resolves asciidoctor#3248 allow encoding of include file to be specified using encoding attribute

Author: mojavelinux

CHANGELOG.adoc

@@ -35,6 +35,7 @@ Improvements::
 
   * Preserve guard around XML-style callout when icons are not enabled (#3319)
   * Remove redundant test for halign and valign attributes on table cell in DocBook converter
+  * Allow encoding of include file to be specified using encoding attribute (#3248)
 
 Build / Infrastructure::
 

lib/asciidoctor/reader.rb

@@ -1060,6 +1060,11 @@ def preprocess_include_directive target, attrlist
         return inc_path
       end
 
+      if (enc = parsed_attrs['encoding']) && (::Encoding.find enc rescue nil)
+        (read_mode_params = read_mode.split ':')[1] = enc
+        read_mode = read_mode_params.join ':'
+      end unless RUBY_ENGINE_OPAL
+
       inc_linenos = inc_tags = nil
       if attrlist
         if parsed_attrs.key? 'lines'

test/fixtures/iso-8859-1.txt

@@ -0,0 +1 @@
+O� est l'h�pital ?

test/reader_test.rb

@@ -730,6 +730,47 @@ class ReaderTest < Minitest::Test
         assert_equal ['last line'], doc.blocks[2].lines
       end
 
+      test 'should fail to read include file if not UTF-8 encoded and encoding is not specified' do
+        input = <<~'EOS'
+        ....
+        include::fixtures/iso-8859-1.txt[]
+        ....
+        EOS
+
+        assert_raises StandardError, 'invalid byte sequence in UTF-8' do
+          doc = document_from_string input, safe: :safe, base_dir: DIRNAME
+          assert_equal 1, doc.blocks.size
+          refute_equal ['Où est l\'hôpital ?'], doc.blocks[0].lines
+          doc.convert
+        end
+      end
+
+      test 'should ignore encoding attribute if value is not an valid encoding' do
+        input = <<~'EOS'
+        ....
+        include::fixtures/encoding.adoc[tag=romé,encoding=iso-1000-1]
+        ....
+        EOS
+
+        doc = document_from_string input, safe: :safe, base_dir: DIRNAME
+        assert_equal 1, doc.blocks.size
+        assert_equal doc.blocks[0].lines[0].encoding, Encoding::UTF_8
+        assert_equal ['Gregory Romé has written an AsciiDoc plugin for the Redmine project management application.'], doc.blocks[0].lines
+      end
+
+      test 'should use encoding specified by encoding attribute when reading include file' do
+        input = <<~'EOS'
+        ....
+        include::fixtures/iso-8859-1.txt[encoding=iso-8859-1]
+        ....
+        EOS
+
+        doc = document_from_string input, safe: :safe, base_dir: DIRNAME
+        assert_equal 1, doc.blocks.size
+        assert_equal doc.blocks[0].lines[0].encoding, Encoding::UTF_8
+        assert_equal ['Où est l\'hôpital ?'], doc.blocks[0].lines
+      end
+
       test 'unresolved target referenced by include directive is skipped when optional option is set' do
         input = <<~'EOS'
         include::fixtures/{no-such-file}[opts=optional]