feat: add support for rendering Infinity (#144)

Signed-off-by: Simon Podlipsky <simon@podlipsky.net>

Author: simPod

src/Prometheus/Sample.php

@@ -4,6 +4,8 @@
 
 namespace Prometheus;
 
+use function is_infinite;
+
 class Sample
 {
     /**
@@ -67,6 +69,9 @@ public function getLabelValues(): array
      */
     public function getValue(): string
     {
+        if (is_float($this->value) && is_infinite($this->value)) {
+            return $this->value > 0 ? '+Inf' : '-Inf';
+        }
         return (string) $this->value;
     }
 

tests/Test/Prometheus/RenderTextFormatTest.php

@@ -13,6 +13,8 @@
 use Prometheus\Storage\Redis;
 use ValueError;
 
+use const INF;
+
 class RenderTextFormatTest extends TestCase
 {
     public function testOutputMatchesExpectations(): void
@@ -37,6 +39,10 @@ private function buildSamples(): array
                  ->inc(['bob', 'al\ice']);
         $registry->getOrRegisterGauge($namespace, 'gauge', 'gauge-help-text', ['label1', 'label2'])
                  ->inc(["bo\nb", 'ali\"ce']);
+        $registry->getOrRegisterGauge($namespace, 'gauge2', '', ['label1'])
+                 ->set(INF, ["infinity"]);
+        $registry->getOrRegisterGauge($namespace, 'gauge2', '', ['label1'])
+                 ->set(-INF, ["infinity-negative"]);
         $registry->getOrRegisterHistogram($namespace, 'histogram', 'histogram-help-text', ['label1', 'label2'], [0, 10, 100])
                  ->observe(5, ['bob', 'alice']);
         $registry->getOrRegisterSummary($namespace, 'summary', 'summary-help-text', ['label1', 'label2'], 60, [0.1, 0.5, 0.9])
@@ -54,6 +60,10 @@ private function getExpectedOutput(): string
 # HELP mynamespace_gauge gauge-help-text
 # TYPE mynamespace_gauge gauge
 mynamespace_gauge{label1="bo\\nb",label2="ali\\\\\"ce"} 1
+# HELP mynamespace_gauge2 
+# TYPE mynamespace_gauge2 gauge
+mynamespace_gauge2{label1="infinity"} +Inf
+mynamespace_gauge2{label1="infinity-negative"} -Inf
 # HELP mynamespace_histogram histogram-help-text
 # TYPE mynamespace_histogram histogram
 mynamespace_histogram_bucket{label1="bob",label2="alice",le="0"} 0