support using prefix and from_pattern/to_pattern at the same time

closes #249.

docs/usage.rst

@@ -170,6 +170,9 @@ prefix
   Strip the prefix string if the version string starts with it. Otherwise the
   version string is returned as-is.
 
+  If both ``prefix`` and ``from_pattern``/``to_pattern`` are used, ``prefix``
+  is applied first.
+
 from_pattern, to_pattern
   Both are Python-compatible regular expressions. If ``from_pattern`` is found
   in the version string, it will be replaced with ``to_pattern``.
@@ -212,13 +215,6 @@ httptoken
 verify_cert
   Whether to verify the HTTPS certificate or not. Default is ``true``.
 
-If both ``prefix`` and ``from_pattern``/``to_pattern`` are used,
-``from_pattern``/``to_pattern`` are ignored. If you want to strip the prefix
-and then do something special, just use ``from_pattern``/``to_pattern``. For
-example, the transformation of ``v1_1_0`` => ``1.1.0`` can be achieved with
-``from_pattern = 'v(\d+)_(\d+)_(\d+)'`` and ``to_pattern = '\1.\2.\3'``.
-(Note that in TOML it's easiler to write regexes in single quotes so you don't need to escape ``\``.)
-
 .. _list options:
 
 List Options

nvchecker/__init__.py

@@ -1,4 +1,4 @@
 # MIT licensed
 # Copyright (c) 2013-2023 lilydjwg <lilydjwg@gmail.com>, et al.
 
-__version__ = '2.13.1'
+__version__ = '2.14dev'

nvchecker/core.py

@@ -279,13 +279,12 @@ def substitute_version(
 ) -> str:
   '''
   Substitute the version string via defined rules in the configuration file.
-  See README.rst#global-options for details.
+  See usage.rst#global-options for details.
   '''
   prefix = conf.get('prefix')
   if prefix:
     if version.startswith(prefix):
       version = version[len(prefix):]
-    return version
 
   from_pattern = conf.get('from_pattern')
   if from_pattern:
@@ -293,9 +292,8 @@ def substitute_version(
     if to_pattern is None:
       raise ValueError("from_pattern exists but to_pattern doesn't")
 
-    return re.sub(from_pattern, to_pattern, version)
+    version = re.sub(from_pattern, to_pattern, version)
 
-  # No substitution rules found. Just return the original version string.
   return version
 
 def apply_list_options(

tests/test_substitute.py

@@ -45,8 +45,8 @@ async def test_substitute_regex_empty_to_pattern(get_version):
 async def test_substitute_prefix_has_higher_priority(get_version):
     assert await get_version("example", {
         "source": "manual",
-        "manual": "r15",
-        "prefix": "r",
-        "from_pattern": r"r(\d+)",
-        "to_pattern": r"R\1",
-    }) == "15"
+        "manual": "Version 1.2 Beta 3",
+        "prefix": "Version ",
+        "from_pattern": r" Beta ",
+        "to_pattern": r"b",
+    }) == "1.2b3"