[lldb] `help(symbol)` in lldb's embedded Python interpreter shows an empty screen

[JDevlieghere]

Using Python's built-in help shows an empty screen when the statusline is enabled.

(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> help(print)

This just shows (END) at the bottom of the screen, where the statusline line is supposed to be.

After disabling the statusline with settings set show-statusline false, things are back to normal, with the help text printed at the bottom of the screen.

Help on built-in function print in module builtins:

print(...)
    print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)

    Prints the values to a stream, or to sys.stdout by default.
    Optional keyword arguments:
    file:  a file-like object (stream); defaults to the current sys.stdout.
    sep:   string inserted between values, default a space.
    end:   string appended after the last value, default a newline.
    flush: whether to forcibly flush the stream.
(END)

rdar://155170974

[llvmbot]

@llvm/issue-subscribers-lldb

Author: Jonas Devlieghere (JDevlieghere)

Using Python's built-in `help` shows an empty screen when the statusline is enabled.

(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> help(print)

This just shows (END) at the bottom of the screen, where the statusline line is supposed to be.

After disabling the statusline with settings set show-statusline false, things are back to normal, with the help text printed at the bottom of the screen.

Help on built-in function print in module builtins:

print(...)
    print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)

    Prints the values to a stream, or to sys.stdout by default.
    Optional keyword arguments:
    file:  a file-like object (stream); defaults to the current sys.stdout.
    sep:   string inserted between values, default a space.
    end:   string appended after the last value, default a newline.
    flush: whether to forcibly flush the stream.
(END)

rdar://155170974

[JDevlieghere]

The issue is the pydoc pager. It's possible to replace it. This fixes the issue:

(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> import pydoc
>>> pydoc.pager = pydoc.plainpager
>>> help(print)
Help on built-in function print in module builtins:

print(...)
    print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)

    Prints the values to a stream, or to sys.stdout by default.
    Optional keyword arguments:
    file:  a file-like object (stream); defaults to the current sys.stdout.
    sep:   string inserted between values, default a space.
    end:   string appended after the last value, default a newline.
    flush: whether to forcibly flush the stream.

>>>

We could make this the default in LLDB's interactive interpreter.

[jimingham]

Might even decide which pager to use depending on the status-line setting?