moved writers.get_writer_class to generic utils.get_entry_point

git-svn-id: http://svn.code.sf.net/p/docutils/code/branches/plugins@4973 929543f6-e4f2-0310-98a6-ba3bd3dd1d04

3 files changed, 33 insertions, 26 deletions

diff --git a/docutils/core.py b/docutils/core.py
index f68f74cea..8c6baa80e 100644
--- a/docutils/core.py
+++ b/docutils/core.py
@@ -82,7 +82,7 @@ class Publisher:
 
     def set_writer(self, writer_name):
         """Set `self.writer` by name."""
-        writer_class = writers.get_writer_class(writer_name)
+        writer_class = utils.get_entry_point('docutils.writers', writer_name)
         self.writer = writer_class()
 
     def set_components(self, reader_name, parser_name, writer_name):
diff --git a/docutils/utils.py b/docutils/utils.py
index ce9d2868e..139efbe1b 100644
--- a/docutils/utils.py
+++ b/docutils/utils.py
@@ -15,10 +15,10 @@ import types
 import warnings
 import unicodedata
 from types import StringType, UnicodeType
+import pkg_resources
 from docutils import ApplicationError, DataError
 from docutils import nodes
 
-
 class SystemMessage(ApplicationError):
 
     def __init__(self, system_message, level):
@@ -577,3 +577,33 @@ class DependencyList:
         else:
             output_file = None
         return '%s(%r, %s)' % (self.__class__.__name__, output_file, self.list)
+
+
+class EntryPointNotFoundError(ApplicationError): pass
+class DuplicateEntryPointError(ApplicationError): pass
+
+def get_entry_point(group, name):
+    """
+    Load the entry point with name `name` in entry point group `group`
+    and return the associated Python object.  If no such entry point
+    is found, raise `EntryPointNotFoundError`.  If more than one entry
+    point is found, raise `DuplicateEntryPointError`.
+    """
+    entry_points = list(pkg_resources.iter_entry_points(group, name))
+    if not len(entry_points):
+        # Retrieving components used to be case-insensitive, but that's
+        # probably a bad idea.
+        if name != name.lower():
+            entry_point = get_entry_point(group, name.lower())
+            print >>sys.stderr, 'Warning: Entry point names are case-'\
+                  'sensitive; using lower-case name "%s.%s"' \
+                  % (group, name.lower())
+            return entry_point
+        else:
+            raise EntryPointNotFoundError(
+                'Entry point "%s.%s" not found.' % (group, name))
+    if len(entry_points) > 1:
+        raise DuplicateEntryPointError('More than one entry point "%s.%s" '
+                                       'installed on system.' % (group, name))
+    entry_point = entry_points[0]
+    return entry_point.load()
diff --git a/docutils/writers/__init__.py b/docutils/writers/__init__.py
index e2b15a74f..17d5e4d87 100644
--- a/docutils/writers/__init__.py
+++ b/docutils/writers/__init__.py
@@ -11,7 +11,7 @@ __docformat__ = 'reStructuredText'
 
 import os.path
 import docutils
-from docutils import languages, Component
+from docutils import languages, utils, Component
 from docutils.transforms import universal
 
 
@@ -113,26 +113,3 @@ class UnfilteredWriter(Writer):
         # later, the then-used writer will add the appropriate
         # transforms.
         return Component.get_transforms(self)
-
-
-_writer_aliases = {
-      'html': 'html4css1',
-      'latex': 'latex2e',
-      'pprint': 'pseudoxml',
-      'pformat': 'pseudoxml',
-      'pdf': 'rlpdf',
-      'xml': 'docutils_xml',
-      's5': 's5_html'}
-
-def get_writer_class(writer_name):
-    """Return the Writer class from the `writer_name` module."""
-    writer_name = writer_name.lower()
-    if _writer_aliases.has_key(writer_name):
-        writer_name = _writer_aliases[writer_name]
-    import pkg_resources
-    writer = None
-    for entrypoint in pkg_resources.iter_entry_points('docutils.writers'):
-        if entrypoint.name == writer_name:
-            writer = entrypoint.load()
-    assert writer is not None, 'writer "%s" not found' % writer_name
-    return writer