fix(processor): Remove form data envelope items

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - Remove the `spool` command from Relay. ([#4423](https://github.com/getsentry/relay/pull/4423))
 - Bump `sentry-native` to `0.7.17` and remove cross compilation in CI. ([#4427](https://github.com/getsentry/relay/pull/4427))
+- Remove `form_data` envelope items from standalone envelopes. ([#4428](https://github.com/getsentry/relay/pull/4428))
 
 ## 24.12.1
 

relay-server/src/services/processor.rs

@@ -94,6 +94,7 @@ mod session;
 mod span;
 pub use span::extract_transaction_span;
 
+mod standalone;
 #[cfg(feature = "processing")]
 mod unreal;
 
@@ -309,7 +310,7 @@ impl ProcessingGroup {
             ))
         }
 
-        // Exract all metric items.
+        // Extract all metric items.
         //
         // Note: Should only be relevant in proxy mode. In other modes we send metrics through
         // a separate pipeline.
@@ -1857,6 +1858,8 @@ impl EnvelopeProcessorService {
         #[allow(unused_mut)]
         let mut extracted_metrics = ProcessingExtractedMetrics::new();
 
+        standalone::process(managed_envelope);
+
         profile::filter(
             managed_envelope,
             &Annotated::empty(),

relay-server/src/services/processor/standalone.rs

@@ -0,0 +1,14 @@
+use crate::envelope::ItemType;
+use crate::services::processor::StandaloneGroup;
+use crate::utils::{ItemAction, TypedEnvelope};
+
+/// Processes a standalone envelope by removing unnecessary items.
+///
+/// This function removes form data items from the envelope since they are not allowed in
+/// standalone processing.
+pub fn process(managed_envelope: &mut TypedEnvelope<StandaloneGroup>) {
+    managed_envelope.retain_items(|i| match i.ty() {
+        ItemType::FormData => ItemAction::DropSilently,
+        _ => ItemAction::Keep,
+    });
+}

relay-server/src/utils/multipart.rs

@@ -184,8 +184,8 @@ where
     let form_data = form_data.into_inner();
     if !form_data.is_empty() {
         let mut item = Item::new(ItemType::FormData);
-        // Content type is Text (since it is not a json object but multiple
-        // json arrays serialized one after the other.
+        // Content type is `Text` (since it is not a json object but multiple
+        // json arrays serialized one after the other).
         item.set_payload(ContentType::Text, form_data);
         items.push(item);
     }

tests/integration/test_attachments.py

@@ -371,3 +371,45 @@ def test_event_with_attachment(
 
     _, event = attachments_consumer.get_event()
     assert event["event_id"] == event_id
+
+
+def test_form_data_is_rejected(
+    mini_sentry, relay_with_processing, attachments_consumer, outcomes_consumer
+):
+    """
+    Test that form data entries (those without filenames) are rejected and generate outcomes.
+    """
+    project_id = 42
+    event_id = "515539018c9b4260a6f999572f1661ee"
+
+    mini_sentry.add_full_project_config(project_id)
+    relay = relay_with_processing()
+    attachments_consumer = attachments_consumer()
+
+    # Create attachments with both file content and form data
+    attachments = [
+        ("att_1", "foo.txt", b"file content"),  # Valid file attachment
+        ("form_key", None, b"form value"),  # Form data that should be rejected
+    ]
+
+    relay.send_attachments(project_id, event_id, attachments)
+
+    # Check that only the file attachment was processed
+    attachment = attachments_consumer.get_individual_attachment()
+    assert attachment["attachment"].pop("id")  # ID is random
+    assert attachment == {
+        "type": "attachment",
+        "attachment": {
+            "attachment_type": "event.attachment",
+            "chunks": 0,
+            "data": b"file content",
+            "name": "foo.txt",
+            "size": len(b"file content"),
+            "rate_limited": False,
+        },
+        "event_id": event_id,
+        "project_id": project_id,
+    }
+
+    # Verify no more attachments were processed
+    attachments_consumer.assert_empty()