Add DownloadTarget.suggested_filename

qutebrowser/browser/qtnetworkdownloads.py

@@ -438,12 +438,9 @@ class DownloadManager(downloads.AbstractDownloadManager):
             The created DownloadItem.
         """
         if not suggested_filename:
-            if isinstance(target, usertypes.FileDownloadTarget):
-                suggested_filename = os.path.basename(target.filename)
-            elif (isinstance(target, usertypes.FileObjDownloadTarget) and
-                  getattr(target.fileobj, 'name', None)):
-                suggested_filename = target.fileobj.name
-            else:
+            try:
+                suggested_filename = target.suggested_filename()
+            except usertypes.NoFilenameError:
                 _, suggested_filename = http.parse_content_disposition(reply)
         log.downloads.debug("fetch: {} -> {}".format(reply.url(),
                                                      suggested_filename))

qutebrowser/utils/usertypes.py

@@ -23,6 +23,7 @@ Module attributes:
     _UNSET: Used as default argument in the constructor so default can be None.
 """
 
+import os.path
 import operator
 import collections.abc
 import enum as pyenum
@@ -268,6 +269,11 @@ JsWorld = enum('JsWorld', ['main', 'application', 'user', 'jseval'])
 MessageLevel = enum('MessageLevel', ['error', 'warning', 'info'])
 
 
+class NoFilenameError(Exception):
+
+    """Raised when we can't find out a filename in DownloadTarget."""
+
+
 # Where a download should be saved
 class DownloadTarget:
 
@@ -276,6 +282,10 @@ class DownloadTarget:
     def __init__(self):
         raise NotImplementedError
 
+    def suggested_filename(self):
+        """Get the suggested filename for this download target."""
+        raise NotImplementedError
+
 
 class FileDownloadTarget(DownloadTarget):
 
@@ -289,6 +299,9 @@ class FileDownloadTarget(DownloadTarget):
         # pylint: disable=super-init-not-called
         self.filename = filename
 
+    def suggested_filename(self):
+        return os.path.basename(self.filename)
+
 
 class FileObjDownloadTarget(DownloadTarget):
 
@@ -302,6 +315,12 @@ class FileObjDownloadTarget(DownloadTarget):
         # pylint: disable=super-init-not-called
         self.fileobj = fileobj
 
+    def suggested_filename(self):
+        try:
+            return self.fileobj.name
+        except AttributeError:
+            raise NoFilenameError
+
 
 class OpenFileDownloadTarget(DownloadTarget):
 
@@ -317,6 +336,9 @@ class OpenFileDownloadTarget(DownloadTarget):
         # pylint: disable=super-init-not-called
         self.cmdline = cmdline
 
+    def suggested_filename(self):
+        raise NoFilenameError
+
 
 class Question(QObject):