feat: use Query for children instead of Record list

examples/README.md

@@ -104,7 +104,7 @@ The built-in field attributes are:
 - `key`: slugified group value, e.g., "a-title"
 - `slug`: url path after root node, e.g. "config/a-title.html" (can be `None`)
 - `record`: parent node, e.g., `Page(path="/")`
-- `children`: the elements of the grouping (`Record` type)
+- `children`: the elements of the grouping (a `Query` of `Record` type)
 - `config`: configuration object (see below)
 
 Without any changes, the `key` value will just be `slugify(group)`.

examples/templates/example-advanced.html

@@ -1,4 +1,4 @@
 <h2>Path: {{ this | url(absolute=True) }}</h2>
 <p>This is: {{this}}</p>
 <p>Custom field, desc: "{{this.desc}}"</p>
-<p>Children: {{this.children}}</p>
+<p>Children: {{this.children.all()}}</p>

lektor_groupby/query.py

@@ -0,0 +1,72 @@
+# adapting https://github.com/dairiki/lektorlib/blob/master/lektorlib/query.py
+from lektor.constants import PRIMARY_ALT
+from lektor.db import Query  # subclass
+
+from typing import TYPE_CHECKING, List, Optional, Iterator, Iterable
+if TYPE_CHECKING:
+    from lektor.db import Record, Pad
+
+
+class FixedRecordsQuery(Query):
+    def __init__(
+        self, pad: 'Pad', child_paths: Iterable[str], alt: str = PRIMARY_ALT
+    ):
+        ''' Query with a pre-defined list of children of type Record. '''
+        super().__init__('/', pad, alt=alt)
+        self.__child_paths = [x.lstrip('/') for x in child_paths]
+
+    def _get(
+        self, path: str, persist: bool = True, page_num: Optional[int] = None
+    ) -> Optional['Record']:
+        ''' Internal getter for a single Record. '''
+        if path not in self.__child_paths:
+            return None
+        if page_num is None:
+            page_num = self._page_num
+        return self.pad.get(  # type: ignore[no-any-return]
+            path, alt=self.alt, page_num=page_num, persist=persist)
+
+    def _iterate(self) -> Iterator['Record']:
+        ''' Iterate over internal set of Record elements. '''
+        # ignore self record dependency from super()
+        for path in self.__child_paths:
+            record = self._get(path, persist=False)
+            if record is None:
+                if self._page_num is not None:
+                    # Sanity check: ensure the unpaginated version exists
+                    unpaginated = self._get(path, persist=False, page_num=None)
+                    if unpaginated is not None:
+                        # Requested explicit page_num, but source does not
+                        # support pagination.  Punt and skip it.
+                        continue
+                raise RuntimeError('could not load source for ' + path)
+
+            is_attachment = getattr(record, 'is_attachment', False)
+            if self._include_attachments and not is_attachment \
+                    or self._include_pages and is_attachment:
+                continue
+            if self._matches(record):
+                yield record
+
+    def get_order_by(self) -> Optional[List[str]]:
+        ''' Return list of attribute strings for sort order. '''
+        # ignore datamodel ordering from super()
+        return self._order_by
+
+    def count(self) -> int:
+        ''' Count matched objects. '''
+        if self._pristine:
+            return len(self.__child_paths)
+        return super().count()  # type: ignore[no-any-return]
+
+    def get(self, path: str, page_num: Optional[int] = None) \
+            -> Optional['Record']:
+        ''' Return Record with given path '''
+        if path in self.__child_paths:
+            return self._get(path, page_num=page_num)
+        return None
+
+    def __bool__(self) -> bool:
+        if self._pristine:
+            return len(self.__child_paths) > 0
+        return super().__bool__()  # type: ignore[no-any-return]

lektor_groupby/vobj.py

@@ -4,7 +4,9 @@ from lektor.db import _CmpHelper
 from lektor.environment import Expression
 from lektor.sourceobj import VirtualSourceObject  # subclass
 from lektor.utils import build_url
+
 from typing import TYPE_CHECKING, List, Any, Optional, Iterator, Iterable
+from .query import FixedRecordsQuery
 from .util import report_config_error, most_used_key
 if TYPE_CHECKING:
     from lektor.builder import Artifact
@@ -28,14 +30,14 @@ class GroupBySource(VirtualSourceObject):
     def __init__(self, record: 'Record', slug: str) -> None:
         super().__init__(record)
         self.key = slug
-        self._group_map = []  # type: List[str]
+        self.__children = []  # type: List[str]
-        self._children = []  # type: List[Record]
+        self.__group_map = []  # type: List[str]
 
