[processor/transform] Improve function errror handling

[TylerHelmuth]

Something to be dealt with in a different PR but... should we error out on this case instead? Silently failing to do what the user asks does not seem like great UX, and if the spec ever changes in this regard, we can't change this without potentially breaking users unless we return an error.

Originally posted by @mx-psi in https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/12632#issuecomment-1191675976

The transform processor's set function is no-op for setting nil, but is silent about it. That can create a bad user experience, where nothing happens if you try to set a field to nil, but it doesn't tell you nothing happened. The set function, and other no-op situations, should log a warning/info stating that nothing happened.

no-op scenarios that should log:

• trying to use the set function to set a field to nil
• trying to use the set function to set a metrics' data type. This should be handled in the metrics context.

no-op scenarios that maybe should log?

• deleting a key that didn't exist

[github-actions[bot]]

Pinging code owners: @Aneurysm9 @bogdandrutu @TylerHelmuth @kentquirk

[frzifus]

Hi, could you assign that to me? :)

[TylerHelmuth]

@frzifus its yours. Forewarned, accepting any changes to functions right now is dependent on some of these PRs being merged

[TylerHelmuth]

@frzifus the issue is closed. You should add the new changes to pkg/telemetryquerylanguage

[github-actions[bot]]

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This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

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[github-actions[bot]]

This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

Pinging code owners:

• processor/transform: @TylerHelmuth @kentquirk @bogdandrutu @evan-bradley

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[TylerHelmuth]

I believe this issue is now superseded by https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/16519