Support incompatible encodings in inspection messages

Author: k-tsj

lib/power_assert.rb

@@ -64,7 +64,16 @@ def initialize(value)
     end
 
     def inspect
-      @value.inspect
+      inspect = @value.inspect
+      if Encoding.compatible?(Encoding.default_external, inspect)
+        inspect
+      else
+        begin
+          "#{inspect.encode(Encoding.default_external)}(#{inspect.encoding})"
+        rescue Encoding::UndefinedConversionError, Encoding::InvalidByteSequenceError
+          inspect.force_encoding(Encoding.default_external)
+        end
+      end
     rescue => e
       "InspectionFailure: #{e.class}: #{e.message.each_line.first}"
     end
@@ -156,7 +165,8 @@ def build_assertion_message(line, methods, return_values, refs, proc_binding)
         inspected_vals = vals.each_with_object({}) do |j, h|
           h[j.column.to_s.to_sym] = [SafeInspectable.new(i.value).inspect, '|', ' '][i.column <=> j.column]
         end
-        ret << sprintf(fmt, inspected_vals).rstrip
+        l = sprintf(fmt, inspected_vals)
+        ret << (l.valid_encoding? ? l.rstrip : l)
       end
       ret.join("\n")
     end

test/test_power_assert.rb

@@ -358,6 +358,38 @@ def test_inspection_failure
     end
   end
 
+  def test_assertion_message_with_incompatible_encodings
+    if Encoding.default_external == Encoding::UTF_8
+      a = "\u3042"
+      def a.inspect
+        super.encode('utf-16le')
+      end
+      assert_equal <<END.chomp, assertion_message {
+        a + a
+        | | |
+        | | "\u3042"(UTF-16LE)
+        | "\u3042\u3042"
+        "\u3042"(UTF-16LE)
+END
+        a + a
+      }
+    end
+
+
+    a = "\xFF"
+    def a.inspect
+      "\xFF".force_encoding('ascii-8bit')
+    end
+    assert_equal <<END.chomp.b, assertion_message {
+      a.length
+      | |
+      | 1
+      \xFF  
+END
+      a.length
+    }.b
+  end
+
   def test_assertion_message_with_string
     a, = 0, a # suppress "assigned but unused variable" warning
     @b = 1