Assume enterprise user/pass login available.

If the enterprise server doesn't return a value for `VerifiablePasswordAuthentication`, or the `api/meta` endpoint fails completely then we're on an older version of enterprise. In this case assume username and password login is available as we have no way to tell.

Fixes #1474

Author: grokys

src/GitHub.App/Services/EnterpriseCapabilitiesService.cs

@@ -30,22 +30,29 @@ public EnterpriseCapabilitiesService(
 
         public async Task<EnterpriseLoginMethods> ProbeLoginMethods(Uri enterpriseBaseUrl)
         {
-            // It's important that we don't use our cached credentials on this connection, as they
-            // may be wrong - we're trying to log in after all.
-            var hostAddress = HostAddress.Create(enterpriseBaseUrl);
-            var connection = new Octokit.Connection(program.ProductHeader, hostAddress.ApiUri);
-            var meta = await GetMetadata(connection).ConfigureAwait(false);
-            var result = EnterpriseLoginMethods.Token;
+            try
+            {
+                // It's important that we don't use our cached credentials on this connection, as they
+                // may be wrong - we're trying to log in after all.
+                var hostAddress = HostAddress.Create(enterpriseBaseUrl);
+                var connection = new Octokit.Connection(program.ProductHeader, hostAddress.ApiUri);
+                var meta = await GetMetadata(connection).ConfigureAwait(false);
+                var result = EnterpriseLoginMethods.Token;
+
+                if (meta.VerifiablePasswordAuthentication != false) result |= EnterpriseLoginMethods.UsernameAndPassword;
 
-            if (meta.VerifiablePasswordAuthentication) result |= EnterpriseLoginMethods.UsernameAndPassword;
+                if (meta.InstalledVersion != null)
+                {
+                    var version = new Version(meta.InstalledVersion);
+                    if (version >= MinimumOAuthVersion) result |= EnterpriseLoginMethods.OAuth;
+                }
 
-            if (meta.InstalledVersion != null)
+                return result;
+            }
+            catch
             {
-                var version = new Version(meta.InstalledVersion);
-                if (version >= MinimumOAuthVersion) result |= EnterpriseLoginMethods.OAuth;
+                return EnterpriseLoginMethods.Token | EnterpriseLoginMethods.UsernameAndPassword;
             }
-
-            return result;
         }
 
         private async Task<EnterpriseMeta> GetMetadata(IConnection connection)
@@ -56,9 +63,10 @@ private async Task<EnterpriseMeta> GetMetadata(IConnection connection)
         }
 
         [SuppressMessage("Microsoft.Performance", "CA1812:AvoidUninstantiatedInternalClasses", Justification = "Created via Octokit reflection")]
-        class EnterpriseMeta : Meta
+        class EnterpriseMeta
         {
             public string InstalledVersion { get; private set; }
+            public bool? VerifiablePasswordAuthentication { get; private set; }
         }
     }
 }

src/GitHub.App/ViewModels/Dialog/LoginToGitHubForEnterpriseViewModel.cs

@@ -140,22 +140,14 @@ async void EnterpriseUrlChanged(string url, bool valid)
 
             var enterpriseInstance = false;
             var loginMethods = (EnterpriseLoginMethods?)null;
+            var uri = new UriBuilder(url).Uri;
 
-            try
-            {
-                var uri = new UriBuilder(url).Uri;
-                ProbeStatus = EnterpriseProbeStatus.Checking;
+            ProbeStatus = EnterpriseProbeStatus.Checking;
 
-                if (await enterpriseCapabilities.Probe(uri) == EnterpriseProbeResult.Ok)
-                {
-                    loginMethods = await enterpriseCapabilities.ProbeLoginMethods(uri);
-                    enterpriseInstance = true;
-                }
-            }
-            catch
+            if (await enterpriseCapabilities.Probe(uri) == EnterpriseProbeResult.Ok)
             {
-                ProbeStatus = EnterpriseProbeStatus.Invalid;
-                loginMethods = null;
+                loginMethods = await enterpriseCapabilities.ProbeLoginMethods(uri);
+                enterpriseInstance = true;
             }
 
             if (url == EnterpriseUrl)