review-feedback: Fix meta_length omitted from Perfetto envelope header

In SentryEnvelopeItemHeader.serialize(), meta_length was being evaluated
before length. For Perfetto profile chunks, the metaLength value is only
populated as a side effect of materializing the payload, which the length
computation triggers.

Added a regression test that drives header.serialize()
directly without first touching item.data. Also renamed the existing
test to describe what it actually covers (payload layout), since the
old name overpromised header coverage.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 43jay

sentry/src/main/java/io/sentry/SentryEnvelopeItemHeader.java

@@ -216,11 +216,11 @@ public void serialize(final @NotNull ObjectWriter writer, final @NotNull ILogger
     if (itemCount != null) {
       writer.name(JsonKeys.ITEM_COUNT).value(itemCount);
     }
+    writer.name(JsonKeys.LENGTH).value(getLength());
     final @Nullable Integer resolvedMetaLength = getMetaLength();
     if (resolvedMetaLength != null) {
       writer.name(JsonKeys.META_LENGTH).value(resolvedMetaLength);
     }
-    writer.name(JsonKeys.LENGTH).value(getLength());
     if (unknown != null) {
       for (String key : unknown.keySet()) {
         Object value = unknown.get(key);

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

@@ -14,6 +14,7 @@ import java.io.File
 import java.io.IOException
 import java.io.InputStreamReader
 import java.io.OutputStreamWriter
+import java.io.StringWriter
 import java.nio.charset.Charset
 import java.nio.file.Files
 import java.util.concurrent.Callable
@@ -24,6 +25,7 @@ import kotlin.test.assertFailsWith
 import kotlin.test.assertFalse
 import kotlin.test.assertNotNull
 import kotlin.test.assertNull
+import kotlin.test.assertTrue
 import org.junit.Assert.assertArrayEquals
 import org.junit.Rule
 import org.junit.rules.TemporaryFolder
@@ -598,7 +600,7 @@ class SentryEnvelopeItemTest {
   }
 
   @Test
-  fun `fromPerfettoProfileChunk creates single item with meta_length header`() {
+  fun `fromPerfettoProfileChunk produces concatenated JSON+binary payload`() {
     val traceFile = tmpDir.newFile("trace.pftrace")
     val traceBytes = byteArrayOf(0x50, 0x65, 0x72, 0x66) // "Perf"
     traceFile.writeBytes(traceBytes)
@@ -640,6 +642,39 @@ class SentryEnvelopeItemTest {
     assertFalse(traceFile.exists())
   }
 
+  @Test
+  fun `fromPerfettoProfileChunk header serializes with meta_length`() {
+    val traceFile = tmpDir.newFile("trace.pftrace")
+    traceFile.writeBytes(byteArrayOf(0x50, 0x65, 0x72, 0x66))
+
+    val profileChunk =
+      ProfileChunk.Builder(
+          SentryId(),
+          SentryId(),
+          emptyMap(),
+          traceFile,
+          SentryNanotimeDate(),
+          ProfileChunk.PLATFORM_ANDROID,
+        )
+        .setContentType("perfetto")
+        .build(fixture.options)
+
+    val item = SentryEnvelopeItem.fromPerfettoProfileChunk(profileChunk, fixture.serializer)
+
+    // Serialize the header without pre-materializing item.data.
+    val sw = StringWriter()
+    val writer = JsonObjectWriter(sw, 100)
+    item.header.serialize(writer, mock<ILogger>())
+
+    val json = sw.toString()
+    val metaLength = item.header.metaLength!!
+    assertTrue(metaLength > 0, "expected positive meta_length, was $metaLength")
+    assertTrue(
+      json.contains("\"meta_length\":$metaLength"),
+      "expected meta_length=$metaLength in header JSON, was: $json",
+    )
+  }
+
   @Test
   fun `fromPerfettoProfileChunk with missing file throws`() {
     val traceFile = File("nonexistent.pftrace")