From 4d3e3f44a1dbcf7671d93b9062f7c968d29a3588 Mon Sep 17 00:00:00 2001
From: LordBaryhobal <lordbaryhobal@gmail.com>
Date: Fri, 3 Jul 2026 12:28:39 +0200
Subject: [PATCH] fix(checker): correctly check length of frame/column

---
 midas/checker/frames/column_methods.py | 25 ++++++++++++++++--------
 midas/checker/frames/frame_methods.py  | 27 ++++++++++++++++----------
 2 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/midas/checker/frames/column_methods.py b/midas/checker/frames/column_methods.py
index 02de5a3..95bce9e 100644
--- a/midas/checker/frames/column_methods.py
+++ b/midas/checker/frames/column_methods.py
@@ -355,6 +355,21 @@ class ColumnMethodRegistry(MethodRegistry[Call]):
 
     def _assert_same_length(self, call_expr: p.Expr, column1: p.Expr, column2: p.Expr):
         func_name: str = "__midas_column_same_length__"
+
+        # Efficiently compute length
+        # https://stackoverflow.com/a/15943975/11109181
+        def len_of_col(col: ast.expr) -> ast.expr:
+            return ast.Call(
+                func=ast.Name(id="len"),
+                args=[
+                    ast.Attribute(
+                        value=col,
+                        attr="index",
+                    )
+                ],
+                keywords=[],
+            )
+
         self.assertions.define(
             func_name,
             ast.FunctionDef(
@@ -372,16 +387,10 @@ class ColumnMethodRegistry(MethodRegistry[Call]):
                 body=[
                     ast.Return(
                         value=ast.Compare(
-                            left=ast.Attribute(
-                                value=ast.Name(id="column1"),
-                                attr="size",
-                            ),
+                            left=len_of_col(ast.Name(id="column1")),
                             ops=[ast.Eq()],
                             comparators=[
-                                ast.Attribute(
-                                    value=ast.Name(id="column2"),
-                                    attr="size",
-                                )
+                                len_of_col(ast.Name(id="column2")),
                             ],
                         )
                     )
diff --git a/midas/checker/frames/frame_methods.py b/midas/checker/frames/frame_methods.py
index bd9e3ee..1be481f 100644
--- a/midas/checker/frames/frame_methods.py
+++ b/midas/checker/frames/frame_methods.py
@@ -434,6 +434,21 @@ class FrameMethodRegistry(MethodRegistry[Call]):
 
     def _assert_same_length(self, call_expr: p.Expr, frame1: p.Expr, frame2: p.Expr):
         func_name: str = "__midas_frame_same_length__"
+
+        # Efficiently compute length
+        # https://stackoverflow.com/a/15943975/11109181
+        def len_of_df(df: ast.expr) -> ast.expr:
+            return ast.Call(
+                func=ast.Name(id="len"),
+                args=[
+                    ast.Attribute(
+                        value=df,
+                        attr="index",
+                    )
+                ],
+                keywords=[],
+            )
+
         self.assertions.define(
             func_name,
             ast.FunctionDef(
@@ -451,17 +466,9 @@ class FrameMethodRegistry(MethodRegistry[Call]):
                 body=[
                     ast.Return(
                         value=ast.Compare(
-                            left=ast.Attribute(
-                                value=ast.Name(id="frame1"),
-                                attr="size",
-                            ),
+                            left=len_of_df(ast.Name(id="frame1")),
                             ops=[ast.Eq()],
-                            comparators=[
-                                ast.Attribute(
-                                    value=ast.Name(id="frame2"),
-                                    attr="size",
-                                )
-                            ],
+                            comparators=[len_of_df(ast.Name(id="frame2"))],
                         )
                     )
                 ],