metricdatatest: Improve printing of diffs

CHANGELOG.md

@@ -24,6 +24,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Introduce the `EMPTY` Type in `go.opentelemetry.io/otel/attribute` to reflect that an empty value is now a valid value, with `INVALID` remaining as a deprecated alias of `EMPTY`. (#8038)
 - Refactor slice handling in `go.opentelemetry.io/otel/attribute` to optimize short slice values with fixed-size fast paths. (#8039)
 - Improve performance of span metric recording in `go.opentelemetry.io/otel/sdk/trace` by returning early if self-observability is not enabled. (#8067)
+- Improve formatting of metric data diffs in `go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest`. (#8073)
 
 ### Deprecated
 

sdk/metric/metricdata/metricdatatest/comparisons.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"reflect"
 	"slices"
+	"strings"
 
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
@@ -23,14 +24,16 @@ func equalResourceMetrics(a, b metricdata.ResourceMetrics, cfg config) (reasons
 		reasons = append(reasons, notEqualStr("Resources", a.Resource, b.Resource))
 	}
 
-	r := compareDiff(diffSlices(
+	r := diffSlices(
 		a.ScopeMetrics,
 		b.ScopeMetrics,
-		func(a, b metricdata.ScopeMetrics) bool {
-			r := equalScopeMetrics(a, b, cfg)
-			return len(r) == 0
+		func(sm metricdata.ScopeMetrics) string {
+			return fmt.Sprintf("Scope %q", sm.Scope.Name)
 		},
-	))
+		func(a, b metricdata.ScopeMetrics) []string {
+			return equalScopeMetrics(a, b, cfg)
+		},
+	)
 	if r != "" {
 		reasons = append(reasons, "ResourceMetrics ScopeMetrics not equal:\n"+r)
 	}
@@ -47,14 +50,16 @@ func equalScopeMetrics(a, b metricdata.ScopeMetrics, cfg config) (reasons []stri
 		reasons = append(reasons, notEqualStr("Scope", a.Scope, b.Scope))
 	}
 
-	r := compareDiff(diffSlices(
+	r := diffSlices(
 		a.Metrics,
 		b.Metrics,
-		func(a, b metricdata.Metrics) bool {
-			r := equalMetrics(a, b, cfg)
-			return len(r) == 0
+		func(m metricdata.Metrics) string {
+			return fmt.Sprintf("Metric %q", m.Name)
+		},
+		func(a, b metricdata.Metrics) []string {
+			return equalMetrics(a, b, cfg)
 		},
-	))
+	)
 	if r != "" {
 		reasons = append(reasons, "ScopeMetrics Metrics not equal:\n"+r)
 	}
@@ -163,14 +168,16 @@ func equalAggregations(a, b metricdata.Aggregation, cfg config) (reasons []strin
 // The DataPoints each Gauge contains are compared based on containing the
 // same DataPoints, not the order they are stored in.
 func equalGauges[N int64 | float64](a, b metricdata.Gauge[N], cfg config) (reasons []string) {
-	r := compareDiff(diffSlices(
+	r := diffSlices(
 		a.DataPoints,
 		b.DataPoints,
-		func(a, b metricdata.DataPoint[N]) bool {
-			r := equalDataPoints(a, b, cfg)
-			return len(r) == 0
+		func(dp metricdata.DataPoint[N]) string {
+			return fmt.Sprintf("DataPoint [%v]", dp.Attributes.Encoded(attribute.DefaultEncoder()))
 		},
-	))
+		func(a, b metricdata.DataPoint[N]) []string {
+			return equalDataPoints(a, b, cfg)
+		},
+	)
 	if r != "" {
 		reasons = append(reasons, "Gauge DataPoints not equal:\n"+r)
 	}
@@ -190,14 +197,16 @@ func equalSums[N int64 | float64](a, b metricdata.Sum[N], cfg config) (reasons [
 		reasons = append(reasons, notEqualStr("IsMonotonic", a.IsMonotonic, b.IsMonotonic))
 	}
 
-	r := compareDiff(diffSlices(
+	r := diffSlices(
 		a.DataPoints,
 		b.DataPoints,
-		func(a, b metricdata.DataPoint[N]) bool {
-			r := equalDataPoints(a, b, cfg)
-			return len(r) == 0
+		func(dp metricdata.DataPoint[N]) string {
+			return fmt.Sprintf("DataPoint [%v]", dp.Attributes.Encoded(attribute.DefaultEncoder()))
+		},
+		func(a, b metricdata.DataPoint[N]) []string {
+			return equalDataPoints(a, b, cfg)
 		},
-	))
+	)
 	if r != "" {
 		reasons = append(reasons, "Sum DataPoints not equal:\n"+r)
 	}
@@ -214,14 +223,16 @@ func equalHistograms[N int64 | float64](a, b metricdata.Histogram[N], cfg config
 		reasons = append(reasons, notEqualStr("Temporality", a.Temporality, b.Temporality))
 	}
 
