Support filters in YAML path

[christiansiegel]

The replace mechanism only supports selecting the YAML path by object key and array index (e.g. foo.bar.[0].baz). This is quite fragile if you have to replace within arrays.

Example:

# kustomizazion.yaml
images:
- name: frontend
  newTag: v2
- name: backend
  newTag: v2

or

# values.yaml
myapp:
   env:
   - name: FOO
     value: foo
   - name: BAR
     value: bar

Replacing the image tags or the env values requires the array to be in a stable order. Also the replacement path is hard to read if you don't know the YAML file: myapp.env.[1].value -> are we replacing FOO or BAR here?

Possible solution:
JsonPath has filter expressions. Selecting the value of FOO would look like this: myapp.env[?(@.name=='FOO')].value

There is a python library jsonpath-ng which can output the matching paths:

>>> jsonpath_expr = parse('foo[*].baz')
# Matches remember where they came from
>>> [str(match.full_path) for match in jsonpath_expr.find({'foo': [{'baz': 1}, {'baz': 2}]})]
['foo.[0].baz', 'foo.[1].baz']

Those returned full_path strings are exactly the simplified YAML path supported by the GitOpsCLI. We could just plug this library in between and translate complicated JsonPath expressions.

The library even has a short form to specify the filters: myapp.env[?name=='FOO'].value

This solution would be backwards compatible. However, we could also choose to just enable this JsonPath translation feature via CLI flag. Any opinions on that?

[christiansiegel]

Just noticed that jsonpath-ng also has an update function. This could replace the whole self-built path parse & replace. It also works in combination with ruamel.yaml because it only operates on the loaded python objects.

WIP on branch feat/json-path

[joachimprinzbach]

I would change the implementation in the back for all cli functions instead of using a feature flag. Reasoning: Feature flag could be great for testing, but in the long term will increase support and maintenance / testing efforts.

[baopso]

🎉 This issue has been resolved in version 5.3.0 🎉

The release is available on:

• v5.3.0
• GitHub release

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