combine conditional filenames into `filename` option (#1394)

docs/configuration.rst

@@ -58,12 +58,27 @@ option (see the example below).
 extractor.*.filename
 --------------------
 Type
-    ``string``
+    ``string`` or ``object``
 Example
-    ``"{manga}_c{chapter}_{page:>03}.{extension}"``
+    * .. code::
+
+        "{manga}_c{chapter}_{page:>03}.{extension}"
+
+    * .. code:: json
+
+        {
+            "extension == 'mp4'": "{id}_video.{extension}",
+            "'nature' in title" : "{id}_{title}.{extension}",
+            ""                  : "{id}_default.{extension}"
+        }
+
 Description
-    A `format string`_ to build the resulting filename
-    for a downloaded file.
+    A `format string`_ to build filenames for downloaded files with.
+
+    If this is an ``object``, it must contain Python expressions mapping to the
+    filename format strings to use.
+    These expressions are evaluated in the order as specified in Python 3.6+
+    and in an undetermined order in Python 3.4 and 3.5.
 
     The available replacement keys depend on the extractor used. A list
     of keys for a specific one can be acquired by calling *gallery-dl*
@@ -97,28 +112,6 @@ Description
     a valid filename extension.
 
 
-extractor.*.filename-conditions
--------------------------------
-Type
-    ``object``
-Example
-    .. code:: json
-
-        {
-            "extension == 'mp4'"        : "{id}_video.{extension}",
-            "extension in ('zip','rar')": "{id}_archive.{extension}",
-            "'nature' in title"         : "{id}_{title}.{extension}"
-        }
-Description
-    An object containing Python expressions mapping to the
-    filename format strings to use.
-
-    When none of the given conditions match, `extractor.*.filename`_ is used.
-
-    Expressions are evaluated in the order as specified in Python 3.6+
-    and in an undetermined order in Python 3.4 and 3.5.
-
-
 extractor.*.directory
 ---------------------
 Type

gallery_dl/util.py

@@ -756,10 +756,6 @@ class PathFormat():
 
     def __init__(self, extractor):
         filename_fmt = extractor.config("filename")
-        filename_conditions = extractor.config("filename-conditions")
-        if filename_fmt is None:
-            filename_fmt = extractor.filename_fmt
-
         directory_fmt = extractor.config("directory")
         if directory_fmt is None:
             directory_fmt = extractor.directory_fmt
@@ -771,13 +767,16 @@ class PathFormat():
 
         kwdefault = extractor.config("keywords-default")
         try:
-            if filename_conditions:
-                self.build_filename = self.build_filename_conditional
+            if filename_fmt is None:
+                filename_fmt = extractor.filename_fmt
+            elif isinstance(filename_fmt, dict):
                 self.filename_conditions = [
                     (compile_expression(expr),
                      Formatter(fmt, kwdefault).format_map)
-                    for expr, fmt in filename_conditions.items()
+                    for expr, fmt in filename_fmt.items() if expr
                 ]
+                self.build_filename = self.build_filename_conditional
+                filename_fmt = filename_fmt.get("", extractor.filename_fmt)
 
             self.filename_formatter = Formatter(
                 filename_fmt, kwdefault).format_map