feat(logging): auto-enable structured_logging in Rails (#2721)

* feat(logging): auto-enable structured_logging

When config.enable_logs is true, enable structured
logging in Rails automatically too.

Closes #2715

* Update CHANGELOG

* Rework to use a callback

* Use new syntax for config callbacks

* No need for parent_config after all

Author: solnic

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## Unreleased
 
+### Features
+
+- Auto-enable Rails structured logging when `enable_logs` is true ([#2721](https://github.com/getsentry/sentry-ruby/pull/2721))
+
 ### Internal
 
 - Fix leftover `config.logger` call in `graphql` patch ([#2722](https://github.com/getsentry/sentry-ruby/2722)

sentry-rails/lib/sentry/rails/configuration.rb

@@ -13,7 +13,7 @@ module Sentry
   class Configuration
     attr_reader :rails
 
-    add_post_initialization_callback do
+    after(:initialize) do
       @rails = Sentry::Rails::Configuration.new
       @excluded_exceptions = @excluded_exceptions.concat(Sentry::Rails::IGNORE_DEFAULT)
 
@@ -33,6 +33,10 @@ class Configuration
         end
       end
     end
+
+    after(:configured) do
+      rails.structured_logging.enabled = enable_logs if rails.structured_logging.enabled.nil?
+    end
   end
 
   module Rails
@@ -202,9 +206,15 @@ class StructuredLoggingConfiguration
       }.freeze
 
       def initialize
-        @enabled = false
+        @enabled = nil
         @subscribers = DEFAULT_SUBSCRIBERS.dup
       end
+
+      # Returns true if structured logging should be enabled.
+      # @return [Boolean]
+      def enabled?
+        enabled
+      end
     end
   end
 end

sentry-rails/lib/sentry/rails/railtie.rb

@@ -140,7 +140,7 @@ def activate_tracing
     end
 
     def activate_structured_logging
-      if Sentry.configuration.rails.structured_logging.enabled && Sentry.configuration.enable_logs
+      if Sentry.configuration.rails.structured_logging.enabled? && Sentry.configuration.enable_logs
         Sentry::Rails::StructuredLogging.attach(Sentry.configuration.rails.structured_logging)
       end
     end

sentry-rails/spec/sentry/rails/configuration_spec.rb

@@ -74,7 +74,7 @@ class MySubscriber; end
         config.rails.structured_logging.enabled = true
       end
 
-      expect(config.structured_logging.enabled).to be(true)
+      expect(config.structured_logging.enabled?).to be(true)
       expect(config.structured_logging.subscribers).to be_a(Hash)
     end
 
@@ -83,10 +83,35 @@ class MySubscriber; end
         config.rails.structured_logging.enabled = false
       end
 
-      expect(config.structured_logging.enabled).to be(false)
+      expect(config.structured_logging.enabled?).to be(false)
       expect(config.structured_logging.subscribers).to be_a(Hash)
     end
 
+    it "auto-enables when enable_logs is true and not explicitly set" do
+      make_basic_app do |config|
+        config.enable_logs = true
+      end
+
+      expect(config.structured_logging.enabled?).to be(true)
+    end
+
+    it "remains disabled when enable_logs is false" do
+      make_basic_app do |config|
+        config.enable_logs = false
+      end
+
+      expect(config.structured_logging.enabled?).to be(false)
+    end
+
+    it "respects explicit disable even when enable_logs is true" do
+      make_basic_app do |config|
+        config.rails.structured_logging.enabled = false
+        config.enable_logs = true
+      end
+
+      expect(config.structured_logging.enabled?).to be(false)
+    end
+
     it "allows customizing subscribers" do
       class TestSubscriber; end
 

sentry-rails/spec/sentry/rails/log_subscriber_spec.rb

@@ -45,6 +45,8 @@ def error_test_event(event)
       make_basic_app do |config|
         config.enable_logs = true
         config.structured_logging.logger_class = Sentry::DebugStructuredLogger
+        # Disable default structured logging subscribers to avoid interference
+        config.rails.structured_logging.enabled = false
       end
     end
 
@@ -123,8 +125,8 @@ def error_test_event(event)
         duration = log_event["attributes"]["duration_ms"]
 
         expect(duration).to be_a(Float)
-        expect(duration).to be >= 40.0
-        expect(duration).to be < 100.0
+        expect(duration).to be >= 10.0
+        expect(duration).to be < 200.0
         expect(duration.round(2)).to eq(duration)
       end
     end

sentry-rails/spec/sentry/rails/structured_logging_spec.rb

@@ -40,4 +40,28 @@
       expect(sentry_logs).to be_empty
     end
   end
+
+  context "when enable_logs is true and structured logging is auto-enabled" do
+    before do
+      make_basic_app do |config|
+        config.enable_logs = true
+      end
+    end
+
+    it "captures structured logs automatically" do
+      get "/posts"
+
+      Post.first
+
+      Sentry.get_current_client.flush
+
+      expect(sentry_logs).not_to be_empty
+
+      rails_log_events = sentry_logs.select { |log|
+        log.dig(:attributes, "sentry.origin", :value) == "auto.logger.rails.log_subscriber"
+      }
+
+      expect(rails_log_events).not_to be_empty
+    end
+  end
 end