feat(goals/edit): funding-accounts editor in the edit modal

Previously a user who linked the wrong account at creation had to
delete + recreate the goal. Now the edit modal carries the same
funding-accounts checkbox group as Step 1 of the stepper, pre-checked
with the goal's current links.

- GoalsController#edit loads @linkable_accounts + @currently_linked_account_ids.
- #update accepts account_ids; when supplied, runs the create / update
  inside a Goal.transaction and syncs linked accounts via
  sync_linked_accounts! (set-diff: destroy_all unselected goal_accounts,
  create the new ones). Validates at least one account before touching
  goal_accounts so the user gets a clean re-render.
- Removing an account preserves the goal's existing contributions —
  GoalContribution#account_must_be_linked_to_goal only fires on save,
  so historical rows stay valid.
- _form_edit partial accepts new locals; edit.html.erb threads them
  through.
- 3 new controller tests: identity-only patch leaves links intact;
  account_ids patch replaces the link set; empty account_ids
  re-renders with error.

app/controllers/goals_controller.rb

@@ -71,20 +71,39 @@ class GoalsController < ApplicationController
   end
 
   def edit
+    @linkable_accounts = linkable_accounts_for_new
+    @currently_linked_account_ids = @goal.goal_accounts.pluck(:account_id).map(&:to_s)
   end
 
   def update
-    if @goal.update(goal_update_params)
-      flash[:notice] = t(".success")
-      respond_to do |format|
-        format.html { redirect_to goal_path(@goal) }
-        format.turbo_stream do
-          render turbo_stream: turbo_stream.action(:redirect, goal_path(@goal))
-        end
-      end
-    else
+    account_ids = params.dig(:goal, :account_ids)
+    accounts_supplied = !account_ids.nil?
+    accounts = accounts_supplied ? lookup_accounts(account_ids) : []
+
+    if accounts_supplied && accounts.empty?
+      @goal.errors.add(:base, :at_least_one_linked_account_required)
+      @linkable_accounts = linkable_accounts_for_new
+      @currently_linked_account_ids = @goal.goal_accounts.pluck(:account_id).map(&:to_s)
       render :edit, status: :unprocessable_entity
+      return
     end
+
+    Goal.transaction do
+      @goal.update!(goal_update_params)
+      sync_linked_accounts!(@goal, accounts) if accounts_supplied
+    end
+
+    flash[:notice] = t(".success")
+    respond_to do |format|
+      format.html { redirect_to goal_path(@goal) }
+      format.turbo_stream do
+        render turbo_stream: turbo_stream.action(:redirect, goal_path(@goal))
+      end
+    end
+  rescue ActiveRecord::RecordInvalid
+    @linkable_accounts = linkable_accounts_for_new
+    @currently_linked_account_ids = @goal.goal_accounts.pluck(:account_id).map(&:to_s)
+    render :edit, status: :unprocessable_entity
   end
 
   def destroy
@@ -148,6 +167,18 @@ class GoalsController < ApplicationController
       Current.family.accounts.where(accountable_type: "Depository").visible.alphabetically.to_a
     end
 
+    def sync_linked_accounts!(goal, accounts)
+      desired = accounts.map(&:id).to_set
+      current = goal.goal_accounts.pluck(:account_id).to_set
+
+      (current - desired).each do |id|
+        goal.goal_accounts.where(account_id: id).destroy_all
+      end
+      (desired - current).each do |id|
+        goal.goal_accounts.create!(account_id: id)
+      end
+    end
+
     def create_initial_contribution_if_provided!(goal, accounts)
       amount = params.dig(:goal, :initial_contribution_amount)
       account_id = params.dig(:goal, :initial_contribution_account_id)

app/views/goals/_form_edit.html.erb

@@ -1,4 +1,4 @@
-<%# locals: (goal:) %>
+<%# locals: (goal:, linkable_accounts:, currently_linked_account_ids:) %>
 
 <% if goal.errors.any? %>
   <%= render "shared/form_errors", model: goal %>
@@ -20,6 +20,36 @@
   <%= f.date_field :target_date,
                    label: t("goals.form_stepper.step1.fields.target_date") %>
 
