yq/pkg/yqlib/doc/operators/comment-operators.md
2023-05-02 15:07:04 +10:00

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# Comment Operators
Use these comment operators to set or retrieve comments. Note that line comments on maps/arrays are actually set on the _key_ node as opposed to the _value_ (map/array). See below for examples.
Like the `=` and `|=` assign operators, the same syntax applies when updating comments:
### plain form: `=`
This will set the LHS nodes' comments equal to the expression on the RHS. The RHS is run against the matching nodes in the pipeline
### relative form: `|=`
This is similar to the plain form, but it evaluates the RHS with _each matching LHS node as context_. This is useful if you want to set the comments as a relative expression of the node, for instance its value or path.
## Where is the comment - map key example
The underlying yaml parser can assign comments in a document to surprising nodes. Use an expression like this to find where you comment is. 'p' indicates the path, 'isKey' is if the node is a map key (as opposed to a map value).
From this, you can see the 'hello-world-comment' is actually on the 'hello' key
Given a sample.yml file of:
```yaml
hello: # hello-world-comment
message: world
```
then
```bash
yq '[... | {"p": path | join("."), "isKey": is_key, "hc": headComment, "lc": lineComment, "fc": footComment}]' sample.yml
```
will output
```yaml
- p: ""
isKey: false
hc: ""
lc: ""
fc: ""
- p: hello
isKey: true
hc: ""
lc: hello-world-comment
fc: ""
- p: hello
isKey: false
hc: ""
lc: ""
fc: ""
- p: hello.message
isKey: true
hc: ""
lc: ""
fc: ""
- p: hello.message
isKey: false
hc: ""
lc: ""
fc: ""
```