Preserve # prefix for unresolved cross-references

When `#name` doesn't resolve to a method, the cross-reference handler
was stripping the `#` and returning just the name. Now the original
text including `#` is restored when the lookup fails.

This fixes rendering of text like `#no-space-heading` in Markdown
paragraphs, where the `#` was silently dropped in the final HTML.

Author: st0012

lib/rdoc/markup/to_html_crossref.rb

@@ -61,19 +61,25 @@ def init_link_notation_regexp_handlings
   def cross_reference(name, text = nil, code = true, rdoc_ref: false)
     lookup = name
 
-    name = name[1..-1] unless @show_hash if name[0, 1] == '#'
+    # Strip '#' from display text for method references (e.g. #method -> method),
+    # but only when @show_hash is false and only for link text, not for fallback.
+    display = !@show_hash && name.start_with?('#') ? name[1..] : name
 
-    if !name.end_with?('+@', '-@') && match = name.match(/(.*[^#:])?@(.*)/)
+    if !display.end_with?('+@', '-@') && match = display.match(/(.*[^#:])?@(.*)/)
       context_name = match[1]
       label = RDoc::Text.decode_legacy_label(match[2])
       text ||= "#{label} at <code>#{context_name}</code>" if context_name
       text ||= label
       code = false
     else
-      text ||= name
+      text ||= display
     end
 
-    link lookup, text, code, rdoc_ref: rdoc_ref
+    result = link lookup, text, code, rdoc_ref: rdoc_ref
+
+    # If the reference didn't resolve to a link, use the original name
+    # so the '#' prefix is preserved for unresolved references.
+    result == text && display != name ? name : result
   end
 
   ##

test/rdoc/markup/to_html_crossref_test.rb

@@ -435,6 +435,13 @@ def hyper(reference)
     "rdoc-ref:#{reference}"
   end
 
+  def test_handle_regexp_CROSSREF_hash_preserved_for_unresolved
+    @to.show_hash = false
+
+    # #no should not lose its '#' when it doesn't resolve to a method
+    assert_equal "#no", REGEXP_HANDLING('#no')
+  end
+
   def tidy(reference)
     "{tidy}[rdoc-ref:#{reference}]"
   end