Add support for compound file extensions.

Created a new class ReaderTree that is an infinitely
nested defaultdict containing components of the extension.
See comments on PR getpelican#2816.

Author: holden-nelson

Diff for: pelican/readers.py

@@ -2,10 +2,12 @@
 import logging
 import os
 import re
-from collections import OrderedDict
+from collections import OrderedDict, defaultdict
 from html import escape
 from html.parser import HTMLParser
 from io import StringIO
+from functools import reduce
+import operator
 
 import docutils
 import docutils.core
@@ -496,8 +498,8 @@ class Readers(FileStampDataCacher):
 
     def __init__(self, settings=None, cache_name=''):
         self.settings = settings or {}
-        self.readers = {}
-        self.reader_classes = {}
+        self.readers = ReaderTree()
+        self.reader_classes = ReaderTree()
 
         for cls in [BaseReader] + BaseReader.__subclasses__():
             if not cls.enabled:
@@ -542,8 +544,7 @@ def read_file(self, base_path, path, content_class=Page, fmt=None,
             source_path, content_class.__name__)
 
         if not fmt:
-            _, ext = os.path.splitext(os.path.basename(path))
-            fmt = ext[1:]
+            fmt = self.readers.get_format(path)
 
         if fmt not in self.readers:
             raise TypeError(
@@ -746,3 +747,152 @@ def parse_path_metadata(source_path, settings=None, process=None):
                                 v = process(k, v)
                             metadata[k] = v
     return metadata
+
+
+class ReaderTree():
+
+    def __init__(self):
+        self.tree_dd = ReaderTree._rec_dd()
+
+    def __str__(self):
+        return str(ReaderTree._rec_dd_to_dict(self.tree_dd))
+
+    def __iter__(self):
+        for key in ReaderTree._rec_get_next_key(self.tree_dd):
+            yield key
+
+    def __setitem__(self, key, value):
+        components = reversed(key.split('.'))
+        reduce(operator.getitem, components, self.tree_dd)[''] = value
+
+    def __getitem__(self, key):
+        components = reversed(key.split('.'))
+        value = reduce(operator.getitem, components, self.tree_dd)
+        if value:
+            return value['']
+        else:
+            raise KeyError
+
+    def __delitem__(self, key):
+        value = ReaderTree._rec_del_item(self.tree_dd, key)
+        if not value:
+            raise KeyError
+
+    def __contains__(self, item):
+        try:
+            self[item]
+            return True
+        except KeyError:
+            return False
+
+    def __len__(self):
+        return len(list(self.keys()))
+
+    def keys(self):
+        return self.__iter__()
+
+    def values(self):
+        for value in ReaderTree._rec_get_next_value(self.tree_dd):
+            yield value
+
+    def items(self):
+        return zip(self.keys(), self.values())
+
+    def get(self, key):
+        return self[key]
+
+    def setdefault(self, key, value):
+        if key in self:
+            return self[key]
+        else:
+            self[key] = value
+            return value
+
+    def clear(self):
+        self.tree_dd.clear()
+
+    def pop(self, key, default=None):
+        if key in self:
+            value = self[key]
+            del self[key]
+            return value
+        elif default:
+            return default
+        else:
+            raise KeyError
+
+    def copy(self):
+        return self.tree_dd.copy()
+
+    def update(self, d):
+        for key, value in d.items():
+            self[key] = value
+
+    def get_format(self, filename):
+        ext = ReaderTree._rec_get_fmt_from_filename(self.tree_dd, filename)
+        return ext[1:]
+
+    def as_dict(self):
+        return ReaderTree._rec_dd_to_dict(self.tree_dd)
+
+    @staticmethod
+    def _rec_dd():
+        return defaultdict(ReaderTree._rec_dd)
+
+    @staticmethod
+    def _rec_dd_to_dict(dd):
+        d = dict(dd)
+
+        for key, value in d.items():
+            if type(value) == defaultdict:
+                d[key] = ReaderTree._rec_dd_to_dict(value)
+
+        return d
+
+    @staticmethod
+    def _rec_get_next_key(d):
+        for key in d:
+            if key != '':
+                if '' in d[key]:
+                    yield key
+                if type(d[key]) == defaultdict:
+                    for component in ReaderTree._rec_get_next_key(d[key]):
+                        yield '.'.join([component, key])
+
+    @staticmethod
+    def _rec_get_next_value(d):
+        for key, value in d.items():
+            if key == '':
+                yield value
+            else:
+                if type(d[key]) == defaultdict:
+                    yield from ReaderTree._rec_get_next_value(d[key])
+
+    @staticmethod
+    def _rec_del_item(d, intended_key):
+        if intended_key in d:
+            value = d[intended_key]['']
+            del d[intended_key]['']
+            return value
+        else:
+            for key in d:
+                if type(d[key]) == defaultdict:
+                    ReaderTree._rec_del_item(d[key], intended_key)
+
+        return None
+
+    @staticmethod
+    def _rec_get_fmt_from_filename(d, filename):
+        if '.' in filename:
+            file, ext = os.path.splitext(filename)
+            fmt = ext[1:]
+
+            if fmt in d:
+                next_component = ReaderTree._rec_get_fmt_from_filename(d[fmt], file)
+                return '.'.join([next_component, fmt])
+            elif '' in d:
+                return fmt
+            else:
+                raise TypeError("No valid extension found")
+        else:
+            return ''

