Flatten a JSON document using jq

Question

I'm considering the following array of JSON objects:

[   {     "index": "index1",     "type": "type1",     "id": "id1",     "fields": {       "deviceOs": [         "Android"       ],       "deviceID": [         "deviceID1"       ],       "type": [         "type"       ],       "country": [         "DE"       ]     }   },   {     "index": "index2",     "type": "type2",     "id": "id2",     "fields": {       "deviceOs": [         "Android"       ],       "deviceID": [         "deviceID2"       ],       "type": [         "type"       ],       "country": [         "US"       ]     }   } ] 

and I would like to flatten it to get:

[   {     "index": "index1",     "type": "type",     "id": "id1",     "deviceOs": "Android",     "deviceID": "deviceID1",     "country": "DE"   },   {     "index": "index2",     "type": "type",     "id": "id2",     "deviceOs": "Android",     "deviceID": "deviceID2",     "country": "US"   } ] 

I'm trying to work with jq but I fail to flatten the "fields". How should I do it? At the moment I'm interested in command-line tools, but I'm open to other suggestions as well.

Answer 1

This one was a tricky one to craft.

map (     with_entries(select(.key != "fields"))     +     (.fields | with_entries(.value = .value[0])) ) 

Let's break it down and explain the bits of it

1. For every item in the array...

   map(...) 

2. Create a new object containing the values for all except the fields property.

   with_entries(select(.key != "fields")) 

3. Combine that with...

   + 

4. Each of the fields projecting each of the values to the first item of each array

   (.fields | with_entries(.value = .value[0]))