Do not escape underscore inside preformat blocks

doc/utils/converters/lammpsdoc/txt2rst.py

@@ -73,10 +73,13 @@ class RSTMarkup(Markup):
     def unescape_rst_chars(self, text):
         text = text.replace('\\*', '*')
         text = text.replace('\\^', '^')
-        text = text.replace('\\_', '_')
+        text = self.unescape_underscore(text)
         text = text.replace('\\|', '|')
         return text
 
+    def unescape_underscore(self, text):
+        return text.replace('\\_', '_')
+
     def inline_math(self, text):
         start_pos = text.find("\\(")
         end_pos = text.find("\\)")
@@ -136,6 +139,7 @@ class RSTFormatting(Formatting):
         return content.strip()
 
     def preformat(self, content):
+        content = self.markup.unescape_underscore(content)
         if self.indent_level > 0:
             return self.list_indent("\n.. parsed-literal::\n\n" + self.indent(content.rstrip()), self.indent_level)
         return "\n.. parsed-literal::\n\n" + self.indent(content.rstrip())

doc/utils/converters/tests/test_txt2rst.py

@@ -169,6 +169,13 @@ class TestFormatting(unittest.TestCase):
                          "       Hello\n"
                          "       World\n\n", s)
 
+    def test_preformat_formatting_with_underscore(self):
+        s = self.txt2rst.convert("if MPI.COMM_WORLD.rank == 0:\n"
+                                 "    print(\"Potential energy: \", L.eval(\"pe\")) :pre\n")
+        self.assertEqual("\n.. parsed-literal::\n\n"
+                         "   if MPI.COMM_WORLD.rank == 0:\n"
+                         "       print(\"Potential energy: \", L.eval(\"pe\"))\n\n", s)
+
     def test_header_formatting(self):
         s = self.txt2rst.convert("Level 1 :h1\n"
                                  "Level 2 :h2\n"