Test Loader: add the concept of test tags

Inside test classes there may docstrings which may contain tags that
give special meaning. The tags are defined by "🥑 <value>" in a
single line. For now the only two "official" Avocado tags values
exist:

 * enable: the class is an Avocado INSTRUMENTED test, even if it
   doesn't "look like" one.
 * disable: the class is *NOT* an Avocado INSTRUMENTED test, even if
   looks like one.

Changes from v0:
 * Use unittest2 on Python 2.6
Signed-off-by: NCleber Rosa <crosa@redhat.com>

avocado/core/loader.py

@@ -23,6 +23,7 @@ import fnmatch
 import imp
 import inspect
 import os
+import re
 import shlex
 import sys
 
@@ -39,6 +40,28 @@ AVAILABLE = None  # Available tests (for listing purposes)
 ALL = True  # All tests (inicluding broken ones)
 
 
+#: Gets the tag value from a string. Used to tag a test class in various ways
+AVOCADO_DOCSTRING_TAG_RE = re.compile(r'\s*:avocado:\s*(\S+)\s*')
+
+
+def get_docstring_tag(docstring):
+    if docstring is None:
+        return None
+    result = AVOCADO_DOCSTRING_TAG_RE.search(docstring)
+    if result is not None:
+        return result.groups()[0]
+
+
+def is_docstring_tag_enable(docstring):
+    result = get_docstring_tag(docstring)
+    return result == 'enable'
+
+
+def is_docstring_tag_disable(docstring):
+    result = get_docstring_tag(docstring)
+    return result == 'disable'
+
+
 class LoaderError(Exception):
 
     """ Loader exception """

selftests/unit/test_loader.py

 import os
+import re
 import sys
-import unittest
 import multiprocessing
 import tempfile
 import shutil
 
+if sys.version_info[:2] == (2, 6):
+    import unittest2 as unittest
+else:
+    import unittest
+
 from avocado.core import test
 from avocado.core import exceptions
 from avocado.core import loader
@@ -154,5 +159,32 @@ class LoaderTest(unittest.TestCase):
         avocado_multiple_tests.remove()
 
 
+class DocstringTagTests(unittest.TestCase):
+
+    def test_longline(self):
+        docstring = ("This is a very long docstring in a single line. "
+                     "Since we have nothing useful to put in here let's just "
+                     "mention avocado: it's awesome, but that was not a tag. "
+                     "a tag would be something line this: :avocado: enable")
+        self.assertIsNotNone(loader.get_docstring_tag(docstring))
+
+    def test_newlines(self):
+        docstring = ("\n\n\nThis is a docstring with many new\n\nlines "
+                     "followed by an avocado tag\n"
+                     "\n\n:avocado: enable\n\n")
+        self.assertIsNotNone(loader.get_docstring_tag(docstring))
+
+    def test_enabled(self):
+        self.assertTrue(loader.is_docstring_tag_enable(":avocado: enable"))
+        self.assertTrue(loader.is_docstring_tag_enable(":avocado:\tenable"))
+        self.assertFalse(loader.is_docstring_tag_enable(":AVOCADO: ENABLE"))
+        self.assertFalse(loader.is_docstring_tag_enable(":avocado: enabled"))
+
+    def test_disabled(self):
+        self.assertTrue(loader.is_docstring_tag_disable(":avocado: disable"))
+        self.assertTrue(loader.is_docstring_tag_disable(":avocado:\tdisable"))
+        self.assertFalse(loader.is_docstring_tag_disable(":AVOCADO: DISABLE"))
+        self.assertFalse(loader.is_docstring_tag_disable(":avocado: disabled"))
+
 if __name__ == '__main__':
     unittest.main()