fix: merge .percy.yml config options with snapshot options for serializeDOM

lib/percy.rb

@@ -66,6 +66,25 @@ def self.create_region(
     region
   end
 
+  # Recursively convert all Hash keys (at every nesting level) to symbols so
+  # config (string keys from JSON) and per-call options (symbol keys) merge on
+  # consistent keys. Arrays are walked; scalars are returned as-is.
+  def self.deep_symbolize(obj)
+    case obj
+    when Hash then obj.each_with_object({}) { |(k, v), h| h[k.to_sym] = deep_symbolize(v) }
+    when Array then obj.map { |e| deep_symbolize(e) }
+    else obj
+    end
+  end
+
+  # Deep-merge `override` onto `base`: nested Hashes merge recursively, while
+  # arrays and scalars from `override` replace those in `base`.
+  def self.deep_merge_options(base, override)
+    base.merge(override) do |_key, old_val, new_val|
+      old_val.is_a?(Hash) && new_val.is_a?(Hash) ? deep_merge_options(old_val, new_val) : new_val
+    end
+  end
+
   def self.snapshot(driver, name, options = {})
     return unless percy_enabled?
 
@@ -79,10 +98,20 @@ def self.snapshot(driver, name, options = {})
     begin
       percy_dom_script = fetch_percy_dom
       driver.execute_script(percy_dom_script)
-      dom_snapshot = if responsive_snapshot_capture?(options)
-        capture_responsive_dom(driver, options, percy_dom_script: percy_dom_script)
+
+      # Merge .percy.yml config options with snapshot options (snapshot options take priority)
+      config_options = @cli_config&.dig('snapshot') || {}
+      # Config keys are strings (JSON parse); per-call options use symbols, as
+      # do downstream consumers (responsive_snapshot_capture?, capture_responsive_dom).
+      # Deep-symbolize both sides so nested keys are consistent, then deep-merge
+      # so nested Hashes merge recursively (per-call wins at leaves; arrays/scalars
+      # replace) instead of a shallow top-level overwrite dropping config siblings.
+      merged_options = deep_merge_options(deep_symbolize(config_options), deep_symbolize(options))
+
+      dom_snapshot = if responsive_snapshot_capture?(merged_options)
+        capture_responsive_dom(driver, merged_options, percy_dom_script: percy_dom_script)
       else
-        get_serialized_dom(driver, options, percy_dom_script: percy_dom_script)
+        get_serialized_dom(driver, merged_options, percy_dom_script: percy_dom_script)
       end
 
       # Strip `readiness` before POSTing -- SDK-local config that the CLI

spec/lib/percy/percy_spec.rb

@@ -342,6 +342,85 @@
 
       expect(data).to eq('sync_data')
     end
+
+    it 'merges .percy.yml config with per-snapshot options (per-call wins)' do
+      # Healthcheck returns a config whose `snapshot` block carries a
+      # config-only key (enableJavaScript) and a percyCSS value that the
+      # per-snapshot call will override.
+      stub_request(:get, "#{Percy::PERCY_SERVER_ADDRESS}/percy/healthcheck")
+        .to_return(
+          status: 200,
+          body: {
+            success: true,
+            config: {'snapshot' => {'enableJavaScript' => true, 'percyCSS' => 'FROM_CONFIG'}},
+          }.to_json,
+          headers: {'x-percy-core-version': '1.0.0'},
+        )
+
+      stub_request(:get, "#{Percy::PERCY_SERVER_ADDRESS}/percy/dom.js")
+        .to_return(status: 200, body: fetch_script_string, headers: {})
+
+      stub_request(:post, 'http://localhost:5338/percy/snapshot')
+        .to_return(status: 200, body: '{"success":true}', headers: {})
+
+      # Capture the argument passed to PercyDOM.serialize so we can assert how
+      # config and per-call options were merged before serialization.
+      captured_serialize_call = nil
+      allow(page).to receive(:execute_script).and_wrap_original do |original, script, *args|
+        captured_serialize_call = script if script.to_s.include?('PercyDOM.serialize')
+        original.call(script, *args)
+      end
+
+      visit 'index.html'
+      Percy.snapshot(page, 'Name', percyCSS: 'FROM_CALL')
+
+      expect(captured_serialize_call).to_not be_nil
+      serialized = JSON.parse(captured_serialize_call[/PercyDOM\.serialize\((.*)\)/m, 1])
+      # Config-only key still reaches serialize...
+      expect(serialized['enableJavaScript']).to eq(true)
+      # ...and the per-call option wins over the config value.
+      expect(serialized['percyCSS']).to eq('FROM_CALL')
+    end
+
+    it 'deep-merges nested config and per-snapshot options (sibling kept, leaf overridden)' do
+      # Config `snapshot` block carries a nested `discovery` hash; the per-call
+      # discovery only overrides one leaf, so the sibling key must survive.
+      stub_request(:get, "#{Percy::PERCY_SERVER_ADDRESS}/percy/healthcheck")
+        .to_return(
+          status: 200,
+          body: {
+            success: true,
+            config: {
+              'snapshot' => {
+                'discovery' => {'networkIdleTimeout' => 50, 'disableCache' => false},
+              },
+            },
+          }.to_json,
+          headers: {'x-percy-core-version': '1.0.0'},
+        )
+
+      stub_request(:get, "#{Percy::PERCY_SERVER_ADDRESS}/percy/dom.js")
+        .to_return(status: 200, body: fetch_script_string, headers: {})
+
+      stub_request(:post, 'http://localhost:5338/percy/snapshot')
+        .to_return(status: 200, body: '{"success":true}', headers: {})
+
+      captured_serialize_call = nil
+      allow(page).to receive(:execute_script).and_wrap_original do |original, script, *args|
+        captured_serialize_call = script if script.to_s.include?('PercyDOM.serialize')
+        original.call(script, *args)
+      end
+
+      visit 'index.html'
+      Percy.snapshot(page, 'Name', discovery: {disableCache: true})
+
+      expect(captured_serialize_call).to_not be_nil
+      serialized = JSON.parse(captured_serialize_call[/PercyDOM\.serialize\((.*)\)/m, 1])
+      # Sibling from config survives; per-call leaf overrides the config value.
+      expect(serialized['discovery']).to eq(
+        'networkIdleTimeout' => 50, 'disableCache' => true,
+      )
+    end
   end
 end
 

spec/spec_helper.rb

@@ -35,8 +35,25 @@
   Kernel.srand config.seed
 
   # See https://github.com/teamcapybara/capybara#selecting-the-driver for other options
-  Capybara.default_driver = :selenium_headless
-  Capybara.javascript_driver = :selenium_headless
+  # Default to Firefox headless (matches CI), but when a Chromium/Chrome binary is
+  # provided via CHROME_BIN (e.g. the containerised e2e image), register and use a
+  # headless Chrome driver pointing at it instead.
+  if ENV['CHROME_BIN'] && !ENV['CHROME_BIN'].empty?
+    Capybara.register_driver :selenium_chrome_headless_bin do |app|
+      options = Selenium::WebDriver::Chrome::Options.new
+      options.binary = ENV['CHROME_BIN']
+      options.add_argument('--headless=new')
+      options.add_argument('--no-sandbox')
+      options.add_argument('--disable-gpu')
+      options.add_argument('--disable-dev-shm-usage')
+      Capybara::Selenium::Driver.new(app, browser: :chrome, options: options)
+    end
+    Capybara.default_driver = :selenium_chrome_headless_bin
+    Capybara.javascript_driver = :selenium_chrome_headless_bin
+  else
+    Capybara.default_driver = :selenium_headless
+    Capybara.javascript_driver = :selenium_headless
+  end
 
   # Capybara's built-in :selenium_headless driver still passes `options:` to
   # driver init, which newer selenium-webdriver logs as a [DEPRECATION]