Fix up preview URL API. Add tests.

This includes:

- Splitting out methods of a class into stand alone functions, to make
  them easier to test.
- Adding unit tests to split out functions, testing HTML -> preview.
- Handle the fact that elements in lxml may have tail text.
This commit is contained in:
Erik Johnston 2016-08-16 14:53:18 +01:00
parent 7c6f4f9427
commit 48b5829aea
2 changed files with 275 additions and 158 deletions

View File

@ -163,7 +163,7 @@ class PreviewUrlResource(Resource):
logger.debug("got media_info of '%s'" % media_info)
if self._is_media(media_info['media_type']):
if _is_media(media_info['media_type']):
dims = yield self.media_repo._generate_local_thumbnails(
media_info['filesystem_id'], media_info
)
@ -184,11 +184,9 @@ class PreviewUrlResource(Resource):
logger.warn("Couldn't get dims for %s" % url)
# define our OG response for this media
elif self._is_html(media_info['media_type']):
elif _is_html(media_info['media_type']):
# TODO: somehow stop a big HTML tree from exploding synapse's RAM
from lxml import etree
file = open(media_info['filename'])
body = file.read()
file.close()
@ -199,17 +197,35 @@ class PreviewUrlResource(Resource):
match = re.match(r'.*; *charset=(.*?)(;|$)', media_info['media_type'], re.I)
encoding = match.group(1) if match else "utf-8"
try:
parser = etree.HTMLParser(recover=True, encoding=encoding)
tree = etree.fromstring(body, parser)
og = yield self._calc_og(tree, media_info, requester)
except UnicodeDecodeError:
# blindly try decoding the body as utf-8, which seems to fix
# the charset mismatches on https://google.com
parser = etree.HTMLParser(recover=True, encoding=encoding)
tree = etree.fromstring(body.decode('utf-8', 'ignore'), parser)
og = yield self._calc_og(tree, media_info, requester)
og = decode_and_calc_og(body, media_info['uri'], encoding)
# pre-cache the image for posterity
# FIXME: it might be cleaner to use the same flow as the main /preview_url
# request itself and benefit from the same caching etc. But for now we
# just rely on the caching on the master request to speed things up.
if 'og:image' in og and og['og:image']:
image_info = yield self._download_url(
_rebase_url(og['og:image'], media_info['uri']), requester.user
)
if _is_media(image_info['media_type']):
# TODO: make sure we don't choke on white-on-transparent images
dims = yield self.media_repo._generate_local_thumbnails(
image_info['filesystem_id'], image_info
)
if dims:
og["og:image:width"] = dims['width']
og["og:image:height"] = dims['height']
else:
logger.warn("Couldn't get dims for %s" % og["og:image"])
og["og:image"] = "mxc://%s/%s" % (
self.server_name, image_info['filesystem_id']
)
og["og:image:type"] = image_info['media_type']
og["matrix:image:size"] = image_info['media_length']
else:
del og["og:image"]
else:
logger.warn("Failed to find any OG data in %s", url)
og = {}
@ -232,139 +248,6 @@ class PreviewUrlResource(Resource):
respond_with_json_bytes(request, 200, json.dumps(og), send_cors=True)
@defer.inlineCallbacks
def _calc_og(self, tree, media_info, requester):
