Allow stdout to redirect to stderr

docs/tutorial.rst

@@ -725,7 +725,7 @@ with the following syntax:
     >>> COMMAND err>o
     >>> COMMAND e>out
     >>> COMMAND e>o
-    >>> COMMAND 2>&1 # included for Bash compatibility
+    >>> COMMAND 2>&1  # included for Bash compatibility
 
 This merge can be combined with other redirections, including pipes (see the
 section on `Pipes`_ above):
@@ -737,6 +737,16 @@ section on `Pipes`_ above):
 
 It is worth noting that this last example is equivalent to: ``COMMAND a> combined.txt``
 
+Similarly, you can also send stdout to stderr with the following syntax:
+
+.. code-block:: xonshcon
+
+    >>> COMMAND out>err
+    >>> COMMAND out>e
+    >>> COMMAND o>err
+    >>> COMMAND o>e
+    >>> COMMAND 1>&2  # included for Bash compatibility
+
 Redirecting ``stdin``
 ---------------------
 
@@ -1037,8 +1047,8 @@ regex globbing:
     def regexsearch(s):
         s = expand_path(s)
         return reglob(s)
-    
-    
+
+
     <function xonsh.built_ins.regexsearch>
 
 Note that both help and superhelp return the object that they are inspecting.

news/to2.rst

@@ -0,0 +1,13 @@
+**Added:**
+
+* Users may now redirect stdout to stderr in subprocess mode.
+
+**Changed:** None
+
+**Deprecated:** None
+
+**Removed:** None
+
+**Fixed:** None
+
+**Security:** None

tests/test_integrations.py

@@ -157,6 +157,25 @@ def test_script(case):
     assert exp_rtn == rtn
 
 
+ALL_PLATFORMS_STDERR = [
+# test redirecting a function alias
+("""
+def _f(args, stdout):
+    print('Wow Mom!', file=stdout)
+
+aliases['f'] = _f
+f o>e
+""", "Wow Mom!\n", 0),
+]
+
+@pytest.mark.parametrize('case', ALL_PLATFORMS_STDERR)
+def test_script_stder(case):
+    script, exp_err, exp_rtn = case
+    out, err, rtn = run_xonsh(script, stderr=sp.PIPE)
+    assert exp_err == err
+    assert exp_rtn == rtn
+
+
 @skip_if_on_windows
 @pytest.mark.parametrize('cmd, fmt, exp', [
     ('pwd', None, lambda: os.getcwd() + '\n'),

tests/test_parser.py

@@ -1816,8 +1816,8 @@ def test_redirect_all(case):
     assert check_xonsh_ast({}, '$[echo "test" {}> test.txt < input.txt]'.format(case), False)
 
 @pytest.mark.parametrize('r',
-    ['e>o', 'e>out', 'err>o', 'err>o',
-     ' 2>1', 'e>1', 'err>1', '2>out',
+    ['e>o', 'e>out', 'err>o',
+     '2>1', 'e>1', 'err>1', '2>out',
      '2>o', 'err>&1', 'e>&1', '2>&1'
 ])
 @pytest.mark.parametrize('o', ['', 'o', 'out', '1'])
@@ -1826,6 +1826,17 @@ def test_redirect_error_to_output(r, o):
     assert check_xonsh_ast({}, '$[< input.txt echo "test" {} {}> test.txt]'.format(r, o), False)
     assert check_xonsh_ast({}, '$[echo "test" {} {}> test.txt < input.txt]'.format(r, o), False)
 
