FIX: Poll: ensure it is not possible to vote with all abstentions in Ranked Choice (#29601)

Make sure Cast Vote button is disabled when all abstain and remove any historic data that fails new zero rank vote validation

plugins/poll/app/models/poll_vote.rb

@@ -15,6 +15,7 @@ end
 #  user_id        :bigint
 #  created_at     :datetime         not null
 #  updated_at     :datetime         not null
+#  rank           :integer          default(0), not null
 #
 # Indexes
 #

plugins/poll/assets/javascripts/discourse/components/poll.gjs

@@ -72,11 +72,13 @@ export default class PollComponent extends Component {
   areRanksValid = (arr) => {
     let ranks = new Set(); // Using a Set to keep track of unique ranks
     let hasNonZeroDuplicate = false;
+    let allZeros = true;
 
     arr.forEach((obj) => {
       const rank = obj.rank;
 
       if (rank !== 0) {
+        allZeros = false; // Set to false if any rank is non-zero
         if (ranks.has(rank)) {
           hasNonZeroDuplicate = true;
           return; // Exit forEach loop if a non-zero duplicate is found
@@ -85,7 +87,7 @@ export default class PollComponent extends Component {
       }
     });
 
-    return !hasNonZeroDuplicate;
+    return !hasNonZeroDuplicate && !allZeros;
   };
 
   _toggleOption = (option, rank = 0) => {

plugins/poll/config/locales/server.en.yml

@@ -39,6 +39,7 @@ en:
     named_poll_with_multiple_choices_has_invalid_parameters: "Poll named <strong>%{name}</strong> with multiple choice has invalid parameters."
 
     requires_at_least_1_valid_option: "You must select at least 1 valid option."
+    requires_that_at_least_one_option_is_ranked: "In ranked-choice polls, you must rank at least one option."
 
     edit_window_expired:
       cannot_edit_default_poll_with_votes: "You cannot change a poll after the first %{minutes} minutes."

plugins/poll/db/migrate/20241105211601_delete_zero_rank_user_vote_collections_from_poll_votes.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+class DeleteZeroRankUserVoteCollectionsFromPollVotes < ActiveRecord::Migration[7.1]
+  def up
+    execute <<~SQL
+      DELETE FROM poll_votes
+      WHERE (poll_id, user_id) IN (
+          SELECT poll_votes.poll_id, poll_votes.user_id
+          FROM poll_votes
+          JOIN polls ON polls.id = poll_votes.poll_id
+          WHERE polls.type = 3
+          GROUP BY poll_votes.poll_id, poll_votes.user_id
+          HAVING SUM(poll_votes.rank) = 0
+      );
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

plugins/poll/lib/poll.rb

@@ -17,6 +17,12 @@ class DiscoursePoll::Poll
         if poll.ranked_choice?
           options = options.values.map { |hash| hash }
           options.select! { |o| available_options.include?(o[:digest]) }
+
+          if options.all? { |o| o[:rank] == "0" }
+            raise DiscoursePoll::Error.new I18n.t(
+                                             "poll.requires_that_at_least_one_option_is_ranked",
+                                           )
+          end
         else
           options.select! { |o| available_options.include?(o) }
         end

plugins/poll/spec/lib/poll_spec.rb

@@ -43,6 +43,36 @@ RSpec.describe DiscoursePoll::Poll do
       end.to raise_error(DiscoursePoll::Error, I18n.t("poll.one_vote_per_user"))
     end
 
+    it "should not allow a ranked vote with all abstentions" do
+      poll = post_with_ranked_choice_poll.polls.first
+      poll_options = poll.poll_options
+
+      expect do
+        DiscoursePoll::Poll.vote(
+          user,
+          post_with_ranked_choice_poll.id,
+          "poll",
+          {
+            "0": {
+              digest: poll_options.first.digest,
+              rank: "0",
+            },
+            "1": {
+              digest: poll_options.second.digest,
+              rank: "0",
+            },
+            "2": {
+              digest: poll_options.third.digest,
+              rank: "0",
+            },
+          },
+        )
+      end.to raise_error(
+        DiscoursePoll::Error,
+        I18n.t("poll.requires_that_at_least_one_option_is_ranked"),
+      )
+    end
+
     it "should clean up bad votes for a regular poll" do
       poll = post_with_regular_poll.polls.first
 

plugins/poll/test/javascripts/component/poll-test.js

@@ -41,6 +41,135 @@ module("Poll | Component | poll", function (hooks) {
     });
   });
 