# suck our tree into lxml and define our OG response.
# if we see any image URLs in the OG response, then spider them
# (although the client could choose to do this by asking for previews of those
# URLs to avoid DoSing the server)
# "og:type" : "video",
# "og:url" : "https://www.youtube.com/watch?v=LXDBoHyjmtw",
# "og:site_name" : "YouTube",
# "og:video:type" : "application/x-shockwave-flash",
# "og:description" : "Fun stuff happening here",
# "og:title" : "RemoteJam - Matrix team hack for Disrupt Europe Hackathon",
# "og:image" : "https://i.ytimg.com/vi/LXDBoHyjmtw/maxresdefault.jpg",
# "og:video:url" : "http://www.youtube.com/v/LXDBoHyjmtw?version=3&autohide=1",
# "og:video:width" : "1280"
# "og:video:height" : "720",
# "og:video:secure_url": "https://www.youtube.com/v/LXDBoHyjmtw?version=3",
og = {}
for tag in tree.xpath("//*/meta[starts-with(@property, 'og:')]"):
if 'content' in tag.attrib:
og[tag.attrib['property']] = tag.attrib['content']
# TODO: grab article: meta tags too, e.g.:
# "article:publisher" : "https://www.facebook.com/thethudonline" />
# "article:author" content="https://www.facebook.com/thethudonline" />
# "article:tag" content="baby" />
# "article:section" content="Breaking News" />
# "article:published_time" content="2016-03-31T19:58:24+00:00" />
# "article:modified_time" content="2016-04-01T18:31:53+00:00" />
if 'og:title' not in og:
# do some basic spidering of the HTML
title = tree.xpath("(//title)[1] | (//h1)[1] | (//h2)[1] | (//h3)[1]")
og['og:title'] = title[0].text.strip() if title else None
if 'og:image' not in og:
# TODO: extract a favicon failing all else
meta_image = tree.xpath(
"//*/meta[translate(@itemprop, 'IMAGE', 'image')='image']/@content"
)
if meta_image:
og['og:image'] = self._rebase_url(meta_image[0], media_info['uri'])
else:
# TODO: consider inlined CSS styles as well as width & height attribs
images = tree.xpath("//img[@src][number(@width)>10][number(@height)>10]")
images = sorted(images, key=lambda i: (
-1 * float(i.attrib['width']) * float(i.attrib['height'])
))
if not images:
images = tree.xpath("//img[@src]")
if images:
og['og:image'] = images[0].attrib['src']
# pre-cache the image for posterity
# FIXME: it might be cleaner to use the same flow as the main /preview_url
# request itself and benefit from the same caching etc. But for now we
# just rely on the caching on the master request to speed things up.
if 'og:image' in og and og['og:image']:
image_info = yield self._download_url(
self._rebase_url(og['og:image'], media_info['uri']), requester.user
)
if self._is_media(image_info['media_type']):
# TODO: make sure we don't choke on white-on-transparent images
dims = yield self.media_repo._generate_local_thumbnails(
image_info['filesystem_id'], image_info
)
if dims:
og["og:image:width"] = dims['width']
og["og:image:height"] = dims['height']
else:
logger.warn("Couldn't get dims for %s" % og["og:image"])
og["og:image"] = "mxc://%s/%s" % (
self.server_name, image_info['filesystem_id']
)
og["og:image:type"] = image_info['media_type']
og["matrix:image:size"] = image_info['media_length']
else:
del og["og:image"]
if 'og:description' not in og:
meta_description = tree.xpath(
"//*/meta"
"[translate(@name, 'DESCRIPTION', 'description')='description']"
"/@content")
if meta_description:
og['og:description'] = meta_description[0]
else:
# grab any text nodes which are inside the <body/> tag...
# unless they are within an HTML5 semantic markup tag...
# <header/>, <nav/>, <aside/>, <footer/>
# ...or if they are within a <script/> or <style/> tag.
# This is a very very very coarse approximation to a plain text
# render of the page.
# We don't just use XPATH here as that is slow on some machines.
# We clone `tree` as we modify it.
cloned_tree = deepcopy(tree.find("body"))
TAGS_TO_REMOVE = ("header", "nav", "aside", "footer", "script", "style",)
for el in cloned_tree.iter(TAGS_TO_REMOVE):
el.getparent().remove(el)
# Split all the text nodes into paragraphs (by splitting on new
# lines)
text_nodes = (
re.sub(r'\s+', '\n', el.text).strip()
for el in cloned_tree.iter()
if el.text and isinstance(el.tag, basestring) # Removes comments
)
og['og:description'] = summarize_paragraphs(text_nodes)
# TODO: delete the url downloads to stop diskfilling,
# as we only ever cared about its OG
defer.returnValue(og)
def _rebase_url(self, url, base):
base = list(urlparse.urlparse(base))
url = list(urlparse.urlparse(url))
if not url[0]: # fix up schema
url[0] = base[0] or "http"
if not url[1]: # fix up hostname
url[1] = base[1]
if not url[2].startswith('/'):
url[2] = re.sub(r'/[^/]+$', '/', base[2]) + url[2]
return urlparse.urlunparse(url)
@defer.inlineCallbacks
def _download_url(self, url, user):
# TODO: we should probably honour robots.txt... except in practice
@ -445,11 +328,167 @@ class PreviewUrlResource(Resource):
"etag": headers["ETag"][0] if "ETag" in headers else None,
})
def _is_media(self, content_type):
def decode_and_calc_og(body, media_uri, request_encoding=None):
from lxml import etree
try:
parser = etree.HTMLParser(recover=True, encoding=request_encoding)
tree = etree.fromstring(body, parser)
og = _calc_og(tree, media_uri)
except UnicodeDecodeError:
# blindly try decoding the body as utf-8, which seems to fix
# the charset mismatches on https://google.com
parser = etree.HTMLParser(recover=True, encoding=request_encoding)
tree = etree.fromstring(body.decode('utf-8', 'ignore'), parser)
og = _calc_og(tree, media_uri)
return og
def _calc_og(tree, media_uri):
# suck our tree into lxml and define our OG response.
# if we see any image URLs in the OG response, then spider them
# (although the client could choose to do this by asking for previews of those
# URLs to avoid DoSing the server)
# "og:type" : "video",
# "og:url" : "https://www.youtube.com/watch?v=LXDBoHyjmtw",
# "og:site_name" : "YouTube",
# "og:video:type" : "application/x-shockwave-flash",
# "og:description" : "Fun stuff happening here",
# "og:title" : "RemoteJam - Matrix team hack for Disrupt Europe Hackathon",
# "og:image" : "https://i.ytimg.com/vi/LXDBoHyjmtw/maxresdefault.jpg",
# "og:video:url" : "http://www.youtube.com/v/LXDBoHyjmtw?version=3&autohide=1",
# "og:video:width" : "1280"
# "og:video:height" : "720",
# "og:video:secure_url": "https://www.youtube.com/v/LXDBoHyjmtw?version=3",
og = {}
for tag in tree.xpath("//*/meta[starts-with(@property, 'og:')]"):
if 'content' in tag.attrib:
og[tag.attrib['property']] = tag.attrib['content']
# TODO: grab article: meta tags too, e.g.:
# "article:publisher" : "https://www.facebook.com/thethudonline" />
# "article:author" content="https://www.facebook.com/thethudonline" />
# "article:tag" content="baby" />
# "article:section" content="Breaking News" />
# "article:published_time" content="2016-03-31T19:58:24+00:00" />
# "article:modified_time" content="2016-04-01T18:31:53+00:00" />
if 'og:title' not in og:
# do some basic spidering of the HTML
title = tree.xpath("(//title)[1] | (//h1)[1] | (//h2)[1] | (//h3)[1]")
og['og:title'] = title[0].text.strip() if title else None
if 'og:image' not in og:
# TODO: extract a favicon failing all else
meta_image = tree.xpath(
"//*/meta[translate(@itemprop, 'IMAGE', 'image')='image']/@content"
)
if meta_image:
og['og:image'] = _rebase_url(meta_image[0], media_uri)
else:
# TODO: consider inlined CSS styles as well as width & height attribs
images = tree.xpath("//img[@src][number(@width)>10][number(@height)>10]")
images = sorted(images, key=lambda i: (
-1 * float(i.attrib['width']) * float(i.attrib['height'])
))
if not images:
images = tree.xpath("//img[@src]")
if images:
og['og:image'] = images[0].attrib['src']
if 'og:description' not in og:
meta_description = tree.xpath(
"//*/meta"
"[translate(@name, 'DESCRIPTION', 'description')='description']"
"/@content")
if meta_description:
og['og:description'] = meta_description[0]
else:
# grab any text nodes which are inside the <body/> tag...
# unless they are within an HTML5 semantic markup tag...
# <header/>, <nav/>, <aside/>, <footer/>
# ...or if they are within a <script/> or <style/> tag.
# This is a very very very coarse approximation to a plain text
# render of the page.
# We don't just use XPATH here as that is slow on some machines.
from lxml import etree
TAGS_TO_REMOVE = (
"header", "nav", "aside", "footer", "script", "style", etree.Comment
)
# Split all the text nodes into paragraphs (by splitting on new
# lines)
text_nodes = (
re.sub(r'\s+', '\n', el).strip()
for el in _iterate_over_text(tree.find("body"), *TAGS_TO_REMOVE)
)
og['og:description'] = summarize_paragraphs(text_nodes)
# TODO: delete the url downloads to stop diskfilling,
# as we only ever cared about its OG
return og
def _iterate_over_text(tree, *tags_to_ignore):
"""Iterate over the tree returning text nodes in a depth first fashion,
skipping text nodes inside certain tags.
"""
import itertools
# This is basically a stack that we extend using itertools.chain.
# This will either consist of an element to iterate over *or* a string
# to be returned.
elements = iter([tree])
while True:
el = elements.next()
if isinstance(el, basestring):
yield el
elif el.tag not in tags_to_ignore:
# el.text is the text before the first child, so we can immediately
# return it if the text exists.
if el.text:
yield el.text
# We add to the stack all the elements children, interspersed with
# each child's tail text (if it exists). The tail text of a node
# is text that comes *after* the node, so we always include it even
# if we ignore the child node.
elements = itertools.chain(
itertools.chain.from_iterable( # Basically a flatmap
[child, child.tail] if child.tail else [child]
for child in el.iterchildren()
),
elements
)
def _rebase_url(url, base):
base = list(urlparse.urlparse(base))
url = list(urlparse.urlparse(url))
if not url[0]: # fix up schema
url[0] = base[0] or "http"
if not url[1]: # fix up hostname
url[1] = base[1]
if not url[2].startswith('/'):
url[2] = re.sub(r'/[^/]+$', '/', base[2]) + url[2]
return urlparse.urlunparse(url)
def _is_media(content_type):
if content_type.lower().startswith("image/"):
return True
def _is_html(self, content_type):
def _is_html(content_type):
content_type = content_type.lower()
if (
content_type.startswith("text/html") or

View File

@ -15,7 +15,9 @@
from . import unittest
from synapse.rest.media.v1.preview_url_resource import summarize_paragraphs
from synapse.rest.media.v1.preview_url_resource import (
summarize_paragraphs, decode_and_calc_og
)
class PreviewTestCase(unittest.TestCase):
@ -137,3 +139,79 @@ class PreviewTestCase(unittest.TestCase):
" of old wooden houses in Northern Norway, the oldest house dating from"
" 1789. The Arctic Cathedral, a modern church…"
)
class PreviewUrlTestCase(unittest.TestCase):
def test_simple(self):
html = """
<html>
<head><title>Foo</title></head>
<body>
Some text.
</body>
</html>
"""
og = decode_and_calc_og(html, "http://example.com/test.html")
self.assertEquals(og, {
"og:title": "Foo",
"og:description": "Some text."
})
def test_comment(self):
html = """
<html>
<head><title>Foo</title></head>
<body>
<!-- HTML comment -->
Some text.
</body>
</html>
"""
og = decode_and_calc_og(html, "http://example.com/test.html")
self.assertEquals(og, {
"og:title": "Foo",
"og:description": "Some text."
})
def test_comment2(self):
html = """
<html>
<head><title>Foo</title></head>
<body>
Some text.
<!-- HTML comment -->
Some more text.
<p>Text</p>
More text
</body>
</html>
"""
og = decode_and_calc_og(html, "http://example.com/test.html")
self.assertEquals(og, {
"og:title": "Foo",
"og:description": "Some text.\n\nSome more text.\n\nText\n\nMore text"
})
def test_script(self):
html = """
<html>
<head><title>Foo</title></head>
<body>
<script> (function() {})() </script>
Some text.
</body>
</html>
"""
og = decode_and_calc_og(html, "http://example.com/test.html")
self.assertEquals(og, {
"og:title": "Foo",
"og:description": "Some text."
})