[cmd/mdatagen] Add support for optional attribute

[sincejune]

Description

Add support for optional attribute, ref: Conditional Required Attribute

Notes:

• Add helper.tmpl for helper templates
• Add With<AttributeName>EventAttribute and With<AttributeName>MetricAttribute for optional attributes
• Add some helper functions in go files.

Link to tracking issue

Relevant to #12571

Testing

Updated

Documentation

Added

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 98.18182% with 2 lines in your changes missing coverage. Please review.

Project coverage is 91.31%. Comparing base (c9aaed8) to head (055c400). Report is 52 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/mdatagen/internal/command.go	92.30%	0 Missing and 2 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13007      +/-   ##
==========================================
+ Coverage   91.29%   91.31%   +0.02%     
==========================================
  Files         509      509              
  Lines       28735    28807      +72     
==========================================
+ Hits        26233    26305      +72     
+ Misses       1988     1986       -2     
- Partials      514      516       +2     

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[sincejune]

I added some helper functions in the Go files to simplify the templates. I'd like to remove the helper functions if possible, but it doesn't seem to be easy.

[dmitryax]

Can you please provide a specific use case? The whole point of the attributes defined in the metadata.yaml is to provide end-users visibility on the exact set of attribute being emitted. It's already possible to add any attributes to the generated metrics/event even without this extra API, but this should be strongly discouraged

[sincejune]

Can you please provide a specific use case? The whole point of the attributes defined in the metadata.yaml is to provide end-users visibility on the exact set of attribute being emitted. It's already possible to add any attributes to the generated metrics/event even without this extra API, but this should be strongly discouraged

I was working on the PR mentioned below, and I noticed that certain attributes in the events are only pushed when there is an increment in their values. Therefore, I created this PR to introduce optional attributes to address this behavior.

https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/40041/files#diff-e3b3d58b3d3a0c9d1db62068e7c47e72edcaa6409091343ce5ed0e9e48947eebR10

[dmitryax]

@sincejune, thanks for clarifying, this makes sense to me. Can you please address the comment from @jinja2

[github-actions[bot]]

This PR was marked stale due to lack of activity. It will be closed in 14 days.