Merge pull request #203 from gsamokovarov/exception-mapper

Map bindings to traces based on the trace __FILE__ and __LINE__

Author: gsamokovarov

lib/web_console.rb

@@ -7,6 +7,7 @@ module WebConsole
 
   autoload :View
   autoload :Evaluator
+  autoload :ExceptionMapper
   autoload :Session
   autoload :Response
   autoload :Request

lib/web_console/exception_mapper.rb

@@ -0,0 +1,33 @@
+module WebConsole
+  class ExceptionMapper
+    def initialize(exception)
+      @backtrace = exception.backtrace
+      @bindings = exception.bindings
+    end
+
+    def first
+      guess_the_first_application_binding || @bindings.first
+    end
+
+    def [](index)
+      guess_binding_for_index(index) || @bindings[index]
+    end
+
+    private
+
+    def guess_binding_for_index(index)
+      file, line = @backtrace[index].to_s.split(':')
+      line = line.to_i
+
+      @bindings.find do |binding|
+        binding.eval('__FILE__') == file && binding.eval('__LINE__') == line
+      end
+    end
+
+    def guess_the_first_application_binding
+      @bindings.find do |binding|
+        binding.eval('__FILE__').to_s.start_with?(Rails.root.to_s)
+      end
+    end
+  end
+end

lib/web_console/session.rb

@@ -30,9 +30,9 @@ def find(id)
       # storage.
       def from(storage)
         if exc = storage[:__web_console_exception]
-          new(exc.bindings)
+          new(ExceptionMapper.new(exc))
         elsif binding = storage[:__web_console_binding]
-          new(binding)
+          new([binding])
         end
       end
     end
@@ -42,8 +42,8 @@ def from(storage)
 
     def initialize(bindings)
       @id = SecureRandom.hex(16)
-      @bindings = Array(bindings)
-      @evaluator = Evaluator.new(application_binding || @bindings.first)
+      @bindings = bindings
+      @evaluator = Evaluator.new(bindings.first)
 
       store_into_memory
     end
@@ -64,10 +64,6 @@ def switch_binding_to(index)
 
     private
 
-      def application_binding
-        @bindings.find { |b| b.eval('__FILE__').to_s.start_with?(Rails.root.to_s) }
-      end
-
       def store_into_memory
         inmemory_storage[id] = self
       end

test/dummy/app/views/helper_error/index.html.erb

@@ -1,2 +1,2 @@
 <% @ok = 42 %>
-<% raise %>
+<% params.fetch(:bad_key) %>

test/web_console/exception_mapper_test.rb

@@ -0,0 +1,33 @@
+require 'test_helper'
+
+module WebConsole
+  class ExcetionMapperTest < ActiveSupport::TestCase
+    test '#first tries to find the first application binding' do
+      Rails.stubs(:root).returns Pathname(__FILE__).parent
+
+      mapper = ExceptionMapper.new(External.exception)
+
+      assert_equal __FILE__, mapper.first.eval('__FILE__')
+    end
+
+    test '.[] tries match the binding for trace index' do
+      exception = External.exception
+      mapper = ExceptionMapper.new(exception)
+
+      last_index = exception.backtrace.count - 1
+      file, line = exception.backtrace.last.split(':')
+
+      assert_equal file, mapper[last_index].eval('__FILE__')
+      assert_equal line.to_i, mapper[last_index].eval('__LINE__')
+    end
+
+    test '.[] fall backs to index if no trace can be found' do
+      exception = External.exception
+      mapper = ExceptionMapper.new(exception)
+
+      unbound_index = exception.backtrace.count
+
+      assert_nil mapper[unbound_index]
+    end
+  end
+end

test/web_console/middleware_test.rb

@@ -124,7 +124,7 @@ def body
     end
 
     test 'can evaluate code and return it as a JSON' do
-      session, line = Session.new(binding), __LINE__
+      session, line = Session.new([binding]), __LINE__
 
       Session.stubs(:from).returns(session)
 
@@ -148,7 +148,7 @@ def body
     test 'can be changed mount point' do
       Middleware.mount_point = '/customized/path'
 
-      session, line = Session.new(binding), __LINE__
+      session, line = Session.new([binding]), __LINE__
       put "/customized/path/repl_sessions/#{session.id}", params: { input: '__LINE__' }, xhr: true
 
       assert_equal({ output: "=> #{line}\n" }.to_json, response.body)

test/web_console/session_test.rb

@@ -17,9 +17,8 @@ def initialize(line)
     end
 
     setup do
-      Rails.stubs(:root).returns Pathname(__FILE__).parent
       Session.inmemory_storage.clear
-      @session = Session.new(binding)
+      @session = Session.new([binding])
     end
 
     test 'returns nil when a session is not found' do
@@ -34,17 +33,19 @@ def initialize(line)
       assert_equal "=> 42\n", @session.eval('40 + 2')
     end
 
-    test 'find first binding of the rails app' do
-      session = Session.new(External.exception.bindings)
-      assert_equal session.eval('__FILE__'), "=> \"#{__FILE__}\"\n"
-    end
-
     test 'use first binding if no application bindings' do
-      binding = Object.new
-      binding.expects(:eval).with('__FILE__').returns 'framework'
-      binding.expects(:eval).with('called?').returns 'yes'
+      binding = Object.new.instance_eval do
+        def eval(string)
+          case string
+          when '__FILE__' then framework
+          when 'called?' then 'yes'
+          end
+        end
+
+        self
+      end
 
-      session = Session.new(binding)
+      session = Session.new([binding])
       assert_equal session.eval('called?'), "=> \"yes\"\n"
     end