resolves #3940 fix crash when resolving next value in sequence for non-numeric counter (PR #4003)

3 files changed, 102 insertions, 18 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index dbd8274c..fef21bb6 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -17,7 +17,8 @@ For a detailed view of what has changed, refer to the {uri-repo}/commits/master[
 
 Bug Fixes::
 
-  * Don't allow counter and counter2 directives in attribute reference to override locked attributes (#3939)
+  * Don't allow counter and counter2 attribute directives to override locked attributes (#3939)
+  * Fix crash when resolving next value in sequence for counter with non-numeric value (#3940)
   * Update default stylesheet to remove dash in front of cite on nested quote block (#3847)
   * Don't escape hyphen in manname in manpage output
   * Remove extra .sp before content of verse block in manpage output
diff --git a/lib/asciidoctor/helpers.rb b/lib/asciidoctor/helpers.rb
index fb56bd4d..789cafe0 100644
--- a/lib/asciidoctor/helpers.rb
+++ b/lib/asciidoctor/helpers.rb
@@ -274,13 +274,10 @@ module Helpers
   def nextval current
     if ::Integer === current
       current + 1
+    elsif (intval = current.to_i).to_s == current.to_s
+      intval + 1
     else
-      intval = current.to_i
-      if intval.to_s != current.to_s
-        (current[0].ord + 1).chr
-      else
-        intval + 1
-      end
+      current.succ
     end
   end
 
diff --git a/test/attributes_test.rb b/test/attributes_test.rb
index be4f744e..d1c44e19 100644
--- a/test/attributes_test.rb
+++ b/test/attributes_test.rb
@@ -1032,34 +1032,120 @@ context 'Attributes' do
       assert_equal 'A', doc.attributes['mycounter']
     end
 
-    test 'increments counter with numeric value' do
+    test 'can seed counter to start at 1' do
       input = <<~'EOS'
-      :mycounter: 1
+      :mycounter: 0
 
       {counter:mycounter}
+      EOS
+
+      output = convert_string_to_embedded input
+      assert_xpath '//p[text()="1"]', output, 1
+    end
+
+    test 'can seed counter to start at A' do
+      input = <<~'EOS'
+      :mycounter: @
+
+      {counter:mycounter}
+      EOS
+
+      output = convert_string_to_embedded input
+      assert_xpath '//p[text()="A"]', output, 1
+    end
 
+    test 'increments counter with positive numeric value' do
+      input = <<~'EOS'
+      [subs=attributes]
+      ++++
+      {counter:mycounter:1}
+      {counter:mycounter}
+      {counter:mycounter}
       {mycounter}
+      ++++
       EOS
 
-      doc = document_from_string input
+      doc = document_from_string input, standalone: false
       output = doc.convert
-      assert_equal 2, doc.attributes['mycounter']
-      assert_xpath '//p[text()="2"]', output, 2
+      assert_equal 3, doc.attributes['mycounter']
+      assert_equal %w(1 2 3 3), output.lines.map {|l| l.rstrip }
     end
 
-    test 'increments counter with character value' do
+    test 'increments counter with negative numeric value' do
       input = <<~'EOS'
-      :mycounter: @
+      [subs=attributes]
+      ++++
+      {counter:mycounter:-2}
+      {counter:mycounter}
+      {counter:mycounter}
+      {mycounter}
+      ++++
+      EOS
+
+      doc = document_from_string input, standalone: false
+      output = doc.convert
+      assert_equal 0, doc.attributes['mycounter']
+      assert_equal %w(-2 -1 0 0), output.lines.map {|l| l.rstrip }
+    end
 
+    test 'increments counter with ASCII character value' do
+      input = <<~'EOS'
+      [subs=attributes]
+      ++++
+      {counter:mycounter:A}
       {counter:mycounter}
+      {counter:mycounter}
+      {mycounter}
+      ++++
+      EOS
+
+      output = convert_string_to_embedded input
+      assert_equal %w(A B C C), output.lines.map {|l| l.rstrip }
+    end
 
+    test 'increments counter with non-ASCII character value' do
+      input = <<~'EOS'
+      [subs=attributes]
+      ++++
+      {counter:mycounter:é}
+      {counter:mycounter}
+      {counter:mycounter}
       {mycounter}
+      ++++
       EOS
 
-      doc = document_from_string input
-      output = doc.convert
-      assert_equal 'A', doc.attributes['mycounter']
-      assert_xpath '//p[text()="A"]', output, 2
+      output = convert_string_to_embedded input
+      assert_equal %w(é ê ë ë), output.lines.map {|l| l.rstrip }
+    end
+
+    test 'increments counter with emoji character value' do
+      input = <<~'EOS'
+      [subs=attributes]
+      ++++
+      {counter:smiley:😋}
+      {counter:smiley}
+      {counter:smiley}
+      {smiley}
+      ++++
+      EOS
+
+      output = convert_string_to_embedded input
+      assert_equal %w(😋 😌 😍 😍), output.lines.map {|l| l.rstrip }
+    end
+
+    test 'increments counter with multi-character value' do
+      input = <<~'EOS'
+      [subs=attributes]
+      ++++
+      {counter:math:1x}
+      {counter:math}
+      {counter:math}
+      {math}
+      ++++
+      EOS
+
+      output = convert_string_to_embedded input
+      assert_equal %w(1x 1y 1z 1z), output.lines.map {|l| l.rstrip }
     end
 
     test 'counter uses 0 as seed value if seed attribute is nil' do