Reduce log noise handling ActionController::RoutingErrors

Each time a missing route is hit 32 lines of internal rails traces
are written to the log. This is overly verbose and doesn't offer
any actionable information to the user.

With this change we'll still write an error message showing the
route error but the trace will be omitted.

actionpack/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Reduced log noise handling ActionController::RoutingErrors.
+
+    *Alberto Fernández-Capel*
+
 *   Keep part when scope option has value
 
     When a route was defined within an optional scope, if that route didn't

actionpack/lib/action_dispatch/middleware/debug_exceptions.rb

@@ -138,9 +138,7 @@ module ActionDispatch
         return unless logger
 
         exception = wrapper.exception
-
-        trace = wrapper.application_trace
-        trace = wrapper.framework_trace if trace.empty?
+        trace = wrapper.exception_trace
 
         ActiveSupport::Deprecation.silence do
           message = []

actionpack/lib/action_dispatch/middleware/exception_wrapper.rb

@@ -62,6 +62,12 @@ module ActionDispatch
       self.class.status_code_for_exception(unwrapped_exception.class.name)
     end
 
+    def exception_trace
+      trace = application_trace
+      trace = framework_trace if trace.empty? && !exception.is_a?(ActionController::RoutingError)
+      trace
+    end
+
     def application_trace
       clean_backtrace(:silent)
     end

actionpack/test/dispatch/debug_exceptions_test.rb

@@ -466,6 +466,8 @@ class DebugExceptionsTest < ActionDispatch::IntegrationTest
   end
 
   test "logs exception backtrace when all lines silenced" do
+    @app = DevelopmentApp
+
     output = StringIO.new
     backtrace_cleaner = ActiveSupport::BacktraceCleaner.new
     backtrace_cleaner.add_silencer { true }
@@ -478,6 +480,27 @@ class DebugExceptionsTest < ActionDispatch::IntegrationTest
     assert_operator((output.rewind && output.read).lines.count, :>, 10)
   end
 
+  test "doesn't log the framework backtrace when error type is a routing error" do
+    @app = ProductionApp
+
+    output = StringIO.new
+    backtrace_cleaner = ActiveSupport::BacktraceCleaner.new
+    backtrace_cleaner.add_silencer { true }
+
+    env = { "action_dispatch.show_exceptions"   => true,
+            "action_dispatch.logger"            => Logger.new(output),
+            "action_dispatch.backtrace_cleaner" => backtrace_cleaner }
+
+    assert_raises ActionController::RoutingError do
+      get "/pass", headers: env
+    end
+
+    log = output.rewind && output.read
+
+    assert_includes log, "ActionController::RoutingError (No route matches [GET] \"/pass\")"
+    assert_equal 3, log.lines.count
+  end
+
   test "display backtrace when error type is SyntaxError" do
     @app = DevelopmentApp