replace invalid sequences with ?

Author: as-op

app/services/import/jira_wiki_markup/parser.rb

@@ -50,7 +50,7 @@ def initialize(text)
         # and invalid byte sequences are dropped so downstream regex/StringScanner
         # operations cannot raise ArgumentError on malformed input.
         @text = text.to_s.dup
-        @text.scrub!("") unless @text.valid_encoding?
+        @text.scrub!("?") unless @text.valid_encoding?
       end
 
       def parse

spec/services/import/jira_wiki_markup_converter_spec.rb

@@ -56,31 +56,31 @@
       it "drops a stray invalid byte and keeps the surrounding text" do
         input = "Hello \xFF world".dup
         expect(input.valid_encoding?).to be(false)
-        expect(described_class.new(input).convert).to eq("Hello  world")
+        expect(described_class.new(input).convert).to eq("Hello ? world")
       end
 
       it "drops a stray continuation byte" do
         input = "abc \x80 def".dup
         expect(input.valid_encoding?).to be(false)
-        expect(described_class.new(input).convert).to eq("abc  def")
+        expect(described_class.new(input).convert).to eq("abc ? def")
       end
 
       it "drops a truncated multi-byte sequence" do
         input = "pre \xC3 post".dup
         expect(input.valid_encoding?).to be(false)
-        expect(described_class.new(input).convert).to eq("pre  post")
+        expect(described_class.new(input).convert).to eq("pre ? post")
       end
 
       it "preserves valid multi-byte characters while dropping only the invalid byte" do
         input = "héllo \xFF world".dup
         expect(input.valid_encoding?).to be(false)
-        expect(described_class.new(input).convert).to eq("héllo  world")
+        expect(described_class.new(input).convert).to eq("héllo ? world")
       end
 
       it "still parses formatting around invalid bytes inside delimiters" do
         input = "*bold\xFFtext*".dup
         expect(input.valid_encoding?).to be(false)
-        expect(described_class.new(input).convert).to eq("**boldtext**")
+        expect(described_class.new(input).convert).to eq("**bold?text**")
       end
     end
   end