Show exact share count in the holding drawer (#3305)

* Show exact share count in the holding drawer

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014YrdY9jvCUtG3GhgZ5Skx1

* Test that the holding drawer does not round the share count

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014YrdY9jvCUtG3GhgZ5Skx1

---------

Co-authored-by: Claude <noreply@anthropic.com>

app/helpers/application_helper.rb

@@ -226,19 +226,21 @@ module ApplicationHelper
     ENV.fetch("DEV_WEBHOOKS_URL", root_url).chomp("/") + "/enable_banking_items/callback"
   end
 
-  # Formats quantity with adaptive precision based on the value size.
+  # Formats a holding quantity with adaptive precision based on the value size.
   # Shows more decimal places for small quantities (common with crypto).
   #
   # @param qty [Numeric] The quantity to format
-  # @param max_precision [Integer] Maximum precision for very small numbers
+  # @param exact [Boolean] Show the full stored precision, without rounding
   # @return [String] Formatted quantity with appropriate precision
-  def format_quantity(qty)
+  def format_quantity(qty, exact: false)
     return "0" if qty.nil? || qty.zero?
 
     abs_qty = qty.abs
 
-    precision = if abs_qty >= 1
-      1     # "10.5"
+    precision = if exact
+      8     # "10.374"
+    elsif abs_qty >= 1
+      1     # "10.4"
     elsif abs_qty >= 0.01
       2     # "0.52"
     elsif abs_qty >= 0.0001

app/views/holdings/show.html.erb

@@ -96,7 +96,7 @@
           </div>
           <div class="flex items-center justify-between text-sm">
             <dt class="text-secondary"><%= t(".shares_label") %></dt>
-            <dd class="text-primary"><%= format_quantity(@holding.qty) %></dd>
+            <dd id="<%= dom_id(@holding, :shares) %>" class="text-primary"><%= format_quantity(@holding.qty, exact: true) %></dd>
           </div>
           <div class="flex items-center justify-between text-sm">
             <dt class="text-secondary"><%= t(".portfolio_weight_label") %></dt>
@@ -141,7 +141,7 @@
                     class: "space-y-3",
                     data: drawer_form_data do |f| %>
                 <p class="text-xs text-secondary mb-2">
-                  <%= t("holdings.cost_basis_cell.set_cost_basis_header", ticker: @holding.ticker, qty: format_quantity(@holding.qty)) %>
+                  <%= t("holdings.cost_basis_cell.set_cost_basis_header", ticker: @holding.ticker, qty: format_quantity(@holding.qty, exact: true)) %>
                 </p>
                 <!-- Total cost basis input -->
                 <div class="form-field">

test/controllers/holdings_controller_test.rb

@@ -18,6 +18,14 @@ class HoldingsControllerTest < ActionDispatch::IntegrationTest
     assert_response :success
   end
 
+  test "shows exact share count without rounding" do
+    @holding.update!(qty: 10.374)
+
+    get holding_path(@holding)
+
+    assert_select "##{dom_id(@holding, :shares)}", text: "10.374"
+  end
+
   test "destroys holding and associated entries" do
     assert_difference -> { Holding.count } => -1,
                       -> { Entry.count } => -1 do