reST rendering can fail for TracStandalone

[Ryan J Ollos]

Rendering WikiRestructuredText can fail with the following error in the log (comment:8:ticket:12245):

2013-07-17 17:30:05,613 Trac[api] WARNING: HTML preview using ReStructuredTextRenderer failed:
Traceback (most recent call last):
  File "/home/user/Workspace/t11245-2.7/teo-rjollos2.git/trac/mimeview/api.py", line 773, in render
    rendered_content, filename, url)
  File "/home/user/Workspace/t11245-2.7/teo-rjollos2.git/trac/mimeview/rst.py", line 278, in render
    'warning_stream': False})
  File "/home/user/Workspace/t11245-2.7/local/lib/python2.7/site-packages/docutils-0.10-py2.7.egg/docutils/core.py", line 448, in publish_parts
    enable_exit_status=enable_exit_status)
  File "/home/user/Workspace/t11245-2.7/local/lib/python2.7/site-packages/docutils-0.10-py2.7.egg/docutils/core.py", line 657, in publish_programmatically
    pub.set_components(reader_name, parser_name, writer_name)
  File "/home/user/Workspace/t11245-2.7/local/lib/python2.7/site-packages/docutils-0.10-py2.7.egg/docutils/core.py", line 93, in set_components
    self.set_reader(reader_name, self.parser, parser_name)
  File "/home/user/Workspace/t11245-2.7/local/lib/python2.7/site-packages/docutils-0.10-py2.7.egg/docutils/core.py", line 82, in set_reader
    reader_class = readers.get_reader_class(reader_name)
  File "/home/user/Workspace/t11245-2.7/local/lib/python2.7/site-packages/docutils-0.10-py2.7.egg/docutils/readers/__init__.py", line 113, in get_reader_class
    return module.Reader
AttributeError: 'module' object has no attribute 'Reader'

The problem is with line 110 in docutils/readers/__init__.py (DocUtils version 0.10):

module = __import__(reader_name, globals(), locals(), level=0)

Since by default the module name is specified as reader_name = 'standalone', this can result in the import of <module 'standalone' from './trac/web/standalone.pyc'>.

The issue can be resolved by explicitly specifying the default reader:

trac/mimeview/rst.py

@@ -29 +29 @@
     from docutils import nodes
     from docutils.core import publish_parts
     from docutils.parsers import rst
+    from docutils.readers import standalone
     from docutils import __version__
     has_docutils = True
 except ImportError:
@@ -270 +271 @@
         inliner.trac = (self.env, context)
         parser = rst.Parser(inliner=inliner)
         content = content_to_unicode(self.env, content, mimetype)
+        # Explicitly specifying the default Reader is a workaround for #11248
         parts = publish_parts(content, writer=writer, parser=parser,
+                              reader=standalone.Reader(parser),
                               settings_overrides={'halt_level': 6,
                                                   'warning_stream': False,
                                                   'file_insertion_enabled': 0,

The lastest DocUtils version is 0.10, released in ​December 2012. The issue has been fixed in ​[7646], ​[7648] but the fix has not yet been incorporated into a formal release, and we'd need to support earlier versions of DocUtils anyway, so I propose to apply the workaround in 1.0-stable.

[Jun Omae]

Trac 0.12-stable with docutils 0.10 has the same issue except Python 2.4. I think we should apply in 0.12-stable.

After the patch, it works. I verified with

	docutils	Python
0.12-stable	0.6 and 0.10	2.4 and 2.6
1.0-stable	0.6 and 0.10	2.6

[Ryan J Ollos]

Thanks for the feedback Jun.

Applied in [11851], merged to 1.0-stable in [11852] and merged to trunk in [11853].

Fixed a benign unrelated issue on 1.0-stable in [11854] and merged to trunk in [11855].

Coincidentally, ​Docutils 0.11 was released today.