+  test("valid ranks with which you can vote", async function (assert) {
+    this.setProperties({
+      post: EmberObject.create({
+        id: 42,
+        topic: {
+          archived: false,
+        },
+        user_id: 29,
+        polls_votes: {
+          poll: [
+            {
+              digest: "1f972d1df351de3ce35a787c89faad29",
+              rank: 1,
+            },
+            {
+              digest: "d7ebc3a9beea2e680815a1e4f57d6db6",
+              rank: 2,
+            },
+            {
+              digest: "6c986ebcde3d5822a6e91a695c388094",
+              rank: 3,
+            },
+          ],
+        },
+      }),
+      poll: new TrackedObject({
+        name: "poll",
+        type: "ranked_choice",
+        status: "open",
+        results: "on_close",
+        options: [
+          {
+            id: "1f972d1df351de3ce35a787c89faad29",
+            html: "this",
+            votes: 0,
+            rank: 1,
+          },
+          {
+            id: "d7ebc3a9beea2e680815a1e4f57d6db6",
+            html: "that",
+            votes: 0,
+            rank: 2,
+          },
+          {
+            id: "6c986ebcde3d5822a6e91a695c388094",
+            html: "other",
+            votes: 0,
+            rank: 3,
+          },
+        ],
+        voters: 0,
+        chart_type: "bar",
+      }),
+    });
+
+    await render(hbs`<Poll @post={{this.post}} @poll={{this.poll}} />`);
+
+    assert.dom(".poll-buttons .cast-votes:disabled").doesNotExist();
+    assert.dom(".poll-buttons .cast-votes").exists();
+  });
+
+  test("invalid ranks with which you cannot vote", async function (assert) {
+    this.setProperties({
+      post: EmberObject.create({
+        id: 42,
+        topic: {
+          archived: false,
+        },
+        user_id: 29,
+      }),
+      poll: new TrackedObject({
+        name: "poll",
+        type: "ranked_choice",
+        status: "open",
+        results: "always",
+        options: [
+          {
+            id: "1f972d1df351de3ce35a787c89faad29",
+            html: "this",
+            votes: 0,
+            rank: 0,
+          },
+          {
+            id: "d7ebc3a9beea2e680815a1e4f57d6db6",
+            html: "that",
+            votes: 0,
+            rank: 0,
+          },
+          {
+            id: "6c986ebcde3d5822a6e91a695c388094",
+            html: "other",
+            votes: 0,
+            rank: 0,
+          },
+        ],
+        voters: 0,
+        chart_type: "bar",
+      }),
+    });
+
+    await render(hbs`<Poll @post={{this.post}} @poll={{this.poll}} />`);
+
+    await click(
+      ".ranked-choice-poll-option[data-poll-option-id='1f972d1df351de3ce35a787c89faad29'] button",
+      "open dropdown"
+    );
+
+    assert
+      .dom(".dropdown-menu__item:nth-child(2)")
+      .hasText(`1 ${I18n.t("poll.options.ranked_choice.highest_priority")}`);
+
+    await click(
+      ".dropdown-menu__item:nth-child(2) button",
+      "select 1st priority"
+    );
+
+    assert.dom(".poll-buttons .cast-votes:disabled").doesNotExist();
+    assert.dom(".poll-buttons .cast-votes").exists();
+
+    await click(
+      ".ranked-choice-poll-option[data-poll-option-id='1f972d1df351de3ce35a787c89faad29'] button",
+      "open dropdown"
+    );
+
+    await click(".dropdown-menu__item:nth-child(1) button", "select Abstain");
+
+    assert.dom(".poll-buttons .cast-votes:disabled").exists();
+  });
+
   test("shows vote", async function (assert) {
     this.setProperties({
       post: EmberObject.create({