Remove dead code.

3 files changed, 3 insertions, 210 deletions

diff --git a/synapse/rest/media/v1/preview_html.py b/synapse/rest/media/v1/preview_html.py
index 1866df60bb..c9711956f1 100644
--- a/synapse/rest/media/v1/preview_html.py
+++ b/synapse/rest/media/v1/preview_html.py
@@ -11,11 +11,10 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-import codecs
 import itertools
 import logging
 import re
-from typing import TYPE_CHECKING, Dict, Generator, Iterable, Iterator, Optional, Set
+from typing import TYPE_CHECKING, Dict, Generator, Iterable, Iterator, Optional
 
 if TYPE_CHECKING:
     from bs4 import BeautifulSoup
@@ -23,88 +22,10 @@ if TYPE_CHECKING:
 
 logger = logging.getLogger(__name__)
 
-_charset_match = re.compile(
-    rb'<\s*meta[^>]*charset\s*=\s*"?([a-z0-9_-]+)"?', flags=re.I
-)
-_xml_encoding_match = re.compile(
-    rb'\s*<\s*\?\s*xml[^>]*encoding="([a-z0-9_-]+)"', flags=re.I
-)
 _content_type_match = re.compile(r'.*; *charset="?(.*?)"?(;|$)', flags=re.I)
 
 
-def _normalise_encoding(encoding: str) -> Optional[str]:
-    """Use the Python codec's name as the normalised entry."""
-    try:
-        return codecs.lookup(encoding).name
-    except LookupError:
-        return None
-
-
-def _get_html_media_encodings(
-    body: bytes, content_type: Optional[str]
-) -> Iterable[str]:
-    """
-    Get potential encoding of the body based on the (presumably) HTML body or the content-type header.
-
-    The precedence used for finding a character encoding is:
-
-    1. <meta> tag with a charset declared.
-    2. The XML document's character encoding attribute.
-    3. The Content-Type header.
-    4. Fallback to utf-8.
-    5. Fallback to windows-1252.
-
-    This roughly follows the algorithm used by BeautifulSoup's bs4.dammit.EncodingDetector.
-
-    Args:
-        body: The HTML document, as bytes.
-        content_type: The Content-Type header.
-
-    Returns:
-        The character encoding of the body, as a string.
-    """
-    # There's no point in returning an encoding more than once.
-    attempted_encodings: Set[str] = set()
-
-    # Limit searches to the first 1kb, since it ought to be at the top.
-    body_start = body[:1024]
-
-    # Check if it has an encoding set in a meta tag.
-    match = _charset_match.search(body_start)
-    if match:
-        encoding = _normalise_encoding(match.group(1).decode("ascii"))
-        if encoding:
-            attempted_encodings.add(encoding)
-            yield encoding
-
-    # TODO Support <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
-
-    # Check if it has an XML document with an encoding.
-    match = _xml_encoding_match.match(body_start)
-    if match:
-        encoding = _normalise_encoding(match.group(1).decode("ascii"))
-        if encoding and encoding not in attempted_encodings:
-            attempted_encodings.add(encoding)
-            yield encoding
-
-    # Check the HTTP Content-Type header for a character set.
-    if content_type:
-        content_match = _content_type_match.match(content_type)
-        if content_match:
-            encoding = _normalise_encoding(content_match.group(1))
-            if encoding and encoding not in attempted_encodings:
-                attempted_encodings.add(encoding)
-                yield encoding
-
-    # Finally, fallback to UTF-8, then windows-1252.
-    for fallback in ("utf-8", "cp1252"):
-        if fallback not in attempted_encodings:
-            yield fallback
-
-
-def decode_body(
-    body: bytes, uri: str, content_type: Optional[str] = None
-) -> Optional["BeautifulSoup"]:
+def decode_body(body: bytes, uri: str) -> Optional["BeautifulSoup"]:
     """
     This uses BeautifulSoup to parse the HTML document.
 
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 2b2db63bf7..e406f6c704 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -303,7 +303,7 @@ class PreviewUrlResource(DirectServeJsonResource):
             with open(media_info.filename, "rb") as file:
                 body = file.read()
 
-            tree = decode_body(body, media_info.uri, media_info.media_type)
+            tree = decode_body(body, media_info.uri)
             if tree is not None:
                 # Check if this HTML document points to oEmbed information and
                 # defer to that.
diff --git a/tests/rest/media/v1/test_html_preview.py b/tests/rest/media/v1/test_html_preview.py
index 62e308814d..5e600450dc 100644
--- a/tests/rest/media/v1/test_html_preview.py
+++ b/tests/rest/media/v1/test_html_preview.py
@@ -13,7 +13,6 @@
 # limitations under the License.
 
