This is coming from D7 feeds, but you may already have a plan for this. Currently it doesn't seem like targets can be created that are not going to actually map to a real field on the end.
The reason this is useful is because for example feeds_ex has a JSON fetcher that only maps to real fields and if you want to "tamper" or modify by merging to you end up having to create a new field and dealing with the tamper in a formatter or something on the entity after the processing. If you had a temporary target you could set the mapping to this and capture the source data for use when doing a ParseEvent listener for example.
This may go against the pure nature (or I missed something and I'll gladly document if you can point me in the right direction) but D7 seemed to have this ability to have fake sources and fake targets, in this case only fake targets, for the use of manipulating would be needed and would be the scope of this proposal.
New generic temporary target option
Hopefully not.
Also hopefully not.
Fixed
3.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
So how can we use Temporary targets with other Tamper plugins? I don't see a [temporary_target] replacement that lets me map that value to another field 🤔
@kopeboy
You can map a source to the target 'Temporary target (temporary_target)', and then that source becomes available in the Tamper interface:
Then for example using the Rewrite plugin you can use that source: