Difference between searching and substituting pattern matching

Question

I have a string in a JSON file which is repeated with different values for chance. I want to replace all of these blocks by moving the miss chance out of the attack array and into a separate property.

"attacks": [
  {
    "name": "miss",
    "chance": "0.25"
  },
  ...
]

"missChance": 0.25,
"attacks": [
  ...
]

I managed to write a (basic) search pattern that would find all of these bits of JSON, and had grouping so I would be able to pull out the chance:

/"attacks":\s*[\_s*{\_s*"name":\s*"miss",\_s*"chance":\s"\(0\.\d*\)"\_s*},

However, although this search pattern would find all of the occurrences I wanted to replace, when I use it in a substitute command it returns "Pattern not found". The substitute I was using was:

:%s/"attacks":\s*[\_s*{\_s*"name":\s*"miss",\_s*"chance":\s"\(0\.\d*\)"\_s*},/"missChance": \1^M"attacks": [/g

I have noticed that the error includes more of the search pattern than I expected; it looks like it's searching for everything after the second "/" separator for some reason. Why would the search be different in the substitute command to in a normal search?

This is the error: Pattern not found: "attacks":\s*[\_s*{\_s*"name":\s*"miss",\_s*"chance":\s"\(0\.\d*\)"\_s*},/"missChance": \1,^M"attacks": [/g

Answer 1

Try to escape the opening square bracket, otherwise the whole command becomes the pattern.

:%s/"attacks":\s*\[\_s*{\_s*"name":\s*"miss",\_s*"chance":\s"\(0\.\d*\)"\_s*},/"missChance": \1^M"attacks": [/g
                 ^

---

If you don't escape it, the pattern in this substitution command:

:%s/"attacks":\s*[\_s*{\_s*"name":\s*"miss",\_s*"chance":\s"\(0\.\d*\)"\_s*},/"missChance": \1^M"attacks": [/g

is not:

"attacks":\s*[\_s*{\_s*"name":\s*"miss",\_s*"chance":\s"\(0\.\d*\)"\_s*},

but instead:

"attacks":\s*[\_s*{\_s*"name":\s*"miss",\_s*"chance":\s"\(0\.\d*\)"\_s*},/"missChance": \1^M"attacks": [/g

This is explained at :h E769:

When the ']' is not there Vim will not give an error message but assume no collection is used. Useful to search for '['. However, you do get E769 for internal searching. And be aware that in a :substitute command the whole command becomes the pattern. E.g. ":s/[/x/" searches for "[/x" and replaces it with nothing. It does not search for "[" and replaces it with "x"!