replace reflection magic in MNTR with reading of MultiNodeConfig pr…

…operties (#4902)

* close #4901 - replace reflection magic in MNTR with reading of MultiNodeConfig properties

* fixed outdated DiscoverySpec

src/core/Akka.MultiNodeTestRunner.Shared.Tests/MultiNodeTestRunnerDiscovery/DiscoveryCases.cs

@@ -5,6 +5,7 @@
 // </copyright>
 //-----------------------------------------------------------------------
 
+using System.Linq;
 using Akka.Remote.TestKit;
 
 namespace Akka.MultiNodeTestRunner.Shared.Tests.MultiNodeTestRunnerDiscovery
@@ -133,6 +134,30 @@ public FloodyChildSpec3(FloodyConfig config) : base(config)
             }
         }
 
+        public class NoReflectionConfig : MultiNodeConfig
+        {
+            public NoReflectionConfig()
+            {
+                foreach(var i in Enumerable.Range(1, 10))
+                {
+                    Role("node-" + i);
+                }
+            }
+        }
+
+        public class NoReflectionSpec
+        {
+            public NoReflectionSpec(NoReflectionConfig config) 
+            {
+
+            }
+
+            [MultiNodeFact(Skip = "Only for discovery tests")]
+            public void Dummy()
+            {
+            }
+        }
+
         public class DiverseConfig : MultiNodeConfig
         {
             public RoleName RoleProp { get; set; }

src/core/Akka.MultiNodeTestRunner.Shared.Tests/MultiNodeTestRunnerDiscovery/DiscoverySpec.cs

@@ -53,11 +53,11 @@ public void Discovered_count_equals_number_of_roles_mult_specs()
             Assert.Equal(5, discoveredSpecs[KeyFromSpecName(nameof(DiscoveryCases.FloodyChildSpec3))].Count);
         }
 
-        [Fact(DisplayName = "Only public props and fields are considered when looking for RoleNames")]
-        public void Public_props_and_fields_are_considered()
+        [Fact(DisplayName = "Only the MultiNodeConfig.Roles property is used to compute the number of Roles in MultiNodeFact")]
+        public void Only_MultiNodeConfig_role_count_used()
         {
             var discoveredSpecs = DiscoverSpecs();
-            Assert.Equal(discoveredSpecs[KeyFromSpecName(nameof(DiscoveryCases.DiverseSpec))].Select(c => c.Role), new[] {"RoleProp", "RoleField"});
+            Assert.Equal(10, discoveredSpecs[KeyFromSpecName(nameof(DiscoveryCases.NoReflectionSpec))].Select(c => c.Role).Count());
         }
 
         private static Dictionary<string, List<NodeTest>> DiscoverSpecs()

src/core/Akka.MultiNodeTestRunner/Discovery.cs

@@ -108,14 +108,8 @@ private IEnumerable<RoleName> RoleNames(Type specType)
             var ctorWithConfig = FindConfigConstructor(specType);
             var configType = ctorWithConfig.GetParameters().First().ParameterType;
             var args = ConfigConstructorParamValues(configType);
-            var configInstance = Activator.CreateInstance(configType, args);
-            var roleType = typeof(RoleName);
-            var configProps = configType.GetProperties(BindingFlags.Instance | BindingFlags.Public);
-            var roleProps = configProps.Where(p => p.PropertyType == roleType && p.Name != "Myself").Select(p => (RoleName)p.GetValue(configInstance));
-            var configFields = configType.GetFields(BindingFlags.Instance | BindingFlags.Public);
-            var roleFields = configFields.Where(f => f.FieldType == roleType && f.Name != "Myself").Select(f => (RoleName)f.GetValue(configInstance));
-            var roles = roleProps.Concat(roleFields).Distinct();
-            return roles;
+            var configInstance = (MultiNodeConfig)Activator.CreateInstance(configType, args);
+            return configInstance.Roles;
         }
 
         internal static ConstructorInfo FindConfigConstructor(Type configUser)

src/core/Akka.Remote.TestKit/MultiNodeSpec.cs

@@ -168,7 +168,7 @@ internal ImmutableList<string> Deployments(RoleName node)
             return deployments == null ? _allDeploy : deployments.AddRange(_allDeploy);
         }
 
-        internal ImmutableList<RoleName> Roles
+        public ImmutableList<RoleName> Roles
         {
             get { return _roles; }
         }