Merge pull request #576 from Shopify/flexible-exception-handler

Allow the exception handler to convert exceptions to hide error messges

lib/liquid/context.rb

@@ -13,7 +13,7 @@ module Liquid
   #   context['bob']  #=> nil  class Context
   class Context
     attr_reader :scopes, :errors, :registers, :environments, :resource_limits
-    attr_accessor :exception_handler, :render_errors
+    attr_accessor :exception_handler
 
     def initialize(environments = {}, outer_scope = {}, registers = {}, rethrow_errors = false, resource_limits = nil)
       @environments     = [environments].flatten
@@ -22,12 +22,11 @@ module Liquid
       @errors           = []
       @resource_limits  = resource_limits || ResourceLimits.new(Template.default_resource_limits)
       squash_instance_assigns_with_environments
-      @render_errors    = true
 
       @this_stack_used = false
 
       if rethrow_errors
-        self.exception_handler = ->(e) { true }
+        self.exception_handler = ->(e) { raise }
       end
 
       @interrupts = []
@@ -68,9 +67,22 @@ module Liquid
         e.set_line_number_from_token(token)
       end
 
+      output = nil
+
+      if exception_handler
+        result = exception_handler.call(e)
+        case result
+        when Exception
+          e = result
+          e.set_line_number_from_token(token) if e.is_a?(Liquid::Error)
+        when String
+          output = result
+        else
+          raise if result
+        end
+      end
       errors.push(e)
-      raise if exception_handler && exception_handler.call(e)
-      render_errors ? Liquid::Error.render(e) : ''
+      output || Liquid::Error.render(e)
     end
 
     def invoke(method, *args)

lib/liquid/template.rb

@@ -17,7 +17,7 @@ module Liquid
       locale: I18n.new
     }
 
-    attr_accessor :root, :render_errors
+    attr_accessor :root
     attr_reader :resource_limits
 
     @@file_system = BlankFileSystem.new
@@ -168,7 +168,7 @@ module Liquid
         c = args.shift
 
         if @rethrow_errors
-          c.exception_handler = ->(e) { true }
+          c.exception_handler = ->(e) { raise }
         end
 
         c
@@ -183,8 +183,6 @@ module Liquid
         raise ArgumentError, "Expected Hash or Liquid::Context as parameter"
       end
 
-      context.render_errors = self.render_errors unless self.render_errors.nil?
-
       case args.last
       when Hash
         options = args.pop

test/integration/error_handling_test.rb

@@ -186,10 +186,21 @@ class ErrorHandlingTest < Minitest::Test
     end
   end
 
-  def test_disabling_error_rendering
+  def test_exception_handler_with_string_result
     template = Liquid::Template.parse('This is an argument error: {{ errors.argument_error }}')
-    template.render_errors = false
-    assert_equal 'This is an argument error: ', template.render('errors' => ErrorDrop.new)
+    output = template.render({ 'errors' => ErrorDrop.new }, exception_handler: ->(e) { '' })
+    assert_equal 'This is an argument error: ', output
     assert_equal [ArgumentError], template.errors.map(&:class)
   end
+
+  class InternalError < Liquid::Error
+  end
+
+  def test_exception_handler_with_exception_result
+    template = Liquid::Template.parse('This is a runtime error: {{ errors.runtime_error }}', line_numbers: true)
+    handler = ->(e) { e.is_a?(Liquid::Error) ? e : InternalError.new('internal') }
+    output = template.render({ 'errors' => ErrorDrop.new }, exception_handler: handler)
+    assert_equal 'This is a runtime error: Liquid error (line 1): internal', output
+    assert_equal [InternalError], template.errors.map(&:class)
+  end
 end

test/test_helper.rb

@@ -102,6 +102,10 @@ class ErrorDrop < Liquid::Drop
     raise Liquid::SyntaxError, 'syntax error'
   end
 
+  def runtime_error
+    raise RuntimeError, 'runtime error'
+  end
+
   def exception
     raise Exception, 'exception'
   end