Preserve relative paths for editable dependencies in output

piptools/_compat/pip_compat.py

@@ -10,6 +10,7 @@
 from pip._internal.metadata import BaseDistribution
 from pip._internal.metadata.pkg_resources import Distribution as _PkgResourcesDist
 from pip._internal.models.direct_url import DirectUrl
+from pip._internal.models.link import Link
 from pip._internal.network.session import PipSession
 from pip._internal.req import InstallRequirement
 from pip._internal.req import parse_requirements as _parse_requirements
@@ -63,6 +64,14 @@ def _from_importlib(cls, dist: _ImportLibDist) -> Distribution:
         return cls(dist._dist.name, dist._dist.version, requires, dist.direct_url)
 
 
+class FileLink(Link):
+
+    @property
+    def file_path(self) -> str:
+        # overriding the actual property to bypass some validation
+        return self._url
+
+
 def parse_requirements(
     filename: str,
     session: PipSession,
@@ -74,7 +83,14 @@ def parse_requirements(
     for parsed_req in _parse_requirements(
         filename, session, finder=finder, options=options, constraint=constraint
     ):
-        yield install_req_from_parsed_requirement(parsed_req, isolated=isolated)
+        install_req = install_req_from_parsed_requirement(parsed_req, isolated=isolated)
+        if install_req.editable and not parsed_req.requirement.startswith("file://"):
+            # link.url is what is saved to the output file
+            # we set the url directly to undo the transformation in pip's Link class
+            file_link = FileLink(install_req.link.url)
+            file_link._url = parsed_req.requirement
+            install_req.link = file_link
+        yield install_req
 
 
 def create_wheel_cache(cache_dir: str, format_control: str | None = None) -> WheelCache:

tests/constants.py

@@ -5,3 +5,6 @@
 TEST_DATA_PATH = os.path.join(os.path.dirname(__file__), "test_data")
 MINIMAL_WHEELS_PATH = os.path.join(TEST_DATA_PATH, "minimal_wheels")
 PACKAGES_PATH = os.path.join(TEST_DATA_PATH, "packages")
+PACKAGES_RELATIVE_PATH = os.path.relpath(
+    PACKAGES_PATH, os.path.commonpath([os.getcwd(), PACKAGES_PATH])
+)

tests/test_pip_compat.py

@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+import os
+import tempfile
+from pathlib import Path, PurePosixPath
+
+import pytest
+
+from piptools._compat.pip_compat import parse_requirements
+from piptools.repositories import PyPIRepository
+
+from .constants import PACKAGES_RELATIVE_PATH
+
+
+def test_parse_requirements_preserve_editable_relative(repository):
+    test_package_path = str(
+        PurePosixPath(Path(PACKAGES_RELATIVE_PATH)) / "small_fake_a"
+    )
+
+    infile = tempfile.NamedTemporaryFile("w", delete=False)
+    try:
+        infile.write(f"-e {test_package_path}")
+        infile.close()
+
+        [install_requirement] = parse_requirements(
+            infile.name, session=repository.session
+        )
+    finally:
+        os.unlink(infile.name)
+
+    assert install_requirement.link.url == test_package_path
+    assert install_requirement.link.file_path == test_package_path