Pycheckbear.py: Add new PyCheckBear

New Bear is added to find
bugs in python file.

Closes #2151

Author: AkshJain99

.ci/deps.apt.sh

@@ -10,6 +10,7 @@ set -x
 export DEBIAN_FRONTEND=noninteractive
 
 deps="libclang1-3.4 astyle indent mono-mcs chktex r-base julia golang-go luarocks verilator cppcheck flawfinder devscripts mercurial"
+deps="libclang1-3.4 indent mono-mcs chktex r-base julia golang-go luarocks verilator cppcheck flawfinder devscripts pychecker"
 deps_infer="m4 opam"
 
 case $CIRCLE_BUILD_IMAGE in

.travis.yml

@@ -129,6 +129,7 @@ addons:
       - php-codesniffer
       - r-base
       - verilator
+      - pychecker
 
 cache:
   pip: true

bears/python/PyCheckerBear.py

@@ -0,0 +1,40 @@
+import shlex
+
+from coalib.bearlib.abstractions.Linter import linter
+from dependency_management.requirements.DistributionRequirement import (
+        DistributionRequirement)
+
+
+@linter(executable='pychecker',
+        output_format='regex',
+        output_regex=r'(?P<filename>\w+\.py):(?P<line>\d+): '
+                     r'(?P<message>.*)')
+class PyCheckerBear:
+    """
+    Find bugs in your Python source code.
+    The code for each function, class, and method is checked for possible
+    problems. Checks for unused globals and locals(module or variable), unused
+    method arguments and using a variable before setting it or if you are
+    redefining a function/class/method in the same scope.
+    """
+    LANGUAGES = {'Python', 'Python 2', 'Python 3'}
+    REQUIREMENTS = {DistributionRequirement(apt_get='pychecker')}
+    AUTHORS = {'The coala developers'}
+    AUTHORS_EMAILS = {'[email protected]'}
+    LICENSE = 'AGPL-3.0'
+    CAN_DETECT = {'Unused method/function arguments',
+                  'No doc string', 'Redefining'}
+    SEE_MORE = 'http://pychecker.sourceforge.net/'
+
+    @staticmethod
+    def create_arguments(filename, file, config_file,
+                         pychecker_cli_options: str = ''):
+        """
+        :param pychecker_cli_options: Command line options you wish to be
+                                      passed to pychecker.
+        """
+        args = ()
+        if pychecker_cli_options:
+            args += tuple(shlex.split(pychecker_cli_options))
+
+        return args + (filename,)

tests/python/PycheckerBearTest.py

@@ -0,0 +1,51 @@
+from queue import Queue
+import os.path
+
+from coalib.settings.Section import Section
+from coalib.results.Result import Result
+from coalib.testing.LocalBearTestHelper import LocalBearTestHelper
+from coalib.testing.BearTestHelper import generate_skip_decorator
+
+from bears.python.PyCheckerBear import PyCheckerBear
+
+
+def get_testfile_path(file):
+    return os.path.join(os.path.dirname(__file__),
+                        'pychecker_test_files', file)
+
+
+def load_testfiles(name):
+    with open(get_testfile_path(name)) as f1:
+        contents = f1.read().splitlines(True)
+
+    return contents
+
+
+@generate_skip_decorator(PyCheckerBear)
+class PyCheckerBearTest(LocalBearTestHelper):
+
+    def setUp(self):
+        self.uut = PyCheckerBear(Section('name'), Queue())
+        self.good_file = get_testfile_path('good_file.py')
+        self.bad_file = get_testfile_path('bad_file.py')
+        self.maxDiff = None
+
+    def test_good_file(self):
+        self.check_results(self.uut, load_testfiles('good_file.py'),
+                           [],
+                           self.good_file)
+
+    def test_bad_file(self):
+        self.check_results(self.uut, load_testfiles('bad_file.py'),
+                           [Result.from_values('PyCheckerBear',
+                                               'Parameter (c) not used',
+                                               self.bad_file,
+                                               line=1)],
+                           self.bad_file)
+
+    def test_cli_options(self):
+        self.check_results(self.uut, load_testfiles('bad_file.py'),
+                           [],
+                           self.bad_file,
+                           settings={'pychecker_cli_options': '--argsused=off'}
+                           )

tests/python/pychecker_test_files/__init__.py

@@ -0,0 +1,5 @@
+def multiply(a, b, c):
+    return a * b
+
+
+result = multiply(1, 2, 3)

tests/python/pychecker_test_files/bad_file.py

@@ -0,0 +1,5 @@
+def multiply(a, b, c):
+    return a * b * c
+
+
+result = multiply(1, 2, 3)