I'm working with a Feeds importer that imports to an image field. I have two tamper plugins attached to this column, one is a required filter, the other is a rewrite plugin to prepend private:// to the image name.
If I configure the weights so the required plugin runs first, I get errors like the following as the rewrite plugin tries to rewrite empty rows that have been unset() by the required filter:
Notice: Undefined offset: 13 in feeds_tamper_rewrite_callback() (line 43 of feeds_tamper/plugins/rewrite.inc).
Warning: Invalid argument supplied for foreach() in feeds_tamper_rewrite_callback() (line 44 of feeds_tamper/plugins/rewrite.inc).
If I have the required plugin run second, then I get file errors because now the field is no longer empty and Feeds tries to import an image with a path of "private://".
At first I was thinking the rewrite plugin could just check isset($result->items[$item_key]) but this bug would affect more than just the rewrite plugin, and the fix should probably be baked into the required plugin if possible or enforced on a higher level.