Issue 28128: Print out better error/warning messages for invalid string escapes. Backport to 3.6.

1 files changed, 61 insertions, 5 deletions

diff --git a/Python/ast.c b/Python/ast.c
index 76daf6f..91e7d01 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -4113,8 +4113,34 @@ decode_utf8(struct compiling *c, const char **sPtr, const char *end)
     return PyUnicode_DecodeUTF8(t, s - t, NULL);
 }
 
+static int
+warn_invalid_escape_sequence(struct compiling *c, const node *n,
+                             char first_invalid_escape_char)
+{
+    PyObject *msg = PyUnicode_FromFormat("invalid escape sequence \\%c",
+                                         first_invalid_escape_char);
+    if (msg == NULL) {
+        return -1;
+    }
+    if (PyErr_WarnExplicitObject(PyExc_DeprecationWarning, msg,
+                                   c->c_filename, LINENO(n),
+                                   NULL, NULL) < 0 &&
+        PyErr_ExceptionMatches(PyExc_DeprecationWarning))
+    {
+        const char *s = PyUnicode_AsUTF8(msg);
+        if (s != NULL) {
+            ast_error(c, n, s);
+        }
+        Py_DECREF(msg);
+        return -1;
+    }
+    Py_DECREF(msg);
+    return 0;
+}
+
 static PyObject *
-decode_unicode_with_escapes(struct compiling *c, const char *s, size_t len)
+decode_unicode_with_escapes(struct compiling *c, const node *n, const char *s,
+                            size_t len)
 {
     PyObject *v, *u;
     char *buf;
@@ -4167,11 +4193,41 @@ decode_unicode_with_escapes(struct compiling *c, const char *s, size_t len)
     len = p - buf;
     s = buf;
 
-    v = PyUnicode_DecodeUnicodeEscape(s, len, NULL);
+    const char *first_invalid_escape;
+    v = _PyUnicode_DecodeUnicodeEscape(s, len, NULL, &first_invalid_escape);
+
+    if (v != NULL && first_invalid_escape != NULL) {
+        if (warn_invalid_escape_sequence(c, n, *first_invalid_escape) < 0) {
+            /* We have not decref u before because first_invalid_escape points
+               inside u. */
+            Py_XDECREF(u);
+            Py_DECREF(v);
+            return NULL;
+        }
+    }
     Py_XDECREF(u);
     return v;
 }
 
+static PyObject *
+decode_bytes_with_escapes(struct compiling *c, const node *n, const char *s,
+                          size_t len)
+{
+    const char *first_invalid_escape;
+    PyObject *result = _PyBytes_DecodeEscape(s, len, NULL, 0, NULL,
+                                             &first_invalid_escape);
+    if (result == NULL)
+        return NULL;
+
+    if (first_invalid_escape != NULL) {
+        if (warn_invalid_escape_sequence(c, n, *first_invalid_escape) < 0) {
+            Py_DECREF(result);
+            return NULL;
+        }
+    }
+    return result;
+}
+
 /* Compile this expression in to an expr_ty.  Add parens around the
    expression, in order to allow leading spaces in the expression. */
 static expr_ty
@@ -4310,7 +4366,7 @@ done:
                                                     literal_end-literal_start,
                                                     NULL, NULL);
         else
-            *literal = decode_unicode_with_escapes(c, literal_start,
+            *literal = decode_unicode_with_escapes(c, n, literal_start,
                                                    literal_end-literal_start);
         if (!*literal)
             return -1;
@@ -5048,12 +5104,12 @@ parsestr(struct compiling *c, const node *n, int *bytesmode, int *rawmode,
         if (*rawmode)
             *result = PyBytes_FromStringAndSize(s, len);
         else
-            *result = PyBytes_DecodeEscape(s, len, NULL, /* ignored */ 0, NULL);
+            *result = decode_bytes_with_escapes(c, n, s, len);
     } else {
         if (*rawmode)
             *result = PyUnicode_DecodeUTF8Stateful(s, len, NULL, NULL);
         else
-            *result = decode_unicode_with_escapes(c, s, len);
+            *result = decode_unicode_with_escapes(c, n, s, len);
     }
     return *result == NULL ? -1 : 0;
 }