gh-113785: csv: fields starting with escapechar are not quoted (GH-122110)

Author: MKuranowski

Lib/test/test_csv.py

@@ -454,6 +454,10 @@ def test_read_quoting(self):
                           quoting=csv.QUOTE_STRINGS)
         self._read_test(['1,@,3,@,5'], [['1', ',3,', '5']], quotechar='@')
         self._read_test(['1,\0,3,\0,5'], [['1', ',3,', '5']], quotechar='\0')
+        self._read_test(['1\\.5,\\.5,.5'], [[1.5, 0.5, 0.5]],
+                        quoting=csv.QUOTE_NONNUMERIC, escapechar='\\')
+        self._read_test(['1\\.5,\\.5,"\\.5"'], [[1.5, 0.5, ".5"]],
+                        quoting=csv.QUOTE_STRINGS, escapechar='\\')
 
     def test_read_skipinitialspace(self):
         self._read_test(['no space, space,  spaces,\ttab'],

Misc/NEWS.d/next/Library/2024-07-22-08-14-04.gh-issue-113785.6B_KNB.rst

@@ -0,0 +1 @@
+:mod:`csv` now correctly parses numeric fields (when used with :const:`csv.QUOTE_NONNUMERIC` or :const:`csv.QUOTE_STRINGS`) which start with an escape character.

Modules/_csv.c

@@ -749,7 +749,6 @@ parse_process_char(ReaderObj *self, _csvstate *module_state, Py_UCS4 c)
         }
         else if (c == dialect->escapechar) {
             /* possible escaped character */
-            self->unquoted_field = false;
             self->state = ESCAPED_CHAR;
         }
         else if (c == ' ' && dialect->skipinitialspace)