feat: return original eqn if invalid

Do not convert it partially

Author: navinkarkera

openedx/core/djangoapps/content/search/plain_text_math.py

@@ -8,7 +8,11 @@
 
 
 class InvalidMathEquation(Exception):
-    """Raised when converting mathjax equations to plain text fails"""
+    """Raised when mathjax equation is invalid. This is used to skip all transformations."""
+
+
+class EqnPatternNotFound(Exception):
+    """Raised when a pattern is not found in equation. This is used to skip a specific transformation."""
 
 
 class PlainTextMath:
@@ -58,7 +62,7 @@ def _nested_bracket_matcher(equation: str, opening_pattern: str) -> str:
         """
         start = equation.find(opening_pattern)
         if start == -1:
-            raise InvalidMathEquation()
+            raise EqnPatternNotFound()
         open_count = 0
         inner_start = start + len(opening_pattern)
         for i, char in enumerate(equation[inner_start:]):
@@ -88,7 +92,7 @@ def _fraction_handler(self, equation: str) -> str:
         """
         try:
             n_start, n_inner_start, n_inner_end, n_end = self._nested_bracket_matcher(equation, "\\frac{")
-        except InvalidMathEquation:
+        except EqnPatternNotFound:
             return equation
 
         numerator = equation[n_inner_start:n_inner_end]
@@ -97,7 +101,7 @@ def _fraction_handler(self, equation: str) -> str:
 
         try:
             _, d_inner_start, d_inner_end, d_end = self._nested_bracket_matcher(equation[n_end:], "{")
-        except InvalidMathEquation:
+        except EqnPatternNotFound:
             return equation
 
         denominator = equation[n_end + d_inner_start:n_end + d_inner_end]
@@ -116,7 +120,7 @@ def _nested_text_extractor(self, equation: str, pattern: str) -> str:
             inner_text = equation[inner_start:inner_end]
             inner_text = self._nested_text_extractor(inner_text, pattern)
             equation = equation[:start] + inner_text + equation[end:]
-        except InvalidMathEquation:
+        except EqnPatternNotFound:
             pass
         return equation
 
@@ -138,10 +142,15 @@ def run(self, eqn_matches: re.Match) -> str:
         """
         groups = eqn_matches.groups()
         for group in groups:
-            if group:
+            if not group:
+                continue
+            original = group
+            try:
                 group = self._handle_replacements(group)
                 group = self._fraction_handler(group)
                 return unicodeit.replace(group)
+            except Exception:  # pylint: disable=broad-except
+                return original
         return None
 
 

openedx/core/djangoapps/content/search/tests/test_documents.py

@@ -574,6 +574,11 @@ def test_mathjax_plain_text_conversion_for_search(self):
             ('Fraction error: \\( \\frac{2} \\)', 'Fraction error:  \\frac{2}'),
             ('Fraction error 2: \\( \\frac{\\frac{2}{3}{4} \\)', 'Fraction error 2:  \\frac{\\frac{2}{3}{4}'),
             ('Unclosed: [mathjaxinline]x^2', 'Unclosed: [mathjaxinline]x^2'),
+            (
+                'Missing closing bracket: \\( \\frac{\\frac{2} {3}{\\frac{4}{3}} \\)',
+                'Missing closing bracket:  \\frac{\\frac{2} {3}{\\frac{4}{3}}'
+            ),
+            ('No equation: normal text', 'No equation: normal text'),
         ]
         # pylint: enable=line-too-long
         block = BlockFactory.create(