log/logtest: Add log.Record initializer

[dmathieu]

Problem Statement

Right now, creating and filling data for a log.Record requires calling method independently, and cannot be chained.

eg:

var record log.Record
record.SetTimestamp(e.Time)
record.SetBody(log.StringValue(e.Message))
record.SetSeverity(severity)
record.AddAttributes(data...)

This is a bit tedious, especially in test environments, where we end up having to setup methods to build records such as this one in the logrus bridge PR:

func buildRecord(body log.Value, timestamp time.Time, severity log.Severity, attrs []log.KeyValue) log.Record {
	var record log.Record
	record.SetBody(body)
	record.SetTimestamp(timestamp)
	record.SetSeverity(severity)
	record.AddAttributes(attrs...)

	return record
}

Proposed Solution

Add a NewRecord() helper method with optional arguments to create a new record.
The example above would become:

record := NewRecord(
    WithTimestamp(e.Time),
    WithBody(message),
    WithSeverity(severity),
    WithAttributes(data),
)

Alternative

I could change my buildRecord in logrus to use functional arguments, but that would have to be repeated across all bridges.

[pellared]

The functional options would introduce heap allocations. I do not support the proposal as we would then provide inefficient API that developers might use and then compliant that the API is not performant. More: https://github.com/open-telemetry/opentelemetry-go/blob/main/log/DESIGN.md#options-as-parameter-to-loggeremit.

[dmathieu]

What if we add it to the logtest package?
Then writing tests for bridges/implementations becomes easier, and there's a clear indication that it shouldn't be used at runtime?

[pellared]

What if we add it to the logtest package? Then writing tests for bridges/implementations becomes easier, and there's a clear indication that it shouldn't be used at runtime?

That makes a lot of sense.

I would also consider implementing it as a "builder" to not "spam" the package with options. So that the user could do something like:

record := logtest.NewRecordBuilder().
  SetBody(log.StringValue("message").
  SetTimestamp(timestamp).
  SetSeverity(severity).
  AddAttributes(data).
  Build()

It might be possible that a builder would not make a heap allocation - however, I doubt it.

[pellared]

@dmathieu, do you think we can do something like #5234 for this issue as well?

[dmathieu]

Yes, definitely. I'll wait for your PR to be approved before I start doing something similar for the API record.