Map nested arrays with JQ

Question

How to transform this:

[
  {
    "author": {
      "name": "Alice"
    },
    "message": "Text 1"
  },
  {
    "author": {
      "name": "Bob"
    },
    "message": "Text 2"
  },
  {
    "author": {
      "name": "Charlie"
    },
    "emotes": [
      {
        "images": [
          {
            "url": "https://www.youtube.com/s/gaming/emoji/828cb648/emoji_u1f600.svg"
          },
          {
            "url": "https://www.youtube.com/s/gaming/emoji/828cb648/emoji_u1f600.svg"
          },
          {
            "url": "https://some-host.com/some-url.svg"
          }
        ],
        "name": ":grinning_face:"
      }
    ],
    "message": "Text 3"
  },
  {
    "author": {
      "name": "Dave"
    },
    "message": "Text 4"
  },
  {
    "author": {
      "name": "Erin"
    },
    "message": "Text 5"
  },
  {
    "author": {
      "name": "Faythe"
    },
    "emotes": [
      {
        "images": [
          {
            "url": "https://www.youtube.com/s/gaming/emoji/828cb648/emoji_u1f44b.svg"
          },
          {
            "url": "https://www.youtube.com/s/gaming/emoji/828cb648/emoji_u1f44b.svg"
          },
          {
            "url": "https://some-host.com/some-other-url.svg"
          }
        ],
        "name": ":waving_hand:"
      }
    ],
    "message": "Text 6"
  }
]

Into this:

[
  {
    "author": "Alice",
    "message": "Text 1"
  },
  {
    "author": "Bob",
    "message": "Text 2"
  },
  {
    "author": "Charlie",
    "message": "Text 3",
    "emotes": [
      {
        "name": ":grinning_face:",
        "images": [
          "https://www.youtube.com/s/gaming/emoji/828cb648/emoji_u1f600.svg",
          "https://some-host.com/some-url.svg"
        ]
      }
    ]
  },
  {
    "author": "Dave",
    "message": "Text 4"
  },
  {
    "author": "Erin",
    "message": "Text 5"
  },
  {
    "author": "Faythe",
    "message": "Text 6",
    "emotes": [
      {
        "name": ":waving_hand:",
        "images": [
          "https://www.youtube.com/s/gaming/emoji/828cb648/emoji_u1f44b.svg",
          "https://some-host.com/some-other-url.svg"
        ]
      }
    ]
  }
]

using jq?

I have no idea how to map nested arrays in "emotes" nodes.

Answer 1

Use (…)? // empty to filter for in-depth existence, unique to remove duplicates, and |= to update:

jq 'map(.author |= .name | ((.emotes[].images)? // empty) |= (map(.url) | unique))'

[
  {
    "author": "Alice",
    "message": "Text 1"
  },
  {
    "author": "Bob",
    "message": "Text 2"
  },
  {
    "author": "Charlie",
    "emotes": [
      {
        "images": [
          "https://some-host.com/some-url.svg",
          "https://www.youtube.com/s/gaming/emoji/828cb648/emoji_u1f600.svg"
        ],
        "name": ":grinning_face:"
      }
    ],
    "message": "Text 3"
  },
  {
    "author": "Dave",
    "message": "Text 4"
  },
  {
    "author": "Erin",
    "message": "Text 5"
  },
  {
    "author": "Faythe",
    "emotes": [
      {
        "images": [
          "https://some-host.com/some-other-url.svg",
          "https://www.youtube.com/s/gaming/emoji/828cb648/emoji_u1f44b.svg"
        ],
        "name": ":waving_hand:"
      }
    ],
    "message": "Text 6"
  }
]

Demo