Allow factory override in make_config()

also add `winsvc` param for `get_config_paths()` to support
RattailFileMonitor service on windows

src/wuttjamaican/conf.py

@@ -620,11 +620,12 @@ def generic_default_files(appname):
 def get_config_paths(
         files=None,
         plus_files=None,
+        appname='wutta',
         env_files_name=None,
         env_plus_files_name=None,
         env=None,
         default_files=None,
-        appname='wutta'):
+        winsvc=None):
     """
     This function determines which files should ultimately be provided
     to the config constructor.  It is normally called by
@@ -696,6 +697,42 @@ def get_config_paths(
 
           files = get_config_paths(default_files=mydefaults)
 
+    :param winsvc: Optional internal name of the Windows service for
+       which the config object is being made.
+
+       This is only needed for true Windows services running via
+       "Python for Windows Extensions" - which probably only includes
+       the Rattail File Monitor service.
+
+       In this context there is no way to tell the app which config
+       files to read on startup, so it can only look for "default"
+       files.  But by passing a ``winsvc`` name to this function, it
+       will first load the default config file, then read a particular
+       value to determine the "real" config file(s) it should use.
+
+       So for example on Windows you might have a config file at
+       ``C:\\ProgramData\\rattail\\rattail.conf`` with contents:
+
+       .. code-block:: ini
+
+          [rattail.config]
+          winsvc.RattailFileMonitor = C:\\ProgramData\\rattail\\filemon.conf
+
+       And then ``C:\\ProgramData\\rattail\\filemon.conf`` would have
+       the actual config for the filemon service.
+
+       When the service starts it calls::
+
+          make_config(winsvc='RattailFileMonitor')
+
+       which first reads the ``rattail.conf`` file (since that is the
+       only sensible default), but then per config it knows to swap
+       that out for ``filemon.conf`` at startup.  This is because it
+       finds a config value matching the requested service name.  The
+       end result is as if it called this instead::
+
+          make_config(files=[r'C:\\ProgramData\\rattail\\filemon.conf'])
+
     :returns: List of file paths.
     """
     if env is None:
@@ -748,6 +785,22 @@ def get_config_paths(
 
     # combine all files
     files.extend(plus_files)
+
+    # when running as a proper windows service, must first read
+    # "default" file(s) and then consult config to see which file
+    # should "really" be used.  because there isn't a way to specify
+    # which config file as part of the actual service definition in
+    # windows, so the service name is used for magic lookup here.
+    if winsvc:
+        config = configparser.SafeConfigParser()
+        config.read(files)
+        section = f'{appname}.config'
+        if config.has_section(section):
+            option = f'winsvc.{winsvc}'
+            if config.has_option(section, option):
+                # replace file paths with whatever config value says
+                files = parse_list(config.get(section, option))
+
     return files
 
 
@@ -759,10 +812,13 @@ def make_config(
         env_plus_files_name=None,
         env=None,
         default_files=None,
+        winsvc=None,
         usedb=None,
         preferdb=None,
+        factory=None,
         extend=True,
-        extension_entry_points=None):
+        extension_entry_points=None,
+        **kwargs):
     """
     Make a new config object (presumably for global use), initialized
     per the given parameters and (usually) further modified by all
@@ -771,20 +827,25 @@ def make_config(
     This function really does 3 things:
 
     * determine the set of config files to use
-    * pass those files to config constructor
+    * pass those files to config factory
     * apply extensions to the resulting config object
 
     Some params are described in :func:`get_config_paths()` since they
     are passed as-is to that function for the first step.
 
-    :param appname: The "app name" to use as basis for other things -
+    :param appname: The :term:`app name` to use as basis for other
-       namely, it affects how config files are located.  This name is
+       things - namely, it affects how config files are located.  This
-       also passed to the config constructor at which point it becomes
+       name is also passed to the config factory at which point it
-       :attr:`wuttjamaican.conf.WuttaConfig.appname`.
+       becomes :attr:`~wuttjamaican.conf.WuttaConfig.appname`.
 
-    :param usedb: Passed to the :class:`WuttaConfig` constructor.
+    :param usedb: Passed to the config factory; becomes
+       :attr:`~wuttjamaican.conf.WuttaConfig.usedb`.
 
-    :param preferdb: Passed to the :class:`WuttaConfig` constructor.
+    :param preferdb: Passed to the config factory; becomes
+       :attr:`~wuttjamaican.conf.WuttaConfig.preferdb`.
+
+    :param factory: Optional factory to use when making the object.
+       Default factory is :class:`WuttaConfig`.
 
     :param extend: Whether to "auto-extend" the config with all
        registered extensions.
@@ -813,11 +874,15 @@ def make_config(
         env_files_name=env_files_name,
         env_plus_files_name=env_plus_files_name,
         env=env,
-        default_files=default_files)
+        default_files=default_files,
+        winsvc=winsvc)
 
     # make config object
-    config = WuttaConfig(files, appname=appname,
+    if not factory:
-                         usedb=usedb, preferdb=preferdb)
+        factory = WuttaConfig
+    config = factory(files, appname=appname,
+                     usedb=usedb, preferdb=preferdb,
+                     **kwargs)
 
     # maybe extend config object
     if extend:

tests/test_conf.py

@@ -417,6 +417,18 @@ class TestGenericDefaultFiles(TestCase):
                 self.assertEqual(len(files), 0)
 
 
+class TestGetConfigPaths(FileConfigTestCase):
+
+    def test_winsvc(self):
+        myconf = self.write_file('my.conf', """
+[wutta.config]
+winsvc.RattailFileMonitor = /path/to/other/file
+""")
+
+        files = conf.get_config_paths(files=[myconf], winsvc='RattailFileMonitor')
+        self.assertEqual(files, ['/path/to/other/file'])
+
+
 class TestMakeConfig(FileConfigTestCase):
 
     # nb. we use appname='wuttatest' in this suite to avoid any