Function convertReaderToMetricFamily

prometheus/testutil/testutil.go:264–286

convertReaderToMetricFamily would read from a io.Reader object and convert it to a slice of dto.MetricFamily.

(reader io.Reader)

// convertReaderToMetricFamily would read from a io.Reader object and convert it to a slice of
// dto.MetricFamily.
func convertReaderToMetricFamily(reader io.Reader) ([]*dto.MetricFamily, error) {
	tp := expfmt.NewTextParser(model.UTF8Validation)
	notNormalized, err := tp.TextToMetricFamilies(reader)
	if err != nil {
		return nil, fmt.Errorf("converting reader to metric families failed: %w", err)
	}

	// The text protocol handles empty help fields inconsistently. When
	// encoding, any non-nil value, include the empty string, produces a
	// "# HELP" line. But when decoding, the help field is only set to a
	// non-nil value if the "# HELP" line contains a non-empty value.
	//
	// Because metrics in a registry always have non-nil help fields, populate
	// any nil help fields in the parsed metrics with the empty string so that
	// when we compare text encodings, the results are consistent.
	for _, metric := range notNormalized {
		if metric.Help == nil {
			metric.Help = proto.String("")
		}
	}

	return internal.NormalizeMetricFamilies(notNormalized), nil
}

// compareMetricFamilies would compare 2 slices of metric families, and optionally filters both of
// them to the `metricNames` provided.