Fix: Do not output undefined as line and column when it's unavailable in checkstyle format

[haya14busa]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[X] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What did you do? Please include the actual source code causing the issue.
Run eslint with checkstyle format and .eslintignore.

$ eslint ./testdata/*.js -f=checkstyle

What did you expect to happen?
eslintignore warning should output line and column as 0 or do not output line and column fields.

What actually happened? Please include the actual, raw output from ESLint.
eslintignore warning output undefined as line and column fields of checkstyle XML.

<?xml version="1.0" encoding="utf-8"?><checkstyle version="4.3"><file name="/home/haya14busa/src/github.com/reviewdog/action-eslint/testdata/test.js"><error line="undefined" column="undefined" severity="warning" message="File ignored because of a matching ignore pattern. Use &quot;--no-ignore&quot; to override." source="" /></file></checkstyle>

What changes did you make? (Give an overview)

Use 0 if line and column are undefined. It's consistent with other formatters.

Is there anything you'd like reviewers to focus on?

N/A

[mdjermanovic]

Hi @haya14busa, thanks for the PR!

eslintignore warning should output line and column as 0 or do not output line and column fields.

I think it's safe to output 0 (just as you implemented) rather than to omit those attributes, because some tools might expect them to be defined.

[mdjermanovic]

@haya14busa is there a specification for this format?

It seems that column="0" should be omitted:

https://github.com/checkstyle/checkstyle/blob/534a1669d67f62f1e64e879899fbeafaec41d364/src/main/java/com/puppycrawl/tools/checkstyle/XMLLogger.java#L191

On the other hand, line = "0" seems fine ("This may be 0 if there is no relation to a file content."):

https://github.com/checkstyle/checkstyle/blob/534a1669d67f62f1e64e879899fbeafaec41d364/src/main/java/com/puppycrawl/tools/checkstyle/api/AuditEvent.java#L94

[haya14busa]

I don't know, unfortunately. I just found this issue because parsing XML itself failed because line and column value was string "undefined".

As far as I know, there are no formal spec of checkstyle XML format (although many tools use it).
I checked the history briefly and looks like line presents from the beginning and column was added later (it's still from very old. May 13, 2002) as optional.
checkstyle/checkstyle@65989e7
This is just my guess, but at that time probably all check results have line number so there is no if check for line.

I'm fine to omit column if you prefer or omit both.
I think there are too many tools which consume checkstyle XML to check which is better.
I'd say both should be much better than "undefined" though.

[mdjermanovic]

Agreed, it definitely shouldn't be "undefined", so marked as accepted.

Since there is no formal spec, and since it seems that checkstyle itself can produce line="0" which should indicate that it isn't a location within the code, line="0" column="0" might be the best choice to start with. We could change it later (e.g., omit the column) based on the feedback.

[mdjermanovic]

LGTM, thanks!