-	r := compareDiff(diffSlices(
+	r := diffSlices(
 		a.DataPoints,
 		b.DataPoints,
-		func(a, b metricdata.HistogramDataPoint[N]) bool {
-			r := equalHistogramDataPoints(a, b, cfg)
-			return len(r) == 0
+		func(dp metricdata.HistogramDataPoint[N]) string {
+			return fmt.Sprintf("HistogramDataPoint [%v]", dp.Attributes.Encoded(attribute.DefaultEncoder()))
 		},
-	))
+		func(a, b metricdata.HistogramDataPoint[N]) []string {
+			return equalHistogramDataPoints(a, b, cfg)
+		},
+	)
 	if r != "" {
 		reasons = append(reasons, "Histogram DataPoints not equal:\n"+r)
 	}
@@ -258,14 +269,16 @@ func equalDataPoints[N int64 | float64](
 	}
 
 	if !cfg.ignoreExemplars {
-		r := compareDiff(diffSlices(
+		r := diffSlices(
 			a.Exemplars,
 			b.Exemplars,
-			func(a, b metricdata.Exemplar[N]) bool {
-				r := equalExemplars(a, b, cfg)
-				return len(r) == 0
+			func(_ metricdata.Exemplar[N]) string {
+				return "Exemplar"
 			},
-		))
+			func(a, b metricdata.Exemplar[N]) []string {
+				return equalExemplars(a, b, cfg)
+			},
+		)
 		if r != "" {
 			reasons = append(reasons, "Exemplars not equal:\n"+r)
 		}
@@ -315,14 +328,16 @@ func equalHistogramDataPoints[N int64 | float64](
 		}
 	}
 	if !cfg.ignoreExemplars {
-		r := compareDiff(diffSlices(
+		r := diffSlices(
 			a.Exemplars,
 			b.Exemplars,
-			func(a, b metricdata.Exemplar[N]) bool {
-				r := equalExemplars(a, b, cfg)
-				return len(r) == 0
+			func(_ metricdata.Exemplar[N]) string {
+				return "Exemplar"
 			},
-		))
+			func(a, b metricdata.Exemplar[N]) []string {
+				return equalExemplars(a, b, cfg)
+			},
+		)
 		if r != "" {
 			reasons = append(reasons, "Exemplars not equal:\n"+r)
 		}
@@ -343,14 +358,16 @@ func equalExponentialHistograms[N int64 | float64](
 		reasons = append(reasons, notEqualStr("Temporality", a.Temporality, b.Temporality))
 	}
 
-	r := compareDiff(diffSlices(
+	r := diffSlices(
 		a.DataPoints,
 		b.DataPoints,
-		func(a, b metricdata.ExponentialHistogramDataPoint[N]) bool {
-			r := equalExponentialHistogramDataPoints(a, b, cfg)
-			return len(r) == 0
+		func(dp metricdata.ExponentialHistogramDataPoint[N]) string {
+			return fmt.Sprintf("ExponentialHistogramDataPoint [%v]", dp.Attributes.Encoded(attribute.DefaultEncoder()))
+		},
+		func(a, b metricdata.ExponentialHistogramDataPoint[N]) []string {
+			return equalExponentialHistogramDataPoints(a, b, cfg)
 		},
-	))
+	)
 	if r != "" {
 		reasons = append(reasons, "Histogram DataPoints not equal:\n"+r)
 	}
@@ -409,14 +426,16 @@ func equalExponentialHistogramDataPoints[N int64 | float64](
 		}
 	}
 	if !cfg.ignoreExemplars {
-		r := compareDiff(diffSlices(
+		r := diffSlices(
 			a.Exemplars,
 			b.Exemplars,
-			func(a, b metricdata.Exemplar[N]) bool {
-				r := equalExemplars(a, b, cfg)
-				return len(r) == 0
+			func(_ metricdata.Exemplar[N]) string {
+				return "Exemplar"
 			},
-		))
+			func(a, b metricdata.Exemplar[N]) []string {
+				return equalExemplars(a, b, cfg)
+			},
+		)
 		if r != "" {
 			reasons = append(reasons, "Exemplars not equal:\n"+r)
 		}
@@ -435,14 +454,16 @@ func equalExponentialBuckets(a, b metricdata.ExponentialBucket, _ config) (reaso
 }
 
