Replace custom template substitution with yt-dlp's evaluate_outtmpl

Replace the hand-rolled _outtmpl_substitute_field() / _compile_outtmpl_pattern()
with a new _resolve_outtmpl_fields() that delegates to yt-dlp's
YoutubeDL.evaluate_outtmpl().  This gives playlist/channel output templates
access to yt-dlp's full template syntax: defaults (%(field|fallback)s),
conditional formatting (%(field&prefix {})s), math (%(field+N)d),
datetime formatting (%(field>%Y-%m-%d)s), and more.

Only field references whose root name matches the targeted prefix (e.g.
"playlist" or "channel") are resolved; all other references remain as
template placeholders for yt-dlp to fill during the actual download.

Agent-Logs-Url: https://github.com/alexta69/metube/sessions/0ae5ff34-540f-4fc8-a81c-358fb92b7c15

Co-authored-by: alexta69 <7450369+alexta69@users.noreply.github.com>

app/tests/test_ytdl_utils.py

@@ -24,7 +24,7 @@ class _ImpersonateTarget:
 
 fake_impersonate.ImpersonateTarget = _ImpersonateTarget
 fake_networking.impersonate = fake_impersonate
-fake_utils.STR_FORMAT_RE_TMPL = r"(?P<prefix>)%\((?P<has_key>{})\)(?P<format>[-0-9.]*{})"
+fake_utils.STR_FORMAT_RE_TMPL = r"(?P<prefix>)%\((?P<has_key>(?P<key>{}))\)(?P<format>[-0-9.]*{})"
 fake_utils.STR_FORMAT_TYPES = "diouxXeEfFgGcrsa"
 fake_yt_dlp.networking = fake_networking
 fake_yt_dlp.utils = fake_utils
@@ -37,11 +37,15 @@ from ytdl import (
     DownloadInfo,
     _compact_persisted_entry,
     _convert_srt_to_txt_file,
-    _outtmpl_substitute_field,
+    _resolve_outtmpl_fields,
     _sanitize_entry_for_pickle,
     _sanitize_path_component,
 )
 
+# Detect whether the real yt-dlp is loaded (as opposed to the minimal fake
+# shim above).  _resolve_outtmpl_fields needs YoutubeDL at runtime.
+_has_real_ytdlp = hasattr(sys.modules.get("yt_dlp"), "YoutubeDL")
+
 
 class SanitizePathComponentTests(unittest.TestCase):
     def test_replaces_windows_invalid_chars(self):
@@ -52,15 +56,39 @@ class SanitizePathComponentTests(unittest.TestCase):
         self.assertEqual(_sanitize_path_component(42), 42)
 
 
-class OuttmplSubstituteFieldTests(unittest.TestCase):
-    def test_simple_substitution(self):
-        self.assertEqual(_outtmpl_substitute_field("%(title)s", "title", "Hello"), "Hello")
+@unittest.skipUnless(_has_real_ytdlp, "requires real yt-dlp")
+class ResolveOuttmplFieldsTests(unittest.TestCase):
+    """Tests for _resolve_outtmpl_fields (delegates to yt-dlp's template engine)."""
+
+    def test_simple_playlist_substitution(self):
+        info = {"playlist_title": "My PL", "playlist_index": "03"}
+        result = _resolve_outtmpl_fields("%(playlist_title)s/%(title)s.%(ext)s", info, ("playlist",))
+        self.assertEqual(result, "My PL/%(title)s.%(ext)s")
 
     def test_format_spec_int(self):
-        self.assertEqual(_outtmpl_substitute_field("%(idx)02d", "idx", 3), "03")
+        info = {"playlist_index": "3"}
+        result = _resolve_outtmpl_fields("%(playlist_index)02d-%(title)s", info, ("playlist",))
+        self.assertEqual(result, "03-%(title)s")
 
-    def test_missing_field_unchanged(self):
-        self.assertEqual(_outtmpl_substitute_field("%(other)s", "title", "x"), "%(other)s")
+    def test_non_targeted_fields_unchanged(self):
+        info = {"playlist_title": "PL"}
+        result = _resolve_outtmpl_fields("%(title)s/%(ext)s", info, ("playlist",))
+        self.assertEqual(result, "%(title)s/%(ext)s")
+
+    def test_default_value(self):
+        info = {"playlist_index": "1"}
+        result = _resolve_outtmpl_fields("%(playlist_title|Unknown)s/%(playlist_index)s", info, ("playlist",))
+        self.assertEqual(result, "Unknown/1")
+
+    def test_channel_prefix(self):
+        info = {"channel": "MyChan", "channel_index": "05"}
+        result = _resolve_outtmpl_fields("%(channel)s/%(channel_index)02d-%(title)s", info, ("channel",))
+        self.assertEqual(result, "MyChan/05-%(title)s")
+
+    def test_math_operation(self):
+        info = {"playlist_index": "3"}
+        result = _resolve_outtmpl_fields("%(playlist_index+100)d", info, ("playlist",))
+        self.assertEqual(result, "103")
 
 
 class SanitizeEntryForPickleTests(unittest.TestCase):

app/ytdl.py

@@ -13,7 +13,6 @@ import logging
 import re
 import types
 from typing import Any, Optional
-from functools import lru_cache
 
 import yt_dlp.networking.impersonate
 from yt_dlp.utils import STR_FORMAT_RE_TMPL, STR_FORMAT_TYPES
@@ -24,13 +23,6 @@ from state_store import AtomicJsonStore, from_json_compatible, read_legacy_shelf
 log = logging.getLogger('ytdl')
 
