fix: resolve channel of related videos published as a collaboration

Related videos published as a collaboration between several channels
carry no "browseEndpoint" in their byline. Their byline opens a
"Collaborators" dialog instead, which holds the channel of each
collaborator, so `get_browse_id` returned an empty string and the
recommendation was rendered without a link to the channel.

Fall back to the first entry of that dialog, which is the channel the
video was published on.

Fixes #5722

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

spec/invidious/videos/related_video_collaboration_spec.cr

@@ -0,0 +1,103 @@
+require "../../parsers_helper.cr"
+
+Spectator.describe "parse_related_video" do
+  it "extracts the channel of a video published as a collaboration" do
+    # A video published as a collaboration between two channels. Its byline
+    # carries no "browseEndpoint"; it opens a "Collaborators" dialog instead,
+    # and the channel of each collaborator sits inside that dialog.
+    #
+    # See: https://github.com/iv-org/invidious/issues/5722
+    related = JSON.parse(<<-JSON)
+      {
+        "videoId": "dbVdnL6HWOg",
+        "title": { "simpleText": "Professor Jiang Debates Iran War, Trump And China Ties" },
+        "lengthInSeconds": 2241,
+        "shortViewCountText": { "simpleText": "1M views" },
+        "publishedTimeText": { "simpleText": "3 months ago" },
+        "shortBylineText": {
+          "runs": [
+            {
+              "text": "Piers Morgan Uncensored and ProfSteveKeen",
+              "navigationEndpoint": {
+                "showDialogCommand": {
+                  "panelLoadingStrategy": {
+                    "inlineContent": {
+                      "dialogViewModel": {
+                        "customContent": {
+                          "listViewModel": {
+                            "listItems": [
+                              {
+                                "listItemViewModel": {
+                                  "title": { "content": "Piers Morgan Uncensored" },
+                                  "rendererContext": {
+                                    "commandContext": {
+                                      "onTap": {
+                                        "innertubeCommand": {
+                                          "browseEndpoint": { "browseId": "UCatt7TBjfBkiJWx8khav_Gg" }
+                                        }
+                                      }
+                                    }
+                                  }
+                                }
+                              },
+                              {
+                                "listItemViewModel": {
+                                  "title": { "content": "ProfSteveKeen" },
+                                  "rendererContext": {
+                                    "commandContext": {
+                                      "onTap": {
+                                        "innertubeCommand": {
+                                          "browseEndpoint": { "browseId": "UCM1ubsbE-tG9ru61mc3zX8A" }
+                                        }
+                                      }
+                                    }
+                                  }
+                                }
+                              }
+                            ]
+                          }
+                        }
+                      }
+                    }
+                  }
+                }
+              }
+            }
+          ]
+        }
+      }
+      JSON
+
+    parsed = Invidious::Videos::Parser.parse_related_video(related).not_nil!
+
+    expect(parsed["ucid"].as_s).to eq("UCatt7TBjfBkiJWx8khav_Gg")
+    expect(parsed["author"].as_s).to eq("Piers Morgan Uncensored and ProfSteveKeen")
+  end
+
+  it "keeps extracting the channel of a single author video" do
+    related = JSON.parse(<<-JSON)
+      {
+        "videoId": "_g4l7YkDQwA",
+        "title": { "simpleText": "The Diary Of A CEO episode" },
+        "lengthInSeconds": 1337,
+        "shortViewCountText": { "simpleText": "2.1M views" },
+        "publishedTimeText": { "simpleText": "1 month ago" },
+        "shortBylineText": {
+          "runs": [
+            {
+              "text": "The Diary Of A CEO",
+              "navigationEndpoint": {
+                "browseEndpoint": { "browseId": "UCGq-a57w-aPwyi3pW7XLiHw" }
+              }
+            }
+          ]
+        }
+      }
+      JSON
+
+    parsed = Invidious::Videos::Parser.parse_related_video(related).not_nil!
+
+    expect(parsed["ucid"].as_s).to eq("UCGq-a57w-aPwyi3pW7XLiHw")
+    expect(parsed["author"].as_s).to eq("The Diary Of A CEO")
+  end
+end

src/invidious/videos/parser.cr

@@ -28,6 +28,13 @@ module Invidious::Videos::Parser
 
     ucid = channel_info.try { |ci| HelperExtractors.get_browse_id(ci) }
 
+    # Videos published as a collaboration have no "browseEndpoint" in their
+    # byline, so the channel has to be read from the "Collaborators" dialog
+    # that the byline opens instead. See `get_collaborator_browse_id`.
+    if ucid.nil? || ucid.empty?
+      ucid = channel_info.try { |ci| HelperExtractors.get_collaborator_browse_id(ci) }
+    end
+
     short_view_count = related.try do |r|
       HelperExtractors.get_short_view_count(r).to_s
     end

src/invidious/yt_backend/extractors.cr

@@ -1143,6 +1143,21 @@ module HelperExtractors
   def self.get_browse_id(container)
     return container.dig?("navigationEndpoint", "browseEndpoint", "browseId").try &.as_s || ""
   end
+
+  # Videos published as a collaboration have no "browseEndpoint" in their
+  # byline. Their byline opens a "Collaborators" dialog instead, which holds
+  # the channel of every collaborator. Retrieves the ID of the first entry,
+  # which is the channel the video was published on.
+  #
+  # Returns an empty string when it's unable to do so
+  def self.get_collaborator_browse_id(container)
+    return container.dig?(
+      "navigationEndpoint", "showDialogCommand", "panelLoadingStrategy",
+      "inlineContent", "dialogViewModel", "customContent", "listViewModel",
+      "listItems", 0, "listItemViewModel", "rendererContext", "commandContext",
+      "onTap", "innertubeCommand", "browseEndpoint", "browseId"
+    ).try &.as_s || ""
+  end
 end
 
 # Parses an item from Youtube's JSON response into a more usable structure.