Proposal v2, with carried state

yt_dlp/extractor/_extractors.py

@@ -2572,3 +2572,4 @@ from .zingmp3 import (
 )
 from .zoom import ZoomIE
 from .zype import ZypeIE
+from .lazy import LazyExtractorIE

yt_dlp/extractor/lazy.py

@@ -0,0 +1,33 @@
+from .common import InfoExtractor
+from ..utils.lazy import lazy_ie, lazy_fields
+
+
+@lazy_ie
+class LazyExtractorIE(InfoExtractor):
+    IE_NAME = 'lazy'
+    _VALID_URL = r"lazy://(?P<id>.*)"
+
+    def _lazy_webpage(self, storage):
+        return self._download_webpage(storage.url, storage.id)
+
+    @lazy_fields("creator")
+    def _extract_other(self, storage):
+        self.to_screen("Extracting something else from webpage")
+        return {
+            "creator": storage.webpage.partition(" - ")[0],
+        }
+
+    @lazy_fields("title", "description")
+    def _extract_website(self, storage):
+        self.to_screen("Extracting title and description from webpage")
+        title, _, description = storage.webpage.partition("\n")
+
+        return {
+            "title": title,
+            "description": description,
+        }
+
+    # Fake downloading the webpage for testing purposes
+    def _download_webpage(self, url_or_request, video_id, *args, **kwargs):
+        self.to_screen(f"[{video_id}] Downloaded webpage ({url_or_request})")
+        return "<creator> - Fake Webpage title\nThis is the description.\n..."

yt_dlp/utils/lazy.py

@@ -0,0 +1,151 @@
+from __future__ import annotations
+
+import functools
+import inspect
+from collections.abc import MutableMapping
+
+from ..utils import try_call
+from ..extractor.common import InfoExtractor
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from typing import Callable, Any
+
+
+class _LazyStorage:
+    def __init__(self, ie, **kwargs):
+        self._ie = ie
+        self._cache = kwargs
+
+    def __setattr__(self, name, value, /) -> None:
+        if name.startswith("_"):
+            super().__setattr__(name, value)
+        else:
+            self._cache[name] = value
+
+    def __getattr__(self, name: str):
+        if name in self._cache:
+            return self._cache[name]
+
+        resolver = getattr(self._ie, f"_lazy_{name}")
+        result = try_call(resolver, args=(self,))
+        self._cache[name] = result
+        return result
+
+    def __delattr__(self, name: str) -> None:
+        if name.startswith("_"):
+            super().__delattr__(name)
+        elif name in self._cache:
+            del self._cache[name]
+
+
+class _LazyInfoDict(MutableMapping):
+    def __init__(self, data: dict, lazy: dict, ie: InfoExtractor, **kwargs):
+        self._data = data
+        self._lazy = lazy
+        self._ie = ie
+        self._storage = _LazyStorage(self._ie, **kwargs)
+
+        for key in self._data.keys() & self._lazy.keys():
+            del self._lazy[key]
+
+        self._data.update(dict.fromkeys(self._lazy.keys()))
+
+    def __contains__(self, key):
+        return key in self._data
+
+    def __getitem__(self, key):
+        if key in self._lazy:
+            compute_func = self._lazy[key]
+
+            # updates = try_call(compute_func, args=(self._storage,), expected_type=dict) or {}
+            updates = compute_func(self._ie, self._storage)
+            self._data.update(updates)
+            for field in updates:
+                self._lazy.pop(field, None)
+
+            fields = getattr(compute_func, lazy_fields._field_name, None) or ()
+            for field in fields:
+                self._lazy.pop(field, None)
+
+        return self._data[key]
+
+    def __setitem__(self, key, value):
+        if key in self._lazy:
+            del self._lazy[key]
+
+        self._data[key] = value
+
+    def __delitem__(self, key):
+        if key in self._lazy:
+            del self._lazy[key]
+
+        del self._data[key]
+
+    def __iter__(self):
+        return iter(self._data)
+
+    def __len__(self):
+        return len(self._data)
+
+    def __repr__(self):
+        if self._lazy:
+            lazy = ", ".join(f"{key!r}: ..." for key in self._lazy.keys())
+            data = ", ".join(f"{key!r}: {value!r}" for key, value in self._data.items() if key not in self._lazy)
+            data = f"{{{data}}}, lazy={{{lazy}}}"
+        else:
+            data = f"{self._data!r}"
+        return f"{type(self).__name__}({data})"
+
+
+def _default_lazy_extract(self, url):
+    return dict(id=self._match_id(url))
+
+
+def lazy_ie(klass: type[InfoExtractor] | None = None, /):
+    if not klass:
+        return lazy_ie
+
+    _old_extract = klass._real_extract
+    if _old_extract is InfoExtractor._real_extract:
+        _old_extract = _default_lazy_extract
+
+    lazy_members = {}
+    for _, member in inspect.getmembers(klass):
+        fields = getattr(member, lazy_fields._field_name, None)
+        if not isinstance(fields, tuple):
+            continue
+
+        for field in fields:
+            lazy_members[field] = member
+
+    @functools.wraps(_old_extract)
+    def _real_extract(self, url):
+        result = _old_extract(self, url)
+        assert isinstance(result, dict), 'Lazy extractors need to return a dict'
+        return _LazyInfoDict(result, lazy_members, self, url=url, **result)
+
+    klass._real_extract = _real_extract
+    return klass
+
+
+def lazy_fields(*fields: str) -> Callable[[Callable[[Any, _LazyStorage], dict[str, Any]]], Callable[[Any, _LazyStorage], dict[str, Any]]]:
+    def _lazy_fields(func):
+        setattr(func, lazy_fields._field_name, fields)
+        return func
+
+    return _lazy_fields
+
+
+lazy_fields._field_name = "_lazy_fields"
+
+if __name__ == '__main__':
+    from yt_dlp import YoutubeDL
+
+    with YoutubeDL() as ydl:
+        result = ydl.extract_info("lazy://<URL>", process=False)
+        assert result
+
+        for name in "id", "title", "creator", "description":
+            print(f"{name:<10} = {result[name]!r}")

