Improve detail in stdout exporter

[rebeccajae]

This addresses the issue raised in #425 regarding the level of detail provided by the stdout exporter.

As per the comments on that issue, I've opted to use just key names to represent unspecified keys. This seemed to be more well-received than putting them in a separate field.

In addition, this adjusts the test TestDefaultSDK in api/global/internal/meter_test.go which uses the stdout exporter. Since this adds a specified label to the counter, the new handling of the stdout exporter changes the output.

[rghetia]

Looks good overall. Can you please add a test for empty label?

[rebeccajae]

@rghetia - I put the test in the api/global/internal/meter_test.go file. Although it's not grouped with the stdout exporter, the test case is similar to a pre-existing test case in that file. Additionally, since global state is stored in internal I couldn't modify it from the stdout_test.go file easily.

I'm not sure if this is the best place for that test, and I felt that just trying to use non-colliding meter names could lead to confusion if the tests grow and re-use meter names.

[rghetia]

@rghetia - I put the test in the api/global/internal/meter_test.go file. Although it's not grouped with the stdout exporter, the test case is similar to a pre-existing test case in that file. Additionally, since global state is stored in internal I couldn't modify it from the stdout_test.go file easily.

I'm not sure if this is the best place for that test, and I felt that just trying to use non-colliding meter names could lead to confusion if the tests grow and re-use meter names.

test in stdout_test.go is preferable. For example (based on TestStdoutCounter),.

func TestStdoutCounterWithUnspecifiedKeys(t *testing.T) {
	fix := newFixture(t, stdout.Config{})

	checkpointSet := test.NewCheckpointSet(sdk.NewDefaultLabelEncoder())

	keys := []core.Key{key.New("E")}

	desc := export.NewDescriptor("test.name", export.CounterKind, keys, "", "", core.Int64NumberKind, false)
	cagg := counter.New()
	aggtest.CheckedUpdate(fix.t, cagg, core.NewInt64Number(123), desc)
	cagg.Checkpoint(fix.ctx, desc)

	checkpointSet.Add(desc, cagg, key.String("A", "B"), key.String("C", "D"))

	fix.Export(checkpointSet)

	require.Equal(t, `{"updates":[{"name":"test.name{A=B,C=D,E}","sum":123}]}`, fix.Output())
}

[lizthegrey]

I'd like @paivagustavo's eyes before we merge.

[paivagustavo]

Very happy with the discussions that you raised on this issue and with your solution, @rebeccajae. Thanks :)