[ruby/rdoc] Print warnings for rdoc-ref links that can't be resolved

(https://github.com/ruby/rdoc/pull/1241)

4a5206ae56

test/rdoc/test_rdoc_markup_to_html_crossref.rb

@@ -1,12 +1,13 @@
 # frozen_string_literal: true
 require_relative 'xref_test_case'
 
-class TestRDocMarkupToHtmlCrossref < XrefTestCase
+class RDocMarkupToHtmlCrossrefTest < XrefTestCase
 
   def setup
     super
 
     @options.hyperlink_all = true
+    @options.warn_missing_rdoc_ref = true
 
     @to = RDoc::Markup::ToHtmlCrossref.new @options, 'index.html', @c1
   end
@@ -67,6 +68,16 @@ class TestRDocMarkupToHtmlCrossref < XrefTestCase
     assert_equal para("<a href=\"C1.html\"><code>C1</code></a>"), result
   end
 
+  def test_convert_RDOCLINK_rdoc_ref_not_found
+    result = nil
+    stdout, _ = capture_output do
+      result = @to.convert 'rdoc-ref:FOO'
+    end
+
+    assert_equal para("FOO"), result
+    assert_include stdout, "index.html: `rdoc-ref:FOO` can't be resolved for `FOO`"
+  end
+
   def test_convert_RDOCLINK_rdoc_ref_method
     result = @to.convert 'rdoc-ref:C1#m'
 
@@ -153,6 +164,14 @@ class TestRDocMarkupToHtmlCrossref < XrefTestCase
                  @to.gen_url('http://example', 'HTTP example')
   end
 
+  def test_gen_url_rdoc_ref_not_found
+    stdout, _ = capture_output do
+      @to.gen_url 'rdoc-ref:FOO', 'FOO'
+    end
+
+    assert_include stdout, "index.html: `rdoc-ref:FOO` can't be resolved for `FOO`"
+  end
+
   def test_handle_regexp_CROSSREF
     assert_equal "<a href=\"C2/C3.html\"><code>C2::C3</code></a>", REGEXP_HANDLING('C2::C3')
   end