yt_dlp/utils/lazy_infodict.py

@@ -1,76 +0,0 @@
-from collections.abc import MutableMapping
-
-from yt_dlp.utils import try_call
-
-
-class LazyInfoDict(MutableMapping):
-    def __init__(self, data=None, lazy=None):
-        self._data = data or {}
-        self._lazy = lazy or {}
-
-        for key in self._data.keys() & self._lazy.keys():
-            del self._lazy[key]
-
-        self._data.update(dict.fromkeys(self._lazy.keys()))
-
-    def __contains__(self, key):
-        return key in self._data
-
-    def __getitem__(self, key):
-        if key in self._lazy:
-            compute_func = self._lazy[key]
-
-            print(f"Evaluating key {key!r}")
-            updates = try_call(compute_func, expected_type=dict) or {}
-            self._data.update(updates)
-            for update in updates:
-                self._lazy.pop(update, None)
-
-        return self._data[key]
-
-    def __setitem__(self, key, value):
-        if key in self._lazy:
-            del self._lazy[key]
-
-        self._data[key] = value
-
-    def __delitem__(self, key):
-        if key in self._lazy:
-            del self._lazy[key]
-
-        del self._data[key]
-
-    def __iter__(self):
-        return iter(self._data)
-
-    def __len__(self):
-        return len(self._data)
-
-    def __repr__(self):
-        data = f"{self._data!r}"
-        if self._lazy:
-            data += f", lazy={set(self._lazy.keys())!r}"
-        return f"{type(self).__name__}({data})"
-
-
-if __name__ == '__main__':
-    def eval_test():
-        print('eval_test')
-        return {'test': 'test'}
-
-    def eval_else():
-        print('eval_else')
-        return {'something': 'something', 'else': 'else'}
-
-    data = LazyInfoDict({
-        'nonlazy': 'nonlazy',
-        'attribute': 'attribute',
-    }, {
-        'test': eval_test,
-        'something': eval_else,
-        'else': eval_else,
-    })
-    print(f'{data["else"]=}')
-    print('-----')
-    for key, value in data.items():
-        print(f'data[{key!r}]={value!r}')