Handle seed-data cycle diagnostics without crashing during migration scaffolding

src/EFCore.Relational/Update/Internal/CommandBatchPreparer.cs

@@ -394,7 +394,11 @@ private string FormatCycle(
             var (command1, command2, edges) = data[i];
             Format(command1, builder);
 
-            switch (edges.First().Metadata)
+            var firstEdge = edges.FirstOrDefault();
+            Check.DebugAssert(
+                firstEdge is not null || (command1.Entries.Count == 0 && command2.Entries.Count == 0),
+                "Edge metadata may be null only when both commands have no entries, which occurs during predecessor traversal of migration data commands.");
+            switch (firstEdge?.Metadata)
             {
                 case IForeignKey foreignKey:
                     Format(foreignKey, command1, command2, builder);
@@ -432,6 +436,30 @@ private string FormatCycle(
 
     private void Format(IReadOnlyModificationCommand command, StringBuilder builder)
     {
+        if (command.Entries.Count == 0)
+        {
+            Check.DebugAssert(
+                command.Table is not null || command.StoreStoredProcedure is not null,
+                "Commands without entries must have table or stored procedure metadata because cycle errors need to identify the store object.");
+
+            if (command.Schema == null)
+            {
+                builder.Append(command.TableName);
+            }
+            else
+            {
+                builder.Append(command.Schema);
+                builder.Append('.');
+                builder.Append(command.TableName);
+            }
+
+            builder.Append(' ');
+            builder.Append('[');
+            builder.Append(command.EntityState);
+            builder.Append(']');
+            return;
+        }
+
         var entry = command.Entries.First();
         var entityType = entry.EntityType;
         builder.Append(entityType.DisplayName());

test/EFCore.Relational.Tests/Migrations/Internal/MigrationsModelDifferTest.cs

@@ -1931,6 +1931,52 @@ public void Throws_on_conflicting_seed_data(bool enableSensitiveLogging)
                 _ => { },
                 enableSensitiveLogging: enableSensitiveLogging)).Message);
 
+    [Fact]
+    public void Throws_circular_dependency_instead_of_sequence_contains_no_elements_for_seed_data_cycle()
+    {
+        var exception = Assert.Throws<InvalidOperationException>(
+            () => Execute(
+                model =>
+                {
+                    model.Entity(
+                        "WorkflowType",
+                        x =>
+                        {
+                            x.ToTable("WorkflowType");
+                            x.Property<string>("Code").IsRequired();
+                            x.Property<string>("FirstStepCode").IsRequired();
+                            x.HasKey("Code");
+                        });
+
+                    model.Entity(
+                        "WorkflowStep",
+                        x =>
+                        {
+                            x.ToTable("WorkflowStep");
+                            x.Property<string>("Code").IsRequired();
+                            x.Property<string>("WorkflowTypeCode").IsRequired();
+                            x.HasKey("Code");
+                        });
+
+                    model.Entity("WorkflowType").HasOne("WorkflowStep").WithMany().HasForeignKey("FirstStepCode");
+                    model.Entity("WorkflowStep").HasOne("WorkflowType").WithMany("Steps").HasForeignKey("WorkflowTypeCode");
+                },
+                _ => { },
+                target =>
+                {
+                    target.Entity("WorkflowType").HasData(
+                        new { Code = "TEST", FirstStepCode = "TEST-01A" });
+
+                    target.Entity("WorkflowStep").HasData(
+                        new { Code = "TEST-01A", WorkflowTypeCode = "TEST" });
+                },
+                _ => { },
+                _ => { }));
+
+        Assert.DoesNotContain("Sequence contains no elements", exception.Message, StringComparison.Ordinal);
+        Assert.Contains("circular dependency", exception.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
     [Fact]
     public void Add_column_with_order()
         => Execute(