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Ensure each charset is attempted only once during media preview. (#11089)
There's no point in trying more than once since it is guaranteed to continually fail.
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3 changed files with 64 additions and 14 deletions
1
changelog.d/11089.bugfix
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1
changelog.d/11089.bugfix
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@ -0,0 +1 @@
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Fix a long-standing bug when attempting to preview URLs which are in the `windows-1252` character encoding.
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@ -12,6 +12,7 @@
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import codecs
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import datetime
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import errno
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import fnmatch
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@ -22,7 +23,7 @@ import re
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import shutil
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import sys
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import traceback
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from typing import TYPE_CHECKING, Dict, Generator, Iterable, Optional, Tuple, Union
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from typing import TYPE_CHECKING, Dict, Generator, Iterable, Optional, Set, Tuple, Union
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from urllib import parse as urlparse
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import attr
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@ -631,6 +632,14 @@ class PreviewUrlResource(DirectServeJsonResource):
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logger.debug("No media removed from url cache")
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def _normalise_encoding(encoding: str) -> Optional[str]:
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"""Use the Python codec's name as the normalised entry."""
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try:
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return codecs.lookup(encoding).name
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except LookupError:
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return None
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def get_html_media_encodings(body: bytes, content_type: Optional[str]) -> Iterable[str]:
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"""
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Get potential encoding of the body based on the (presumably) HTML body or the content-type header.
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@ -652,30 +661,43 @@ def get_html_media_encodings(body: bytes, content_type: Optional[str]) -> Iterab
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Returns:
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The character encoding of the body, as a string.
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"""
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# There's no point in returning an encoding more than once.
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attempted_encodings: Set[str] = set()
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# Limit searches to the first 1kb, since it ought to be at the top.
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body_start = body[:1024]
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# Check if it has an encoding set in a meta tag.
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match = _charset_match.search(body_start)
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if match:
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yield match.group(1).decode("ascii")
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encoding = _normalise_encoding(match.group(1).decode("ascii"))
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if encoding:
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attempted_encodings.add(encoding)
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yield encoding
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# TODO Support <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
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# Check if it has an XML document with an encoding.
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match = _xml_encoding_match.match(body_start)
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if match:
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yield match.group(1).decode("ascii")
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encoding = _normalise_encoding(match.group(1).decode("ascii"))
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if encoding and encoding not in attempted_encodings:
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attempted_encodings.add(encoding)
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yield encoding
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# Check the HTTP Content-Type header for a character set.
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if content_type:
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content_match = _content_type_match.match(content_type)
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if content_match:
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yield content_match.group(1)
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encoding = _normalise_encoding(content_match.group(1))
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if encoding and encoding not in attempted_encodings:
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attempted_encodings.add(encoding)
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yield encoding
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# Finally, fallback to UTF-8, then windows-1252.
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yield "utf-8"
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yield "windows-1252"
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for fallback in ("utf-8", "cp1252"):
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if fallback not in attempted_encodings:
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yield fallback
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def decode_body(
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@ -307,7 +307,7 @@ class CalcOgTestCase(unittest.TestCase):
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self.assertEqual(og, {"og:title": "ÿÿ Foo", "og:description": "Some text."})
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def test_windows_1252(self):
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"""A body which uses windows-1252, but doesn't declare that."""
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"""A body which uses cp1252, but doesn't declare that."""
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html = b"""
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<html>
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<head><title>\xf3</title></head>
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@ -333,7 +333,7 @@ class MediaEncodingTestCase(unittest.TestCase):
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""",
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"text/html",
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)
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self.assertEqual(list(encodings), ["ascii", "utf-8", "windows-1252"])
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self.assertEqual(list(encodings), ["ascii", "utf-8", "cp1252"])
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# A less well-formed version.
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encodings = get_html_media_encodings(
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@ -345,7 +345,7 @@ class MediaEncodingTestCase(unittest.TestCase):
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""",
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"text/html",
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)
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self.assertEqual(list(encodings), ["ascii", "utf-8", "windows-1252"])
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self.assertEqual(list(encodings), ["ascii", "utf-8", "cp1252"])
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def test_meta_charset_underscores(self):
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"""A character encoding contains underscore."""
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@ -358,7 +358,7 @@ class MediaEncodingTestCase(unittest.TestCase):
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""",
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"text/html",
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)
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self.assertEqual(list(encodings), ["Shift_JIS", "utf-8", "windows-1252"])
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self.assertEqual(list(encodings), ["shift_jis", "utf-8", "cp1252"])
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def test_xml_encoding(self):
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"""A character encoding is found via the meta tag."""
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@ -370,7 +370,7 @@ class MediaEncodingTestCase(unittest.TestCase):
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""",
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"text/html",
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)
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self.assertEqual(list(encodings), ["ascii", "utf-8", "windows-1252"])
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self.assertEqual(list(encodings), ["ascii", "utf-8", "cp1252"])
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def test_meta_xml_encoding(self):
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"""Meta tags take precedence over XML encoding."""
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@ -384,7 +384,7 @@ class MediaEncodingTestCase(unittest.TestCase):
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""",
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"text/html",
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)
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self.assertEqual(list(encodings), ["UTF-16", "ascii", "utf-8", "windows-1252"])
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self.assertEqual(list(encodings), ["utf-16", "ascii", "utf-8", "cp1252"])
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def test_content_type(self):
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"""A character encoding is found via the Content-Type header."""
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@ -399,9 +399,36 @@ class MediaEncodingTestCase(unittest.TestCase):
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)
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for header in headers:
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encodings = get_html_media_encodings(b"", header)
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self.assertEqual(list(encodings), ["ascii", "utf-8", "windows-1252"])
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self.assertEqual(list(encodings), ["ascii", "utf-8", "cp1252"])
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def test_fallback(self):
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"""A character encoding cannot be found in the body or header."""
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encodings = get_html_media_encodings(b"", "text/html")
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self.assertEqual(list(encodings), ["utf-8", "windows-1252"])
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self.assertEqual(list(encodings), ["utf-8", "cp1252"])
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def test_duplicates(self):
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"""Ensure each encoding is only attempted once."""
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encodings = get_html_media_encodings(
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b"""
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<?xml version="1.0" encoding="utf8"?>
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<html>
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<head><meta charset="UTF-8">
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</head>
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</html>
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""",
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'text/html; charset="UTF_8"',
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)
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self.assertEqual(list(encodings), ["utf-8", "cp1252"])
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def test_unknown_invalid(self):
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"""A character encoding should be ignored if it is unknown or invalid."""
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encodings = get_html_media_encodings(
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b"""
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<html>
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<head><meta charset="invalid">
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</head>
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</html>
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""",
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'text/html; charset="invalid"',
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)
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self.assertEqual(list(encodings), ["utf-8", "cp1252"])
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