From 713e6eb604002f6afff0bcfd8edcd7a15685b1e4 Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Mon, 17 Sep 2018 11:50:42 +0200
Subject: [PATCH] Let NewConst... functions detect invalid Desc

The error of the invalid Desc is returned in that case.

Signed-off-by: beorn7 <beorn@soundcloud.com>
---
 prometheus/histogram.go | 5 ++++-
 prometheus/summary.go   | 5 ++++-
 prometheus/value.go     | 6 +++++-
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/prometheus/histogram.go b/prometheus/histogram.go
index a1868d2..7086b76 100644
--- a/prometheus/histogram.go
+++ b/prometheus/histogram.go
@@ -554,7 +554,7 @@ func (h *constHistogram) Write(out *dto.Metric) error {
 // bucket.
 //
 // NewConstHistogram returns an error if the length of labelValues is not
-// consistent with the variable labels in Desc.
+// consistent with the variable labels in Desc or if Desc is invalid.
 func NewConstHistogram(
 	desc *Desc,
 	count uint64,
@@ -562,6 +562,9 @@ func NewConstHistogram(
 	buckets map[float64]uint64,
 	labelValues ...string,
 ) (Metric, error) {
+	if desc.err != nil {
+		return nil, desc.err
+	}
 	if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
 		return nil, err
 	}
diff --git a/prometheus/summary.go b/prometheus/summary.go
index 38ee98c..12ff034 100644
--- a/prometheus/summary.go
+++ b/prometheus/summary.go
@@ -586,7 +586,7 @@ func (s *constSummary) Write(out *dto.Metric) error {
 //     map[float64]float64{0.5: 0.23, 0.99: 0.56}
 //
 // NewConstSummary returns an error if the length of labelValues is not
-// consistent with the variable labels in Desc.
+// consistent with the variable labels in Desc or if Desc is invalid.
 func NewConstSummary(
 	desc *Desc,
 	count uint64,
@@ -594,6 +594,9 @@ func NewConstSummary(
 	quantiles map[float64]float64,
 	labelValues ...string,
 ) (Metric, error) {
+	if desc.err != nil {
+		return nil, desc.err
+	}
 	if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
 		return nil, err
 	}
diff --git a/prometheus/value.go b/prometheus/value.go
index 5e7d4b6..eb248f1 100644
--- a/prometheus/value.go
+++ b/prometheus/value.go
@@ -77,8 +77,12 @@ func (v *valueFunc) Write(out *dto.Metric) error {
 // operations. However, when implementing custom Collectors, it is useful as a
 // throw-away metric that is generated on the fly to send it to Prometheus in
 // the Collect method. NewConstMetric returns an error if the length of
-// labelValues is not consistent with the variable labels in Desc.
+// labelValues is not consistent with the variable labels in Desc or if Desc is
+// invalid.
 func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) (Metric, error) {
+	if desc.err != nil {
+		return nil, desc.err
+	}
 	if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
 		return nil, err
 	}