Add an option to disable sys.path patching.

CONTRIBUTORS.txt

@@ -391,6 +391,7 @@ contributors:
 - Michael Hudson-Doyle <michael.hudson@canonical.com>
 - Michael Giuffrida <mgiuffrida@users.noreply.github.com>
 - Melvin Hazeleger <31448155+melvio@users.noreply.github.com> (melvio)
+- Mehdi Drissi: Added an option to disable sys path patching
 - Matěj Grabovský <mgrabovs@redhat.com>
 - Matthijs Blom <19817960+MatthijsBlom@users.noreply.github.com>
 - Matej Marušák <marusak.matej@gmail.com>

ChangeLog

@@ -785,6 +785,12 @@ Release date: 2021-11-24
   longer relies on counting if statements anymore and uses known if statements locations instead.
   It should not crash on badly parsed if statements anymore.
 
+* Add an option ``disable-path-patching`` to better support namespace packages.
+  This option is disabled by default as it has a trade off with being able
+  to lint uninstalled packages.
+
+  Closes #5266
+
 * Fix ``simplify-boolean-expression`` when condition can be inferred as False.
 
   Closes #5200

doc/faq.rst

@@ -280,12 +280,24 @@ behavior. Likewise, since negative values are still technically supported,
 ``evaluation`` can be set to a version of the above expression that does not
 enforce a floor of zero.
 
-6.2 I think I found a bug in Pylint. What should I do?
+6.2 I have import errors working with a namespace package. How can I fix it?
+------------------------------------------------------------------------------
+
+If you have an implicit namespace package (i.e. a package without ``__init__.py``)
+then pylint may not be able to determine base of the package. Normally when you run
+pylint it adjusts PYTHONPATH to include the parent directory of the package you are
+working in. For namespace packages you can disable path inference with
+``--disable-path-patching`` setting. For this to work you must have the namespace package
+installed in your environment or run pylint from the directory containing the package.
+
+
+
+6.3 I think I found a bug in Pylint. What should I do?
 -------------------------------------------------------
 
 Read :ref:`Bug reports, feedback`
 
-6.3 I have a question about Pylint that isn't answered here.
+6.4 I have a question about Pylint that isn't answered here.
 ------------------------------------------------------------
 
 Read :ref:`Mailing lists`

doc/whatsnew/2.14.rst

@@ -42,6 +42,12 @@ Extensions
 Other Changes
 =============
 
+* Add an option ``disable-path-patching`` to better support namespace packages.
+  This option is disabled by default as it has a trade off with being able
+  to lint uninstalled packages.
+
+  Closes #5266
+
 * Only raise ``not-callable`` when all the inferred values of a property are not callable.
 
   Closes #5931

pylint/lint/pylinter.py

@@ -536,6 +536,21 @@ def make_options() -> Tuple[Tuple[str, OptionDict], ...]:
                     ),
                 },
             ),
+            (
+                "disable-path-patching",
+                {
+                    "type": "yn",
+                    "metavar": "<y or n>",
+                    "default": False,
+                    "help": (
+                        "Disable the patching of sys.path when searching for "
+                        "modules. This is useful for implicit namespace packages where "
+                        "inferring base path of package is ambiguous. The downside is without "
+                        "patching, the files being linted must be importable from the location "
+                        "the script is run in interpreter."
+                    ),
+                },
+            ),
         )
 
     base_option_groups = (
@@ -1058,13 +1073,13 @@ def check(self, files_or_modules: Union[Sequence[str], str]) -> None:
                 )
 
             filepath = files_or_modules[0]
-            with fix_import_path(files_or_modules):
+            with fix_import_path(files_or_modules, self.config.disable_path_patching):
                 self._check_files(
                     functools.partial(self.get_ast, data=_read_stdin()),
                     [self._get_file_descr_from_stdin(filepath)],
                 )
         elif self.config.jobs == 1:
-            with fix_import_path(files_or_modules):
+            with fix_import_path(files_or_modules, self.config.disable_path_patching):
                 self._check_files(
                     self.get_ast, self._iterate_file_descrs(files_or_modules)
                 )

pylint/lint/utils.py

@@ -108,7 +108,6 @@ def preprocess_options(args, search_for):
 
 
 def _patch_sys_path(args):
-    original = list(sys.path)
     changes = []
     seen = set()
     for arg in args:
@@ -118,19 +117,25 @@ def _patch_sys_path(args):
             seen.add(path)
 
     sys.path[:] = changes + sys.path
-    return original
 
 
 @contextlib.contextmanager
-def fix_import_path(args):
+def fix_import_path(args, disable_path_patching: bool = False):
     """Prepare 'sys.path' for running the linter checks.
 
+    'disable_path_patching' if True will make this context manager a no-op.
+    The reason for disabling path patching is to allow running the linter
+    using default path which can be safer then patching the path for implicit
+    namespace packages.
+
     Within this context, each of the given arguments is importable.
     Paths are added to 'sys.path' in corresponding order to the arguments.
     We avoid adding duplicate directories to sys.path.
     `sys.path` is reset to its original value upon exiting this context.
     """
-    original = _patch_sys_path(args)
+    original = list(sys.path)
+    if not disable_path_patching:
+        _patch_sys_path(args)
     try:
         yield
     finally:

pylint/pyreverse/main.py

@@ -191,6 +191,21 @@
             help="set the output directory path.",
         ),
     ),
+    (
+        "disable-path-patching",
+        dict(
+            type="yn",
+            metavar="<y or n>",
+            default=False,
+            help=(
+                "Disable the patching of sys.path when searching for "
+                "modules. This is useful for implicit namespace packages where "
+                "inferring base path of package is ambiguous. The downside is without "
+                "patching, the files being linted must be importable from the location "
+                "the script is run in interpreter."
+            ),
+        ),
+    ),
 )
 
 
@@ -217,7 +232,7 @@ def run(self, args):
         if not args:
             print(self.help())
             return 1
-        with fix_import_path(args):
+        with fix_import_path(args, self.config.disable_path_patching):
             project = project_from_files(
                 args,
                 project_name=self.config.project,

pylint/testutils/_fake.py

@@ -0,0 +1,12 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
+# Copyright (c) https://github.com/PyCQA/pylint/blob/main/CONTRIBUTORS.txt
+
+"""This file is intended to only be used for testing namespace package importing.
+
+   Importing a file has a global side effect of adding a module to sys.modules.
+   As namespace packages are sensitive to sys.path, to test them we check
+   an intentional import error and a successful import. To avoid the imports
+   messing up the test environment, we need to make the import error use
+   a file that is never imported by any other test. This serves as that file.
+"""

tests/functional/n/namespace_package/pylint/testutils/namespace_package.py

@@ -0,0 +1,2 @@
+# pylint: disable=missing-docstring,unused-import
+from pylint.testutils import _fake  # [no-name-in-module]

tests/functional/n/namespace_package/pylint/testutils/namespace_package.txt

@@ -0,0 +1 @@
+no-name-in-module:2:0::No name '_fake' in module 'pylint.testutils':HIGH

tests/functional/n/namespace_package/pylint/testutils/namespace_package_disable_path_patching.py

@@ -0,0 +1,2 @@
+# pylint: disable=missing-docstring,unused-import
+from pylint import lint

tests/functional/n/namespace_package/pylint/testutils/namespace_package_disable_path_patching.rc

@@ -0,0 +1,2 @@
+[master]
+disable-path-patching=yes