 from synapse.rest.media.v1.preview_html import (
-    _get_html_media_encodings,
     decode_body,
     parse_html_to_open_graph,
     summarize_paragraphs,
@@ -292,20 +291,6 @@ class CalcOgTestCase(unittest.TestCase):
         og = parse_html_to_open_graph(tree)
         self.assertEqual(og, {"og:title": "Foo", "og:description": "Some text."})
 
-    def test_invalid_encoding(self) -> None:
-        """An invalid character encoding should be ignored and treated as UTF-8, if possible."""
-        html = b"""
-        <html>
-        <head><title>Foo</title></head>
-        <body>
-        Some text.
-        </body>
-        </html>
-        """
-        tree = decode_body(html, "http://example.com/test.html", "invalid-encoding")
-        og = parse_html_to_open_graph(tree)
-        self.assertEqual(og, {"og:title": "Foo", "og:description": "Some text."})
-
     def test_invalid_encoding2(self) -> None:
         """A body which doesn't match the sent character encoding."""
         # Note that this contains an invalid UTF-8 sequence in the title.
@@ -334,116 +319,3 @@ class CalcOgTestCase(unittest.TestCase):
         tree = decode_body(html, "http://example.com/test.html")
         og = parse_html_to_open_graph(tree)
         self.assertEqual(og, {"og:title": "ó", "og:description": "Some text."})
-
-
-class MediaEncodingTestCase(unittest.TestCase):
-    def test_meta_charset(self) -> None:
-        """A character encoding is found via the meta tag."""
-        encodings = _get_html_media_encodings(
-            b"""
-        <html>
-        <head><meta charset="ascii">
-        </head>
-        </html>
-        """,
-            "text/html",
-        )
-        self.assertEqual(list(encodings), ["ascii", "utf-8", "cp1252"])
-
-        # A less well-formed version.
-        encodings = _get_html_media_encodings(
-            b"""
-        <html>
-        <head>< meta charset = ascii>
-        </head>
-        </html>
-        """,
-            "text/html",
-        )
-        self.assertEqual(list(encodings), ["ascii", "utf-8", "cp1252"])
-
-    def test_meta_charset_underscores(self) -> None:
-        """A character encoding contains underscore."""
-        encodings = _get_html_media_encodings(
-            b"""
-        <html>
-        <head><meta charset="Shift_JIS">
-        </head>
-        </html>
-        """,
-            "text/html",
-        )
-        self.assertEqual(list(encodings), ["shift_jis", "utf-8", "cp1252"])
-
-    def test_xml_encoding(self) -> None:
-        """A character encoding is found via the meta tag."""
-        encodings = _get_html_media_encodings(
-            b"""
-        <?xml version="1.0" encoding="ascii"?>
-        <html>
-        </html>
-        """,
-            "text/html",
-        )
-        self.assertEqual(list(encodings), ["ascii", "utf-8", "cp1252"])
-
-    def test_meta_xml_encoding(self) -> None:
-        """Meta tags take precedence over XML encoding."""
-        encodings = _get_html_media_encodings(
-            b"""
-        <?xml version="1.0" encoding="ascii"?>
-        <html>
-        <head><meta charset="UTF-16">
-        </head>
-        </html>
-        """,
-            "text/html",
-        )
-        self.assertEqual(list(encodings), ["utf-16", "ascii", "utf-8", "cp1252"])
-
-    def test_content_type(self) -> None:
-        """A character encoding is found via the Content-Type header."""
-        # Test a few variations of the header.
-        headers = (
-            'text/html; charset="ascii";',
-            "text/html;charset=ascii;",
-            'text/html;  charset="ascii"',
-            "text/html; charset=ascii",
-            'text/html; charset="ascii;',
-            'text/html; charset=ascii";',
-        )
-        for header in headers:
-            encodings = _get_html_media_encodings(b"", header)
-            self.assertEqual(list(encodings), ["ascii", "utf-8", "cp1252"])
-
-    def test_fallback(self) -> None:
-        """A character encoding cannot be found in the body or header."""
-        encodings = _get_html_media_encodings(b"", "text/html")
-        self.assertEqual(list(encodings), ["utf-8", "cp1252"])
-
-    def test_duplicates(self) -> None:
-        """Ensure each encoding is only attempted once."""
-        encodings = _get_html_media_encodings(
-            b"""
-        <?xml version="1.0" encoding="utf8"?>
-        <html>
-        <head><meta charset="UTF-8">
-        </head>
-        </html>
-        """,
-            'text/html; charset="UTF_8"',
-        )
-        self.assertEqual(list(encodings), ["utf-8", "cp1252"])
-
-    def test_unknown_invalid(self) -> None:
-        """A character encoding should be ignored if it is unknown or invalid."""
-        encodings = _get_html_media_encodings(
-            b"""
-        <html>
-        <head><meta charset="invalid">
-        </head>
-        </html>
-        """,
-            'text/html; charset="invalid"',
-        )
-        self.assertEqual(list(encodings), ["utf-8", "cp1252"])