From 614144312da9907a87f8340fd5ba2414b504401b Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Mon, 15 Dec 2025 18:29:37 +0000
Subject: [PATCH] feat: add `Session.read_ibis` method

This method allows creating a `leanframe.DataFrame` from an existing Ibis table expression.
This is useful for interoperability when users have constructed Ibis expressions directly.

Added unit tests in `tests/unit/session/test_read_ibis.py`.
---
 leanframe/core/session.py            |  6 ++++
 tests/unit/session/test_read_ibis.py | 41 ++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100644 tests/unit/session/test_read_ibis.py

diff --git a/leanframe/core/session.py b/leanframe/core/session.py
index 401e28b..836e4b6 100644
--- a/leanframe/core/session.py
+++ b/leanframe/core/session.py
@@ -45,6 +45,12 @@ def read_sql_table(self, table_name: str):
         #TODO: will crash if self._backend is None. 
         return leanframe.core.frame.DataFrame(self._backend.table(table_name)) # type: ignore
 
+    def read_ibis(self, table_expression: ibis_types.Table):
+        """Create a DataFrame from an Ibis table expression."""
+        import leanframe.core.frame
+
+        return leanframe.core.frame.DataFrame(table_expression)
+
     def DataFrame(self, data: ibis_types.Table | pandas.DataFrame):
         """Construct a DataFrame."""
         import leanframe.core.frame
diff --git a/tests/unit/session/test_read_ibis.py b/tests/unit/session/test_read_ibis.py
new file mode 100644
index 0000000..4454b21
--- /dev/null
+++ b/tests/unit/session/test_read_ibis.py
@@ -0,0 +1,41 @@
+
+import ibis
+import pandas as pd
+import pytest
+from unittest.mock import MagicMock
+
+from leanframe.core import session
+
+@pytest.fixture
+def mock_backend():
+    return MagicMock()
+
+def test_read_ibis_returns_dataframe(mock_backend):
+    """Test that read_ibis returns a leanframe DataFrame."""
+    s = session.Session(mock_backend)
+    df = pd.DataFrame({'a': [1, 2, 3]})
+    t = ibis.memtable(df)
+
+    lf_df = s.read_ibis(t)
+
+    # Check that it is a leanframe DataFrame
+    # Note: importing DataFrame inside the function to avoid circular imports if any,
+    # though it should be fine at module level for type checking
+    from leanframe.core.frame import DataFrame
+    assert isinstance(lf_df, DataFrame)
+
+    # Check that the underlying data is correct
+    assert lf_df.to_ibis().equals(t)
+
+def test_read_ibis_with_complex_expression(mock_backend):
+    """Test read_ibis with a more complex ibis expression."""
+    s = session.Session(mock_backend)
+    df = pd.DataFrame({'a': [1, 2, 3], 'b': [4, 5, 6]})
+    t = ibis.memtable(df)
+    expr = t.mutate(c=t.a + t.b)
+
+    lf_df = s.read_ibis(expr)
+
+    from leanframe.core.frame import DataFrame
+    assert isinstance(lf_df, DataFrame)
+    assert lf_df.to_ibis().equals(expr)