help adding and deleting nested array elements in v4

[olets]

I'm moving my project git-replay from yq v3 to v4, and am having trouble finding the correct new syntax for two things.

Working with a file like

# myfile.yaml
array_1:
  array_2:
    - array_element_1
    - array_element_2

in v3 I would use

yq d myfile.yaml array_1.array_2.array_element_1

to delete array_element_1 and

yq w myfile.yaml "array_1.array_2[+]" array_element_3

to add array_element_3.

What's the best v4 approach? Thanks!

[mikefarah]

https://mikefarah.gitbook.io/yq/operators/delete#delete-nested-entry-in-array

https://mikefarah.gitbook.io/yq/operators/add#add-string-to-array

[olets]

Thanks for your help and for this great tool!

For deleting I'm trying to delete a string array entry by value. For example delete c in

a:
  b:
    - c
    - d

I've tried del(.a.b.c), del([0].a.b.c), del(.a.b.c.[0]), del([0].a.b.c.[0]), and del(.a.b["c"]) and all give a "Cannot index array with <the problem node> (strconv.ParseInt: parsing <the problem node>: invalid syntax)". I've also tried del(.a.b.[0].c) and that does not error but it returns the input unchanged. I've also tried del(.a.b.[0].["c"]), del(.a.b["c"]), and .a.b = .a.b - "c" all of which are errors.

Is it possible to look up an array item's index? del(.a.b[i]) and del(.a.b.[i]) where i is the string element's index might work if I could get i (I'm not currently requiring uniqueness but I could). I have not found that in the docs.

---

For anyone else reading, the add solution to my problem combines the "add string to array" and "update array (append)" examples: yq e '.a.b = .a.b + "e"' input

edit: My add solution will not work

#myfile
a:
  b:
    - c

yq e '.a.d = .a.d + "e"' myfile --inplace

#myfile
a:
  b:
    - c
  d: e

yq e '.a.d = .a.d + "f"' myfile --inplace

#myfile
a:
  b:
    - c
  d: ef

where the goal is

#myfile
a:
  b:
    - c
  d:
    - e
    - f

.a.d[0] = e followed by .a.d[1] = f would work. Is there an array append? Tried .a.d[+] = and .a.d +=. Or is it possible to get the length of the array? Tried length(.a.b), length .a.b and .a.b length.

[mikefarah]

I'm getting confused - I think this should have been two posts.

To delete 'c' in the a.b. array:

yq e 'del(.a.b.[] | select(.=="c"))' examples/data1.yaml

This basically splats the a.b array, then selects the matching elements to delete.

To do the append thing, the issue is it has no value to start with, so when you += a scalar (string/number) it has no way of knowing that what you want is an array.

You can fix this by either wrapping it in an array:

yq e '.a.d = .a.d + ["e"]' myfile --inplace

or providing a default value when it's not defined:

yq e '.a.d = (.a.d // []) + "e"'

[olets]

I think this should have been two posts.

Fair. I'll move follow ups to new questions.

Thanks for the help!