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Code Issues Releases Wiki Activity

Fix preview of imgur and Tenor URLs. (#11669) 

By scraping Open Graph information from the HTML even
when an autodiscovery endpoint is found. The results are
then combined to capture as much information as possible
from the page.
pull/11768/head
Philippe Daouadi 2022-01-18 19:20:24 +01:00 committed by GitHub
parent 9eab71aa93
commit 15ffc4143c
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4 changed files with 39 additions and 14 deletions
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1
changelog.d/11669.bugfix Normal file
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@ -0,0 +1 @@
Fix preview of some gif URLs (like tenor.com). Contributed by Philippe Daouadi.

7
docs/development/url_previews.md
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@ -35,7 +35,12 @@ When Synapse is asked to preview a URL it does the following:
5. If the media is HTML:
1. Decodes the HTML via the stored file.
2. Generates an Open Graph response from the HTML.
3. If an image exists in the Open Graph response:
3. If a JSON oEmbed URL was found in the HTML via autodiscovery:
1. Downloads the URL and stores it into a file via the media storage provider
and saves the local media metadata.
2. Convert the oEmbed response to an Open Graph response.
3. Override any Open Graph data from the HTML with data from oEmbed.
4. If an image exists in the Open Graph response:
1. Downloads the URL and stores it into a file via the media storage
provider and saves the local media metadata.
2. Generates thumbnails.

10
synapse/rest/media/v1/oembed.py
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@ -33,6 +33,8 @@ logger = logging.getLogger(__name__)
class OEmbedResult:
# The Open Graph result (converted from the oEmbed result).
open_graph_result: JsonDict
# The author_name of the oEmbed result
author_name: Optional[str]
# Number of milliseconds to cache the content, according to the oEmbed response.
#
# This will be None if no cache-age is provided in the oEmbed response (or
@ -154,11 +156,12 @@ class OEmbedProvider:
"og:url": url,
}
# Use either title or author's name as the title.
title = oembed.get("title") or oembed.get("author_name")
title = oembed.get("title")
if title:
open_graph_response["og:title"] = title
author_name = oembed.get("author_name")
# Use the provider name and as the site.
provider_name = oembed.get("provider_name")
if provider_name:
@ -193,9 +196,10 @@ class OEmbedProvider:
# Trap any exception and let the code follow as usual.
logger.warning("Error parsing oEmbed metadata from %s: %r", url, e)
open_graph_response = {}
author_name = None
cache_age = None
return OEmbedResult(open_graph_response, cache_age)
return OEmbedResult(open_graph_response, author_name, cache_age)
def _fetch_urls(tree: "etree.Element", tag_name: str) -> List[str]:

35
synapse/rest/media/v1/preview_url_resource.py
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@ -262,6 +262,7 @@ class PreviewUrlResource(DirectServeJsonResource):
# The number of milliseconds that the response should be considered valid.
expiration_ms = media_info.expires
author_name: Optional[str] = None
if _is_media(media_info.media_type):
file_id = media_info.filesystem_id
@ -294,17 +295,25 @@ class PreviewUrlResource(DirectServeJsonResource):
# Check if this HTML document points to oEmbed information and
# defer to that.
oembed_url = self._oembed.autodiscover_from_html(tree)
og = {}
og_from_oembed: JsonDict = {}
if oembed_url:
oembed_info = await self._download_url(oembed_url, user)
og, expiration_ms = await self._handle_oembed_response(
(
og_from_oembed,
author_name,
expiration_ms,
) = await self._handle_oembed_response(
url, oembed_info, expiration_ms
)
# If there was no oEmbed URL (or oEmbed parsing failed), attempt
# to generate the Open Graph information from the HTML.
if not oembed_url or not og:
og = parse_html_to_open_graph(tree, media_info.uri)
# Parse Open Graph information from the HTML in case the oEmbed
# response failed or is incomplete.
og_from_html = parse_html_to_open_graph(tree, media_info.uri)
# Compile the Open Graph response by using the scraped
# information from the HTML and overlaying any information
# from the oEmbed response.
og = {**og_from_html, **og_from_oembed}
await self._precache_image_url(user, media_info, og)
else:
@ -312,7 +321,7 @@ class PreviewUrlResource(DirectServeJsonResource):
elif oembed_url:
# Handle the oEmbed information.
og, expiration_ms = await self._handle_oembed_response(
og, author_name, expiration_ms = await self._handle_oembed_response(
url, media_info, expiration_ms
)
await self._precache_image_url(user, media_info, og)
@ -321,6 +330,11 @@ class PreviewUrlResource(DirectServeJsonResource):
logger.warning("Failed to find any OG data in %s", url)
og = {}
# If we don't have a title but we have author_name, copy it as
# title
if not og.get("og:title") and author_name:
og["og:title"] = author_name
# filter out any stupidly long values
keys_to_remove = []
for k, v in og.items():
@ -484,7 +498,7 @@ class PreviewUrlResource(DirectServeJsonResource):
async def _handle_oembed_response(
self, url: str, media_info: MediaInfo, expiration_ms: int
) -> Tuple[JsonDict, int]:
) -> Tuple[JsonDict, Optional[str], int]:
"""
Parse the downloaded oEmbed info.
@ -497,11 +511,12 @@ class PreviewUrlResource(DirectServeJsonResource):
Returns:
A tuple of:
The Open Graph dictionary, if the oEmbed info can be parsed.
The author name if it could be retrieved from oEmbed.
The (possibly updated) length of time, in milliseconds, the media is valid for.
"""
# If JSON was not returned, there's nothing to do.
if not _is_json(media_info.media_type):
return {}, expiration_ms
return {}, None, expiration_ms
with open(media_info.filename, "rb") as file:
body = file.read()
@ -513,7 +528,7 @@ class PreviewUrlResource(DirectServeJsonResource):
if open_graph_result and oembed_response.cache_age is not None:
expiration_ms = oembed_response.cache_age
return open_graph_result, expiration_ms
return open_graph_result, oembed_response.author_name, expiration_ms
def _start_expire_url_cache_data(self) -> Deferred:
return run_as_background_process(