Safely evaluate literals in case fstring check has been disbaled

Author: sambhav

src/pydocstyle/checker.py

@@ -2,8 +2,6 @@
 
 import ast
 import string
-import sys
-import textwrap
 import tokenize as tk
 from collections import namedtuple
 from itertools import chain, takewhile
@@ -28,8 +26,10 @@
 from .utils import (
     common_prefix_length,
     is_blank,
+    is_fstring,
     log,
     pairwise,
+    safe_literal_eval,
     strip_non_alphanumeric,
 )
 from .wordlists import IMPERATIVE_BLACKLIST, IMPERATIVE_VERBS, stem
@@ -46,14 +46,6 @@ def decorator(f):
     return decorator
 
 
-_FSTRING_REGEX = re(r'^[rR]?[fF]')
-
-
-def _is_fstring(docstring):
-    """Return True if docstring is an f-string."""
-    return _FSTRING_REGEX.match(str(docstring))
-
-
 class ConventionChecker:
     """Checker for PEP 257, NumPy and Google conventions.
 
@@ -201,7 +193,7 @@ def check_docstring_fstring(self, definition, docstring):
         and users may attempt to use them as docstrings. This is an
         outright mistake so we issue a specific error code.
         """
-        if _is_fstring(docstring):
+        if is_fstring(docstring):
             return violations.D303()
 
     @check_for(Definition, terminal=True)
@@ -222,7 +214,7 @@ def check_docstring_missing(self, definition, docstring):
             not docstring
             and definition.is_public
             or docstring
-            and is_blank(docstring, literal_eval=True)
+            and is_blank(safe_literal_eval(docstring))
         ):
             codes = {
                 Module: violations.D100,
@@ -252,7 +244,7 @@ def check_one_liners(self, definition, docstring):
 
         """
         if docstring:
-            lines = ast.literal_eval(docstring).split('\n')
+            lines = safe_literal_eval(docstring).split('\n')
             if len(lines) > 1:
                 non_empty_lines = sum(1 for l in lines if not is_blank(l))
                 if non_empty_lines == 1:
@@ -328,7 +320,7 @@ def check_blank_after_summary(self, definition, docstring):
 
         """
         if docstring:
-            lines = ast.literal_eval(docstring).strip().split('\n')
+            lines = safe_literal_eval(docstring).strip().split('\n')
             if len(lines) > 1:
                 post_summary_blanks = list(map(is_blank, lines[1:]))
                 blanks_count = sum(takewhile(bool, post_summary_blanks))
@@ -381,7 +373,7 @@ def check_newline_after_last_paragraph(self, definition, docstring):
         if docstring:
             lines = [
                 l
-                for l in ast.literal_eval(docstring).split('\n')
+                for l in safe_literal_eval(docstring).split('\n')
                 if not is_blank(l)
             ]
             if len(lines) > 1:
@@ -392,7 +384,7 @@ def check_newline_after_last_paragraph(self, definition, docstring):
     def check_surrounding_whitespaces(self, definition, docstring):
         """D210: No whitespaces allowed surrounding docstring text."""
         if docstring:
-            lines = ast.literal_eval(docstring).split('\n')
+            lines = safe_literal_eval(docstring).split('\n')
             if (
                 lines[0].startswith(' ')
                 or len(lines) == 1
@@ -420,7 +412,7 @@ def check_multi_line_summary_start(self, definition, docstring):
                 "ur'''",
             ]
 
-            lines = ast.literal_eval(docstring).split('\n')
+            lines = safe_literal_eval(docstring).split('\n')
             if len(lines) > 1:
                 first = docstring.split("\n")[0].strip().lower()
                 if first in start_triple:
@@ -442,7 +434,7 @@ def check_triple_double_quotes(self, definition, docstring):
 
         '''
         if docstring:
-            if '"""' in ast.literal_eval(docstring):
+            if '"""' in safe_literal_eval(docstring):
                 # Allow ''' quotes if docstring contains """, because
                 # otherwise """ quotes could not be expressed inside
                 # docstring. Not in PEP 257.
@@ -486,7 +478,7 @@ def _check_ends_with(docstring, chars, violation):
 
         """
         if docstring:
-            summary_line = ast.literal_eval(docstring).strip().split('\n')[0]
+            summary_line = safe_literal_eval(docstring).strip().split('\n')[0]
             if not summary_line.endswith(chars):
                 return violation(summary_line[-1])
 
@@ -521,7 +513,7 @@ def check_imperative_mood(self, function, docstring):  # def context
 
         """
         if docstring and not function.is_test:
-            stripped = ast.literal_eval(docstring).strip()
+            stripped = safe_literal_eval(docstring).strip()
             if stripped:
                 first_word = strip_non_alphanumeric(stripped.split()[0])
                 check_word = first_word.lower()
@@ -547,7 +539,7 @@ def check_no_signature(self, function, docstring):  # def context
 
         """
         if docstring:
-            first_line = ast.literal_eval(docstring).strip().split('\n')[0]
+            first_line = safe_literal_eval(docstring).strip().split('\n')[0]
             if function.name + '(' in first_line.replace(' ', ''):
                 return violations.D402()
 
@@ -559,7 +551,7 @@ def check_capitalized(self, function, docstring):
 
         """
         if docstring:
-            first_word = ast.literal_eval(docstring).split()[0]
+            first_word = safe_literal_eval(docstring).split()[0]
             if first_word == first_word.upper():
                 return
             for char in first_word:
@@ -579,7 +571,7 @@ def check_starts_with_this(self, function, docstring):
         if not docstring:
             return
 
-        stripped = ast.literal_eval(docstring).strip()
+        stripped = safe_literal_eval(docstring).strip()
         if not stripped:
             return
 

src/pydocstyle/utils.py

@@ -13,15 +13,8 @@
 NON_ALPHANUMERIC_STRIP_RE = re.compile(r'[\W_]+')
 
 
-def is_blank(string: str, literal_eval: bool = False) -> bool:
+def is_blank(string: str) -> bool:
     """Return True iff the string contains only whitespaces."""
-    if literal_eval:
-        try:
-            string = ast.literal_eval(string)
-        except ValueError:
-            # This happens in case of an fstring
-            # in which case let's return false
-            return False
     return not string.strip()
 
 
@@ -54,3 +47,24 @@ def common_prefix_length(a: str, b: str) -> int:
 def strip_non_alphanumeric(string: str) -> str:
     """Strip string from any non-alphanumeric characters."""
     return NON_ALPHANUMERIC_STRIP_RE.sub('', string)
+
+
+FSTRING_REGEX = re.compile(r'^([rR]?)[fF]')
+
+
+def is_fstring(docstring):
+    """Return True if docstring is an f-string."""
+    return FSTRING_REGEX.match(str(docstring))
+
+
+def safe_literal_eval(string):
+    """Safely evaluate a literal even if it is an fstring."""
+    try:
+        return ast.literal_eval(string)
+    except ValueError:
+        # In case we hit a value error due to an fstring
+        # we do a literal eval by subtituting the fstring
+        # with a normal string.
+        # We keep the first captured group if any. This includes
+        # the raw identifiers (r/R) and replace f/F with a blank.
+        return ast.literal_eval(FSTRING_REGEX.sub(r"\1", string))

src/tests/test_cases/fstrings.py

@@ -50,3 +50,8 @@ def fstring_with_other_errors(arg=1, missing_arg=2):
 @D303
 def fstring_with_blank_doc_string():
     f"""  """
+
+
+@expect("D103: Missing docstring in public function")
+def fstring_with_ignores():  # noqa: D303
+    f"""  """