location = configuration.WindowLoc;
             Size = configuration.WindowSize;
 
-            if (!configuration.CheckForUpdatesOnLaunchNoNag)
+            if (!configuration.CheckForUpdatesOnLaunchNoNag && AutoUpdate.CanUpdate)
             {
                 log.Debug("Asking user if they wish for autoupdates");
                 if (new AskUserForAutoUpdatesDialog().ShowDialog() == DialogResult.OK)
@@ -300,7 +300,7 @@ protected override void OnLoad(EventArgs e)
 
             bool autoUpdating = false;
 
-            if (configuration.CheckForUpdatesOnLaunch)
+            if (configuration.CheckForUpdatesOnLaunch && AutoUpdate.CanUpdate)
             {
                 try
                 {