gpython: Implement -W

We'll need warnings control in the next patch to fix Pytest integration
wrt python3-dbg with `-W ignore::DeprecationWarning`.

gpython/__init__.py

@@ -50,6 +50,7 @@ def pymain(argv):
     from six.moves import input as raw_input
 
     run = None          # function to run according to -c/-m/file/interactive
+    warnoptions = []    # collected `-W arg`
 
     while len(argv) > 0:
         # -V / --version
@@ -117,6 +118,15 @@ def pymain(argv):
                                  run_name='__main__', alter_sys=True)
             break
 
+        # -W arg  (warning control)
+        elif argv[0].startswith('-W'):
+            wopt = argv[0][2:] # -W<arg> also works
+            argv = argv[1:]
+            if wopt == '':
+                wopt = argv[0]
+                argv = argv[1:]
+            warnoptions.append(wopt)
+
         elif argv[0].startswith('-'):
             print("unknown option: '%s'" % argv[0], file=sys.stderr)
             sys.exit(2)
@@ -125,6 +135,7 @@ def pymain(argv):
         else:
             sys.argv = argv
             filepath = argv[0]
+
             sys.path.insert(0, dirname(filepath))
             def run():
                 # exec with same globals `python file.py` does
@@ -160,6 +171,19 @@ def pymain(argv):
 
             console.interact()
 
+    # init warnings
+    if len(warnoptions) > 0:
+        # NOTE warnings might be already imported by code that calls pymain.
+        # This way we cannot set `sys.warnoptions = warnoptions` and just
+        # import/reload warnings (if we reload warnings, it will loose all
+        # previous setup that pymain caller might have done to it).
+        # -> only amend warnings setup
+        #
+        # NOTE $PYTHONWARNINGS is handled by underlying python natively.
+        import warnings
+        sys.warnoptions += warnoptions
+        warnings._processoptions(warnoptions)
+
     # execute -m/-c/file/interactive
     run()
 

gpython/gpython_test.py

@@ -20,7 +20,7 @@
 
 from __future__ import print_function, absolute_import
 
-import sys, os, platform, golang
+import sys, os, platform, re, golang
 from golang.golang_test import pyout, _pyrun
 from subprocess import PIPE
 from six import PY2
@@ -182,6 +182,30 @@ def test_pymain():
     _ = pyout(['testdata/hello.py', 'abc', 'def'], cwd=here)
     assert _ == b"hello\nworld\n['testdata/hello.py', 'abc', 'def']\n"
 
+    # -W <opt>
+    _ = pyout(['-Werror', '-Whello', '-W', 'ignore::DeprecationWarning',
+               'testprog/print_warnings_setup.py'], cwd=here)
+    if PY2:
+        # py2 threading, which is imported after gpython startup, adds ignore
+        # for sys.exc_clear
+        _ = grepv(r'ignore:sys.exc_clear:DeprecationWarning:threading:*', _)
+    assert _.startswith(
+        b"sys.warnoptions: ['error', 'hello', 'ignore::DeprecationWarning']\n\n" + \
+        b"warnings.filters:\n" + \
+        b"- ignore::DeprecationWarning::*\n" + \
+        b"- error::Warning::*\n"), _
+    # $PYTHONWARNINGS
+    _ = pyout(['testprog/print_warnings_setup.py'], cwd=here,
+              envadj={'PYTHONWARNINGS': 'ignore,world,error::SyntaxWarning'})
+    if PY2:
+        # see ^^^
+        _ = grepv(r'ignore:sys.exc_clear:DeprecationWarning:threading:*', _)
+    assert _.startswith(
+        b"sys.warnoptions: ['ignore', 'world', 'error::SyntaxWarning']\n\n" + \
+        b"warnings.filters:\n" + \
+        b"- error::SyntaxWarning::*\n" + \
+        b"- ignore::Warning::*\n"), _
+
 # pymain -V/--version
 # gpython_only because output differs from !gpython.
 @gpython_only
@@ -230,3 +254,20 @@ def test_Xruntime(runtime):
 
     out = pyout(argv, env=env)
     assert out == b'ok\n'
+
+
+# ---- misc ----
+
+# grepv filters out lines matching pattern from text.
+def grepv(pattern, text): # -> text
+    if isinstance(text, bytes):
+        t = b''
+    else:
+        t = ''
+    p = re.compile(pattern)
+    v = []
+    for l in text.splitlines(True):
+        m = p.search(l)
+        if not m:
+            v.append(l)
+    return t.join(v)

gpython/testprog/print_warnings_setup.py

+# -*- coding: utf-8 -*-
+# Copyright (C) 2020  Nexedi SA and Contributors.
+#                     Kirill Smelkov <kirr@nexedi.com>
+#
+# This program is free software: you can Use, Study, Modify and Redistribute
+# it under the terms of the GNU General Public License version 3, or (at your
+# option) any later version, as published by the Free Software Foundation.
+#
+# You can also Link and Combine this program with other software covered by
+# the terms of any of the Free Software licenses or any of the Open Source
+# Initiative approved licenses and Convey the resulting work. Corresponding
+# source of such a combination shall include the source code for all other
+# software used.
+#
+# This program is distributed WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See COPYING file for full licensing terms.
+# See https://www.nexedi.com/licensing for rationale and options.
+"""Program print_warnings_setup prints information about warnings module
+configuration."""
+
+from __future__ import print_function, absolute_import
+
+import sys, warnings, re
+
+def main():
+    print('sys.warnoptions: %s' % sys.warnoptions)
+    print('\nwarnings.filters:')
+    for f in warnings.filters:
+        print_filter(f)
+
+def print_filter(f):
+    # see Lib/warnings.py
+    action, message, klass, module, line = f
+    message = wstr(message)
+    module  = wstr(module)
+    klass   = klass.__name__
+    if line == 0:
+        line = '*'
+    print('- %s:%s:%s:%s:%s' % (action, message, klass, module, line))
+
+# wstr returns str corresponding to warning filter's message or module.
+REPattern = re.compile('').__class__
+def wstr(obj):
+    if obj is None:
+        return ''
+    if isinstance(obj, REPattern):
+        return obj.pattern
+    return obj
+
+
+if __name__ == '__main__':
+    main()