fixing empty tracestate header handling (#936)

if an empty tracestate header was passed, we were emitting a warning (discovered in the demo app after enabling logging).
to fix this, check for empty string as well as null.

phpstan.neon.dist

@@ -27,5 +27,9 @@ parameters:
  - tests
  -
  message: "#Call to an undefined method .*:shouldHaveReceived.*#"
+ paths:
+ - tests
+ -
+ message: "#Call to an undefined method .*:expects.*#"
  paths:
  - tests

src/API/Trace/TraceState.php

@@ -30,9 +30,10 @@ class TraceState implements TraceStateInterface
 
  public function __construct(string $rawTracestate = null)
  {
- if ($rawTracestate !== null) {
- $this->traceState = $this->parse($rawTracestate);
+ if ($rawTracestate === null || trim($rawTracestate) === '') {
+ return;
  }
+ $this->traceState = $this->parse($rawTracestate);
  }
 
  /**

tests/Unit/API/Trace/TraceStateTest.php

@@ -7,18 +7,22 @@
 use OpenTelemetry\API\Common\Log\LoggerHolder;
 use OpenTelemetry\API\Trace\TraceState;
 use PHPUnit\Framework\TestCase;
-use Psr\Log\NullLogger;
+use Psr\Log\LoggerInterface;
 use function str_repeat;
 use function strlen;
 
 /**
  * @covers OpenTelemetry\API\Trace\TraceState
+ * @psalm-suppress UndefinedInterfaceMethod
  */
 class TraceStateTest extends TestCase
 {
+ private LoggerInterface $logger;
+
  public function setUp(): void
  {
- LoggerHolder::set(new NullLogger());
+ $this->logger = $this->createMock(LoggerInterface::class);
+ LoggerHolder::set($this->logger);
  }
 
  public function test_get_tracestate_value(): void
@@ -28,6 +32,19 @@ public function test_get_tracestate_value(): void
  $this->assertSame('value1', $tracestate->get('vendor1'));
  }
 
+ public function test_get_tracestate_with_empty_string(): void
+ {
+ $this->logger->expects($this->never())->method('log')->with(
+ $this->equalTo('warning'),
+ $this->anything(),
+ $this->anything(),
+ );
+
+ $tracestate = new TraceState('');
+
+ $this->assertSame(0, $tracestate->getListMemberCount());
+ }
+
  public function test_with_tracestate_value(): void
  {
  $tracestate = new TraceState('vendor1=value1');