Added the possibility to manage the placeholders from outside ocelot (#724)

src/Ocelot/Errors/OcelotErrorCode.cs

@@ -35,6 +35,8 @@
         FileValidationFailedError,
         UnableToFindDelegatingHandlerProviderError,
         CouldNotFindPlaceholderError,
-        CouldNotFindAggregatorError
+        CouldNotFindAggregatorError,
+        CannotAddPlaceholderError,
+        CannotRemovePlaceholderError
     }
 }

src/Ocelot/Infrastructure/CannotAddPlaceholderError.cs

@@ -0,0 +1,12 @@
+using Ocelot.Errors;
+
+namespace Ocelot.Infrastructure
+{
+    public class CannotAddPlaceholderError : Error
+    {
+        public CannotAddPlaceholderError(string message)
+            : base(message, OcelotErrorCode.CannotAddPlaceholderError)
+        {
+        }
+    }
+}

src/Ocelot/Infrastructure/CannotRemovePlaceholderError.cs

@@ -0,0 +1,12 @@
+using Ocelot.Errors;
+
+namespace Ocelot.Infrastructure
+{
+    public class CannotRemovePlaceholderError : Error
+    {
+        public CannotRemovePlaceholderError(string message)
+            : base(message, OcelotErrorCode.CannotRemovePlaceholderError)
+        {
+        }
+    }
+}

src/Ocelot/Infrastructure/IPlaceholders.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Net.Http;
 using Ocelot.Request.Middleware;
 using Ocelot.Responses;
@@ -8,5 +9,7 @@ namespace Ocelot.Infrastructure
     {
         Response<string> Get(string key);
         Response<string> Get(string key, DownstreamRequest request);
+        Response Add(string key, Func<Response<string>> func);
+        Response Remove(string key);
     }
 }

src/Ocelot/Infrastructure/Placeholders.cs

@@ -59,6 +59,28 @@ namespace Ocelot.Infrastructure
             return new ErrorResponse<string>(new CouldNotFindPlaceholderError(key));
         }
 
+        public Response Add(string key, Func<Response<string>> func)
+        {
+            if(_placeholders.ContainsKey(key))
+            {
+                return new ErrorResponse(new CannotAddPlaceholderError($"Unable to add placeholder: {key}, placeholder already exists"));
+            }
+            
+            _placeholders.Add(key, func);
+            return new OkResponse();
+        }
+
+        public Response Remove(string key)
+        {
+            if(!_placeholders.ContainsKey(key))
+            {
+                return new ErrorResponse(new CannotRemovePlaceholderError($"Unable to remove placeholder: {key}, placeholder does not exists"));
+            }
+            
+            _placeholders.Remove(key);
+            return new OkResponse();
+        }
+
         private Func<Response<string>> GetRemoteIpAddress()
         {
             return () =>

test/Ocelot.UnitTests/Infrastructure/PlaceholdersTests.cs

@@ -91,5 +91,37 @@ namespace Ocelot.UnitTests.Infrastructure
             var result = _placeholders.Get("{TraceId}");
             result.Data.ShouldBe(traceId);
         }
+
+        [Fact]
+        public void should_return_ok_when_added()
+        {
+            var result = _placeholders.Add("{Test}", () => new OkResponse<string>("test"));
+            result.IsError.ShouldBeFalse();
+        }
+
+        [Fact]
+        public void should_return_ok_when_removed()
+        {
+            var result = _placeholders.Add("{Test}", () => new OkResponse<string>("test"));
+            result = _placeholders.Remove("{Test}");
+            result.IsError.ShouldBeFalse();
+        }
+
+        [Fact]
+        public void should_return_error_when_added()
+        {
+            var result = _placeholders.Add("{Test}", () => new OkResponse<string>("test"));
+            result = _placeholders.Add("{Test}", () => new OkResponse<string>("test"));
+            result.IsError.ShouldBeTrue();
+            result.Errors[0].Message.ShouldBe("Unable to add placeholder: {Test}, placeholder already exists");
+        }
+
+        [Fact]
+        public void should_return_error_when_removed()
+        {
+            var result = _placeholders.Remove("{Test}");
+            result.IsError.ShouldBeTrue();
+            result.Errors[0].Message.ShouldBe("Unable to remove placeholder: {Test}, placeholder does not exists");
+        }
     }
 }

test/Ocelot.UnitTests/Responder/ErrorsToHttpStatusCodeMapperTests.cs

@@ -125,7 +125,7 @@ namespace Ocelot.UnitTests.Responder
             // If this test fails then it's because the number of error codes has changed.
             // You should make the appropriate changes to the test cases here to ensure
             // they cover all the error codes, and then modify this assertion.
-            Enum.GetNames(typeof(OcelotErrorCode)).Length.ShouldBe(34, "Looks like the number of error codes has changed. Do you need to modify ErrorsToHttpStatusCodeMapper?");
+            Enum.GetNames(typeof(OcelotErrorCode)).Length.ShouldBe(36, "Looks like the number of error codes has changed. Do you need to modify ErrorsToHttpStatusCodeMapper?");
         }
 
         private void ShouldMapErrorToStatusCode(OcelotErrorCode errorCode, HttpStatusCode expectedHttpStatusCode)