Add handling for FormatException thrown by invalid feature flag json

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AzureAppConfigurationProvider.cs

@@ -492,6 +492,12 @@ public async Task<bool> TryRefreshAsync(CancellationToken cancellationToken)
 
                 return false;
             }
+            catch (FormatException fe)
+            {
+                _logger.LogWarning(LogHelper.BuildRefreshFailedDueToFormattingErrorMessage(fe.Message));
+
+                return false;
+            }
 
             return true;
         }
@@ -634,6 +640,7 @@ exception is KeyVaultReferenceException ||
                 exception is TimeoutException ||
                 exception is OperationCanceledException ||
                 exception is InvalidOperationException ||
+                exception is FormatException ||
                 ((exception as AggregateException)?.InnerExceptions?.Any(e =>
                     e is RequestFailedException ||
                     e is OperationCanceledException) ?? false)))

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/Constants/LoggingConstants.cs

@@ -15,6 +15,7 @@ internal class LoggingConstants
         public const string RefreshFailedDueToKeyVaultError = "A refresh operation failed while resolving a Key Vault reference.";
         public const string PushNotificationUnregisteredEndpoint = "Ignoring the push notification received for the unregistered endpoint";
         public const string FallbackClientLookupError = "Failed to perform fallback client lookup.";
+        public const string RefreshFailedDueToFormattingError = "A refresh operation failed due to a formatting error.";
 
         // Successful update, debug log level
         public const string RefreshKeyValueRead = "Key-value read from App Configuration.";

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/FeatureManagement/FeatureManagementKeyValueAdapter.cs

@@ -188,7 +188,7 @@ private FeatureFlag ParseFeatureFlag(string settingKey, string settingValue)
             }
             catch (JsonException e)
             {
-                throw new FormatException(settingKey, e);
+                throw new FormatException(string.Format(ErrorMessages.FeatureFlagInvalidFormat, settingKey), e);
             }
 
             return featureFlag;

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/LogHelper.cs

@@ -89,5 +89,10 @@ public static string BuildFallbackClientLookupFailMessage(string exceptionMessag
         {
             return $"{LoggingConstants.FallbackClientLookupError}\n{exceptionMessage}";
         }
+
+        public static string BuildRefreshFailedDueToFormattingErrorMessage(string exceptionMessage)
+        {
+            return $"{LoggingConstants.RefreshFailedDueToFormattingError}\n{exceptionMessage}";
+        }
     }
 }