Fix #3025 -- add METADATA_VALUE_MAPPING setting

Signed-off-by: Chris Warrick <kwpolska@gmail.com>
getnikola · Apr 14, 2018 · f4ee382 · f4ee382
1 parent c30320c
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Showing 6 changed files with 35 additions and 2 deletions.
diff --git a/CHANGES.txt b/CHANGES.txt
@@ -4,6 +4,8 @@ New in master
 Features
 --------
 
+* New ``METADATA_VALUE_MAPPING`` setting to allow for flexible global
+  modification of metadata (Issue #3025)
 * Recognize both TEASER_END and (new) END_TEASER (Issue #3010)
 * New MARKDOWN_EXTENSION_CONFIGS setting (Issue #2970)
 * Replace ``flowr.js`` with ``justified-layout.js`` by Flickr

diff --git a/docs/manual.rst b/docs/manual.rst
@@ -580,6 +580,18 @@ For Hugo, use:
 
 The following source names are supported: ``yaml``, ``toml``, ``rest_docinfo``, ``markdown_metadata``.
 
+Additionally, you can use ``METADATA_VALUE_MAPPING`` to perform any extra conversions on metadata for **all** posts of a given format (``nikola`` metadata is also supported). A few examples:
+
+.. code:: python
+
+    METADATA_VALUE_MAPPING = {
+        "yaml": {"keywords": lambda value: ', '.join(value)},  # yaml: 'keywords' list -> str
+        "nikola": {
+            "widgets": lambda value: value.split(', '),  # nikola: 'widgets' comma-separated string -> list
+            "tags": str.lower  # nikola: force lowercase 'tags' (input would be string)
+         }
+    }
+
 Multilingual posts
 ~~~~~~~~~~~~~~~~~~
 
@@ -1772,7 +1784,7 @@ to one of "disqus", "intensedebate", "livefyre", "moot", "facebook", "isso" or "
    * For isso, it is the URL of isso (must be world-accessible, encoded with
      Punycode (if using Internationalized Domain Names) and **have a trailing slash**,
      default ``http://localhost:8080/``)
-   * For commento it's the URL of the commento instance as required by the ``serverUrl`` 
+   * For commento it's the URL of the commento instance as required by the ``serverUrl``
      parameter in commento's documentation.
 
 To use comments in a visible site, you should register with the service and

diff --git a/nikola/conf.py.in b/nikola/conf.py.in
@@ -1179,6 +1179,19 @@ MARKDOWN_EXTENSIONS = ['markdown.extensions.fenced_code', 'markdown.extensions.c
 # }
 # Other examples: https://getnikola.com/handbook.html#mapping-metadata-from-other-formats
 
+# Map metadata between types/values. (Runs after METADATA_MAPPING.)
+# Supported formats: nikola, ${_METADATA_MAPPING_FORMATS}
+# The value on the right should be a dict of callables.
+# METADATA_VALUE_MAPPING = {}
+# Examples:
+# METADATA_VALUE_MAPPING = {
+#     "yaml": {"keywords": lambda value: ', '.join(value)},  # yaml: 'keywords' list -> str
+#     "nikola": {
+#         "widgets": lambda value: value.split(', '),  # nikola: 'widgets' comma-separated string -> list
+#         "tags": str.lower  # nikola: force lowercase 'tags' (input would be string)
+#      }
+# }
+
 # Additional metadata that is added to a post when creating a new_post
 # ADDITIONAL_METADATA = {}
 

diff --git a/nikola/metadata_extractors.py b/nikola/metadata_extractors.py
@@ -142,6 +142,7 @@ class NikolaMetadata(MetadataExtractor):
     supports_write = True
     split_metadata_re = re.compile('\n\n')
     nikola_re = re.compile(r'^\s*\.\. (.*?): (.*)')
+    map_from = 'nikola'  # advertised in values mapping only
 
     def _extract_metadata_from_text(self, source_text: str) -> dict:
         """Extract metadata from text."""

diff --git a/nikola/post.py b/nikola/post.py
@@ -973,6 +973,7 @@ def get_metadata_from_file(source_path, post, config, lang, metadata_extractors_
                 found_in_priority = True
                 used_extractor = extractor
                 # Map metadata from other platforms to names Nikola expects (Issue #2817)
+                # Map metadata values (Issue #3025)
                 map_metadata(new_meta, extractor.map_from, config)
 
                 meta.update(new_meta)

diff --git a/nikola/utils.py b/nikola/utils.py
@@ -1932,12 +1932,16 @@ def rss_writer(rss_obj, output_path):
 def map_metadata(meta, key, config):
     """Map metadata from other platforms to Nikola names.
 
-    This uses the METADATA_MAPPING setting (via ``config``) and modifies the dict in place.
+    This uses the METADATA_MAPPING and METADATA_VALUE_MAPPING settings (via ``config``) and modifies the dict in place.
     """
     for foreign, ours in config.get('METADATA_MAPPING', {}).get(key, {}).items():
         if foreign in meta:
             meta[ours] = meta[foreign]
 
+    for meta_key, hook in config.get('METADATA_VALUE_MAPPING', {}).get(key, {}).items():
+        if meta_key in meta:
+            meta[meta_key] = hook(meta[meta_key])
+
 
 class ClassificationTranslationManager(object):
     """Keeps track of which classifications could be translated as which others.