test.py

"""
Run chardet on a bunch of documents and see that we get the correct encodings.

:author: Dan Blanchard
:author: Ian Cordasco
"""

from __future__ import with_statement

import textwrap
from difflib import ndiff
from io import open
from os import listdir
from os.path import dirname, isdir, join, realpath, relpath, splitext

try:
    import hypothesis.strategies as st
    from hypothesis import given, assume, settings, Verbosity
    HAVE_HYPOTHESIS = True
except ImportError:
    HAVE_HYPOTHESIS = False
import pytest

import chardet


# TODO: Restore Hungarian encodings (iso-8859-2 and windows-1250) after we
#       retrain model.
MISSING_ENCODINGS = {'iso-8859-2', 'iso-8859-6', 'windows-1250',
                     'windows-1254', 'windows-1256'}
EXPECTED_FAILURES = {'tests/iso-8859-7-greek/disabled.gr.xml',
                     'tests/iso-8859-9-turkish/divxplanet.com.xml',
                     'tests/iso-8859-9-turkish/subtitle.srt',
                     'tests/iso-8859-9-turkish/wikitop_tr_ISO-8859-9.txt'}

def gen_test_params():
    """Yields tuples of paths and encodings to use for test_encoding_detection"""
    base_path = relpath(join(dirname(realpath(__file__)), 'tests'))
    for encoding in listdir(base_path):
        path = join(base_path, encoding)
        # Skip files in tests directory
        if not isdir(path):
            continue
        # Remove language suffixes from encoding if pressent
        encoding = encoding.lower()
        for postfix in ['-arabic', '-bulgarian', '-cyrillic', '-greek',
                        '-hebrew', '-hungarian', '-turkish']:
            if encoding.endswith(postfix):
                encoding = encoding.rpartition(postfix)[0]
                break
        # Skip directories for encodings we don't handle yet.
        if encoding in MISSING_ENCODINGS:
            continue
        # Test encoding detection for each file we have of encoding for
        for file_name in listdir(path):
            ext = splitext(file_name)[1].lower()
            if ext not in ['.html', '.txt', '.xml', '.srt']:
                continue
            full_path = join(path, file_name)
            test_case = full_path, encoding
            if full_path in EXPECTED_FAILURES:
                test_case = pytest.param(*test_case, marks=pytest.mark.xfail)
            yield test_case


@pytest.mark.parametrize ('file_name, encoding', gen_test_params())
def test_encoding_detection(file_name, encoding):
    with open(file_name, 'rb') as f:
        input_bytes = f.read()
        result = chardet.detect(input_bytes)
        try:
            expected_unicode = input_bytes.decode(encoding)
        except LookupError:
            expected_unicode = ''
        try:
            detected_unicode = input_bytes.decode(result['encoding'])
        except (LookupError, UnicodeDecodeError, TypeError):
            detected_unicode = ''
    if result:
        encoding_match = (result['encoding'] or '').lower() == encoding
    else:
        encoding_match = False
    # Only care about mismatches that would actually result in different
    # behavior when decoding
    if not encoding_match and expected_unicode != detected_unicode:
        wrapped_expected = '\n'.join(textwrap.wrap(expected_unicode, 100)) + '\n'
        wrapped_detected = '\n'.join(textwrap.wrap(detected_unicode, 100)) + '\n'
        diff = ''.join(ndiff(wrapped_expected.splitlines(True),
                             wrapped_detected.splitlines(True)))
    else:
        diff = ''
        encoding_match = True
    assert encoding_match, ("Expected %s, but got %s for %s.  Character "
                            "differences: \n%s" % (encoding,
                                                   result,
                                                   file_name,
                                                   diff))


if HAVE_HYPOTHESIS:
    class JustALengthIssue(Exception):
        pass


    @pytest.mark.xfail
    @given(st.text(min_size=1), st.sampled_from(['ascii', 'utf-8', 'utf-16',
                                                 'utf-32', 'iso-8859-7',
                                                 'iso-8859-8', 'windows-1255']),
           st.randoms())
    @settings(max_examples=200)
    def test_never_fails_to_detect_if_there_is_a_valid_encoding(txt, enc, rnd):
        try:
            data = txt.encode(enc)
        except UnicodeEncodeError:
            assume(False)
        detected = chardet.detect(data)['encoding']
        if detected is None:
            with pytest.raises(JustALengthIssue):
                @given(st.text(), random=rnd)
                @settings(verbosity=Verbosity.quiet, max_shrinks=0, max_examples=50)
                def string_poisons_following_text(suffix):
                    try:
                        extended = (txt + suffix).encode(enc)
                    except UnicodeEncodeError:
                        assume(False)
                    result = chardet.detect(extended)
                    if result and result['encoding'] is not None:
                        raise JustALengthIssue()


    @given(st.text(min_size=1), st.sampled_from(['ascii', 'utf-8', 'utf-16',
                                                 'utf-32', 'iso-8859-7',
                                                 'iso-8859-8', 'windows-1255']),
           st.randoms())
    @settings(max_examples=200)
    def test_detect_all_and_detect_one_should_agree(txt, enc, rnd):
        try:
            data = txt.encode(enc)
        except UnicodeEncodeError:
            assume(False)
        try:
            result = chardet.detect(data)
            results = chardet.detect_all(data)
            assert result['encoding'] == results[0]['encoding']
        except Exception:
            raise Exception('%s != %s' % (result, results))