Fix/tcolor preserve metadata

bindings/pyroot/pythonizations/python/ROOT/_pythonization/_tcolor.py

@@ -7,20 +7,23 @@
 # For the licensing terms see $ROOTSYS/LICENSE.                                #
 # For the list of contributors see $ROOTSYS/README/CREDITS.                    #
 ################################################################################
+
+import functools
+
 from . import pythonization
 
 
-def _TColor_constructor(self, *args, **kwargs):
-    """
-    Forward the arguments to the C++ constructor and retain ownership. This
-    helps avoiding double deletes due to ROOT automatic memory management.
-    """
-    self._cpp_constructor(*args, **kwargs)
-    import ROOT
-    ROOT.SetOwnership(self, False)
+def _tcolor_constructor(original_init):
+    @functools.wraps(original_init)
+    def wrapper(self, *args, **kwargs):
+        original_init(self, *args, **kwargs)
+        import ROOT
+
+        ROOT.SetOwnership(self, False)
+
+    return wrapper
 
 
 @pythonization("TColor")
 def pythonize_tcolor(klass):
-    klass._cpp_constructor = klass.__init__
-    klass.__init__ = _TColor_constructor
+    klass.__init__ = _tcolor_constructor(klass.__init__)

roottest/python/JupyROOT/CMakeLists.txt

@@ -15,7 +15,8 @@ set(NOTEBOOKS importROOT.ipynb
               simpleCppMagic.ipynb
               thread_local.ipynb
               ROOT_kernel.ipynb
-              tpython.ipynb)
+              tpython.ipynb
+              tcolor_definedcolors.ipynb)
 
 # Test all modules with doctest. All new tests will be automatically picked up
 file(GLOB pyfiles ${MODULES_LOCATION}/*.py)

roottest/python/JupyROOT/tcolor_definedcolors.ipynb

@@ -0,0 +1,95 @@
+{
+    "cells": [
+        {
+            "cell_type": "code",
+            "execution_count": null,
+            "id": "b8ef0e09",
+            "metadata": {},
+            "outputs": [],
+            "source": [
+                "import ROOT"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": null,
+            "id": "ac871508",
+            "metadata": {},
+            "outputs": [],
+            "source": [
+                "ROOT.TColor.DefinedColors(1)"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": null,
+            "id": "4800d2c7",
+            "metadata": {},
+            "outputs": [],
+            "source": [
+                "c = ROOT.TCanvas(\"c\", \"Basic ROOT Plot\", 800, 600)"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": null,
+            "id": "f3900d8a",
+            "metadata": {},
+            "outputs": [],
+            "source": [
+                "h = ROOT.TH1F(\"h\", \"Example Histogram;X axis;Entries\", 100, 0, 10)"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": null,
+            "id": "d83cc9da",
+            "metadata": {},
+            "outputs": [],
+            "source": [
+                "for _ in range(10000):\n",
+                "    h.Fill(ROOT.gRandom.Gaus(5, 1))"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": null,
+            "id": "1df7d032",
+            "metadata": {},
+            "outputs": [],
+            "source": [
+                "h.Draw()"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": null,
+            "id": "3743fddc",
+            "metadata": {},
+            "outputs": [],
+            "source": [
+                "c.Draw()"
+            ]
+        }
+    ],
+    "metadata": {
+        "kernelspec": {
+            "display_name": "Python 3",
+            "language": "python",
+            "name": "python3"
+        },
+        "language_info": {
+            "codemirror_mode": {
+                "name": "ipython",
+                "version": 3
+            },
+            "file_extension": ".py",
+            "mimetype": "text/x-python",
+            "name": "python",
+            "nbconvert_exporter": "python",
+            "pygments_lexer": "ipython3"
+        }
+    },
+    "nbformat": 4,
+    "nbformat_minor": 5
+}

roottest/python/JupyROOT/test_tcolor_metadata.py

@@ -0,0 +1,111 @@
+#!/usr/bin/env python3
+"""
+Test script to verify that TColor.DefinedColors works correctly in Jupyter-like environments.
+This test verifies the fix for issue #20018.
+"""
+import sys
+
+
+def test_tcolor_metadata_preservation():
+    """
+    Test that TColor.__init__ preserves metadata after pythonization.
+    This ensures that introspection-heavy environments like Jupyter can
+    properly inspect the method.
+    """
+    import ROOT
+
+    # Check that __init__ has the expected attributes from functools.wraps
+    assert hasattr(ROOT.TColor.__init__, '__wrapped__'), \
+        "TColor.__init__ should have __wrapped__ attribute from functools.wraps"
+
+    # Check that __name__ is preserved
+    assert hasattr(ROOT.TColor.__init__, '__name__'), \
+        "TColor.__init__ should have __name__ attribute"
+
+    # Check that __doc__ is preserved
+    assert hasattr(ROOT.TColor.__init__, '__doc__'), \
+        "TColor.__init__ should have __doc__ attribute"
+
+    print("Metadata preservation test: PASSED")
+    return True
+
+def test_tcolor_definedcolors():
+    """
+    Test the original issue: TColor.DefinedColors(1) should work without errors.
+    """
+    import ROOT
+
+    try:
+        # This was the problematic call in Jupyter notebooks
+        result = ROOT.TColor.DefinedColors(1)
+        print(f"TColor.DefinedColors(1) returned: {result}")
+        print("DefinedColors test: PASSED")
+        return True
+    except Exception as e:
+        print(f"TColor.DefinedColors(1) failed with error: {e}")
+        print("DefinedColors test: FAILED")
+        return False
+
+def test_tcolor_full_workflow():
+    """
+    Test the full workflow from the original issue report.
+    """
+    import ROOT
+
+    try:
+        # Create a canvas
+        ROOT.TColor.DefinedColors(1)
+        c = ROOT.TCanvas("c", "Basic ROOT Plot", 800, 600)
+
+        # Create a histogram with 100 bins from 0 to 10
+        h = ROOT.TH1F("h", "Example Histogram;X axis;Entries", 100, 0, 10)
+
+        # Fill histogram with random Gaussian numbers
+        for _ in range(10000):
+            h.Fill(ROOT.gRandom.Gaus(5, 1))
+
+        # Draw the histogram
+        h.Draw()
+
+        # Draw canvas
+        c.Draw()
+
+        print("Full workflow test: PASSED")
+        return True
+    except Exception as e:
+        print(f"Full workflow test failed with error: {e}")
+        print("Full workflow test: FAILED")
+        return False
+
+def main():
+    """
+    Run all tests and return exit code.
+    """
+    print("=" * 60)
+    print("Testing TColor metadata preservation fix for issue #20018")
+    print("=" * 60)
+
+    tests = [
+        test_tcolor_metadata_preservation,
+        test_tcolor_definedcolors,
+        test_tcolor_full_workflow
+    ]
+
+    results = []
+    for test in tests:
+        print(f"\nRunning {test.__name__}...")
+        try:
+            result = test()
+            results.append(result)
+        except Exception as e:
+            print(f"Test {test.__name__} raised exception: {e}")
+            results.append(False)
+
+    print("\n" + "=" * 60)
+    print(f"Test Results: {sum(results)}/{len(results)} passed")
+    print("=" * 60)
+
+    return 0 if all(results) else 1
+
+if __name__ == "__main__":
+    sys.exit(main())