Fix nested SelectExpr inconsistency between playground and source generator (#221)

* Initial plan

* Add shared IsNestedInsideAnotherSelectExpr helper and use in playground and source generator

Co-authored-by: arika0093 <[email protected]>

* Add comprehensive tests for nested SelectExpr consistency fix

Co-authored-by: arika0093 <[email protected]>

* Remove tests for nested SelectExpr type verification

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: arika0093 <[email protected]>
Co-authored-by: Arika Ishinami <[email protected]>

Author: Copilot

playground/Services/CodeGenerationService.cs

@@ -161,7 +161,17 @@ SemanticModel semanticModel
     private static bool IsSelectExprInvocation(InvocationExpressionSyntax invocation)
     {
         var expression = invocation.Expression;
-        return SelectExprHelper.IsSelectExprInvocationSyntax(expression);
+        if (!SelectExprHelper.IsSelectExprInvocationSyntax(expression))
+            return false;
+
+        // Skip if this SelectExpr is nested inside another SelectExpr.
+        // When SelectExpr is used inside another SelectExpr (nested SelectExpr),
+        // only the outermost SelectExpr should generate an interceptor.
+        // The inner SelectExpr will be converted to a regular Select call by the outer one.
+        if (SelectExprHelper.IsNestedInsideAnotherSelectExpr(invocation))
+            return false;
+
+        return true;
     }
 
     private static SelectExprInfo? GetSelectExprInfo(

src/Linqraft.Core/SelectExprHelper.cs

@@ -82,4 +82,31 @@ SemanticModel semanticModel
         var symbolInfo = semanticModel.GetSymbolInfo(invocation);
         return IsSelectExprMethod(symbolInfo.Symbol);
     }
+
+    /// <summary>
+    /// Checks if the given SelectExpr invocation is nested inside another SelectExpr invocation.
+    /// When SelectExpr is used inside another SelectExpr (nested SelectExpr),
+    /// only the outermost SelectExpr should generate an interceptor.
+    /// The inner SelectExpr will be converted to a regular Select call by the outer one.
+    /// </summary>
+    /// <param name="invocation">The invocation expression to check</param>
+    /// <returns>True if the invocation is nested inside another SelectExpr</returns>
+    public static bool IsNestedInsideAnotherSelectExpr(InvocationExpressionSyntax invocation)
+    {
+        // Walk up the syntax tree to find any ancestor that is also a SelectExpr invocation
+        var current = invocation.Parent;
+        while (current is not null)
+        {
+            // If we find a parent InvocationExpression that is also a SelectExpr, we are nested
+            if (current is InvocationExpressionSyntax parentInvocation)
+            {
+                if (IsSelectExprInvocationSyntax(parentInvocation.Expression))
+                {
+                    return true;
+                }
+            }
+            current = current.Parent;
+        }
+        return false;
+    }
 }

src/Linqraft.SourceGenerator/SelectExprGenerator.cs

@@ -106,34 +106,12 @@ private static bool IsSelectExprInvocation(SyntaxNode node)
         // When SelectExpr is used inside another SelectExpr (nested SelectExpr),
         // only the outermost SelectExpr should generate an interceptor.
         // The inner SelectExpr will be converted to a regular Select call by the outer one.
-        if (IsNestedInsideAnotherSelectExpr(invocation))
+        if (SelectExprHelper.IsNestedInsideAnotherSelectExpr(invocation))
             return false;
 
         return true;
     }
 
-    /// <summary>
-    /// Checks if the given SelectExpr invocation is nested inside another SelectExpr invocation.
-    /// </summary>
-    private static bool IsNestedInsideAnotherSelectExpr(InvocationExpressionSyntax invocation)
-    {
-        // Walk up the syntax tree to find any ancestor that is also a SelectExpr invocation
-        var current = invocation.Parent;
-        while (current is not null)
-        {
-            // If we find a parent InvocationExpression that is also a SelectExpr, we are nested
-            if (current is InvocationExpressionSyntax parentInvocation)
-            {
-                if (SelectExprHelper.IsSelectExprInvocationSyntax(parentInvocation.Expression))
-                {
-                    return true;
-                }
-            }
-            current = current.Parent;
-        }
-        return false;
-    }
-
     private static SelectExprInfo? GetSelectExprInfo(GeneratorSyntaxContext context)
     {
         var invocation = (InvocationExpressionSyntax)context.Node;