Diff for: pelican/tests/test_readers.py

@@ -1,5 +1,5 @@
 import os
-from unittest.mock import patch
+from unittest.mock import patch, Mock
 
 from pelican import readers
 from pelican.tests.support import get_settings, unittest
@@ -76,6 +76,18 @@ def test_readfile_unknown_extension(self):
         with self.assertRaises(TypeError):
             self.read_file(path='article_with_metadata.unknownextension')
 
+        with self.assertRaises(TypeError):
+            self.read_file(path='article_with.compound.extension')
+
+    def test_readfile_compound_extension(self):
+        CompoundReader = Mock()
+
+        # throws type error b/c of mock
+        with self.assertRaises(TypeError):
+            self.read_file(path='article_with.compound.extension',
+                           READERS={'compound.extension': CompoundReader})
+            CompoundReader.read.assert_called_with('article_with.compound.extension')
+
     def test_readfile_path_metadata_implicit_dates(self):
         test_file = 'article_with_metadata_implicit_dates.html'
         page = self.read_file(path=test_file, DEFAULT_DATE='fs')
@@ -918,3 +930,72 @@ def test_article_with_inline_svg(self):
             'title': 'Article with an inline SVG',
         }
         self.assertDictHasSubset(page.metadata, expected)
+
+
+class ReaderTreeTest(unittest.TestCase):
+
+    def setUp(self):
+
+        readers_and_exts = {
+            'BaseReader': ['static'],
+            'RstReader': ['rst'],
+            'HtmlReader': ['htm', 'html'],
+            'MDReader': ['md', 'mk', 'mkdown', 'mkd'],
+            'MDeepReader': ['md.html'],
+            'FooReader': ['foo.bar.baz.yaz']
+        }
+
+        self.reader_classes = readers.ReaderTree()
+
+        for reader, exts in readers_and_exts.items():
+            for ext in exts:
+                self.reader_classes[ext] = reader
+
+    def test_correct_mapping_generated(self):
+        expected_mapping = {
+            'static': {'': 'BaseReader'},
+            'rst': {'': 'RstReader'},
+            'htm': {'': 'HtmlReader'},
+            'html': {
+                '': 'HtmlReader',
+                'md': {'': 'MDeepReader'}
+            },
+            'md': {'': 'MDReader'},
+            'mk': {'': 'MDReader'},
+            'mkdown': {'': 'MDReader'},
+            'mkd': {'': 'MDReader'},
+            'yaz': {
+                'baz': {
+                    'bar': {
+                        'foo': {'': 'FooReader'}}}}}
+
+        self.assertEqual(expected_mapping, self.reader_classes.as_dict())
+
+    def test_containment(self):
+        self.assertTrue('md.html' in self.reader_classes)
+        self.assertTrue('html' in self.reader_classes)
+        self.assertFalse('txt' in self.reader_classes)
+
+    def test_deletion(self):
+        self.assertTrue('rst' in self.reader_classes)
+        del self.reader_classes['rst']
+        self.assertFalse('rst' in self.reader_classes)
+
+    def test_update(self):
+        self.reader_classes.update({
+            'new.ext': 'NewExtReader',
+            'txt': 'TxtReader'
+        })
+        self.assertEqual(self.reader_classes['new.ext'], 'NewExtReader')
+        self.assertEqual(self.reader_classes['txt'], 'TxtReader')
+
+    def test_get_format(self):
+        html_ext = self.reader_classes.get_format('text.html')
+        md_ext = self.reader_classes.get_format('another.md')
+        compound_ext = self.reader_classes.get_format('compound.md.html')
+        no_ext = self.reader_classes.get_format('no_extension')
+
+        self.assertEqual(html_ext, 'html')
+        self.assertEqual(md_ext, 'md')
+        self.assertEqual(compound_ext, 'md.html')
+        self.assertEqual(no_ext, '')