Unify Python project root detection logic

A Python project root is now defined as containing a pyproject.toml, or
a setup.py (pre-PEP-517 legacy layout). After this patch, this logic
applies to all checks except parse_editable, where we check for setup.py
and setup.cfg instead since non-setuptools PEP 517 projects cannot be
installed as editable right now.

news/10080.bugfix.rst

@@ -0,0 +1 @@
+Correctly allow PEP 517 projects to be detected without warnings in ``pip freeze``.

src/pip/_internal/operations/prepare.py

@@ -39,7 +39,7 @@
 from pip._internal.utils.filesystem import copy2_fixed
 from pip._internal.utils.hashes import Hashes, MissingHashes
 from pip._internal.utils.logging import indent_log
-from pip._internal.utils.misc import display_path, hide_url, rmtree
+from pip._internal.utils.misc import display_path, hide_url, is_installable_dir, rmtree
 from pip._internal.utils.temp_dir import TempDirectory
 from pip._internal.utils.unpacking import unpack_file
 from pip._internal.vcs import vcs
@@ -376,7 +376,7 @@ def _ensure_link_req_src_dir(self, req, parallel_builds):
         # installation.
         # FIXME: this won't upgrade when there's an existing
         # package unpacked in `req.source_dir`
-        if os.path.exists(os.path.join(req.source_dir, 'setup.py')):
+        if is_installable_dir(req.source_dir):
             raise PreviousBuildDirError(
                 "pip can't proceed with requirements '{}' due to a"
                 "pre-existing build directory ({}). This is likely "

src/pip/_internal/req/constructors.py

@@ -248,8 +248,8 @@ def _looks_like_path(name):
 def _get_url_from_path(path, name):
     # type: (str, str) -> Optional[str]
     """
-    First, it checks whether a provided path is an installable directory
-    (e.g. it has a setup.py). If it is, returns the path.
+    First, it checks whether a provided path is an installable directory. If it
+    is, returns the path.
 
     If false, check if the path is an archive file (such as a .whl).
     The function checks if the path is a file. If false, if the path has

src/pip/_internal/utils/misc.py

@@ -270,13 +270,20 @@ def tabulate(rows):
 
 
 def is_installable_dir(path: str) -> bool:
-    """Is path is a directory containing pyproject.toml, setup.cfg or setup.py?"""
+    """Is path is a directory containing pyproject.toml or setup.py?
+
+    If pyproject.toml exists, this is a PEP 517 project. Otherwise we look for
+    a legacy setuptools layout by identifying setup.py. We don't check for the
+    setup.cfg because using it without setup.py is only available for PEP 517
+    projects, which are already covered by the pyproject.toml check.
+    """
     if not os.path.isdir(path):
         return False
-    return any(
-        os.path.isfile(os.path.join(path, signifier))
-        for signifier in ("pyproject.toml", "setup.cfg", "setup.py")
-    )
+    if os.path.isfile(os.path.join(path, "pyproject.toml")):
+        return True
+    if os.path.isfile(os.path.join(path, "setup.py")):
+        return True
+    return False
 
 
 def read_chunks(file, size=io.DEFAULT_BUFFER_SIZE):

src/pip/_internal/vcs/git.py

@@ -18,7 +18,7 @@
     RemoteNotValidError,
     RevOptions,
     VersionControl,
-    find_path_to_setup_from_repo_root,
+    find_path_to_project_root_from_repo_root,
     vcs,
 )
 
@@ -410,8 +410,8 @@ def get_revision(cls, location, rev=None):
     def get_subdirectory(cls, location):
         # type: (str) -> Optional[str]
         """
-        Return the path to setup.py, relative to the repo root.
-        Return None if setup.py is in the repo root.
+        Return the path to Python project root, relative to the repo root.
+        Return None if the project root is in the repo root.
         """
         # find the repo root
         git_dir = cls.run_command(
@@ -423,7 +423,7 @@ def get_subdirectory(cls, location):
         if not os.path.isabs(git_dir):
             git_dir = os.path.join(location, git_dir)
         repo_root = os.path.abspath(os.path.join(git_dir, '..'))
-        return find_path_to_setup_from_repo_root(location, repo_root)
+        return find_path_to_project_root_from_repo_root(location, repo_root)
 
