[pkg/stanza] `TimeParser` unmarshaling ignores original configuration

[mx-psi]

Component(s)

pkg/stanza

What happened?

Description

The TimeParser struct seems to ignore the original configuration if the struct was initialized with something other than the default values:

opentelemetry-collector-contrib/pkg/stanza/operator/helper/time.go

Lines 49 to 57 in b25b78a

	func (t *TimeParser) Unmarshal(component *confmap.Conf) error {
	cfg := NewTimeParser()
	err := component.Unmarshal(&cfg, confmap.WithIgnoreUnused())
	if err != nil {
	return err
	}
	*t = cfg
	return nil
	}

Steps to Reproduce

This test reproduces it

func TestUnmarshal(t *testing.T) {
	conf := confmap.NewFromStringMap(map[string]any{
		"location": "America/Shiprock",
	})
	tp := TimeParser{
		Layout: "1/2/2006 15:04:05",
	}

	require.NoError(t, tp.Unmarshal(conf))
	assert.Equal(t, "America/Shiprock", tp.Location) // ok
	assert.Equal(t, "strptime", tp.LayoutType)           // ok, although weird
	assert.Equal(t, "1/2/2006 15:04:05", tp.Layout)  // FAIL --> empty
}

Expected Result

All assertions pass

Actual Result

The last assertion fails

Collector version

Tested as of b25b78a

Environment information

No response

OpenTelemetry Collector configuration

No response

Log output

No response

Additional context

I think NewTimeParser should be part of the default configuration of time parser instead of this, and we should do the 'set to nil' trick from https://github.com/open-telemetry/opentelemetry-collector/blob/c72092e00151ce8e4cfef32c73b3a80d54076278/receiver/otlpreceiver/config.go#L68-L70 if we want to only set default config if the key exists.

[github-actions]

Pinging code owners:

• pkg/stanza: @djaglowski

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[mx-psi]

Found on open-telemetry/opentelemetry-collector#9862 (comment), cc @atoulme

[atoulme]

Agreed that this can be considered a bug.

[atoulme]

I believe #31802 addresses this bug.