     def append_child(self, child: 'Record', group: str) -> None:
-        if child not in self._children:
+        if child not in self.__children:
-            self._children.append(child)
+            self.__children.append(child.path)
-        # _group_map is later used to find most used group
+        # __group_map is later used to find most used group
-        self._group_map.append(group)
+        self.__group_map.append(group)
 
     # -------------------------
     #   Evaluate Extra Fields
@@ -44,8 +46,14 @@ class GroupBySource(VirtualSourceObject):
     def finalize(self, config: 'Config', group: Optional[str] = None) \
             -> 'GroupBySource':
         self.config = config
-        self.group = group or most_used_key(self._group_map)
+        # make a sorted children query
-        del self._group_map
+        self._children = FixedRecordsQuery(self.pad, self.__children, self.alt)
+        self._children._order_by = config.order_by
+        # set group name
+        self.group = group or most_used_key(self.__group_map)
+        # cleanup temporary data
+        del self.__children
+        del self.__group_map
         # evaluate slug Expression
         if config.slug and '{key}' in config.slug:
             self.slug = config.slug.replace('{key}', self.key)
@@ -57,10 +65,6 @@ class GroupBySource(VirtualSourceObject):
         # extra fields
         for attr, expr in config.fields.items():
             setattr(self, attr, self._eval(expr, field='fields.' + attr))
-        # sort children
-        if config.order_by:
-            # using get_sort_key() of Record
-            self._children.sort(key=lambda x: x.get_sort_key(config.order_by))
         return self
 
     def _eval(self, value: Any, *, field: str) -> Any:
@@ -93,7 +97,7 @@ class GroupBySource(VirtualSourceObject):
         ''' Enumerate all dependencies '''
         if self.config.dependencies:
             yield from self.config.dependencies
-        for record in self._children:
+        for record in self.children:
             yield from record.iter_source_filenames()
 
     # def get_checksum(self, path_cache: 'PathCache') -> Optional[str]:
@@ -101,20 +105,9 @@ class GroupBySource(VirtualSourceObject):
     #         self.config.template).filename]
     #     deps.extend(self.iter_source_filenames())
     #     sums = '|'.join(path_cache.get_file_info(x).filename_and_checksum
-    #                     for x in deps if x) + str(len(self._children))
+    #                     for x in deps if x) + str(self.children.count())
     #     return hashlib.sha1(sums.encode('utf-8')).hexdigest() if sums else None
 
-    # @property
-    # def pagination(self):
-    #     print('pagination')
-    #     return None
-
-    # def __for_page__(self, page_num):
-    #     """Get source object for a (possibly) different page number.
-    #     """
-    #     print('for page', page_num)
-    #     return self
-
     def get_sort_key(self, fields: Iterable[str]) -> List:
         def cmp_val(field: str) -> Any:
             reverse = field.startswith('-')
@@ -129,17 +122,10 @@ class GroupBySource(VirtualSourceObject):
     # -----------------------
 
     @property
-    def children(self) -> List['Record']:
+    def children(self) -> FixedRecordsQuery:
-        ''' Returns dict with page record key and (optional) extra value. '''
+        ''' Return query of children of type Record. '''
         return self._children
 
-    @property
-    def first_child(self) -> Optional['Record']:
-        ''' Returns first referencing page record. '''
-        if self._children:
-            return iter(self._children).__next__()
-        return None
-
     def __getitem__(self, key: str) -> Any:
         # Used for virtual path resolver
         if key in ('_path', '_alt'):
@@ -163,7 +149,7 @@ class GroupBySource(VirtualSourceObject):
 
     def __repr__(self) -> str:
         return '<GroupBySource path="{}" children={}>'.format(
-            self.path, len(self._children))
+            self.path, self.children.count())
 
 
 # -----------------------------------