Issue #6676: Ensure a meaningful exception is raised when attempting

to parse more than one XML document per pyexpat xmlparser instance.
(Original patches by Hirokazu Yamamoto and Amaury Forgeot d'Arc, with
suggested wording by David Gutteridge)

4 files changed, 26 insertions, 2 deletions

diff --git a/Doc/library/pyexpat.rst b/Doc/library/pyexpat.rst
index 3d88d85d1cc..cb8ab65d644 100644
--- a/Doc/library/pyexpat.rst
+++ b/Doc/library/pyexpat.rst
@@ -100,6 +100,11 @@ The :mod:`xml.parsers.expat` module contains two functions:
       http://www.python.org/ns/ elem1
       elem2
 
+   Due to limitations in the ``Expat`` library used by :mod:`pyexpat`,
+   the :class:`xmlparser` instance returned can only be used to parse a single
+   XML document.  Call ``ParserCreate`` for each document to provide unique
+   parser instances.
+
 
 .. seealso::
 
@@ -119,7 +124,9 @@ XMLParser Objects
 
    Parses the contents of the string *data*, calling the appropriate handler
    functions to process the parsed data.  *isfinal* must be true on the final call
-   to this method.  *data* can be the empty string at any time.
+   to this method; it allows the parsing of a single file in fragments,
+   not the submission of multiple files.
+   *data* can be the empty string at any time.
 
 
 .. method:: xmlparser.ParseFile(file)
diff --git a/Lib/test/test_pyexpat.py b/Lib/test/test_pyexpat.py
index 8ef391791f7..95a614bb9b7 100644
--- a/Lib/test/test_pyexpat.py
+++ b/Lib/test/test_pyexpat.py
@@ -236,6 +236,18 @@ class ParseTest(unittest.TestCase):
         operations = out.out
         self._verify_parse_output(operations)
 
+    def test_parse_again(self):
+        parser = expat.ParserCreate()
+        file = BytesIO(data)
+        parser.ParseFile(file)
+        # Issue 6676: ensure a meaningful exception is raised when attempting
+        # to parse more than one XML document per xmlparser instance,
+        # a limitation of the Expat library.
+        with self.assertRaises(expat.error) as cm:
+            parser.ParseFile(file)
+        self.assertEqual(expat.ErrorString(cm.exception.code),
+                          expat.errors.XML_ERROR_FINISHED)
+
 class NamespaceSeparatorTest(unittest.TestCase):
     def test_legal(self):
         # Tests that make sure we get errors when the namespace_separator value
diff --git a/Misc/NEWS b/Misc/NEWS
index 10ddd9a4bbe..5240f6997ff 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -89,6 +89,11 @@ Library
 - Issue #20817: Fix inspect.getcallargs() to fail correctly if more
   than 3 arguments are missing. Patch by Jeremiah Lowin.
 
+- Issue #6676: Ensure a meaningful exception is raised when attempting
+  to parse more than one XML document per pyexpat xmlparser instance.
+  (Original patches by Hirokazu Yamamoto and Amaury Forgeot d'Arc, with
+  suggested wording by David Gutteridge)
+
 Documentation
 -------------
 
diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index a71ecc530e4..97f2b567717 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -908,7 +908,7 @@ xmlparse_ParseFile(xmlparseobject *self, PyObject *f)
         void *buf = XML_GetBuffer(self->itself, BUF_SIZE);
         if (buf == NULL) {
             Py_XDECREF(readmethod);
-            return PyErr_NoMemory();
+            return get_parse_result(self, 0);
         }
 
         bytes_read = readinst(buf, BUF_SIZE, readmethod);