 func equalSummary(a, b metricdata.Summary, cfg config) (reasons []string) {
-	r := compareDiff(diffSlices(
+	r := diffSlices(
 		a.DataPoints,
 		b.DataPoints,
-		func(a, b metricdata.SummaryDataPoint) bool {
-			r := equalSummaryDataPoint(a, b, cfg)
-			return len(r) == 0
+		func(dp metricdata.SummaryDataPoint) string {
+			return fmt.Sprintf("SummaryDataPoint [%v]", dp.Attributes.Encoded(attribute.DefaultEncoder()))
+		},
+		func(a, b metricdata.SummaryDataPoint) []string {
+			return equalSummaryDataPoint(a, b, cfg)
 		},
-	))
+	)
 	if r != "" {
 		reasons = append(reasons, "Summary DataPoints not equal:\n"+r)
 	}
@@ -472,14 +493,16 @@ func equalSummaryDataPoint(a, b metricdata.SummaryDataPoint, cfg config) (reason
 		if a.Sum != b.Sum {
 			reasons = append(reasons, notEqualStr("Sum", a.Sum, b.Sum))
 		}
-		r := compareDiff(diffSlices(
+		r := diffSlices(
 			a.QuantileValues,
 			b.QuantileValues,
-			func(a, b metricdata.QuantileValue) bool {
-				r := equalQuantileValue(a, b, cfg)
-				return len(r) == 0
+			func(qv metricdata.QuantileValue) string {
+				return fmt.Sprintf("QuantileValue %v", qv.Quantile)
 			},
-		))
+			func(a, b metricdata.QuantileValue) []string {
+				return equalQuantileValue(a, b, cfg)
+			},
+		)
 		if r != "" {
 			reasons = append(reasons, r)
 		}
@@ -590,15 +613,18 @@ func equalExemplars[N int64 | float64](a, b metricdata.Exemplar[N], cfg config)
 	return reasons
 }
 
-func diffSlices[T any](a, b []T, equal func(T, T) bool) (extraA, extraB []T) {
+func diffSlices[T any](a, b []T, formatContext func(T) string, compare func(T, T) []string) string {
 	visited := make([]bool, len(b))
+	var extraA []T
+	var extraB []T
+
 	for i := range a {
 		found := false
 		for j := range b {
 			if visited[j] {
 				continue
 			}
-			if equal(a[i], b[j]) {
+			if len(compare(a[i], b[j])) == 0 {
 				visited[j] = true
 				found = true
 				break
@@ -616,30 +642,40 @@ func diffSlices[T any](a, b []T, equal func(T, T) bool) (extraA, extraB []T) {
 		extraB = append(extraB, b[j])
 	}
 
-	return extraA, extraB
-}
-
-func compareDiff[T any](extraExpected, extraActual []T) string {
-	if len(extraExpected) == 0 && len(extraActual) == 0 {
+	if len(extraA) == 0 && len(extraB) == 0 {
 		return ""
 	}
 
+	var msg bytes.Buffer
+	minLen := min(len(extraB), len(extraA))
+
+	for i := range minLen {
+		reasons := compare(extraA[i], extraB[i])
+		_, _ = msg.WriteString(formatContext(extraA[i]) + ":\n")
+		for _, reason := range reasons {
+			// Indent reasons
+			lines := strings.SplitSeq(reason, "\n")
+			for line := range lines {
+				if line != "" {
+					_, _ = msg.WriteString("\t" + line + "\n")
+				}
+			}
+		}
+	}
+
 	formatter := func(v T) string {
 		return fmt.Sprintf("%#v", v)
 	}
-
-	var msg bytes.Buffer
-	if len(extraExpected) > 0 {
+	if len(extraA) > minLen {
 		_, _ = msg.WriteString("missing expected values:\n")
-		for _, v := range extraExpected {
-			_, _ = msg.WriteString(formatter(v) + "\n")
+		for i := minLen; i < len(extraA); i++ {
+			_, _ = msg.WriteString(formatter(extraA[i]) + "\n")
 		}
 	}
-
-	if len(extraActual) > 0 {
+	if len(extraB) > minLen {
 		_, _ = msg.WriteString("unexpected additional values:\n")
-		for _, v := range extraActual {
-			_, _ = msg.WriteString(formatter(v) + "\n")
+		for i := minLen; i < len(extraB); i++ {
+			_, _ = msg.WriteString(formatter(extraB[i]) + "\n")
 		}
 	}