Removes large pypi image in Slack link unfurling

tests/unit/test_filters.py

@@ -301,3 +301,36 @@ def test_remove_invalid_xml_unicode(inp, expected):
     Test that invalid XML unicode characters are removed.
     """
     assert filters.remove_invalid_xml_unicode(inp) == expected
+
+
+def test_show_share_image():
+    # Missing user-agent header
+    assert filters.show_share_image(None) is True
+    # Empty user-agent header
+    assert filters.show_share_image("") is True
+
+    # Twitter/X - shows image
+    # https://developer.x.com/en/docs/x-for-websites/cards/guides/troubleshooting-cards#validate_twitterbot
+    assert filters.show_share_image("Twitterbot/1.0") is True
+
+    # Facebook - shows image
+    # https://developers.facebook.com/docs/sharing/webmasters/web-crawlers
+    assert (
+        filters.show_share_image(
+            "facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)"
+        )
+        is True
+    )
+    assert filters.show_share_image("facebookexternalhit/1.1") is True
+    assert filters.show_share_image("facebookcatalog/1.0") is True
+
+    # LinkedIn - shows image (https://www.linkedin.com/robots.txt)
+    assert filters.show_share_image("LinkedInBot") is True
+
+    # Slack - don't show image (https://api.slack.com/robots)
+    assert (
+        filters.show_share_image(
+            "Slackbot-LinkExpanding 1.0 (+https://api.slack.com/robots)"
+        )
+        is False
+    )

warehouse/config.py

@@ -683,6 +683,7 @@ def configure(settings=None):
     filters.setdefault(
         "remove_invalid_xml_unicode", "warehouse.filters:remove_invalid_xml_unicode"
     )
+    filters.setdefault("show_share_image", "warehouse.filters:show_share_image")
 
     # We also want to register some global functions for Jinja
     jglobals = config.get_settings().setdefault("jinja2.globals", {})

warehouse/filters.py

@@ -201,3 +201,22 @@ def remove_invalid_xml_unicode(value: str | None) -> str | None:
 
 def includeme(config):
     config.add_request_method(_camo_url, name="camo_url")
+
+
+def show_share_image(user_agent: str | None) -> bool:
+    """
+    Whether the og:image meta-tag should be included based on the user-agent
+
+    Used to exclude the image from Slack link-expansion.
+
+    """
+
+    # User agent header not included or empty
+    if not user_agent:
+        return True
+
+    # Don't show the og:image for Slackbot link-expansion requests
+    if user_agent.strip().startswith("Slackbot-LinkExpanding"):
+        return False
+
+    return True

warehouse/templates/base.html

@@ -113,9 +113,13 @@
     <meta property="og:url" content="{% if request.matched_route %}{{ request.current_route_url() }}{% else %}{{ request.url }}{% endif %}">
     <meta property="og:site_name" content="PyPI">
     <meta property="og:type" content="website">
+    {% if request.user_agent | show_share_image %}
     <meta property="og:image" content="{% block image %}{{ request.static_url('warehouse:static/dist/images/twitter.jpg') }}{% endblock %}">
+    {% endif %}
     <meta property="og:title" content="{{ self.title()|default('Python Package Index') }}">
     <meta property="og:description" content="{{ self.description() }}">
+    <meta name="twitter:card" content="summary">
+    <meta name="twitter:site" content="@pypi">
     {% block extra_meta %}{% endblock %}
 
     <link rel="search" type="application/opensearchdescription+xml" title="PyPI" href="{{ request.route_path('opensearch.xml') }}">