Fix pip freeze not showing correct entry for mercurial packages that use subdirectories.

news/7071.bugfix

@@ -0,0 +1 @@
+Fix `pip freeze` not showing correct entry for mercurial packages that use subdirectories.

src/pip/_internal/vcs/git.py

@@ -362,8 +362,8 @@ def update_submodules(cls, location):
 
     @classmethod
     def controls_location(cls, location):
-        if super(Git, cls).controls_location(location):
-            return True
+        if not super(Git, cls).controls_location(location):
+            return False
         try:
             r = cls.run_command(['rev-parse'],
                                 cwd=location,

src/pip/_internal/vcs/mercurial.py

@@ -5,6 +5,8 @@
 
 from pip._vendor.six.moves import configparser
 
+from pip._internal.exceptions import BadCommand
+from pip._internal.utils.compat import samefile
 from pip._internal.utils.misc import display_path, make_command, path_to_url
 from pip._internal.utils.temp_dir import TempDirectory
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
@@ -111,5 +113,47 @@ def is_commit_id_equal(cls, dest, name):
         """Always assume the versions don't match"""
         return False
 
+    @classmethod
+    def get_subdirectory(cls, location):
+        # find the repo root
+        root_dir = cls.run_command(['root'],
+                                   show_stdout=False, cwd=location).strip()
+        if not os.path.isabs(root_dir):
+            root_dir = os.path.join(location, root_dir)
+        # find setup.py
+        orig_location = location
+        while not os.path.exists(os.path.join(location, 'setup.py')):
+            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
+                logger.warning(
+                    "Could not find setup.py for directory %s (tried all "
+                    "parent directories)",
+                    orig_location,
+                )
+                return None
+        # relative path of setup.py to repo root
+        if samefile(root_dir, location):
+            return None
+        return os.path.relpath(location, root_dir)
+
+    @classmethod
+    def controls_location(cls, location):
+        if not super(Mercurial, cls).controls_location(location):
+            return False
+        try:
+            r = cls.run_command(['identify'],
+                                cwd=location,
+                                show_stdout=False,
+                                on_returncode='ignore',
+                                extra_ok_returncodes=[255])
+            return not r.startswith('abort:')
+        except BadCommand:
+            logger.debug("could not determine if %s is under hg control "
+                         "because hg is not available", location)
+            return False
+
 
 vcs.register(Mercurial)

src/pip/_internal/vcs/versioncontrol.py

@@ -621,10 +621,17 @@ def controls_location(cls, location):
         # type: (str) -> bool
         """
         Check if a location is controlled by the vcs.
-        It is meant to be overridden to implement smarter detection
-        mechanisms for specific vcs.
 
-        This can do more than is_repository_directory() alone.  For example,
-        the Git override checks that Git is actually available.
+        Searches up the filesystem and checks is_repository_directory().
+
+        It is meant to be extended to add smarter detection mechanisms for
+        specific vcs.  For example, the Git override checks that Git is
+        actually available.
         """
-        return cls.is_repository_directory(location)
+        while not cls.is_repository_directory(location):
+            last_location = location
+            location = os.path.dirname(location)
+            if location == last_location:
+                # We've traversed up to the root of the filesystem.
+                return False
+        return True

tests/functional/test_freeze.py

@@ -322,6 +322,49 @@ def test_freeze_git_clone_srcdir(script, tmpdir):
     _check_output(result.stdout, expected)
 
 
+@need_mercurial
+def test_freeze_mercurial_clone_srcdir(script, tmpdir):
+    """
+    Test freezing a Mercurial clone where setup.py is in a subdirectory
+    relative to the repo root and the source code is in a subdirectory
+    relative to setup.py.
+    """
+    # Returns path to a generated package called "version_pkg"
+    pkg_version = _create_test_package_with_srcdir(script, vcs='hg')
+
+    result = script.run(
+        'hg', 'clone', pkg_version, 'pip-test-package',
+        expect_stderr=True,
+    )
+    repo_dir = script.scratch_path / 'pip-test-package'
+    result = script.run(
+        'python', 'setup.py', 'develop',
+        cwd=repo_dir / 'subdir',
+        expect_stderr=True,
+    )
+    result = script.pip('freeze', expect_stderr=True)
+    expected = textwrap.dedent(
+        """
+            ...-e hg+...#egg=version_pkg&subdirectory=subdir
+            ...
+        """
+    ).strip()
+    _check_output(result.stdout, expected)
+
+    result = script.pip(
+        'freeze', '-f', '%s#egg=pip_test_package' % repo_dir,
+        expect_stderr=True,
+    )
+    expected = textwrap.dedent(
+        """
+            -f %(repo)s#egg=pip_test_package...
+            -e hg+...#egg=version_pkg&subdirectory=subdir
+            ...
+        """ % {'repo': repo_dir},
+    ).strip()
+    _check_output(result.stdout, expected)
+
+
 @pytest.mark.git
 def test_freeze_git_remote(script, tmpdir):
     """