resolve #4046 change ifeval directive to resolve to false if comparison operation cannot be performed (PR #4047)

3 files changed, 37 insertions, 4 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 47acdedd..a472b3e3 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -20,6 +20,7 @@ This project utilizes semantic versioning.
 Bug Fixes::
 
   * Include all lines outside of specified tagged region when tag filter on include directive is a single negated tag (#4048)
+  * Change ifeval directive to resolve to false if comparison operation cannot be performed (#4046)
   * Update default stylesheet to indent blocks attached to list item in checklist (#2550)
   * Update default stylesheet to reenable styling of implicit lead role on first paragraph of preamble inside AsciiDoc table cell
 
diff --git a/lib/asciidoctor/reader.rb b/lib/asciidoctor/reader.rb
index 103644f1..3a35ef19 100644
--- a/lib/asciidoctor/reader.rb
+++ b/lib/asciidoctor/reader.rb
@@ -961,11 +961,11 @@ class PreprocessorReader < Reader
         if no_target
           # the text in brackets must match a conditional expression
           if text && EvalExpressionRx =~ text.strip
-            lhs = $1
-            op = $2
-            rhs = $3
+            lhs = resolve_expr_val $1
             # regex enforces a restricted set of math-related operations (==, !=, <=, >=, <, >)
-            skip = ((resolve_expr_val lhs).send op, (resolve_expr_val rhs)) ? false : true
+            op = $2
+            rhs = resolve_expr_val $3
+            skip = (lhs.send op, rhs) ? false : true rescue true
           else
             logger.error message_with_context %(malformed preprocessor directive - #{text ? 'invalid expression' : 'missing expression'}: ifeval::[#{text}]), source_location: cursor
             return true
diff --git a/test/reader_test.rb b/test/reader_test.rb
index 985a3361..cf566ea1 100644
--- a/test/reader_test.rb
+++ b/test/reader_test.rb
@@ -2267,6 +2267,38 @@ class ReaderTest < Minitest::Test
         assert_equal '', (lines * ::Asciidoctor::LF)
       end
 
+      test 'ifeval running unsupported operation on missing attribute drops content' do
+        input = <<~'EOS'
+        ifeval::[{leveloffset} >= 3]
+        I didn't make the cut!
+        endif::[]
+        EOS
+
+        doc = Asciidoctor::Document.new input
+        reader = doc.reader
+        lines = []
+        while reader.has_more_lines?
+          lines << reader.read_line
+        end
+        assert_equal '', (lines * ::Asciidoctor::LF)
+      end
+
+      test 'ifeval running invalid operation drops content' do
+        input = <<~'EOS'
+        ifeval::[{asciidoctor-version} > true]
+        I didn't make the cut!
+        endif::[]
+        EOS
+
+        doc = Asciidoctor::Document.new input
+        reader = doc.reader
+        lines = []
+        while reader.has_more_lines?
+          lines << reader.read_line
+        end
+        assert_equal '', (lines * ::Asciidoctor::LF)
+      end
+
       test 'ifeval comparing double-quoted attribute to matching string includes content' do
         input = <<~'EOS'
         ifeval::["{gem}" == "asciidoctor"]