python-uncompyle6/pytest/test_fstring.py

# std
import os
# test
import pytest
import hypothesis
from hypothesis import strategies as st
# uncompyle6
from uncompyle6 import PYTHON_VERSION, deparse_code


@st.composite
def expressions(draw):
    # todo : would be nice to generate expressions using hypothesis however
    # this is pretty involved so for now just use a corpus of expressions
    # from which to select.
    return draw(st.sampled_from((
        'abc',
        'len(items)',
        'x + 1',
        'lineno',
        'container',
        'self.attribute',
        'self.method()',
        # These expressions are failing, I think these are control
        # flow problems rather than problems with FORMAT_VALUE,
        # however I need to confirm this...
        #'sorted(items, key=lambda x: x.name)',
        #'func(*args, **kwargs)',
        #'text or default',
        #'43 if life_the_universe and everything else None'
    )))


@st.composite
def format_specifiers(draw):
    """
    Generate a valid format specifier using the rules:

    format_spec ::=  [[fill]align][sign][#][0][width][,][.precision][type]
    fill        ::=  <any character>
    align       ::=  "<" | ">" | "=" | "^"
    sign        ::=  "+" | "-" | " "
    width       ::=  integer
    precision   ::=  integer
    type        ::=  "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"

    See https://docs.python.org/2/library/string.html

    :param draw: Let hypothesis draw from other strategies.

    :return: An example format_specifier.
    """
    alphabet_strategy = st.characters(min_codepoint=ord('a'), max_codepoint=ord('z'))
    fill = draw(st.one_of(alphabet_strategy, st.none()))
    align = draw(st.sampled_from(list('<>=^')))
    fill_align = (fill + align or '') if fill else ''

    type_ = draw(st.sampled_from('bcdeEfFgGnosxX%'))
    can_have_sign = type_ in 'deEfFgGnoxX%'
    can_have_comma = type_ in 'deEfFgG%'
    can_have_precision = type_ in 'fFgG'
    can_have_pound = type_ in 'boxX%'
    can_have_zero = type_ in 'oxX'

    sign = draw(st.sampled_from(list('+- ') + [''])) if can_have_sign else ''
    pound = draw(st.sampled_from(('#', '',))) if can_have_pound else ''
    zero = draw(st.sampled_from(('0', '',))) if can_have_zero else ''

    int_strategy = st.integers(min_value=1, max_value=1000)

    width = draw(st.one_of(int_strategy, st.none()))
    width = str(width) if width is not None else ''

    comma = draw(st.sampled_from((',', '',))) if can_have_comma else ''
    if can_have_precision:
        precision = draw(st.one_of(int_strategy, st.none()))
        precision = '.' + str(precision) if precision else ''
    else:
        precision = ''

    return ''.join((fill_align, sign, pound, zero, width, comma, precision, type_,))


@st.composite
def fstrings(draw):
    """
    Generate a valid f-string.
    See https://www.python.org/dev/peps/pep-0498/#specification

    :param draw: Let hypothsis draw from other strategies.

    :return: A valid f-string.
    """
    character_strategy = st.characters(
        blacklist_characters='\r\n\'\\s{}',
        min_codepoint=1,
        max_codepoint=1000,
    )
    is_raw = draw(st.booleans())
    integer_strategy = st.integers(min_value=0, max_value=3)
    expression_count = draw(integer_strategy)
    content = []
    for _ in range(expression_count):
        expression = draw(expressions())
        conversion = draw(st.sampled_from(('', '!s', '!r', '!a',)))
        has_specifier = draw(st.booleans())
        specifier = ':' + draw(format_specifiers()) if has_specifier else ''
        content.append('{{{}{}}}'.format(expression, conversion, specifier))
        content.append(draw(st.text(character_strategy)))
    content = ''.join(content)
    return "f{}'{}'".format('r' if is_raw else '', content)


@pytest.mark.skipif(PYTHON_VERSION < 3.6, reason='need at least python 3.6')
@hypothesis.given(format_specifiers())
def test_format_specifiers(format_specifier):
    """Verify that format_specifiers generates valid specifiers"""
    try:
        exec('"{:' + format_specifier + '}".format(0)')
    except ValueError as e:
        if 'Unknown format code' not in str(e):
            raise


def run_test(text):
    hypothesis.assume(len(text))
    hypothesis.assume("f'{" in text)
    expr = text + '\n'
    code = compile(expr, '<string>', 'single')
    deparsed = deparse_code(PYTHON_VERSION, code, compile_mode='single')
    recompiled = compile(deparsed.text, '<string>', 'single')
    if recompiled != code:
        assert 'dis(' + deparsed.text.strip('\n') + ')' == 'dis(' + expr.strip('\n') + ')'


@pytest.mark.skipif(PYTHON_VERSION < 3.6, reason='need at least python 3.6')
@hypothesis.given(fstrings())
def test_uncompyle_fstring(fstring):
    """Verify uncompyling fstring bytecode"""
    run_test(fstring)


@pytest.mark.skipif(PYTHON_VERSION < 3.6, reason='need at least python 3.6')
@pytest.mark.parametrize('fstring', [
    #"f'{abc}{abc!s}'",
    "f'{abc}0'",
])
def test_uncompyle_direct(fstring):
    """useful for debugging"""
    run_test(fstring)