+  <div>
+    <div class="mb-2">
+      <span class="block text-sm font-medium text-primary"><%= t("goals.form_stepper.step1.fields.funding_accounts") %></span>
+      <p class="text-xs text-secondary mt-0.5"><%= t("goals.form_stepper.step1.fields.funding_accounts_hint") %></p>
+    </div>
+    <div class="bg-container-inset rounded-lg p-1">
+      <% grouped = linkable_accounts.group_by { |a| a.subtype.to_s.presence || "other" } %>
+      <% grouped.each_with_index do |(subtype, accts), group_idx| %>
+        <div class="px-3 py-2 text-[11px] font-medium uppercase tracking-wide text-secondary"><%= t("goals.form_stepper.step1.subtypes.#{subtype}", default: subtype.titleize) %></div>
+        <div class="bg-container rounded-md <%= "mb-1" if group_idx < grouped.size - 1 %>">
+          <% accts.each_with_index do |account, idx| %>
+            <label class="flex items-center gap-3 px-3 py-2.5 cursor-pointer <%= "border-t border-subdued" if idx > 0 %>">
+              <%= check_box_tag "goal[account_ids][]",
+                                account.id,
+                                currently_linked_account_ids.include?(account.id.to_s),
+                                id: "goal_account_ids_#{account.id}",
+                                class: "checkbox checkbox--light shrink-0" %>
+              <%= render Goals::AvatarComponent.new(name: account.name, color: Goals::AvatarComponent.color_for(account.name), size: "md") %>
+              <div class="flex-1 min-w-0">
+                <p class="text-sm font-medium text-primary truncate"><%= account.name %></p>
+                <p class="text-xs text-secondary"><%= (account.subtype || subtype).titleize %></p>
+              </div>
+              <span class="text-sm text-primary tabular-nums"><%= Money.new(account.balance, account.currency).format %></span>
+            </label>
+          <% end %>
+        </div>
+      <% end %>
+    </div>
+  </div>
+
   <div>
     <span class="block text-sm text-secondary mb-2"><%= t("goals.form_stepper.step1.fields.color") %></span>
     <div class="flex flex-wrap gap-2">

app/views/goals/edit.html.erb

@@ -1,6 +1,6 @@
 <%= render DS::Dialog.new do |dialog| %>
   <% dialog.with_header(title: t(".heading")) %>
   <% dialog.with_body do %>
-    <%= render "form_edit", goal: @goal %>
+    <%= render "form_edit", goal: @goal, linkable_accounts: @linkable_accounts, currently_linked_account_ids: @currently_linked_account_ids %>
   <% end %>
 <% end %>

test/controllers/goals_controller_test.rb

@@ -104,6 +104,25 @@ class GoalsControllerTest < ActionDispatch::IntegrationTest
     assert_equal "Renamed", @goal.reload.name
   end
 
+  test "update without account_ids leaves linked accounts intact" do
+    before = @goal.goal_accounts.pluck(:account_id).sort
+    patch goal_url(@goal), params: { goal: { name: "Still here" } }
+    assert_redirected_to goal_path(@goal)
+    assert_equal before, @goal.reload.goal_accounts.pluck(:account_id).sort
+  end
+
+  test "update with account_ids syncs linked accounts (add + remove)" do
+    patch goal_url(@goal), params: { goal: { account_ids: [ @connected.id ] } }
+    assert_redirected_to goal_path(@goal)
+    assert_equal [ @connected.id ], @goal.reload.goal_accounts.pluck(:account_id)
+  end
+
+  test "update with empty account_ids re-renders with error" do
+    patch goal_url(@goal), params: { goal: { account_ids: [ "" ] } }
+    assert_response :unprocessable_entity
+    assert_not_empty @goal.reload.goal_accounts
+  end
+
   test "pause/resume/complete/archive/unarchive flow" do
     fresh = goals(:emergency_fund)
     patch pause_goal_url(fresh)