2 new tools: display-{fpathconf.maxcanon}.py

tests/test_maxcanon.py has been deleted and turned into
an "autodetection" tool of sorts, no longer attempting
to assert exacting values, but determine it programmatically.

pexpect/pty_spawn.py

@@ -492,9 +492,9 @@ def send(self, s):
 
         This value may be discovered using fpathconf(3)::
 
-        >>> from os import fpathconf
-        >>> print(fpathconf(0, 'PC_MAX_CANON'))
-        256
+            >>> from os import fpathconf
+            >>> print(fpathconf(0, 'PC_MAX_CANON'))
+            256
 
         On such a system, only 256 bytes may be received per line. Any
         subsequent bytes received will be discarded. BEL (``'\a'``) is then
@@ -505,10 +505,10 @@ def send(self, s):
         Canonical input processing may be disabled altogether by executing
         a shell, then stty(1), before executing the final program::
 
-        >>> bash = pexpect.spawn('/bin/bash', echo=False)
-        >>> bash.sendline('stty -icanon')
-        >>> bash.sendline('base64')
-        >>> bash.sendline('x' * 5000)
+            >>> bash = pexpect.spawn('/bin/bash', echo=False)
+            >>> bash.sendline('stty -icanon')
+            >>> bash.sendline('base64')
+            >>> bash.sendline('x' * 5000)
         '''
 
         time.sleep(self.delaybeforesend)

tools/display-fpathconf.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python
+"""Displays os.fpathconf values related to terminals. """
+from __future__ import print_function
+import sys
+import os
+
+
+def display_fpathconf():
+    DISP_VALUES = (
+        ('PC_MAX_CANON', ('Max no. of bytes in a '
+                          'terminal canonical input line.')),
+        ('PC_MAX_INPUT', ('Max no. of bytes for which '
+                          'space is available in a terminal input queue.')),
+        ('PC_PIPE_BUF', ('Max no. of bytes which will '
+                         'be written atomically to a pipe.')),
+        ('PC_VDISABLE', 'Terminal character disabling value.')
+    )
+    FMT = '{name:<13} {value:<5} {description}'
+
+    # column header
+    print(FMT.format(name='name', value='value', description='description'))
+    print(FMT.format(name=('-' * 13), value=('-' * 5), description=('-' * 11)))
+
+    fd = sys.stdin.fileno()
+    for name, description in DISP_VALUES:
+        key = os.pathconf_names.get(name, None)
+        if key is None:
+            value = 'UNDEF'
+        else:
+            try:
+                value = os.fpathconf(fd, name)
+            except OSError as err:
+                value = 'OSErrno {0.errno}'.format(err)
+        if name == 'PC_VDISABLE':
+            value = hex(value)
+        print(FMT.format(name=name, value=value, description=description))
+    print()
+
+
+if __name__ == '__main__':
+    display_fpathconf()

tools/display-maxcanon.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python
+"""
+This tool uses pexpect to test expected Canonical mode length.
+
+All systems use the value of MAX_CANON which can be found using
+fpathconf(3) value PC_MAX_CANON -- with the exception of Linux
+and FreeBSD.
+
+Linux, though defining a value of 255, actually honors the value
+of 4096 from linux kernel include file tty.h definition
+N_TTY_BUF_SIZE.
+
+Linux also does not honor IMAXBEL. termios(3) states, "Linux does not
+implement this bit, and acts as if it is always set." Although these
+tests ensure it is enabled, this is a non-op for Linux.
+
+FreeBSD supports neither, and instead uses a fraction (1/5) of the tty
+speed which is always 9600.  Therefor, the maximum limited input line
+length is 9600 / 5 = 1920.
+
+These tests only ensure the correctness of the behavior described by
+the sendline() docstring -- the values listed there, and above should
+be equal to the output of the given OS described, but no promises!
+"""
+# std import
+from __future__ import print_function
+import sys
+import os
+
+
+def detect_maxcanon():
+    import pexpect
+    bashrc = os.path.join(
+        # re-use pexpect/replwrap.py's bashrc file,
+        os.path.dirname(__file__), os.path.pardir, 'pexpect', 'bashrc.sh')
+
+    child = pexpect.spawn('bash', ['--rcfile', bashrc],
+                          echo=True, encoding='utf8', timeout=3)
+
+    child.sendline(u'echo -n READY_; echo GO')
+    child.expect_exact(u'READY_GO')
+
+    child.sendline(u'stty icanon imaxbel erase ^H; echo -n retval: $?')
+    child.expect_exact(u'retval: 0')
+
+    child.sendline(u'echo -n GO_; echo AGAIN')
+    child.expect_exact(u'GO_AGAIN')
+    child.sendline(u'cat')
+
+    child.delaybeforesend = 0
+
+    column, blocksize = 0, 64
+    ch_marker = u'_'
+
+    print('auto-detecting MAX_CANON: ', end='')
+    sys.stdout.flush()
+
+    while True:
+        child.send(ch_marker * blocksize)
+        result = child.expect([ch_marker * blocksize, u'\a'])
+        if result == 0:
+            # entire block fit without emitting bel
+            column += blocksize
+        elif result == 1:
+            # an '\a' was emitted, count the number of ch_markers
+            # found since last blocksize, determining our MAX_CANON
+            column += child.before.count(ch_marker)
+            break
+    print(column)
+
+if __name__ == '__main__':
+    try:
+        detect_maxcanon()
+    except ImportError:
+        # we'd like to use this with CI -- but until we integrate
+        # with tox, we can't determine a period in testing when
+        # the pexpect module has been installed 
+        print('warning: pexpect not in module path, MAX_CANON '
+              'could not be determined by systems test.',
+              file=sys.stderr)