 
-@lru_cache(maxsize=None)
-def _compile_outtmpl_pattern(field: str) -> re.Pattern:
-    """Compile a regex pattern to match a specific field in an output template, including optional format specifiers."""
-    conversion_types = f"[{re.escape(STR_FORMAT_TYPES)}]"
-    return re.compile(STR_FORMAT_RE_TMPL.format(re.escape(field), conversion_types))
-
-
 # Characters that are invalid in Windows/NTFS path components. These are pre-
 # sanitised when substituting playlist/channel titles into output templates so
 # that downloads do not fail on NTFS-mounted volumes or Windows Docker hosts.
@@ -41,44 +33,51 @@ def _sanitize_path_component(value: Any) -> Any:
     """Replace characters that are invalid in Windows path components with '_'.
 
     Non-string values (int, float, None, …) are passed through unchanged so
-    that ``_outtmpl_substitute_field`` can still coerce them with format specs
-    (e.g. ``%(playlist_index)02d``).  Only string values are sanitised because
-    Windows-invalid characters are only a concern for human-readable strings
-    (titles, channel names, etc.) that may end up as directory names.
+    that numeric format specs (e.g. ``%(playlist_index)02d``) still work.
+    Only string values are sanitised because Windows-invalid characters are
+    only a concern for human-readable strings (titles, channel names, etc.)
+    that may end up as directory names.
     """
     if not isinstance(value, str):
         return value
     return _WINDOWS_INVALID_PATH_CHARS.sub('_', value)
 
 
-def _outtmpl_substitute_field(template: str, field: str, value: Any) -> str:
-    """Substitute a single field in an output template, applying any format specifiers to the value."""
-    pattern = _compile_outtmpl_pattern(field)
+# Regex matching yt-dlp output-template field references, e.g. ``%(title)s``
+# or ``%(playlist_index)03d``.  Built from yt-dlp's own ``STR_FORMAT_RE_TMPL``
+# so that it stays in sync with upstream changes to the template syntax.
+_OUTTMPL_FIELD_RE = re.compile(
+    STR_FORMAT_RE_TMPL.format('[^)]+', f'[{STR_FORMAT_TYPES}ljhqBUDS]')
+)
 
-    def replacement(match: re.Match) -> str:
-        if match.group("has_key") is None:
-            return match.group(0)
 
-        prefix = match.group("prefix") or ""
-        format_spec = match.group("format")
+def _resolve_outtmpl_fields(template: str, info_dict: dict, prefixes: tuple[str, ...]) -> str:
+    """Resolve specific fields in an output template using yt-dlp's template engine.
 
-        if not format_spec:
-            return f"{prefix}{value}"
+    Only field references whose root name starts with one of *prefixes* are
+    evaluated.  All other references are left untouched so that yt-dlp can
+    resolve them later during the actual download.
 
-        conversion_type = format_spec[-1]
-        try:
-            if conversion_type in "diouxX":
-                coerced_value = int(value)
-            elif conversion_type in "eEfFgG":
-                coerced_value = float(value)
-            else:
-                coerced_value = value
+    This delegates to ``YoutubeDL.evaluate_outtmpl`` for each targeted field
+    reference, giving access to the full yt-dlp template syntax (defaults,
+    conditional formatting, math operations, datetime formatting, etc.).
+    """
+    matches = list(_OUTTMPL_FIELD_RE.finditer(template))
+    if not matches:
+        return template
 
-            return f"{prefix}{('%' + format_spec) % coerced_value}"
-        except (ValueError, TypeError):
-            return f"{prefix}{value}"
+    with yt_dlp.YoutubeDL({'quiet': True}) as ydl:
+        for match in reversed(matches):
+            key = match.group('key')
+            if key is None:
+                continue
+            root = re.match(r'\w+', key)
+            if root is None or not root.group(0).startswith(prefixes):
+                continue
+            resolved = ydl.evaluate_outtmpl(match.group(0), info_dict)
+            template = template[:match.start()] + resolved + template[match.end():]
 
-    return pattern.sub(replacement, template)
+    return template
 
 _MAX_ENTRY_SANITIZE_DEPTH = 64
 
@@ -818,15 +817,13 @@ class DownloadQueue:
         if entry is not None and entry.get('playlist_index') is not None:
             if len(self.config.OUTPUT_TEMPLATE_PLAYLIST):
                 output = self.config.OUTPUT_TEMPLATE_PLAYLIST
-            for property, value in entry.items():
-                if property.startswith("playlist"):
-                    output = _outtmpl_substitute_field(output, property, _sanitize_path_component(value))
+            sanitized = {k: _sanitize_path_component(v) for k, v in entry.items()}
+            output = _resolve_outtmpl_fields(output, sanitized, ('playlist',))
         if entry is not None and entry.get('channel_index') is not None:
             if len(self.config.OUTPUT_TEMPLATE_CHANNEL):
                 output = self.config.OUTPUT_TEMPLATE_CHANNEL
-            for property, value in entry.items():
-                if property.startswith("channel"):
-                    output = _outtmpl_substitute_field(output, property, _sanitize_path_component(value))
+            sanitized = {k: _sanitize_path_component(v) for k, v in entry.items()}
+            output = _resolve_outtmpl_fields(output, sanitized, ('channel',))
         ytdl_options = dict(self.config.YTDL_OPTIONS)
         playlist_item_limit = getattr(dl, 'playlist_item_limit', 0)
         if playlist_item_limit > 0: