chore: add UseLocalJobOnlyAttribute and modify related codes

Author: filzrev

src/BenchmarkDotNet/Attributes/UseLocalJobOnlyAttribute.cs

@@ -0,0 +1,19 @@
+using System;
+using BenchmarkDotNet.Configs;
+using JetBrains.Annotations;
+
+namespace BenchmarkDotNet.Attributes;
+
+[PublicAPI]
+[AttributeUsage(AttributeTargets.Class)]
+public class UseLocalJobOnlyAttribute : Attribute, IConfigSource
+{
+    public IConfig Config { get; }
+
+    public UseLocalJobOnlyAttribute()
+    {
+        Config = ManualConfig.CreateEmpty();
+
+        // `WithUnionRule(ConfigUnionRule.UnionAndUseLocalJob)` is not set here. Because it's not used.
+    }
+}

src/BenchmarkDotNet/Configs/ConfigUnionRule.cs

@@ -2,6 +2,13 @@
 {
     public enum ConfigUnionRule
     {
-        Union, AlwaysUseLocal, AlwaysUseGlobal
+        Union,
+        AlwaysUseLocal,
+        AlwaysUseGlobal,
+
+        /// <summary>
+        /// Union global/local configs except for jobs.
+        /// </summary>
+        UnionAndUseLocalJob,
     }
 }

src/BenchmarkDotNet/Configs/ManualConfig.cs

@@ -273,6 +273,11 @@ public static ManualConfig Union(IConfig globalConfig, IConfig localConfig)
                     manualConfig.Add(globalConfig);
                     manualConfig.Add(localConfig);
                     break;
+                case ConfigUnionRule.UnionAndUseLocalJob:
+                    manualConfig.Add(globalConfig);
+                    manualConfig.RemoveAllJobs();
+                    manualConfig.Add(localConfig);
+                    break;
                 default:
                     throw new ArgumentOutOfRangeException();
             }

src/BenchmarkDotNet/Running/BenchmarkConverter.cs

@@ -92,12 +92,31 @@ private static ImmutableConfig GetFullTypeConfig(Type type, IConfig? config)
         {
             config = config ?? DefaultConfig.Instance;
 
-            var typeAttributes = type.GetCustomAttributes(true).OfType<IConfigSource>();
             var assemblyAttributes = type.Assembly.GetCustomAttributes().OfType<IConfigSource>();
-
-            foreach (var configFromAttribute in assemblyAttributes.Concat(typeAttributes))
+            foreach (var configFromAttribute in assemblyAttributes)
                 config = ManualConfig.Union(config, configFromAttribute.Config);
 
+            var typeAttributes = type.GetCustomAttributes(true).OfType<IConfigSource>().ToArray();
+            if (typeAttributes.Any(x => x is UseLocalJobOnlyAttribute))
+            {
+                // UseLocalJobOnlyAttribute.can't be combined with other benchmark attribute that set non-default UnionRule.
+                if (typeAttributes.Any(x => x.Config.UnionRule != ConfigUnionRule.Union))
+                    throw new InvalidBenchmarkDeclarationException($"{type.Name} using UseLocalJobOnlyAttribute, but other benchmarks attribute set another UnionRule.");
+
+                // Aggregate attribute-based configs.
+                var typeConfig = ManualConfig.CreateEmpty();
+                foreach (var configFromAttribute in typeAttributes)
+                    typeConfig = ManualConfig.Union(typeConfig, configFromAttribute.Config);
+
+                typeConfig.WithUnionRule(ConfigUnionRule.UnionAndUseLocalJob);
+                config = ManualConfig.Union(config, typeConfig);
+            }
+            else
+            {
+                foreach (var configFromAttribute in typeAttributes)
+                    config = ManualConfig.Union(config, configFromAttribute.Config);
+            }
+
             return ImmutableConfigBuilder.Create(config);
         }