tests and benchmark for baggage parsing

src/API/Baggage/Metadata.php

@@ -10,11 +10,7 @@ final class Metadata implements MetadataInterface
 
     public static function getEmpty(): Metadata
     {
-        if (null === self::$instance) {
-            self::$instance = new self('');
-        }
-
-        return self::$instance;
+        return self::$instance ??= new self('');
     }
 
     private string $metadata;

src/API/Baggage/Propagation/Parser.php

@@ -25,9 +25,6 @@ public function __construct(string $baggageHeader)
         $this->baggageHeader = $baggageHeader;
     }
 
-    /**
-     * @todo: Make this algorithm more robust/performant.
-     */
     public function parseInto(BaggageBuilderInterface $baggageBuilder): void
     {
         foreach (explode(',', $this->baggageHeader) as $baggageString) {

tests/Benchmark/BaggageParsingBench.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+use OpenTelemetry\API\Baggage\BaggageBuilder;
+use OpenTelemetry\API\Baggage\Propagation\Parser;
+
+class BaggageParsingBench
+{
+    /**
+     * @Revs(1000)
+     * @Iterations(10)
+     * @OutputTimeUnit("microseconds")
+     */
+    public function benchParseInto(): void
+    {
+        $builder = new BaggageBuilder();
+        $header = 'value1=foo,value2=bar';
+        $parser = new Parser($header);
+        $parser->parseInto($builder);
+    }
+
+    /**
+     * @Revs(1000)
+     * @Iterations(10)
+     * @OutputTimeUnit("microseconds")
+     */
+    public function benchParseWithMetadata(): void
+    {
+        $builder = new BaggageBuilder();
+        $header = 'value1=foo;metadata1;metadata2,value2=bar;meta=baz';
+        $parser = new Parser($header);
+        $parser->parseInto($builder);
+    }
+}

tests/Unit/API/Baggage/Propagation/ParserTest.php

@@ -0,0 +1,104 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OpenTelemetry\Example\Unit\API\Baggage\Propagation;
+
+use OpenTelemetry\API\Baggage\BaggageBuilderInterface;
+use OpenTelemetry\API\Baggage\Metadata;
+use OpenTelemetry\API\Baggage\Propagation\Parser;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers \OpenTelemetry\API\Baggage\Propagation\Parser
+ */
+class ParserTest extends TestCase
+{
+    /** @var BaggageBuilderInterface&\PHPUnit\Framework\MockObject\MockObject */
+    private BaggageBuilderInterface $builder;
+
+    public function setUp(): void
+    {
+        $this->builder = $this->createMock(BaggageBuilderInterface::class);
+    }
+
+    public function test_parse_into(): void
+    {
+        $header = 'foo_key=foo_value,bar_key=bar_value';
+        $parser = new Parser($header);
+
+        $this->builder
+            ->expects($this->exactly(2))
+            ->method('set')
+            ->withConsecutive(
+                [$this->equalTo('foo_key'), $this->equalTo('foo_value'), $this->anything()],
+                [$this->equalTo('bar_key'), $this->equalTo('bar_value'), $this->anything()],
+            );
+
+        $parser->parseInto($this->builder);
+    }
+
+    public function test_parse_into_with_properties(): void
+    {
+        //@see https://www.w3.org/TR/baggage/#example
+        $header = 'key1=value1;property1;property2, key2 = value2, key3=value3; propertyKey=propertyValue';
+        $parser = new Parser($header);
+
+        $this->builder
+            ->expects($this->exactly(3))
+            ->method('set')
+            ->withConsecutive(
+                [
+                    $this->equalTo('key1'),
+                    $this->equalTo('value1'),
+                    $this->callback(function (Metadata $metadata) {
+                        $this->assertSame('property1;property2', $metadata->getValue());
+
+                        return true;
+                    }),
+                ],
+                [
+                    $this->equalTo('key2'),
+                    $this->equalTo('value2'),
+                    $this->equalTo(null),
+                ],
+                [
+                    $this->equalTo('key3'),
+                    $this->equalTo('value3'),
+                    $this->callback(function (Metadata $metadata) {
+                        $this->assertSame('propertyKey=propertyValue', $metadata->getValue());
+
+                        return true;
+                    }),
+                ],
+            );
+
+        $parser->parseInto($this->builder);
+    }
+
+    /**
+     * @dataProvider invalidHeaderProvider
+     */
+    public function test_parse_into_with_invalid_header(string $header): void
+    {
+        $parser = new Parser($header);
+
+        $this->builder
+            ->expects($this->never())
+            ->method('set');
+
+        $parser->parseInto($this->builder);
+    }
+
+    public function invalidHeaderProvider(): array
+    {
+        return [
+            'nothing' => [''],
+            'empty values' => [',,,,,'],
+            'no equals' => ['key1,key2'],
+            'empty key' => ['=value'],
+            'key with invalid char' => ['@foo=bar'],
+            'value with invalid char' => ['foo="bar"'],
+        ];
+    }
+}