Add a static flag in EF that will be set when code is being executed …

…for design-time discovery

Fixes #27306.

src/EFCore.Design/Design/OperationExecutor.cs

@@ -697,6 +697,7 @@ public abstract class OperationBase : MarshalByRefObject
         /// <param name="resultHandler">The <see cref="IOperationResultHandler" />.</param>
         protected OperationBase(IOperationResultHandler resultHandler)
         {
+            EF.IsDesignTime = true;
             _resultHandler = resultHandler;
         }
 

src/EFCore/EF.cs

@@ -17,6 +17,22 @@ public static partial class EF
     internal static readonly MethodInfo PropertyMethod
         = typeof(EF).GetTypeInfo().GetDeclaredMethod(nameof(Property))!;
 
+    /// <summary>
+    ///     This flag is set to <see langword="true" /> when code is being run from a design-time tool, such
+    ///     as "dotnet ef" or one of the Package Manager Console PowerShell commands "Add-Migration", "Update-Database", etc.
+    /// </summary>
+    /// <remarks>
+    ///     <para>
+    ///         This flag can be inspected to change application behavior. For example, if the application is being executed by an EF
+    ///         design-time tool, then it may choose to skip executing migrations commands as part of startup.
+    ///     </para>
+    ///     <para>
+    ///         See <see href="https://aka.ms/efcore-docs-commandline">EF Core command-line reference </see> for more information
+    ///         and examples.
+    ///     </para>
+    /// </remarks>
+    public static bool IsDesignTime { get; set; }
+
     /// <summary>
     ///     References a given property or navigation on an entity instance. This is useful for shadow state properties, for
     ///     which no CLR property exists. Currently this method can only be used in LINQ queries and can not be used to

test/EFCore.Design.Tests/Design/OperationExecutorTest.cs

@@ -17,6 +17,21 @@ public void Ctor_validates_arguments()
 
     public class OperationBaseTests
     {
+        [ConditionalFact]
+        public void Operations_have_design_time_flag_set()
+        {
+            var handler = new OperationResultHandler();
+            var result = "Twilight Sparkle";
+
+            new MockOperation<string>(handler, () =>
+            {
+                Assert.True(EF.IsDesignTime);
+                return result;
+            });
+
+            Assert.Equal(result, handler.Result);
+        }
+
         [ConditionalFact]
         public void Execute_catches_exceptions()
         {