[utils] Allow partial application for more functions (#11391)

Also adds the `trim_str` traversal helper

Authored by: bashonly, Grub4K

Co-authored-by: Simon Sawicki <contact@grub4k.xyz>

test/test_traversal.py

@@ -12,9 +12,10 @@ from yt_dlp.utils import (
     str_or_none,
 )
 from yt_dlp.utils.traversal import (
-    traverse_obj,
     require,
     subs_list_to_dict,
+    traverse_obj,
+    trim_str,
 )
 
 _TEST_DATA = {
@@ -495,6 +496,20 @@ class TestTraversalHelpers:
             {'url': 'https://example.com/subs/en2', 'ext': 'ext'},
         ]}, '`quality` key should sort subtitle list accordingly'
 
+    def test_trim_str(self):
+        with pytest.raises(TypeError):
+            trim_str('positional')
+
+        assert callable(trim_str(start='a'))
+        assert trim_str(start='ab')('abc') == 'c'
+        assert trim_str(end='bc')('abc') == 'a'
+        assert trim_str(start='a', end='c')('abc') == 'b'
+        assert trim_str(start='ab', end='c')('abc') == ''
+        assert trim_str(start='a', end='bc')('abc') == ''
+        assert trim_str(start='ab', end='bc')('abc') == ''
+        assert trim_str(start='abc', end='abc')('abc') == ''
+        assert trim_str(start='', end='')('abc') == 'abc'
+
 
 class TestDictGet:
     def test_dict_get(self):

test/test_utils.py

@@ -4,6 +4,7 @@
 import os
 import sys
 import unittest
+import unittest.mock
 import warnings
 import datetime as dt
 
@@ -71,6 +72,7 @@ from yt_dlp.utils import (
     intlist_to_bytes,
     iri_to_uri,
     is_html,
+    join_nonempty,
     js_to_json,
     limit_length,
     locked_file,
@@ -343,11 +345,13 @@ class TestUtil(unittest.TestCase):
         self.assertEqual(remove_start(None, 'A - '), None)
         self.assertEqual(remove_start('A - B', 'A - '), 'B')
         self.assertEqual(remove_start('B - A', 'A - '), 'B - A')
+        self.assertEqual(remove_start('non-empty', ''), 'non-empty')
 
     def test_remove_end(self):
         self.assertEqual(remove_end(None, ' - B'), None)
         self.assertEqual(remove_end('A - B', ' - B'), 'A')
         self.assertEqual(remove_end('B - A', ' - B'), 'B - A')
+        self.assertEqual(remove_end('non-empty', ''), 'non-empty')
 
     def test_remove_quotes(self):
         self.assertEqual(remove_quotes(None), None)
@@ -2148,6 +2152,16 @@ Line 1
             assert run_shell(args) == expected
             assert run_shell(shell_quote(args, shell=True)) == expected
 
+    def test_partial_application(self):
+        assert callable(int_or_none(scale=10)), 'missing positional parameter should apply partially'
+        assert int_or_none(10, scale=0.1) == 100, 'positionally passed argument should call function'
+        assert int_or_none(v=10) == 10, 'keyword passed positional should call function'
+        assert int_or_none(scale=0.1)(10) == 100, 'call after partial applicatino should call the function'
+
+        assert callable(join_nonempty(delim=', ')), 'varargs positional should apply partially'
+        assert callable(join_nonempty()), 'varargs positional should apply partially'
+        assert join_nonempty(None, delim=', ') == '', 'passed varargs should call the function'
+
 
 if __name__ == '__main__':
     unittest.main()

yt_dlp/utils/_utils.py

@@ -212,6 +212,23 @@ def write_json_file(obj, fn):
         raise
 
 
+def partial_application(func):
+    sig = inspect.signature(func)
+    required_args = [
+        param.name for param in sig.parameters.values()
+        if param.kind in (inspect.Parameter.POSITIONAL_ONLY, inspect.Parameter.POSITIONAL_OR_KEYWORD, inspect.Parameter.VAR_POSITIONAL)
+        if param.default is inspect.Parameter.empty
+    ]
+
+    @functools.wraps(func)
+    def wrapped(*args, **kwargs):
+        if set(required_args[len(args):]).difference(kwargs):
+            return functools.partial(func, *args, **kwargs)
+        return func(*args, **kwargs)
+
+    return wrapped
+
+
 def find_xpath_attr(node, xpath, key, val=None):
     """ Find the xpath xpath[@key=val] """
     assert re.match(r'^[a-zA-Z_-]+$', key)
@@ -1192,6 +1209,7 @@ def extract_timezone(date_str, default=None):
     return timezone, date_str
 
 
+@partial_application
 def parse_iso8601(date_str, delimiter='T', timezone=None):
     """ Return a UNIX timestamp from the given date """
 
@@ -1269,6 +1287,7 @@ def unified_timestamp(date_str, day_first=True):
         return calendar.timegm(timetuple) + pm_delta * 3600 - timezone.total_seconds()
 
 
+@partial_application
 def determine_ext(url, default_ext='unknown_video'):
     if url is None or '.' not in url:
         return default_ext
@@ -1944,7 +1963,7 @@ def remove_start(s, start):
 
 
 def remove_end(s, end):
-    return s[:-len(end)] if s is not None and s.endswith(end) else s
+    return s[:-len(end)] if s is not None and end and s.endswith(end) else s
 
 
 def remove_quotes(s):
@@ -1973,6 +1992,7 @@ def base_url(url):
     return re.match(r'https?://[^?#]+/', url).group()
 
 
+@partial_application
 def urljoin(base, path):
     if isinstance(path, bytes):
         path = path.decode()
@@ -1988,21 +2008,6 @@ def urljoin(base, path):
     return urllib.parse.urljoin(base, path)
 
 
-def partial_application(func):
-    sig = inspect.signature(func)
-
-    @functools.wraps(func)
-    def wrapped(*args, **kwargs):
-        try:
-            sig.bind(*args, **kwargs)
-        except TypeError:
-            return functools.partial(func, *args, **kwargs)
-        else:
-            return func(*args, **kwargs)
-
-    return wrapped
-
-
 @partial_application
 def int_or_none(v, scale=1, default=None, get_attr=None, invscale=1, base=None):
     if get_attr and v is not None:
@@ -2583,6 +2588,7 @@ def urlencode_postdata(*args, **kargs):
     return urllib.parse.urlencode(*args, **kargs).encode('ascii')
 
 
+@partial_application
 def update_url(url, *, query_update=None, **kwargs):
     """Replace URL components specified by kwargs
        @param url           str or parse url tuple
@@ -2603,6 +2609,7 @@ def update_url(url, *, query_update=None, **kwargs):
     return urllib.parse.urlunparse(url._replace(**kwargs))
 
 
+@partial_application
 def update_url_query(url, query):
     return update_url(url, query_update=query)
 
@@ -2924,6 +2931,7 @@ def error_to_str(err):
     return f'{type(err).__name__}: {err}'
 
 
+@partial_application
 def mimetype2ext(mt, default=NO_DEFAULT):
     if not isinstance(mt, str):
         if default is not NO_DEFAULT:
@@ -4664,6 +4672,7 @@ def to_high_limit_path(path):
     return path
 
 
+@partial_application
 def format_field(obj, field=None, template='%s', ignore=NO_DEFAULT, default='', func=IDENTITY):
     val = traversal.traverse_obj(obj, *variadic(field))
     if not val if ignore is NO_DEFAULT else val in variadic(ignore):
@@ -4828,6 +4837,7 @@ def number_of_digits(number):
     return len('%d' % number)
 
 
+@partial_application
 def join_nonempty(*values, delim='-', from_dict=None):
     if from_dict is not None:
         values = (traversal.traverse_obj(from_dict, variadic(v)) for v in values)
@@ -5278,6 +5288,7 @@ class RetryManager:
             time.sleep(delay)
 
 
+@partial_application
 def make_archive_id(ie, video_id):
     ie_key = ie if isinstance(ie, str) else ie.ie_key()
     return f'{ie_key.lower()} {video_id}'

yt_dlp/utils/traversal.py

@@ -435,6 +435,20 @@ def find_elements(*, tag=None, cls=None, attr=None, value=None, html=False):
     return functools.partial(func, cls)
 
 
+def trim_str(*, start=None, end=None):
+    def trim(s):
+        if s is None:
+            return None
+        start_idx = 0
+        if start and s.startswith(start):
+            start_idx = len(start)
+        if end and s.endswith(end):
+            return s[start_idx:-len(end)]
+        return s[start_idx:]
+
+    return trim
+
+
 def get_first(obj, *paths, **kwargs):
     return traverse_obj(obj, *((..., *variadic(keys)) for keys in paths), **kwargs, get_all=False)