+@pytest.mark.parametrize('r',
+    ['o>e', 'o>err', 'out>e',
+     '1>2', 'o>2', 'out>2', '1>err',
+     '1>e', 'out>&2', 'o>&2', '1>&2'
+])
+@pytest.mark.parametrize('e', ['e', 'err', '2'])
+def test_redirect_output_to_error(r, e):
+    assert check_xonsh_ast({}, '$[echo "test" {} {}> test.txt]'.format(r, e), False)
+    assert check_xonsh_ast({}, '$[< input.txt echo "test" {} {}> test.txt]'.format(r, e), False)
+    assert check_xonsh_ast({}, '$[echo "test" {} {}> test.txt < input.txt]'.format(r, e), False)
+
 def test_macro_call_empty():
     assert check_xonsh_ast({}, 'f!()', False)
 

xonsh/built_ins.py

@@ -265,6 +265,10 @@ _E2O_MAP = LazyObject(lambda: frozenset({'{}>{}'.format(e, o)
                                          for e in _REDIR_ERR
                                          for o in _REDIR_OUT
                                          if o != ''}), globals(), '_E2O_MAP')
+_O2E_MAP = LazyObject(lambda: frozenset({'{}>{}'.format(o, e)
+                                         for e in _REDIR_ERR
+                                         for o in _REDIR_OUT
+                                         if o != ''}), globals(), '_O2E_MAP')
 
 
 def _is_redirect(x):
@@ -323,10 +327,14 @@ def _parse_redirects(r):
 def _redirect_streams(r, loc=None):
     """Returns stdin, stdout, stderr tuple of redirections."""
     stdin = stdout = stderr = None
+    no_ampersand = r.replace('&', '')
     # special case of redirecting stderr to stdout
-    if r.replace('&', '') in _E2O_MAP:
+    if no_ampersand in _E2O_MAP:
         stderr = subprocess.STDOUT
         return stdin, stdout, stderr
+    elif no_ampersand in _O2E_MAP:
+        stdout = 2  # using 2 as a flag, rather than using a file object
+        return stdin, stdout, stderr
     # get streams
     orig, mode, dest = _parse_redirects(r)
     if mode == 'r':
@@ -718,6 +726,10 @@ def _update_last_spec(last):
         r, w = pty.openpty() if use_tty else os.pipe()
         last.stderr = safe_open(w, 'w')
         last.captured_stderr = safe_open(r, 'r')
+    # redirect stdout to stderr, if we should
+    if isinstance(last.stdout, int) and last.stdout == 2:
+        # need to use private interface to avoid duplication.
+        last._stdout = last.stderr
 
 
 def cmds_to_specs(cmds, captured=False):

xonsh/tokenize.py

@@ -227,10 +227,16 @@ SearchPath = r"((?:[rgp]+|@\w*)?)`([^\n`\\]*(?:\\.[^\n`\\]*)*)`"
 # longest operators first (e.g., if = came before ==, == would get
 # recognized as two instances of =).
 _redir_names = ('out', 'all', 'err', 'e', '2', 'a', '&', '1', 'o')
-_e2o_map = ('err>out', 'err>&1', '2>out', 'err>o', 'err>1', 'e>out', 'e>&1',
-            '2>&1', 'e>o', '2>o', 'e>1', '2>1')
-IORedirect = group(group(*_e2o_map), '{}>>?'.format(group(*_redir_names)))
-_redir_check = set(_e2o_map)
+_redir_map = (
+    # stderr to stdout
+    'err>out', 'err>&1', '2>out', 'err>o', 'err>1', 'e>out', 'e>&1',
+    '2>&1', 'e>o', '2>o', 'e>1', '2>1',
+    # stdout to stderr
+    'out>err', 'out>&2', '1>err', 'out>e', 'out>2', 'o>err', 'o>&2',
+    '1>&2', 'o>e', '1>e', 'o>2', '1>2',
+    )
+IORedirect = group(group(*_redir_map), '{}>>?'.format(group(*_redir_names)))
+_redir_check = set(_redir_map)
 _redir_check = {'{}>'.format(i) for i in _redir_names}.union(_redir_check)
 _redir_check = {'{}>>'.format(i) for i in _redir_names}.union(_redir_check)
 _redir_check = frozenset(_redir_check)