Allow plugins to provide metadata

AUTHORS.txt

@@ -9,6 +9,7 @@ Aurelien Naldi <https://github.com/aurelien-naldi>
 Ben Mather <https://github.com/bwhmather>
 Boris Kaul <https://github.com/localvoid>
 Brandon W. Maister <https://github.com/quodlibetor>
+Bussonnier Matthias <https://gtihub.com/carreau>
 Carsten Grohmann <https://github.com/CarstenGrohmann>
 Casey M. Bessette <https://github.com/caseybessette>
 Chris Lee <https://github.com/clee>

CHANGES.txt

@@ -26,6 +26,7 @@ New in v7.3.0
 Features
 --------
 
+* Added possibility for plugins to define how to read metadata from files
 * Added ``-a``, ``--author`` option to set post author field
 * Added option INDEXES_PRETTY_PAGE_URL to make URLs for indexes
   pages more pretty. (Issue #1548)

docs/extending.txt

@@ -374,6 +374,10 @@ They must provide:
 If the compiler produces something other than HTML files, it should also implement ``extension`` which
 returns the preferred extension for the output file.
 
+These plugin can also be used to extract metadata from file. To do so, the
+plugin may implement ``read_metadata`` that will return a dict containing some
+metadata contained in the file.
+
 RestExtension Plugins
 ---------------------
 

nikola/plugin_categories.py

@@ -245,6 +245,12 @@ def extension(self):
         """The preferred extension for the output of this compiler."""
         return ".html"
 
+    def read_metadata(self, post, file_metadata_regexp=None, unslugify_titles=False, lang=None):
+        """
+        Read the metadata from a post, and return a metadata dict
+        """
+        return {}
+
 
 class RestExtension(BasePlugin):
     name = "dummy_rest_extension"

nikola/plugins/compile/ipynb/__init__.py

@@ -69,6 +69,19 @@ def compile_html(self, source, dest, is_two_file=True):
             (body, resources) = exportHtml.from_notebook_node(nb_json)
             out_file.write(body)
 
+    def read_metadata(self, post, file_metadata_regexp=None, unslugify_titles=False, lang=None):
+        """read metadata directly from ipynb file.
+
+        As ipynb file support arbitrary metadata as json, the metadata used by Nikola
+        will be assume to be in the 'nikola' subfield.
+        """
+        source = post.source_path
+        with io.open(source, "r", encoding="utf8") as in_file:
+            nb_json = nbformat.read(in_file, current_nbformat)
+        # metadata shoudl always exist, but we never know
+        # if Someone craft an ipynb by hand.
+        return nb_json.get('metadata', {}).get('nikola', {})
+
     def create_post(self, path, **kw):
         content = kw.pop('content', None)
         onefile = kw.pop('onefile', False)

nikola/post.py

@@ -917,8 +917,6 @@ def get_meta(post, file_metadata_regexp=None, unslugify_titles=False, lang=None)
     """
     meta = defaultdict(lambda: '')
 
-    newstylemeta = True
-
     try:
         config = post.config
     except AttributeError:
@@ -927,9 +925,8 @@ def get_meta(post, file_metadata_regexp=None, unslugify_titles=False, lang=None)
     _, newstylemeta = get_metadata_from_meta_file(post.metadata_path, config, lang)
     meta.update(_)
 
-    if meta:
-        return meta, newstylemeta
-    post.is_two_file = False
+    if not meta:
+        post.is_two_file = False
 
     if file_metadata_regexp is not None:
         meta.update(_get_metadata_from_filename_by_regex(post.source_path,
@@ -938,6 +935,10 @@ def get_meta(post, file_metadata_regexp=None, unslugify_titles=False, lang=None)
 
     meta.update(get_metadata_from_file(post.source_path, config, lang))
 
+    if getattr(post, 'compiler', None):
+        compiler_meta = post.compiler.read_metadata(post, file_metadata_regexp, unslugify_titles, lang)
+        meta.update(compiler_meta)
+
     if lang is None:
         # Only perform these checks for the default language
 

tests/test_rss_feeds.py

@@ -34,6 +34,9 @@ class FakeCompiler(object):
     compile_html = None
     extension = lambda self: '.html'
 
+    def read_metadata(*args, **kwargs):
+        return {}
+
     def register_extra_dependencies(self, post):
         pass