formatter_ltsv: suppress delimiters in output

Replace tabs with spaces before writing them to the output, to prevent
creating malformed LTSV files.

Also add test cases to verify this behaviour.

Signed-off-by: Mike Playle <mike@mythik.co.uk>

lib/fluent/plugin/formatter_ltsv.rb

@@ -27,14 +27,15 @@ class LabeledTSVFormatter < Formatter
 
       config_param :delimiter, :string, default: "\t".freeze
       config_param :label_delimiter, :string, default: ":".freeze
+      config_param :replacement, :string, default: " ".freeze
       config_param :add_newline, :bool, default: true
 
       # TODO: escaping for \t in values
       def format(tag, time, record)
         formatted = ""
         record.each do |label, value|
           formatted << @delimiter if formatted.length.nonzero?
-          formatted << "#{label}#{@label_delimiter}#{value}"
+          formatted << "#{label}#{@label_delimiter}#{value.to_s.gsub(@delimiter, @replacement)}"
         end
         formatted << @newline if @add_newline
         formatted

test/test_formatter.rb

@@ -184,6 +184,36 @@ def test_format_with_customized_delimiters
 
       assert_equal("message=awesome,greeting=hello#{@newline}", formatted)
     end
+
+    def record_with_tab
+      {'message' => "awe\tsome", 'greeting' => "hello\t"}
+    end
+
+    def test_format_suppresses_tab
+      @formatter.configure({})
+      formatted = @formatter.format(tag, @time, record_with_tab)
+
+      assert_equal("message:awe some\tgreeting:hello \n", formatted)
+    end
+
+    def test_format_suppresses_tab_custom_replacement
+      @formatter.configure(
+        'replacement'      => 'X',
+      )
+      formatted = @formatter.format(tag, @time, record_with_tab)
+
+      assert_equal("message:aweXsome\tgreeting:helloX\n", formatted)
+    end
+
+    def test_format_suppresses_custom_delimiter
+      @formatter.configure(
+        'delimiter'       => 'w',
+        'label_delimiter' => '=',
+      )
+      formatted = @formatter.format(tag, @time, record)
+
+      assert_equal("message=a esomewgreeting=hello\n", formatted)
+    end
   end
 
   class CsvFormatterTest < ::Test::Unit::TestCase