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Refactor oEmbed previews (#10814)
The major change is moving the decision of whether to use oEmbed further up the call-stack. This reverts the _download_url method to being a "dumb" functionwhich takes a single URL and downloads it (as it was before #7920). This also makes more minor refactorings: * Renames internal variables for clarity. * Factors out shared code between the HTML and rich oEmbed previews. * Fixes tests to preview an oEmbed image.
This commit is contained in:
Patrick Cloke
GitHub
parent
2843058a8b
commit
ba7a91aea5
5 changed files with 299 additions and 220 deletions
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@ -12,11 +12,14 @@
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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 logging
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import urllib.parse
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from typing import TYPE_CHECKING, Optional
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import attr
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from synapse.http.client import SimpleHttpClient
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from synapse.types import JsonDict
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from synapse.util import json_decoder
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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@ -24,18 +27,15 @@ if TYPE_CHECKING:
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logger = logging.getLogger(__name__)
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@attr.s(slots=True, auto_attribs=True)
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@attr.s(slots=True, frozen=True, auto_attribs=True)
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class OEmbedResult:
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# Either HTML content or URL must be provided.
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html: Optional[str]
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url: Optional[str]
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title: Optional[str]
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# Number of seconds to cache the content.
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cache_age: int
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class OEmbedError(Exception):
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"""An error occurred processing the oEmbed object."""
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# The Open Graph result (converted from the oEmbed result).
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open_graph_result: JsonDict
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# Number of seconds to cache the content, according to the oEmbed response.
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#
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# This will be None if no cache-age is provided in the oEmbed response (or
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# if the oEmbed response cannot be turned into an Open Graph response).
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cache_age: Optional[int]
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class OEmbedProvider:
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@ -81,75 +81,106 @@ class OEmbedProvider:
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"""
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for url_pattern, endpoint in self._oembed_patterns.items():
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if url_pattern.fullmatch(url):
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return endpoint
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# TODO Specify max height / width.
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# Note that only the JSON format is supported, some endpoints want
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# this in the URL, others want it as an argument.
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endpoint = endpoint.replace("{format}", "json")
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args = {"url": url, "format": "json"}
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query_str = urllib.parse.urlencode(args, True)
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return f"{endpoint}?{query_str}"
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# No match.
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return None
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async def get_oembed_content(self, endpoint: str, url: str) -> OEmbedResult:
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def parse_oembed_response(self, url: str, raw_body: bytes) -> OEmbedResult:
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"""
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Request content from an oEmbed endpoint.
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Parse the oEmbed response into an Open Graph response.
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Args:
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endpoint: The oEmbed API endpoint.
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url: The URL to pass to the API.
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url: The URL which is being previewed (not the one which was
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requested).
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raw_body: The oEmbed response as JSON encoded as bytes.
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Returns:
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An object representing the metadata returned.
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Raises:
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OEmbedError if fetching or parsing of the oEmbed information fails.
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json-encoded Open Graph data
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"""
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try:
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logger.debug("Trying to get oEmbed content for url '%s'", url)
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# Note that only the JSON format is supported, some endpoints want
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# this in the URL, others want it as an argument.
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endpoint = endpoint.replace("{format}", "json")
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result = await self._client.get_json(
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endpoint,
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# TODO Specify max height / width.
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args={"url": url, "format": "json"},
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)
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# oEmbed responses *must* be UTF-8 according to the spec.
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oembed = json_decoder.decode(raw_body.decode("utf-8"))
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# Ensure there's a version of 1.0.
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if result.get("version") != "1.0":
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raise OEmbedError("Invalid version: %s" % (result.get("version"),))
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oembed_type = result.get("type")
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oembed_version = oembed["version"]
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if oembed_version != "1.0":
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raise RuntimeError(f"Invalid version: {oembed_version}")
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# Ensure the cache age is None or an int.
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cache_age = result.get("cache_age")
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cache_age = oembed.get("cache_age")
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if cache_age:
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cache_age = int(cache_age)
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oembed_result = OEmbedResult(None, None, result.get("title"), cache_age)
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# The results.
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open_graph_response = {"og:title": oembed.get("title")}
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# HTML content.
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# If a thumbnail exists, use it. Note that dimensions will be calculated later.
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if "thumbnail_url" in oembed:
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open_graph_response["og:image"] = oembed["thumbnail_url"]
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# Process each type separately.
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oembed_type = oembed["type"]
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if oembed_type == "rich":
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oembed_result.html = result.get("html")
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return oembed_result
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calc_description_and_urls(open_graph_response, oembed["html"])
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if oembed_type == "photo":
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oembed_result.url = result.get("url")
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return oembed_result
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elif oembed_type == "photo":
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# If this is a photo, use the full image, not the thumbnail.
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open_graph_response["og:image"] = oembed["url"]
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# TODO Handle link and video types.
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if "thumbnail_url" in result:
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oembed_result.url = result.get("thumbnail_url")
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return oembed_result
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raise OEmbedError("Incompatible oEmbed information.")
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except OEmbedError as e:
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# Trap OEmbedErrors first so we can directly re-raise them.
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logger.warning("Error parsing oEmbed metadata from %s: %r", url, e)
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raise
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else:
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raise RuntimeError(f"Unknown oEmbed type: {oembed_type}")
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except Exception as e:
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# Trap any exception and let the code follow as usual.
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# FIXME: pass through 404s and other error messages nicely
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logger.warning("Error downloading oEmbed metadata from %s: %r", url, e)
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raise OEmbedError() from e
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logger.warning(f"Error parsing oEmbed metadata from {url}: {e:r}")
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open_graph_response = {}
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cache_age = None
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return OEmbedResult(open_graph_response, cache_age)
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def calc_description_and_urls(open_graph_response: JsonDict, html_body: str) -> None:
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"""
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Calculate description for an HTML document.
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This uses lxml to convert the HTML document into plaintext. If errors
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occur during processing of the document, an empty response is returned.
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Args:
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open_graph_response: The current Open Graph summary. This is updated with additional fields.
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html_body: The HTML document, as bytes.
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Returns:
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The summary
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"""
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# If there's no body, nothing useful is going to be found.
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if not html_body:
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return
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from lxml import etree
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# Create an HTML parser. If this fails, log and return no metadata.
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parser = etree.HTMLParser(recover=True, encoding="utf-8")
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# Attempt to parse the body. If this fails, log and return no metadata.
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tree = etree.fromstring(html_body, parser)
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# The data was successfully parsed, but no tree was found.
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if tree is None:
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return
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from synapse.rest.media.v1.preview_url_resource import _calc_description
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description = _calc_description(tree)
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if description:
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open_graph_response["og:description"] = description
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