bpo-43555: Report the column offset for invalid line continuation character

Author: pablogsal

Lib/test/test_syntax.py

@@ -1162,6 +1162,11 @@ def func2():
 """
         self._check_error(code, "expected ':'")
 
+    def test_invalid_line_continuation_error_position(self):
+        self._check_error(r"a = 3 \ 4",
+                          "unexpected character after line continuation character",
+                          lineno=1, offset=9)
+
     def test_invalid_line_continuation_left_recursive(self):
         # Check bpo-42218: SyntaxErrors following left-recursive rules
         # (t_primary_raw in this case) need to be tested explicitly

Misc/NEWS.d/next/Core and Builtins/2021-03-19-22-49-40.bpo-43555.ZmhYSA.rst

@@ -0,0 +1,2 @@
+Report the column offset for :exc:`SyntaxError` for invalid line
+continuation characters. Patch by Pablo Galindo.

Parser/pegen.c

@@ -324,6 +324,7 @@ tokenizer_error(Parser *p)
 
     const char *msg = NULL;
     PyObject* errtype = PyExc_SyntaxError;
+    Py_ssize_t col_offset = -1;
     switch (p->tok->done) {
         case E_TOKEN:
             msg = "invalid token";
@@ -355,16 +356,14 @@ tokenizer_error(Parser *p)
             msg = "too many levels of indentation";
             break;
         case E_LINECONT:
+            col_offset = strlen(strtok(p->tok->buf, "\n")) - 1;
             msg = "unexpected character after line continuation character";
             break;
         default:
             msg = "unknown parsing error";
     }
 
-    PyErr_Format(errtype, msg);
-    // There is no reliable column information for this error
-    PyErr_SyntaxLocationObject(p->tok->filename, p->tok->lineno, 0);
-
+    RAISE_ERROR_KNOWN_LOCATION(p, errtype, p->tok->lineno, col_offset, msg);
     return -1;
 }
 

Parser/pegen.h

@@ -136,8 +136,9 @@ void *_PyPegen_raise_error_known_location(Parser *p, PyObject *errtype,
 void *_PyPegen_dummy_name(Parser *p, ...);
 
 Py_LOCAL_INLINE(void *)
-RAISE_ERROR_KNOWN_LOCATION(Parser *p, PyObject *errtype, int lineno,
-                           int col_offset, const char *errmsg, ...)
+RAISE_ERROR_KNOWN_LOCATION(Parser *p, PyObject *errtype,
+                           Py_ssize_t lineno, Py_ssize_t col_offset,
+                           const char *errmsg, ...)
 {
     va_list va;
     va_start(va, errmsg);