From 732a5bce66a1167811f0c0b3eee4afd5d0e18974 Mon Sep 17 00:00:00 2001
From: Marco Roth <marco.roth@intergga.ch>
Date: Sat, 8 Aug 2026 05:44:40 +0200
Subject: [PATCH 1/2] Only emit dev tools markup when debug mode is enabled

`reactionview_dev_tools_markup` gated its meta tags and the dev tools script on
`debug_mode_enabled?`, but the `data-herb-dismiss-hint` template was gated only
on `validation_mode == :overlay`. That is the default outside of test, so the
hint was injected into every layout in production, mailer layouts included.

Browsers never render the contents of a `<template>`, so this stayed invisible on
the web. Email clients strip the tag but keep its text, which put "You can also
disable this overlay by setting config.validation_mode = :none" at the top of
production emails.

The hint is only ever read by `getDismissHint()` in `@herb-tools/dev-tools`,
which runs while the dev tools bundle renders an overlay, and that bundle is only
loaded in debug mode. It also falls back to a generic message when the template
is absent, so nothing is lost by leaving it out.

Resolves #95
---
 lib/reactionview/template/handlers/herb.rb    | 32 +++---
 .../handlers/dev_tools_markup_test.rb         | 98 +++++++++++++++++++
 2 files changed, 113 insertions(+), 17 deletions(-)
 create mode 100644 test/template/handlers/dev_tools_markup_test.rb

diff --git a/lib/reactionview/template/handlers/herb.rb b/lib/reactionview/template/handlers/herb.rb
index 5488a89..3262609 100644
--- a/lib/reactionview/template/handlers/herb.rb
+++ b/lib/reactionview/template/handlers/herb.rb
@@ -76,29 +76,27 @@ def dev_server_port_meta_tag
         end
 
         def reactionview_dev_tools_markup(template)
+          return nil unless ::ReActionView.config.debug_mode_enabled?
           return nil unless layout_template?(template)
           return nil unless local_template?(template)
 
-          markup = +""
+          <<~HTML
+            <meta name="herb-debug-mode" content="true">
+            <meta name="herb-project-path" content="#{Rails.root}">
+            #{dev_server_port_meta_tag}
+            #{editor_meta_tag}
 
-          if ::ReActionView.config.debug_mode_enabled?
-            markup << <<~HTML
-              <meta name="herb-debug-mode" content="true">
-              <meta name="herb-project-path" content="#{Rails.root}">
-              #{dev_server_port_meta_tag}
-              #{editor_meta_tag}
-
-              #{ActionController::Base.new.view_context.javascript_include_tag "reactionview-dev-tools.umd.js", defer: true}
-            HTML
-          end
+            #{ActionController::Base.new.view_context.javascript_include_tag "reactionview-dev-tools.umd.js", defer: true}
+            #{dismiss_hint_template}
+          HTML
+        end
 
-          if ::ReActionView.config.validation_mode == :overlay
-            markup << <<~HTML
-              <template data-herb-dismiss-hint>You can also disable this overlay by setting <code style="color: #ffeb3b; font-family: monospace; font-size: 12pt;">config.validation_mode = :none</code> in <code style="color: #ffeb3b; font-family: monospace; font-size: 12pt;">config/initializers/reactionview.rb</code>.</template>
-            HTML
-          end
+        def dismiss_hint_template
+          return unless ::ReActionView.config.validation_mode == :overlay
 
