Merge pull request #265 from yuki24/support-for-nested-exceptions

Add support for nested exceptions

lib/web_console/exception_mapper.rb

@@ -2,9 +2,28 @@
 
 module WebConsole
   class ExceptionMapper
+    attr_reader :exc
+
+    def self.follow(exc)
+      mappers = [new(exc)]
+
+      while cause = (cause || exc).cause
+        mappers << new(cause)
+      end
+
+      mappers
+    end
+
+    def self.find_binding(mappers, exception_object_id)
+      mappers.detect do |exception_mapper|
+        exception_mapper.exc.object_id == exception_object_id.to_i
+      end || mappers.first
+    end
+
     def initialize(exception)
       @backtrace = exception.backtrace
       @bindings = exception.bindings
+      @exc = exception
     end
 
     def first

lib/web_console/middleware.rb

@@ -110,7 +110,7 @@ def update_repl_session(id, request)
 
       def change_stack_trace(id, request)
         json_response_with_session(id, request) do |session|
-          session.switch_binding_to(request.params[:frame_id])
+          session.switch_binding_to(request.params[:frame_id], request.params[:exception_object_id])
 
           { ok: true }
         end

lib/web_console/session.rb

@@ -31,20 +31,21 @@ def find(id)
       # storage.
       def from(storage)
         if exc = storage[:__web_console_exception]
-          new(ExceptionMapper.new(exc))
+          new(ExceptionMapper.follow(exc))
         elsif binding = storage[:__web_console_binding]
-          new([binding])
+          new([[binding]])
         end
       end
     end
 
     # An unique identifier for every REPL.
     attr_reader :id
 
-    def initialize(bindings)
+    def initialize(exception_mappers)
       @id = SecureRandom.hex(16)
-      @bindings = bindings
-      @evaluator = Evaluator.new(@current_binding = bindings.first)
+
+      @exception_mappers = exception_mappers
+      @evaluator         = Evaluator.new(@current_binding = exception_mappers.first.first)
 
       store_into_memory
     end
@@ -59,8 +60,10 @@ def eval(input)
     # Switches the current binding to the one at specified +index+.
     #
     # Returns nothing.
-    def switch_binding_to(index)
-      @evaluator = Evaluator.new(@current_binding = @bindings[index.to_i])
+    def switch_binding_to(index, exception_object_id)
+      bindings = ExceptionMapper.find_binding(@exception_mappers, exception_object_id)
+
+      @evaluator = Evaluator.new(@current_binding = bindings[index.to_i])
     end
 
     # Returns context of the current binding

lib/web_console/templates/console.js.erb

@@ -871,10 +871,14 @@ REPLConsole.prototype.scrollToBottom = function() {
 };
 
 // Change the binding of the console.
-REPLConsole.prototype.switchBindingTo = function(frameId, callback) {
+REPLConsole.prototype.switchBindingTo = function(frameId, exceptionObjectId, callback) {
   var url = this.getSessionUrl('trace');
   var params = "frame_id=" + encodeURIComponent(frameId);
 
+  if (exceptionObjectId) {
+    params = params + "&exception_object_id=" + encodeURIComponent(exceptionObjectId);
+  }
+
   var _this = this;
   postRequest(url, params, function() {
     var text = "Context has changed to: " + callback();

lib/web_console/templates/error_page.js.erb

@@ -8,9 +8,10 @@ for (var i = 0; i < traceFrames.length; i++) {
     e.preventDefault();
     var target = e.target;
     var frameId = target.dataset.frameId;
+    var exceptionObjectId = target.dataset.exceptionObjectId;
 
     // Change the binding of the console.
-    changeBinding(frameId, function() {
+    changeBinding(frameId, exceptionObjectId, function() {
       // Rails already handles toggling the select class
       selectedFrame = target;
       return target.innerHTML;
@@ -22,8 +23,8 @@ for (var i = 0; i < traceFrames.length; i++) {
 }
 
 // Change the binding of the current session and prompt the user.
-function changeBinding(frameId, callback) {
-  REPLConsole.currentSession.switchBindingTo(frameId, callback);
+function changeBinding(frameId, exceptionObjectId, callback) {
+  REPLConsole.currentSession.switchBindingTo(frameId, exceptionObjectId, callback);
 }
 
 function changeSourceExtract(frameId) {

test/web_console/middleware_test.rb

@@ -157,7 +157,7 @@ def headers
     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)
 
@@ -168,7 +168,7 @@ def headers
     end
 
     test "can switch bindings on error pages" do
-      session = Session.new(raise_exception.bindings)
+      session = Session.new([WebConsole::ExceptionMapper.new(raise_exception)])
 
       Session.stubs(:from).returns(session)
 
@@ -178,18 +178,35 @@ def headers
       assert_equal({ ok: true }.to_json, response.body)
     end
 
+    test "can switch to the cause on error pages" do
+      nested_error = begin
+                       raise "First error"
+                     rescue
+                       raise "Second Error" rescue $!
+                     end
+
+      session = Session.new(WebConsole::ExceptionMapper.follow(nested_error))
+
+      Session.stubs(:from).returns(session)
+
+      get "/", params: nil
+      post "/repl_sessions/#{session.id}/trace", xhr: true, params: { frame_id: 1, exception_object_id: nested_error.cause.object_id }
+
+      assert_equal({ ok: true }.to_json, response.body)
+    end
+
     test "can be changed mount point" do
       Middleware.mount_point = "/customized/path"
 
-      session, value = Session.new([binding]), __LINE__
+      session, value = Session.new([[binding]]), __LINE__
       put "/customized/path/repl_sessions/#{session.id}", params: { input: "value" }, xhr: true
 
       assert_equal("=> #{value}\n", JSON.parse(response.body)["output"])
     end
 
     test "can return context information by passing a context param" do
       hello = hello = "world"
-      session = Session.new([binding])
+      session = Session.new([[binding]])
       Session.stubs(:from).returns(session)
 
       get "/"

test/web_console/session_test.rb

@@ -11,6 +11,13 @@ def self.raise(value)
         exc
       end
 
+      def self.raise_nested_error(value)
+        ::Kernel.raise self, value
+      rescue
+        value = 1 # Override value so we can target the binding here
+        ::Kernel.raise "Second Error" rescue $!
+      end
+
       attr_reader :value
 
       def initialize(value)
@@ -20,7 +27,7 @@ def initialize(value)
 
     setup do
       Session.inmemory_storage.clear
-      @session = Session.new([binding])
+      @session = Session.new([[binding]])
     end
 
     test "returns nil when a session is not found" do
@@ -47,7 +54,7 @@ def eval(string)
         self
       end
 
-      session = Session.new([binding])
+      session = Session.new([[binding]])
       assert_equal session.eval("called?"), "=> \"yes\"\n"
     end
 
@@ -74,7 +81,17 @@ def eval(string)
       exc = ValueAwareError.raise(value)
 
       session = Session.from(__web_console_exception: exc)
-      session.switch_binding_to(1)
+      session.switch_binding_to(1, exc.object_id)
+
+      assert_equal "=> #{value}\n", session.eval("value")
+    end
+
+    test "#from can switch to the cause" do
+      value = __LINE__
+      exc = ValueAwareError.raise_nested_error(value)
+
+      session = Session.from(__web_console_exception: exc)
+      session.switch_binding_to(1, exc.cause.object_id)
 
       assert_equal "=> #{value}\n", session.eval("value")
     end