Extend custom FormBuilder to DRY in forms

Closes #8
Closes #45

app/assets/stylesheets/application.css

@@ -159,6 +159,12 @@ textarea:hover {
   border-color: var(--color-blue);
   outline: solid 1px var(--color-blue);
 }
+input:invalid,
+select:invalid,
+textarea:invalid {
+  border-color: var(--color-red);
+  outline: solid 1px var(--color-red);
+}
 select:hover {
   cursor: pointer;
 }

app/helpers/application_helper.rb

@@ -56,24 +56,64 @@ module ApplicationHelper
   end
 
   class TabularFormBuilder < ActionView::Helpers::FormBuilder
+    def initialize(...)
+      super(...)
+      @default_options.merge!(@options.slice(:form))
+    end
+
+    [:text_field, :password_field, :text_area].each do |selector|
+      class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
+        def #{selector}(method, options = {})
+          options[:maxlength] ||= object.class.type_for_attribute(method).limit
+          if object.errors.include?(method)
+            options[:pattern] = except_pattern(object.public_send(method), options[:pattern])
+          end
+          super
+        end
+      RUBY_EVAL
+    end
+
+    def number_field(method, options = {})
+      value = object.public_send(method)
+      if value.is_a? BigDecimal
+        options[:value] = value.to_scientific
+        type = object.class.type_for_attribute(method)
+        options[:step] ||= BigDecimal(10).power(-type.scale)
+        options[:max] ||= BigDecimal(10).power(type.precision - type.scale) - options[:step]
+        options[:min] = options[:min] == :step ? options[:step] : options[:min] || -options[:max]
+      end
+      super
+    end
+
+    def button(value = nil, options = {}, &block)
+      # button does not use #objectify_options
+      options.merge!(@options.slice(:form))
+      super
+    end
+
     private
 
     def submit_default_value
       svg_name = object ? (object.persisted? ? 'update' : 'plus-circle-outline') : ''
       @template.svg_tag("pictograms/#{svg_name}") + super
     end
+
+    def except_pattern(value, pattern = nil)
+      "(?!^#{Regexp.escape(value)}$)" + (pattern || ".*")
+    end
   end
 
   def tabular_fields_for(record_name, record_object = nil, options = {}, &block)
     # skip_default_ids causes turbo to generate unique ID for element with [autofocus].
     # Otherwise IDs are not unique when multiple forms are open and the first input gets focus.
+    record_object, options = nil, record_object if record_object.is_a? Hash
     options.merge! builder: TabularFormBuilder, skip_default_ids: true
     render_errors(record_name)
     fields_for(record_name, record_object, **options, &block)
   end
 
   def tabular_form_with(**options, &block)
-    options.merge! builder: TabularFormBuilder
+    options = options.deep_merge builder: TabularFormBuilder, html: {autocomplete: 'off'}
     form_with(**options, &block)
   end
 
@@ -151,10 +191,4 @@ module ApplicationHelper
   def disabled_attributes(disabled)
     disabled ? {disabled: true, aria: {disabled: true}, tabindex: -1} : {}
   end
-
-  def number_attributes(type)
-    step = BigDecimal(10).power(-type.scale)
-    max = BigDecimal(10).power(type.precision - type.scale) - step
-    {min: -max, max: max, step: step}
-  end
 end

app/views/units/_form.html.erb

@@ -1,26 +1,22 @@
-<%= tabular_fields_for @unit do |form| %>
+<%= tabular_fields_for @unit, form: form_tag do |form| %>
   <%- tag.tr id: row, class: "form", onkeydown: "processKey(event)",
     data: {link: link, form: form_tag, hidden_row: hidden_row} do %>
 
     <td class="<%= class_names({subunit: @unit.base}) %>">
-      <%= form.text_field :symbol, form: form_tag, required: true, autofocus: true, size: 12,
-        maxlength: @unit.class.type_for_attribute(:symbol).limit, autocomplete: "off" %>
+      <%= form.text_field :symbol, required: true, autofocus: true, size: 12 %>
     </td>
     <td>
-      <%= form.text_area :description, form: form_tag, cols: 30, rows: 1, escape: false,
-        maxlength: @unit.class.type_for_attribute(:description).limit, autocomplete: "off" %>
+      <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
     </td>
     <td>
       <% unless @unit.base.nil? %>
-        <%= form.hidden_field :base_id, form: form_tag %>
-        <%= form.number_field :multiplier, form: form_tag, required: true,
-          size: 10, autocomplete: "off",
-          **number_attributes(@unit.class.type_for_attribute(:multiplier)) %>
+        <%= form.hidden_field :base_id %>
+        <%= form.number_field :multiplier, required: true, size: 10 %>
       <% end %>
     </td>
 
     <td class="actions">
-      <%= form.button form: form_tag %>
+      <%= form.button %>
       <%= image_link_to t(:cancel), "close-outline", units_path, class: 'dangerous',
         name: :cancel, onclick: render_turbo_stream('form_close', {row: row}) %>
     </td>