-          markup.presence
+          <<~HTML.chomp
+            <template data-herb-dismiss-hint>You can also disable this overlay by setting <code style="color: #ffeb3b; font-family: monospace; font-size: 12pt;">config.validation_mode = :none</code> in <code style="color: #ffeb3b; font-family: monospace; font-size: 12pt;">config/initializers/reactionview.rb</code>.</template>
+          HTML
         end
       end
     end
diff --git a/test/template/handlers/dev_tools_markup_test.rb b/test/template/handlers/dev_tools_markup_test.rb
new file mode 100644
index 0000000..1306055
--- /dev/null
+++ b/test/template/handlers/dev_tools_markup_test.rb
@@ -0,0 +1,98 @@
+# frozen_string_literal: true
+
+require_relative "../../test_helper"
+
+require "action_controller"
+
+class ReActionView::DevToolsMarkupTest < Minitest::Spec
+  RAILS_ROOT = "/app"
+  LAYOUT = "/app/app/views/layouts/application.html.erb"
+  MAILER_LAYOUT = "/app/app/views/layouts/mailer.html.erb"
+  VIEW = "/app/app/views/users/show.html.erb"
+
+  SOURCE = %(<html><head></head><body></body></html>)
+
+  DISMISS_HINT = "data-herb-dismiss-hint"
+
+  before do
+    @previous_debug_mode = ReActionView.config.debug_mode
+    @previous_validation_mode = ReActionView.config.validation_mode
+
+    ReActionView.config.intercept_erb = true
+  end
+
+  after do
+    ReActionView.config.debug_mode = @previous_debug_mode
+    ReActionView.config.validation_mode = nil
+  end
+
+  def compile(identifier: LAYOUT, virtual_path: "layouts/application")
+    template = ActionView::Template.new(
+      SOURCE,
+      identifier,
+      ReActionView::Template::Handlers::Herb,
+      virtual_path: virtual_path,
+      format: :html,
+      locals: []
+    )
+
+    Rails.stub(:root, Pathname.new(RAILS_ROOT)) do
+      ReActionView::Template::Handlers::Herb.call(template, SOURCE)
+    end
+  end
+
+  test "does not emit the dismiss hint when debug mode is off" do
+    ReActionView.config.debug_mode = false
+    ReActionView.config.validation_mode = :overlay
+
+    refute_includes compile, DISMISS_HINT
+  end
+
+  test "does not emit the dismiss hint in mailer layouts when debug mode is off" do
+    ReActionView.config.debug_mode = false
+    ReActionView.config.validation_mode = :overlay
+
+    refute_includes compile(identifier: MAILER_LAYOUT, virtual_path: "layouts/mailer"), DISMISS_HINT
+  end
+
+  test "emits nothing at all into the head when debug mode is off" do
+    ReActionView.config.debug_mode = false
+    ReActionView.config.validation_mode = :overlay
+
+    compiled = compile
+
+    refute_includes compiled, "herb-debug-mode"
+    refute_includes compiled, "reactionview-dev-tools"
+    refute_includes compiled, DISMISS_HINT
+  end
+
+  test "emits the dismiss hint when debug mode is on and validation mode is :overlay" do
+    ReActionView.config.debug_mode = true
+    ReActionView.config.validation_mode = :overlay
+
+    compiled = compile
+
+    assert_includes compiled, DISMISS_HINT
+    assert_includes compiled, "herb-debug-mode"
+  end
+
+  test "does not emit the dismiss hint when validation mode is not :overlay" do
+    ReActionView.config.debug_mode = true
+    ReActionView.config.validation_mode = :none
+
+    compiled = compile
+
+    refute_includes compiled, DISMISS_HINT
+    assert_includes compiled, "herb-debug-mode"
+  end
+
+  test "emits nothing for templates that are not layouts" do
+    ReActionView.config.debug_mode = true
+    ReActionView.config.validation_mode = :overlay
+
+    compiled = compile(identifier: VIEW, virtual_path: "users/show")
+
+    refute_includes compiled, DISMISS_HINT
+    refute_includes compiled, "herb-debug-mode"
+  end
+end

From 7d580f3ed6329d3d355a85c4ac7bec275f3b260d Mon Sep 17 00:00:00 2001
From: Marco Roth <marco.roth@intergga.ch>
Date: Sat, 8 Aug 2026 05:53:41 +0200
Subject: [PATCH 2/2] Cleanup

---
 test/template/handlers/dev_tools_markup_test.rb | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/test/template/handlers/dev_tools_markup_test.rb b/test/template/handlers/dev_tools_markup_test.rb
index 1306055..ab4b5c8 100644
--- a/test/template/handlers/dev_tools_markup_test.rb
+++ b/test/template/handlers/dev_tools_markup_test.rb
@@ -16,9 +16,6 @@ class ReActionView::DevToolsMarkupTest < Minitest::Spec
 
   before do
     @previous_debug_mode = ReActionView.config.debug_mode
-    @previous_validation_mode = ReActionView.config.validation_mode
-
-    ReActionView.config.intercept_erb = true
   end
 
   after do