FIX globals for functions defined in __main__ (#188)

Fix #187 

The cause of this issue is that global variables defined in `__main__` are not shared by unpickled functions and their value are overwritten at each unpickling.

.coveragerc

@@ -1,5 +1,6 @@
 [run]
 branch = True
+parallel = True
 source = cloudpickle
 
 [report]

.travis.yml

@@ -26,9 +26,11 @@ before_script:
   - flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics
   # exit-zero treats all errors as warnings.  The GitHub editor is 127 chars wide
   - flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+  - python ci/install_coverage_subprocess_pth.py
 script:
   - if [[ $TRAVIS_PYTHON_VERSION != 'pypy'* ]]; then source activate testenv; fi
-  - PYTHONPATH='.:tests' py.test -r s --cov-config .coveragerc --cov=cloudpickle
+  - COVERAGE_PROCESS_START="$TRAVIS_BUILD_DIR/.coveragerc" PYTHONPATH='.:tests' py.test -r s
 after_success:
   - if [[ $TRAVIS_PYTHON_VERSION != 'pypy'* ]]; then source activate testenv; fi
+  - coverage combine --append
   - codecov

ci/install_coverage_subprocess_pth.py

@@ -0,0 +1,16 @@
+# Make it possible to enable test coverage reporting for Python
+# code run in children processes.
+# http://coverage.readthedocs.io/en/latest/subprocess.html
+
+import os.path as op
+from distutils.sysconfig import get_python_lib
+
+FILE_CONTENT = u"""\
+import coverage; coverage.process_startup()
+"""
+
+filename = op.join(get_python_lib(), 'coverage_subprocess.pth')
+with open(filename, 'wb') as f:
+    f.write(FILE_CONTENT.encode('ascii'))
+
+print('Installed subprocess coverage support: %s' % filename)

cloudpickle/cloudpickle.py

@@ -431,6 +431,7 @@ def _save_subimports(self, code, top_level_dependencies):
         Ensure de-pickler imports any package child-modules that
         are needed by the function
         """
+
         # check if any known dependency is an imported package
         for x in top_level_dependencies:
             if isinstance(x, types.ModuleType) and hasattr(x, '__package__') and x.__package__:
@@ -632,7 +633,15 @@ def extract_func_data(self, func):
         # save the dict
         dct = func.__dict__
 
-        base_globals = self.globals_ref.get(id(func.__globals__), {})
+        base_globals = self.globals_ref.get(id(func.__globals__), None)
+        if base_globals is None:
+            # For functions defined in __main__, use vars(__main__) for
+            # base_global. This is necessary to share the global variables
+            # across multiple functions in this module.
+            if func.__module__ == "__main__":
+                base_globals = "__main__"
+            else:
+                base_globals = {}
         self.globals_ref[id(func.__globals__)] = base_globals
 
         return (code, f_globals, defaults, closure, dct, base_globals)
@@ -1037,7 +1046,11 @@ def _fill_function(*args):
     else:
         raise ValueError('Unexpected _fill_value arguments: %r' % (args,))
 
-    func.__globals__.update(state['globals'])
+    # Only set global variables that do not exist.
+    for k, v in state['globals'].items():
+        if k not in func.__globals__:
+            func.__globals__[k] = v
+
     func.__defaults__ = state['defaults']
     func.__dict__ = state['dict']
     if 'annotations' in state:
@@ -1076,6 +1089,8 @@ def _make_skel_func(code, cell_count, base_globals=None):
     """
     if base_globals is None:
         base_globals = {}
+    elif isinstance(base_globals, str):
+        base_globals = vars(sys.modules[base_globals])
     base_globals['__builtins__'] = __builtins__
 
     closure = (

tests/cloudpickle_test.py

@@ -848,6 +848,45 @@ def f4(x):
         """.format(protocol=self.protocol)
         assert_run_python_script(textwrap.dedent(code))
 
+    def test_interactively_defined_global_variable(self):
+        # Check that callables defined in the __main__ module of a Python
+        # script (or jupyter kernel) correctly retrieve global variables.
+        code_template = """\
+        from testutils import subprocess_pickle_echo
+        from cloudpickle import dumps, loads
+
+        def local_clone(obj, protocol=None):
+            return loads(dumps(obj, protocol=protocol))
+
+        VARIABLE = "default_value"
+
+        def f0():
+            global VARIABLE
+            VARIABLE = "changed_by_f0"
+
+        def f1():
+            return VARIABLE
+
+        cloned_f0 = {clone_func}(f0, protocol={protocol})
+        cloned_f1 = {clone_func}(f1, protocol={protocol})
+        pickled_f1 = dumps(f1, protocol={protocol})
+
+        # Change the value of the global variable
+        cloned_f0()
+
+        # Ensure that the global variable is the same for another function
+        result_f1 = cloned_f1()
+        assert result_f1 == "changed_by_f0", result_f1
+
+        # Ensure that unpickling the global variable does not change its value
+        result_pickled_f1 = loads(pickled_f1)()
+        assert result_pickled_f1 == "changed_by_f0", result_pickled_f1
+        """
+        for clone_func in ['local_clone', 'subprocess_pickle_echo']:
+            code = code_template.format(protocol=self.protocol,
+                                        clone_func=clone_func)
+            assert_run_python_script(textwrap.dedent(code))
+
     @pytest.mark.skipif(sys.version_info >= (3, 0),
                         reason="hardcoded pickle bytes for 2.7")
     def test_function_pickle_compat_0_4_0(self):

tests/testutils.py

@@ -93,6 +93,10 @@ def assert_run_python_script(source_code, timeout=5):
             'stderr': STDOUT,
             'env': {'PYTHONPATH': pythonpath},
         }
+        # If coverage is running, pass the config file to the subprocess
+        coverage_rc = os.environ.get("COVERAGE_PROCESS_START")
+        if coverage_rc:
+            kwargs['env']['COVERAGE_PROCESS_START'] = coverage_rc
         if timeout_supported:
             kwargs['timeout'] = timeout
         try: