pager.py

from __future__ importannotations

importio
importos
importre
importsys


# types
ifFalse:
fromtypingimportProtocol
classPager(Protocol):
def__call__(self, text: str, title: str="") ->None:
 ...


defget_pager() ->Pager:
"""Decide what method to use for paging through text."""
ifnothasattr(sys.stdin, "isatty"):
returnplain_pager
ifnothasattr(sys.stdout, "isatty"):
returnplain_pager
ifnotsys.stdin.isatty() ornotsys.stdout.isatty():
returnplain_pager
ifsys.platform=="emscripten":
returnplain_pager
use_pager=os.environ.get('MANPAGER') oros.environ.get('PAGER')
ifuse_pager:
ifsys.platform=='win32': # pipes completely broken in Windows
returnlambdatext, title='': tempfile_pager(plain(text), use_pager)
elifos.environ.get('TERM') in ('dumb', 'emacs'):
returnlambdatext, title='': pipe_pager(plain(text), use_pager, title)
else:
returnlambdatext, title='': pipe_pager(text, use_pager, title)
ifos.environ.get('TERM') in ('dumb', 'emacs'):
returnplain_pager
ifsys.platform=='win32':
returnlambdatext, title='': tempfile_pager(plain(text), 'more <')
ifhasattr(os, 'system') andos.system('(pager) 2>/dev/null') ==0:
returnlambdatext, title='': pipe_pager(text, 'pager', title)
ifhasattr(os, 'system') andos.system('(less) 2>/dev/null') ==0:
returnlambdatext, title='': pipe_pager(text, 'less', title)

importtempfile
 (fd, filename) =tempfile.mkstemp()
os.close(fd)
try:
ifhasattr(os, 'system') andos.system('more "%s"'%filename) ==0:
returnlambdatext, title='': pipe_pager(text, 'more', title)
else:
returntty_pager
finally:
os.unlink(filename)


defescape_stdout(text: str) ->str:
# Escape non-encodable characters to avoid encoding errors later
encoding=getattr(sys.stdout, 'encoding', None) or'utf-8'
returntext.encode(encoding, 'backslashreplace').decode(encoding)


defescape_less(s: str) ->str:
returnre.sub(r'([?:.%\\])', r'\\\1', s)


defplain(text: str) ->str:
"""Remove boldface formatting from text."""
returnre.sub('.\b', '', text)


deftty_pager(text: str, title: str='') ->None:
"""Page through text on a text terminal."""
lines=plain(escape_stdout(text)).split('\n')
has_tty=False
try:
importtty
importtermios
fd=sys.stdin.fileno()
old=termios.tcgetattr(fd)
tty.setcbreak(fd)
has_tty=True

defgetchar() ->str:
returnsys.stdin.read(1)

except (ImportError, AttributeError, io.UnsupportedOperation):
defgetchar() ->str:
returnsys.stdin.readline()[:-1][:1]

try:
try:
h=int(os.environ.get('LINES', 0))
exceptValueError:
h=0
ifh<=1:
h=25
r=inc=h-1
sys.stdout.write('\n'.join(lines[:inc]) +'\n')
whilelines[r:]:
sys.stdout.write('-- more --')
sys.stdout.flush()
c=getchar()

ifcin ('q', 'Q'):
sys.stdout.write('\r\r')
break
elifcin ('\r', '\n'):
sys.stdout.write('\r\r'+lines[r] +'\n')
r=r+1
continue
ifcin ('b', 'B', '\x1b'):
r=r-inc-inc
ifr<0: r=0
sys.stdout.write('\n'+'\n'.join(lines[r:r+inc]) +'\n')
r=r+inc

finally:
ifhas_tty:
termios.tcsetattr(fd, termios.TCSAFLUSH, old)


defplain_pager(text: str, title: str='') ->None:
"""Simply print unformatted text. This is the ultimate fallback."""
sys.stdout.write(plain(escape_stdout(text)))


defpipe_pager(text: str, cmd: str, title: str='') ->None:
"""Page through text by feeding it to another program."""
importsubprocess
env=os.environ.copy()
iftitle:
title+=' '
esc_title=escape_less(title)
prompt_string= (
f' {esc_title}'+
'?ltline %lt?L/%L.'
':byte %bB?s/%s.'
'.'
'?e (END):?pB %pB\\%..'
' (press h for help or q to quit)')
env['LESS'] ='-RmPm{0}$PM{0}$'.format(prompt_string)
proc=subprocess.Popen(cmd, shell=True, stdin=subprocess.PIPE,
errors='backslashreplace', env=env)
assertproc.stdinisnotNone
try:
withproc.stdinaspipe:
try:
pipe.write(text)
exceptKeyboardInterrupt:
# We've hereby abandoned whatever text hasn't been written,
# but the pager is still in control of the terminal.
pass
exceptOSError:
pass# Ignore broken pipes caused by quitting the pager program.
whileTrue:
try:
proc.wait()
break
exceptKeyboardInterrupt:
# Ignore ctl-c like the pager itself does. Otherwise the pager is
# left running and the terminal is in raw mode and unusable.
pass


deftempfile_pager(text: str, cmd: str, title: str='') ->None:
"""Page through text by invoking a program on a temporary file."""
importtempfile
withtempfile.TemporaryDirectory() astempdir:
filename=os.path.join(tempdir, 'pydoc.out')
withopen(filename, 'w', errors='backslashreplace',
encoding=os.device_encoding(0) if
sys.platform=='win32'elseNone
 ) asfile:
file.write(text)
os.system(cmd+' "'+filename+'"')