Reject malformed header with trailing slash and add test case

Author: alexander-alderman-webb

sentry/src/main/java/io/sentry/SentryTraceHeader.java

@@ -17,7 +17,7 @@ public final class SentryTraceHeader {
 
   final Pattern SENTRY_TRACEPARENT_HEADER_REGEX =
       Pattern.compile(
-          "^[ \\t]*(?<traceId>[0-9a-f]{32})-(?<spanId>[0-9a-f]{16})-?(?<sampled>[01])?[ \\t]*$",
+          "^[ \\t]*(?<traceId>[0-9a-f]{32})-(?<spanId>[0-9a-f]{16})(?<sampled>-[01])?[ \\t]*$",
           Pattern.CASE_INSENSITIVE);
 
   public SentryTraceHeader(
@@ -39,7 +39,8 @@ public SentryTraceHeader(final @NotNull String value) throws InvalidSentryTraceH
 
     this.traceId = new SentryId(matcher.group("traceId"));
     this.spanId = new SpanId(matcher.group("spanId"));
-    this.sampled = matcher.group("sampled") == null ? null : "1".equals(matcher.group("sampled"));
+    this.sampled =
+        matcher.group("sampled") == null ? null : "1".equals(matcher.group("sampled").substring(1));
   }
 
   public @NotNull String getName() {

sentry/src/test/java/io/sentry/SentryTraceHeaderTest.kt

@@ -16,6 +16,18 @@ class SentryTraceHeaderTest {
     assertEquals("sentry-trace header does not conform to expected format: $sentryId", ex.message)
   }
 
+  @Test
+  fun `when there is a trailing dash without sampling decision throws exception`() {
+    val sentryId = SentryId()
+    val spanId = SpanId()
+    val ex =
+      assertFailsWith<InvalidSentryTraceHeaderException> { SentryTraceHeader("$sentryId-$spanId-") }
+    assertEquals(
+      "sentry-trace header does not conform to expected format: $sentryId-$spanId-",
+      ex.message,
+    )
+  }
+
   @Test
   fun `when trace-id has less than 32 characters throws exception`() {
     val sentryId = SentryId().toString().substring(0, 8)