Thanks, you got it through now. So with, 'I will have to go shopping.' the speaker is referring to the future point in time at which they will have to go. With, 'I will have had to go shopping.', the speaker is referring to the future point in time when they will already have had to go (before)! So,
The speaker said they would have to go shopping. (before going shopping)
The speaker said they would have had to go shopping. (after shopping)
Also,
I have had to go shopping (this morning).
I had to go shopping (this morning).
I have have to go shopping.
BulbulTada The speaker said they would have to go shopping. Yes, this is 'before going shopping', but in the past. Also, we don't know if they ever went shopping because this is the future of the past (the future as it was seen at that time in the past).
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BulbulTadaThe speaker said they would have to go shopping.
Yes, this is 'before going shopping', but in the past. Also, we don't know if they ever went shopping because this is the future of the past (the future as it was seen at that time in the past).
BulbulTadaThe speaker said they would have had to go shopping.