add custom editable_wheel command to hijack pdb in editable installs

pdbpp_hijack_pdb.pth

@@ -2,6 +2,8 @@
 # Doc: https://docs.python.org/3/library/site.html
 # Code: https://github.com/blueyed/cpython/blob/1b293b600/Lib/site.py#L148-L187
 #
+# See `setup.py` for a similar setup for editable installs.
+#
 # Add our "_pdbpp_path_hack" to the beginning of `sys.path` if:
 # 1. the environment variable PDBPP_HIJACK_PDB is trueish (as an int), defaults to 1.
 #    i.e. PDBPP_HIJACK_PDB=0 can be used to disable it.

setup.py

@@ -1,10 +1,20 @@
-import os.path
+from collections.abc import Mapping
+from pathlib import Path
+from typing import TYPE_CHECKING
 
 from setuptools import setup
 from setuptools.command.build_py import build_py
+from setuptools.command.editable_wheel import _encode_pth, _StaticPth, editable_wheel
 
-readme_path = os.path.join(os.path.dirname(__file__), "README.rst")
-changelog_path = os.path.join(os.path.dirname(__file__), "CHANGELOG")
+if TYPE_CHECKING:
+    from setuptools.command.editable_wheel import (
+        Distribution,
+        EditableStrategy,
+        WheelFile,
+    )
+
+readme_path = Path(__file__).parent / "README.rst"
+changelog_path = Path(__file__).parent / "CHANGELOG"
 
 with open(readme_path, encoding="utf-8") as fh:
     readme = fh.read()
@@ -14,6 +24,58 @@
 long_description = readme + "\n\n" + changelog
 
 
+class CustomEditablePth(_StaticPth):
+    """Inserts a custom module (path_hack_name) as the first element of sys.path"""
+
+    def __init__(
+        self, path_hack_name: str, dist: Distribution, name: str, src_dir: Path
+    ) -> None:
+        super().__init__(dist, name, [src_dir])
+        self.path_hack = src_dir / path_hack_name
+
+    def __call__(
+        self, wheel: WheelFile, files: list[str], mapping: Mapping[str, str]
+    ) -> None:
+        assert all([p.resolve().exists() for p in self.path_entries]), (
+            "module path does not exist"
+        )
+
+        path_hack = f"import sys; sys.path.insert(0, \"{self.path_hack.resolve()}\") if int(os.environ.get('PDBPP_HIJACK_PDB', 1)) else None"
+        contents = _encode_pth(
+            "\n".join(
+                [
+                    path_hack,
+                    self.path_entries[0].resolve().as_posix(),
+                ]
+            ),
+        )
+
+        wheel.writestr(f"__editable__.{self.name}.pth", contents)
+
+
+class editable_install_with_pth_file(editable_wheel):
+    """custom editable_wheel install so that `pip install -e .` also hijacks pdb with pdbpp"""
+
+    _path_hack_name: str = "_pdbpp_path_hack"  # must match name of module in `./src/`
+
+    def _select_strategy(
+        self,
+        name: str,
+        tag: str,
+        build_lib: str | Path,
+    ) -> EditableStrategy:
+        # note: this requires src-layout
+        src_dir = self.package_dir.get("", ".")
+
+        src_dir = Path(self.project_dir, src_dir)
+        return CustomEditablePth(
+            self._path_hack_name,
+            self.distribution,
+            name,
+            src_dir,
+        )
+
+
 class build_py_with_pth_file(build_py):
     """Include the .pth file for this project, in the generated wheel."""
 
@@ -24,13 +86,17 @@ def run(self):
 
         self.copy_file(
             self.pth_file,
-            os.path.join(self.build_lib, self.pth_file),
+            Path(self.build_lib, self.pth_file),
             preserve_mode=0,
         )
+        print(f"build_py_with_pth_file: include {self.pth_file} in wheel")
 
 
 setup(
-    cmdclass={"build_py": build_py_with_pth_file},
+    cmdclass={
+        "editable_wheel": editable_install_with_pth_file,
+        "build_py": build_py_with_pth_file,
+    },
     platforms=[
         "unix",
         "linux",

testing/conftest.py

@@ -212,9 +212,3 @@ def import_mock(name, *args):
             yield m
 
     return cm
-
-
-def skip_with_missing_pth_file():
-    pth = os.path.join(sysconfig.get_path("purelib"), "pdbpp_hijack_pdb.pth")
-    if not os.path.exists(pth):
-        pytest.skip(f"Missing pth file ({pth}), editable install?")

testing/test_integration.py

@@ -1,13 +1,17 @@
+import glob
+import importlib
 import re
+import subprocess
 import sys
+import sysconfig
 from os import spawnl
+from pathlib import Path
+from shutil import which
 from textwrap import dedent
 
 import pexpect
 import pytest
 
-from .conftest import skip_with_missing_pth_file
-
 
 def test_integration(pytester, readline_param):
     with (pytester.path / "test_file.py").open("w") as fh:
@@ -60,7 +64,6 @@ def test_ipython(testdir):
     - `up` used to crash due to conflicting `hidden_frames` attribute/method.
     """
     pytest.importorskip("IPython")
-    skip_with_missing_pth_file()
 
     child = testdir.spawn(
         f"{sys.executable} -m IPython --colors=nocolor --simple-prompt",
@@ -75,3 +78,74 @@ def test_ipython(testdir):
     child.sendeof()
     child.sendline("y")
     assert child.wait() == 0
+
+
+def test_hijacking():
+    """make sure that _pdbpp_path_hack is one of the first items in sys.path"""
+
+    spec = importlib.util.find_spec("pdbpp")
+    if spec is None or spec.origin is None:
+        return False
+
+    package_path = Path(spec.origin).parent
+
+    if package_path.parts[-1] == "src":
+        # editable install
+        path_entry = sys.path[2]
+    elif package_path.parts[-1] == "site-packages":
+        # full install
+        path_entry = sys.path[1]
+    else:
+        pytest.fail("Unknown install location/method?")
+
+    stdlib_path = sysconfig.get_path("stdlib")
+
+    path_hack_found = False
+    for path_entry in sys.path:
+        if "_pdbpp_path_hack" in path_entry:
+            path_hack_found = True
+
+        if path_entry != stdlib_path:
+            continue
+
+        if path_hack_found:
+            break
+
+        pytest.fail("stdlib path is not hijacked")
+
+
+def test_editable_install_pth(tmp_path):
+    """Make sure that running `pip install -e .` installs the .pth file for pdb hijacking"""
+
+    has_uv = which("uv")
+    if has_uv:  # uv is faster in creating venvs
+        venv_command = f"uv venv --python={sys.executable} --seed {tmp_path}"  # seed the env with pip
+    else:
+        venv_command = f"{sys.executable} -m venv {tmp_path}"
+
+    subprocess.check_call(venv_command.split())
+
+    python = tmp_path / "bin/python"
+
+    pdbpp_root = Path(__file__).parent.parent
+
+    install_command = f"pip install --no-deps -e {pdbpp_root}"
+    if has_uv:
+        install_command = f"uv {install_command} --python={python}"
+    else:
+        install_command = f"{python} -m {install_command}"
+
+    subprocess.check_call(install_command.split())
+
+    pths: list[Path] = list(
+        glob.glob((tmp_path / "lib/*/site-packages/__editable__.pdbpp*.pth").as_posix())
+    )
+
+    assert len(pths) == 1
+
+    editable_pth = Path(pths[0])
+    pth_contents = editable_pth.read_text()
+
+    pattern = r"sys.path.insert\(0, \".*_pdbpp_path_hack\"\)"
+    result = re.search(pattern, pth_contents)
+    assert result is not None

testing/test_pdb.py

@@ -23,8 +23,6 @@
 import pdbpp
 from pdbpp import DefaultConfig, Pdb, StringIO
 
-from .conftest import skip_with_missing_pth_file
-
 pygments_major, pygments_minor, _ = pygments_version.split(".")
 
 
@@ -5704,9 +5702,6 @@ def test_python_m_pdb_usage():
 
 @pytest.mark.parametrize("PDBPP_HIJACK_PDB", (1, 0))
 def test_python_m_pdb_uses_pdbpp_and_env(PDBPP_HIJACK_PDB, monkeypatch, tmpdir):
-    if PDBPP_HIJACK_PDB:
-        skip_with_missing_pth_file()
-
     monkeypatch.setenv("PDBPP_HIJACK_PDB", str(PDBPP_HIJACK_PDB))
 
     f = tmpdir.ensure("test.py")