[pkg/pmetrictest] option to ignore float precision discrepancies when…

… using `CompareMetrics` (open-telemetry#35085)

**Description:** <Describe what has changed.>
Addresses issue:
open-telemetry#35060
Adds option to `CompareMetrics` testing function that rounds floats to
an arbitrary number of decimals. This is needed to avoid issues with
float precision during testing.

**Link to tracking Issue:** <Issue number if applicable>

open-telemetry#35060

**Testing:** <Describe what testing was performed and which tests were
added.>
Test and test data added for this CompareMetrics option

**Documentation:** 
No new docs. Let me know if I should be adding something somewhere!

Co-authored-by: Antoine Toulme <atoulme@splunk.com>

pkg/pdatatest/pmetrictest/metrics_test.go

@@ -240,6 +240,13 @@ func TestCompareMetrics(t *testing.T) {
 			},
 			withoutOptions: errors.New(`resource "map[]": scope "": metric "gauge.one": datapoint "map[]": double value doesn't match expected: 123.456000, actual: 654.321000`),
 		},
+		{
+			name: "ignore-data-point-value-double-precision",
+			compareOptions: []CompareMetricsOption{
+				IgnoreMetricFloatPrecision(3),
+			},
+			withoutOptions: errors.New(`resource "map[]": scope "": metric "gauge.one": datapoint "map[]": double value doesn't match expected: 654.321110, actual: 654.321000`),
+		},
 		{
 			name: "ignore-data-point-value-int-mismatch",
 			compareOptions: []CompareMetricsOption{

pkg/pdatatest/pmetrictest/options.go

@@ -6,6 +6,7 @@ package pmetrictest // import "github.com/open-telemetry/opentelemetry-collector
 import (
 	"bytes"
 	"fmt"
+	"math"
 	"regexp"
 	"sort"
 	"time"
@@ -110,6 +111,56 @@ func maskHistogramDataPointSliceValues(dataPoints pmetric.HistogramDataPointSlic
 	}
 }
 
+// IgnoreMetricFloatPrecision is a CompareMetricsOption that rounds away float precision discrepancies in metric values.
+func IgnoreMetricFloatPrecision(precision int, metricNames ...string) CompareMetricsOption {
+	return compareMetricsOptionFunc(func(expected, actual pmetric.Metrics) {
+		floatMetricValues(precision, expected, metricNames...)
+		floatMetricValues(precision, actual, metricNames...)
+	})
+}
+
+func floatMetricValues(precision int, metrics pmetric.Metrics, metricNames ...string) {
+	rms := metrics.ResourceMetrics()
+	for i := 0; i < rms.Len(); i++ {
+		ilms := rms.At(i).ScopeMetrics()
+		for j := 0; j < ilms.Len(); j++ {
+			floatMetricSliceValues(precision, ilms.At(j).Metrics(), metricNames...)
+		}
+	}
+}
+
+// floatMetricSliceValues sets all data point values to zero.
+func floatMetricSliceValues(precision int, metrics pmetric.MetricSlice, metricNames ...string) {
+	metricNameSet := make(map[string]bool, len(metricNames))
+	for _, metricName := range metricNames {
+		metricNameSet[metricName] = true
+	}
+	for i := 0; i < metrics.Len(); i++ {
+		if len(metricNames) == 0 || metricNameSet[metrics.At(i).Name()] {
+			switch metrics.At(i).Type() {
+			case pmetric.MetricTypeEmpty, pmetric.MetricTypeSum, pmetric.MetricTypeGauge:
+				roundDataPointSliceValues(getDataPointSlice(metrics.At(i)), precision)
+			default:
+				panic(fmt.Sprintf("data type not supported: %s", metrics.At(i).Type()))
+			}
+		}
+	}
+}
+
+// maskDataPointSliceValues rounds all data point values at a given decimal.
+func roundDataPointSliceValues(dataPoints pmetric.NumberDataPointSlice, precision int) {
+	for i := 0; i < dataPoints.Len(); i++ {
+		dataPoint := dataPoints.At(i)
+		factor := math.Pow(10, float64(precision))
+		switch {
+		case dataPoint.DoubleValue() != 0.0:
+			dataPoint.SetDoubleValue(math.Round(dataPoint.DoubleValue()*factor) / factor)
+		case dataPoint.IntValue() != 0:
+			panic(fmt.Sprintf("integers can not have float precision ignored: %v", dataPoints.At(i)))
+		}
+	}
+}
+
 // IgnoreTimestamp is a CompareMetricsOption that clears Timestamp fields on all the data points.
 func IgnoreTimestamp() CompareMetricsOption {
 	return compareMetricsOptionFunc(func(expected, actual pmetric.Metrics) {

pkg/pdatatest/pmetrictest/testdata/ignore-data-point-value-double-precision/actual.yaml

@@ -0,0 +1,9 @@
+resourceMetrics:
+  - resource: {}
+    scopeMetrics:
+      - metrics:
+          - gauge:
+              dataPoints:
+                - asDouble: 654.321
+            name: gauge.one
+        scope: {}

pkg/pdatatest/pmetrictest/testdata/ignore-data-point-value-double-precision/expected.yaml

@@ -0,0 +1,9 @@
+resourceMetrics:
+  - resource: {}
+    scopeMetrics:
+      - metrics:
+          - gauge:
+              dataPoints:
+                - asDouble: 654.32111
+            name: gauge.one
+        scope: {}