Merge pull request #13797 from gcomneno/pr-13226-constraint-error

Fix constraint file open error message

Author: pfmoore

news/13226.bugfix.rst

@@ -0,0 +1 @@
+Fix misleading error message when a constraint file cannot be opened.

src/pip/_internal/req/req_file.py

@@ -412,7 +412,7 @@ def _parse_and_recurse(
     def _parse_file(
         self, filename: str, constraint: bool
     ) -> Generator[ParsedLine, None, None]:
-        _, content = get_file_content(filename, self._session)
+        _, content = get_file_content(filename, self._session, constraint=constraint)
 
         lines_enum = preprocess(content)
 
@@ -572,7 +572,9 @@ def expand_env_variables(lines_enum: ReqFileLines) -> ReqFileLines:
         yield line_number, line
 
 
-def get_file_content(url: str, session: PipSession) -> tuple[str, str]:
+def get_file_content(
+    url: str, session: PipSession, *, constraint: bool = False
+) -> tuple[str, str]:
     """Gets the content of a file; it may be a filename, file: URL, or
     http: URL.  Returns (location, content).  Content is unicode.
     Respects # -*- coding: declarations on the retrieved files.
@@ -595,7 +597,8 @@ def get_file_content(url: str, session: PipSession) -> tuple[str, str]:
         with open(url, "rb") as f:
             raw_content = f.read()
     except OSError as exc:
-        raise InstallationError(f"Could not open requirements file: {exc}")
+        kind = "constraint" if constraint else "requirements"
+        raise InstallationError(f"Could not open {kind} file: {exc}")
 
     content = _decode_req_file(raw_content, url)
 

tests/unit/test_req_file.py

@@ -84,6 +84,17 @@ def parse_reqfile(
         )
 
 
+def test_missing_constraint_file_message_mentions_constraints(
+    tmp_path: Path, session: PipSession
+) -> None:
+    missing = tmp_path / "does-not-exist.txt"
+
+    with pytest.raises(InstallationError) as exc:
+        list(parse_reqfile(missing, session=session, constraint=True))
+
+    assert "Could not open constraint file:" in str(exc.value)
+
+
 def test_read_file_url(tmp_path: Path, session: PipSession) -> None:
     reqs = tmp_path.joinpath("requirements.txt")
     reqs.write_text("foo")