_elementtree import can fail silently

[naufraghi]

BPO	5779
Nosy	@naufraghi

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2009-04-17.09:40:09.744>
created_at = <Date 2009-04-17.09:35:08.872>
labels = ['expert-XML']
title = '_elementtree import can fail silently'
updated_at = <Date 2009-04-18.00:12:16.477>
user = 'https://github.com/naufraghi'

bugs.python.org fields:

activity = <Date 2009-04-18.00:12:16.477>
actor = 'benjamin.peterson'
assignee = 'none'
closed = True
closed_date = <Date 2009-04-17.09:40:09.744>
closer = 'naufraghi'
components = ['XML']
creation = <Date 2009-04-17.09:35:08.872>
creator = 'naufraghi'
dependencies = []
files = []
hgrepos = []
issue_num = 5779
keywords = []
message_count = 2.0
messages = ['86062', '86064']
nosy_count = 1.0
nosy_names = ['naufraghi']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue5779'
versions = []

[naufraghi]

(the patch is old, I forwarded it to Fredrik but I forgot to open the bug)

Playing with PyInstaller I have found that the final part of _elementtree.c:

Index: Modules/_elementtree.c
===================================================================
--- Modules/_elementtree.c (revisione 59540)
+++ Modules/_elementtree.c (copia locale)
@@ -2780,7 +2780,10 @@

    );

-    PyRun_String(bootstrap, Py_file_input, g, NULL);
+    if (PyRun_String(bootstrap, Py_file_input, g, NULL) == NULL) {
+        m = PyErr_Occurred();
+        return;
+    }

     elementpath_obj = PyDict_GetItemString(g, "ElementPath");

executes a bit of python code without checking the return value.
That can lead to weird things playing with import hooks,
for example an assert like this can fail:

Index: Lib/test/test_elemettree.py
===================================================================

--- Lib/test/test_elemettree.py (revisione 0)
+++ Lib/test/test_elemettree.py (revisione 0)
@@ -0,0 +1,21 @@
+#! /usr/bin/env python
+
+def importHook(*args, **kwargs):
+    if 'xml.etree' in args:
+        raise ImportError
+    else:
+        return __real__import__(*args, **kwargs)
+
+import os
+import __builtin__
+__real__import__ = __builtin__.__import__
+__builtin__.__import__ = importHook
+
+try:
+    import xml.etree.cElementTree as cET
+except ImportError:
+    pass
+else:
+    out = os.popen("python -c 'import xml.etree.cElementTree as cET;
print dir(cET)'").read().strip()
+    assert str(dir(cET)) == out, (str(dir(cET)), out)
+

Quite a novice with python internals, so comments are welcome.
Matteo Bertini

[naufraghi]

Ups, I duplicated myself... bpo-3475