     @classmethod
     def get_url_rev_and_auth(cls, url):

src/pip/_internal/vcs/mercurial.py

@@ -10,7 +10,7 @@
 from pip._internal.vcs.versioncontrol import (
     RevOptions,
     VersionControl,
-    find_path_to_setup_from_repo_root,
+    find_path_to_project_root_from_repo_root,
     vcs,
 )
 
@@ -120,16 +120,16 @@ def is_commit_id_equal(cls, dest, name):
     def get_subdirectory(cls, location):
         # type: (str) -> Optional[str]
         """
-        Return the path to setup.py, relative to the repo root.
-        Return None if setup.py is in the repo root.
+        Return the path to Python project root, relative to the repo root.
+        Return None if the project root is in the repo root.
         """
         # find the repo root
         repo_root = cls.run_command(
             ['root'], show_stdout=False, stdout_only=True, cwd=location
         ).strip()
         if not os.path.isabs(repo_root):
             repo_root = os.path.abspath(os.path.join(location, repo_root))
-        return find_path_to_setup_from_repo_root(location, repo_root)
+        return find_path_to_project_root_from_repo_root(location, repo_root)
 
     @classmethod
     def get_repository_root(cls, location):

src/pip/_internal/vcs/subversion.py

@@ -7,6 +7,7 @@
     HiddenText,
     display_path,
     is_console_interactive,
+    is_installable_dir,
     split_auth_from_netloc,
 )
 from pip._internal.utils.subprocess import CommandArgs, make_command
@@ -111,18 +112,17 @@ def make_rev_args(username, password):
     @classmethod
     def get_remote_url(cls, location):
         # type: (str) -> str
-        # In cases where the source is in a subdirectory, not alongside
-        # setup.py we have to look up in the location until we find a real
-        # setup.py
+        # In cases where the source is in a subdirectory, we have to look up in
+        # the location until we find a valid project root.
         orig_location = location
-        while not os.path.exists(os.path.join(location, 'setup.py')):
+        while not is_installable_dir(location):
             last_location = location
             location = os.path.dirname(location)
             if location == last_location:
                 # We've traversed up to the root of the filesystem without
-                # finding setup.py
+                # finding a Python project.
                 logger.warning(
-                    "Could not find setup.py for directory %s (tried all "
+                    "Could not find Python project for directory %s (tried all "
                     "parent directories)",
                     orig_location,
                 )

src/pip/_internal/vcs/versioncontrol.py

@@ -27,6 +27,7 @@
     display_path,
     hide_url,
     hide_value,
+    is_installable_dir,
     rmtree,
 )
 from pip._internal.utils.subprocess import CommandArgs, call_subprocess, make_command
@@ -68,23 +69,23 @@ def make_vcs_requirement_url(repo_url, rev, project_name, subdir=None):
     return req
 
 
-def find_path_to_setup_from_repo_root(location, repo_root):
+def find_path_to_project_root_from_repo_root(location, repo_root):
     # type: (str, str) -> Optional[str]
     """
-    Find the path to `setup.py` by searching up the filesystem from `location`.
-    Return the path to `setup.py` relative to `repo_root`.
-    Return None if `setup.py` is in `repo_root` or cannot be found.
+    Find the the Python project's root by searching up the filesystem from
+    `location`. Return the path to project root relative to `repo_root`.
+    Return None if the project root is `repo_root`, or cannot be found.
     """
-    # find setup.py
+    # find project root.
     orig_location = location
-    while not os.path.exists(os.path.join(location, 'setup.py')):
+    while not is_installable_dir(location):
         last_location = location
         location = os.path.dirname(location)
         if location == last_location:
             # We've traversed up to the root of the filesystem without
-            # finding setup.py
+            # finding a Python project.
             logger.warning(
-                "Could not find setup.py for directory %s (tried all "
+                "Could not find a Python project for directory %s (tried all "
                 "parent directories)",
                 orig_location,
             )
@@ -296,8 +297,8 @@ def should_add_vcs_url_prefix(cls, remote_url):
     def get_subdirectory(cls, location):
         # type: (str) -> Optional[str]
         """
-        Return the path to setup.py, relative to the repo root.
-        Return None if setup.py is in the repo root.
+        Return the path to Python project root, relative to the repo root.
+        Return None if the project root is in the repo root.
         """
         return None