feat: add settings to set custom function to format prompt

[jnoortheen]

Now the users can format the prompt as they like.

[jnoortheen]

here is a script to implement powerline like prompt

import os
from typing import NamedTuple, List
import builtins
from xonsh.prompt.base import ParsedTokens, _ParsedToken

GRAY = '#273746'
BLUE = '#004C99'
PROMPT_FIELD_COLORS = {
    "cwd": ("WHITE", "CYAN"),
    "gitstatus": ("WHITE", "BLACK"),
    "ret_code": ("WHITE", "RED"),
    "full_env_name": ("white", "green"),
    "hostname": ("white", BLUE),
    "localtime": ("#DAF7A6", "black")
}
POWERLINE_MODE = 'flame'

modes = {
    "powerline": "",
    "round": "",
    "down": "",
    "up": "",
    "flame": "",
    "squares": "",
    "ruiny": "",
    "lego": "",
}


class Section(NamedTuple):
    line: str
    fg: str = ''
    bg: str = ''


def prompt_builder(tokens: List[Section], right=False):
    size = len(tokens)
    prompt = []
    SEP, THIN, PL_RSEP, _ = modes[POWERLINE_MODE]
    for i, sec in enumerate(tokens):
        last = (i == size - 1)
        first = (i == 0)

        if right:
            prompt.append('{%s}%s{BACKGROUND_%s}{%s}%s' % (sec.bg, PL_RSEP, sec.bg, sec.fg, sec.line))
        else:
            if first:
                if sec.bg:
                    prompt.append('{BACKGROUND_%s}' % sec.bg)
            if sec.fg:
                prompt.append('{%s}' % sec.fg)

            prompt.append(sec.line)
            if last:
                prompt.append('{RESET}')
                if sec.bg:
                    prompt.append('{%s}' % sec.bg)
                prompt.append('%s{RESET}' % SEP)
            else:
                if tokens[i + 1].bg:
                    prompt.append('{BACKGROUND_%s}' % tokens[i + 1].bg)
                if sec.bg:
                    prompt.append('{%s}' % sec.bg)
                prompt.append(SEP)
    return ''.join(prompt)


def create_sections(tokens: List[_ParsedToken]):
    for tok in tokens:
        if not tok.value:  # skip empty strings
            continue
        args = PROMPT_FIELD_COLORS.get(
            tok.field,
            (
                'white',
                GRAY
            ))
        yield Section(tok.value, *[a.upper() for a in args])


def split_by_lines(tokens: List[_ParsedToken]):
    line = []
    for tok in tokens:
        if tok.value == os.linesep:
            yield list(create_sections(line))
            line.clear()
        else:
            line.append(tok)
    yield list(create_sections(line))


def process_prompt_tokens(container: ParsedTokens) -> str:
    prompt = builtins.__xonsh__.env['PROMPT']
    rprompt = builtins.__xonsh__.env["RIGHT_PROMPT"]
    if container.template in {prompt, rprompt}:
        # it is $PROMPT
        is_right = container.template == rprompt
        return os.linesep.join([
            prompt_builder(line, right=is_right) for line in split_by_lines(container.tokens)
        ])

    # for title
    return "".join([c.value for c in container.tokens])

# $PROMPT_TOKENS_FORMATTER = process_prompt_tokens

and sample prompt

[scopatz]

Thanks for putting this in @jnoortheen! The code looks good to me, other than the logging issue.

[scopatz]

Thanks!