If a line contains X, how do I replace the next line with Y?

Question

I'm trying to take a file with a whole bunch of text in a JSON file, and mass-edit the thing with Find & Replace rather than going through it line-by-line and copy+pasting the changes I want to make.

So for example, if I have a list of fruits and I want to simplify what type of tree it's grouped under then I would take this:

  "Fruit And Veg\\Fruits\\Apples - fuji apple": {
    "group": "Fuji apple tree"
  },
  "Fruit And Veg\\Fruits\\Apples - granny smith": {
    "group": "GrannySmith tree"
  },
  "Fruit And Veg\\Fruits\\Pears - nashi": {
    "group": "Nashi tree"
  },
  "Fruit And Veg\\Fruits\\Pears - concorde": {
    "group": "concorde pear tree"
  },

and have the find-and-replace tool change it to this:

  "Fruit And Veg\\Fruits\\Apples - fuji apple": {
    "group": "Apple Tree"
  },
  "Fruit And Veg\\Fruits\\Apples - granny smith": {
    "group": "Apple Tree"
  },
  "Fruit And Veg\\Fruits\\Pears - nashi": {
    "group": "Pear Tree"
  },
  "Fruit And Veg\\Fruits\\Pears - concorde": {
    "group": "Pear Tree"
  },

I want to have it search for a string of text within line 1 (in this case, Apples or Pears), then replace the contents of line 2 (so the line matches the Apple Tree or Pear Tree group, as applicable), and make no changes to line 3, for each entry in the file. I understand I would need to run a Find & Replace for Apples and Pears separately, and that's okay, but I'm not sure how to make this work.

At the moment, I think the file has the text I'm using to search only as plurals - but if that turns out not to be the case, is there a way for me to specify the Find part of the Find&Replace to be looking for "\\Apple" (to include the previous characters) instead of searching for "Apple" or "Apples"?

I've tried looking at other questions here, to see if I can find an identical issue, but haven't had much luck with that - and while I've been trying to figure out how to use ^.* \r\n $1, etc. from examples given on those pages on Stack Overflow, I don't really know what I'm doing at all. Even with 'Search Mode - Regular Expression', and toggling on '. matches newline', most of the things I've tried so far have either resulted in "Find: Can't find the text" or "Find: Invalid regular expression".

Answer 1

• Ctrl+H
• Find what: Fruit And Veg.+?(?:(Apple)|(Pear))s?.+\R.+?"group": \K".+tree"
• Replace with: (?1"Apple Tree")(?2"Pear Tree")
• TICK Match case
• TICK Wrap around
• Search Mode Regular expression
• UNTICK . matches newline
• Replace all

Explanation:

Fruit And Veg   # literally
.+?             # 1 or more any character, not greedy
(?:             # non capture group
    (Apple)         # group 1, Apples
  |               # OR
    (Pear)          # group 2, Pears
)               # end group
s?              # optional s
.+              # 1 or more any character
\R              # any kind of linebreak
.+?             # 1 or more any character, not greedy
"group":        # literally
\K              # forget all we have seen until this position
".+tree"        # 1 or more character and tree

Replacement:

(?1"Apple Tree")    # if group 1 exists, pur Apple Tree
(?2"Pear Tree")     # if group 2 exists, put Pear Tree

Screenshot (before):

Screenshot (after):