Allow skipping variable inspection by class name

README.md

@@ -93,6 +93,16 @@ See [the wiki for instructions on configuring the editor](https://github.com/Bet
 BetterErrors.maximum_variable_inspect_size = 100_000
 ```
 
+## Ignore inspection of variables with certain classes.
+
+```ruby
+# e.g. in config/initializers/better_errors.rb
+# This will stop BetterErrors from trying to inspect objects of these classes, which can cause
+# slow loading times and unneccessary database queries. Does not check inheritance chain, use
+# strings not contants.
+# default value: ['ActionDispatch::Request', 'ActionDispatch::Response']
+BetterErrors.ignored_classes = ['ActionDispatch::Request', 'ActionDispatch::Response']
+```
 
 ## Get in touch!
 

lib/better_errors.rb

@@ -54,9 +54,14 @@ class << self
     # the variable won't be returned.
     # @return int
     attr_accessor :maximum_variable_inspect_size
+
+    # List of classes that are excluded from inspection.
+    # @return [Array]
+    attr_accessor :ignored_classes
   end
   @ignored_instance_variables = []
   @maximum_variable_inspect_size = 100_000
+  @ignored_classes = ['ActionDispatch::Request', 'ActionDispatch::Response']
 
   # Returns a proc, which when called with a filename and line number argument,
   # returns a URL to open the filename and line in the selected editor.

lib/better_errors/error_page.rb

@@ -105,7 +105,13 @@ def text_heading(char, str)
     end
 
     def inspect_value(obj)
-      InspectableValue.new(obj).to_html
+      if BetterErrors.ignored_classes.include? obj.class.name
+        "<span class='unsupported'>(Instance of ignored class. "\
+        "#{obj.class.name ? "Remove #{CGI.escapeHTML(obj.class.name)} from" : "Modify"}"\
+        " BetterErrors.ignored_classes if you need to see it.)</span>"
+      else
+        InspectableValue.new(obj).to_html
+      end
     rescue BetterErrors::ValueLargerThanConfiguredMaximum
       "<span class='unsupported'>(Object too large. "\
         "#{obj.class.name ? "Modify #{CGI.escapeHTML(obj.class.name)}#inspect or a" : "A"}"\

spec/better_errors/error_page_spec.rb

@@ -1,5 +1,7 @@
 require "spec_helper"
 
+class ErrorPageTestIgnoredClass; end
+
 module BetterErrors
   describe ErrorPage do
     # It's necessary to use HTML matchers here that are specific as possible.
@@ -45,28 +47,70 @@ module BetterErrors
 
         it "shows local variables" do
           html = error_page.do_variables("index" => 0)[:html]
-          expect(html).to have_tag('div.variables') do
+          expect(html).to have_tag('div.variables tr') do
             with_tag('td.name', text: 'local_a')
             with_tag('pre', text: ':value_for_local_a')
+          end
+          expect(html).to have_tag('div.variables tr') do
             with_tag('td.name', text: 'local_b')
             with_tag('pre', text: ':value_for_local_b')
           end
         end
 
         it "shows instance variables" do
           html = error_page.do_variables("index" => 0)[:html]
-          expect(html).to have_tag('div.variables') do
+          expect(html).to have_tag('div.variables tr') do
             with_tag('td.name', text: '@inst_c')
             with_tag('pre', text: ':value_for_inst_c')
+          end
+          expect(html).to have_tag('div.variables tr') do
             with_tag('td.name', text: '@inst_d')
             with_tag('pre', text: ':value_for_inst_d')
           end
         end
 
+        context 'when ignored_classes includes the class name of a local variable' do
+          before do
+            allow(BetterErrors).to receive(:ignored_classes).and_return(['ErrorPageTestIgnoredClass'])
+          end
+
+          let(:exception_binding) {
+            local_a = :value_for_local_a
+            local_b = ErrorPageTestIgnoredClass.new
+
+            @inst_c = :value_for_inst_c
+            @inst_d = ErrorPageTestIgnoredClass.new
+
+            binding
+          }
+
+          it "does not include that value" do
+            html = error_page.do_variables("index" => 0)[:html]
+            expect(html).to have_tag('div.variables tr') do
+              with_tag('td.name', text: 'local_a')
+              with_tag('pre', text: ':value_for_local_a')
+            end
+            expect(html).to have_tag('div.variables tr') do
+              with_tag('td.name', text: 'local_b')
+              with_tag('.unsupported', text: /Instance of ignored class/)
+              with_tag('.unsupported', text: /BetterErrors\.ignored_classes/)
+            end
+            expect(html).to have_tag('div.variables tr') do
+              with_tag('td.name', text: '@inst_c')
+              with_tag('pre', text: ':value_for_inst_c')
+            end
+            expect(html).to have_tag('div.variables tr') do
+              with_tag('td.name', text: '@inst_d')
+              with_tag('.unsupported', text: /Instance of ignored class/)
+              with_tag('.unsupported', text: /BetterErrors\.ignored_classes/)
+            end
+          end
+        end
+
         it "does not show filtered variables" do
           allow(BetterErrors).to receive(:ignored_instance_variables).and_return([:@inst_d])
           html = error_page.do_variables("index" => 0)[:html]
-          expect(html).to have_tag('div.variables') do
+          expect(html).to have_tag('div.variables tr') do
             with_tag('td.name', text: '@inst_c')
             with_tag('pre', text: ':value_for_inst_c')
           end
@@ -149,7 +193,7 @@ def initialize
 
                 it "does not attempt to show the class name" do
                   html = error_page.do_variables("index" => 0)[:html]
-                  expect(html).to have_tag('div.variables') do
+                  expect(html).to have_tag('div.variables tr') do
                     with_tag('td.name', text: '@big_anonymous')
                     with_tag('.unsupported', text: /Object too large/)
                     with_tag('.unsupported', text: /Adjust BetterErrors.maximum_variable_inspect_size/)
@@ -235,7 +279,7 @@ def initialize
 
               it "does not attempt to show the class name" do
                 html = error_page.do_variables("index" => 0)[:html]
-                expect(html).to have_tag('div.variables') do
+                expect(html).to have_tag('div.variables tr') do
                   with_tag('td.name', text: '@big_anonymous')
                   with_tag('.unsupported', text: /Object too large/)
                   with_tag('.unsupported', text: /Adjust BetterErrors.maximum_variable_inspect_size/)