Remove stdout/stderr from subprocesses (redirected to /dev/null)

This means that the subprocess should now not crash anymore because of people
writing to stdout in c modules and stderr should be empty.

Fixes #793.

jedi/evaluate/compiled/subprocess/__init__.py

@@ -142,7 +142,6 @@ def _process(self):
             args,
             stdin=subprocess.PIPE,
             stdout=subprocess.PIPE,
-            # stderr=subprocess.PIPE
         )
 
     def run(self, evaluator, function, args=(), kwargs={}):
@@ -266,6 +265,11 @@ def _run(self, evaluator_id, function, args, kwargs):
 
     def listen(self):
         stdout = sys.stdout
+        # Mute stdout/stderr. Nobody should actually be able to write to those,
+        # because stdout is used for IPC and stderr will just be annoying if it
+        # leaks (on module imports).
+        sys.stdout = open(os.devnull, 'w')
+        sys.stderr = open(os.devnull, 'w')
         stdin = sys.stdin
         if sys.version_info[0] > 2:
             stdout = stdout.buffer

jedi/evaluate/compiled/subprocess/functions.py

@@ -2,7 +2,7 @@
 import os
 
 from jedi._compatibility import find_module, cast_path, force_unicode, \
-    iter_modules, all_suffixes
+    iter_modules, all_suffixes, print_to_stderr
 from jedi.evaluate.compiled import access
 from jedi import parser_utils
 
@@ -85,6 +85,18 @@ def _test_raise_error(evaluator, exception_type):
     raise exception_type
 
 
+def _test_print(evaluator, stderr=None, stdout=None):
+    """
+    Force some prints in the subprocesses. This exists for unit tests.
+    """
+    if stderr is not None:
+        print_to_stderr(stderr)
+        sys.stderr.flush()
+    if stdout is not None:
+        print(stdout)
+        sys.stdout.flush()
+
+
 def _get_init_path(directory_path):
     """
     The __init__ file can be searched in a directory. If found return it, else

test/test_api/test_environment.py

@@ -67,6 +67,11 @@ def test_error_in_environment(evaluator, Script):
     assert def_.name == 'str'
 
 
+def test_stdout_in_subprocess(evaluator, Script):
+    evaluator.compiled_subprocess._test_print(stdout='.')
+    Script('1').goto_definitions()
+
+
 def test_killed_subprocess(evaluator, Script):
     # Just kill the subprocess.
     evaluator.compiled_subprocess._compiled_subprocess._process.kill()