fix(rails): exclude MimeNegotiation::InvalidType by default

posthog-rails/lib/generators/posthog/templates/posthog.rb

@@ -130,6 +130,7 @@
 # - ActionController::RoutingError
 # - ActionController::UnknownFormat
 # - ActionController::UnknownHttpMethod
+# - ActionDispatch::Http::MimeNegotiation::InvalidType
 # - ActionDispatch::Http::Parameters::ParseError
 # - ActiveRecord::RecordNotFound
 # - ActiveRecord::RecordNotUnique

posthog-rails/lib/posthog/rails/configuration.rb

@@ -56,6 +56,7 @@ def default_excluded_exceptions
           'ActionController::RoutingError',
           'ActionController::UnknownFormat',
           'ActionController::UnknownHttpMethod',
+          'ActionDispatch::Http::MimeNegotiation::InvalidType',
           'ActionDispatch::Http::Parameters::ParseError',
           'ActiveRecord::RecordNotFound',
           'ActiveRecord::RecordNotUnique'

spec/posthog/rails/configuration_spec.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'action_controller'
+require 'action_dispatch'
+
+$LOAD_PATH.unshift File.expand_path('../../../posthog-rails/lib', __dir__)
+
+require 'posthog/rails/configuration'
+
+RSpec.describe PostHog::Rails::Configuration do
+  subject(:config) { described_class.new }
+
+  describe '#should_capture_exception?' do
+    # MimeNegotiation::InvalidType is raised when a client sends a malformed
+    # Accept / Content-Type header (typically scanner traffic). Rails maps it
+    # to a 406 — see ActionDispatch::ExceptionWrapper.rescue_responses — so it
+    # is not a bug worth capturing.
+    {
+      'ActionController::RoutingError' => ActionController::RoutingError.new('No route matches'),
+      'ActionDispatch::Http::MimeNegotiation::InvalidType' =>
+        ActionDispatch::Http::MimeNegotiation::InvalidType.new('"foo" is not a valid MIME type')
+    }.each do |name, exception|
+      it "excludes #{name} by default" do
+        expect(config.should_capture_exception?(exception)).to be false
+      end
+    end
+
+    it 'captures application exceptions that are not in the excluded list' do
+      exception = StandardError.new('something broke')
+      expect(config.should_capture_exception?(exception)).to be true
+    end
+
+    it 'honours user-supplied excluded_exceptions in addition to defaults' do
+      config.excluded_exceptions = ['MyApp::IgnorableError']
+      stub_const('MyApp::IgnorableError', Class.new(StandardError))
+      expect(config.should_capture_exception?(MyApp::IgnorableError.new)).to be false
+      # defaults still apply
+      expect(config.should_capture_exception?(ActionController::RoutingError.new('x'))).to be false
+    end
+  end
+end