test-store, tests: Add tests for VID collision prevention

Add a unit test that simulates the ipfs.map() pattern (multiple
EntityCache instances sharing one SeqGenerator) and verifies VIDs are
sequential. Extend the file_data_sources runner test so that two
offchain triggers in the same block each create an entity, exercising
the shared VID generator end-to-end.

Author: lutter

store/test-store/tests/graph/entity_cache.rs

@@ -463,6 +463,37 @@ async fn offchain_trigger_vid_no_collision_with_shared_generator() {
     );
 }
 
+// Simulate the ipfs.map() pattern: multiple EntityCache instances each create
+// an entity using a shared SeqGenerator. VIDs must be unique and sequential.
+#[graph::test]
+async fn ipfs_map_pattern_vid_uniqueness() {
+    let block: i32 = 42;
+    let vid_gen = SeqGenerator::new(block);
+
+    let mut all_vids = Vec::new();
+    for i in 0..5u32 {
+        let store = Arc::new(MockStore::new(BTreeMap::new()));
+        let mut cache = EntityCache::new(store, vid_gen.cheap_clone());
+        let data = entity! { SCHEMA => id: format!("band{i}"), name: format!("Band {i}") };
+        let key = make_band_key(&format!("band{i}"));
+        cache.set(key, data, None).await.unwrap();
+        let result = cache.as_modifications(block, &STOPWATCH).await.unwrap();
+        let vid = match &result.modifications[0] {
+            EntityModification::Insert { data, .. } => data.vid(),
+            _ => panic!("expected Insert"),
+        };
+        all_vids.push(vid);
+    }
+
+    for i in 1..all_vids.len() {
+        assert_eq!(
+            all_vids[i],
+            all_vids[i - 1] + 1,
+            "VIDs should be sequential"
+        );
+    }
+}
+
 const ACCOUNT_GQL: &str = "
     type Account @entity {
         id: ID!

tests/runner-tests/file-data-sources/src/mapping.ts

@@ -126,6 +126,13 @@ export function handleFile(data: Bytes): void {
   let contextCommand = context.getString('command');
 
   if (contextCommand == SPAWN_FDS_FROM_OFFCHAIN_HANDLER) {
+    // Create an entity for THIS file data source too, so that two offchain
+    // triggers in the same block each write an entity. This exercises the
+    // shared VID generator: if VIDs collide the DB will reject the insert.
+    let entity = new FileEntity(dataSource.stringParam());
+    entity.content = data.toString();
+    entity.save();
+
     let hash = context.getString('hash');
     log.info('Creating file data source from handleFile: {}', [hash]);
     dataSource.createWithContext('File', [hash], new DataSourceContext());

tests/tests/runner_tests.rs

@@ -673,11 +673,25 @@ async fn file_data_sources() {
         assert!(datasources.len() == 1);
     }
 
-    // Create a File data source from a same type of file data source handler
+    // Create a File data source from a same type of file data source handler.
+    // Both hash_2 and hash_3 handlers create entities in the same block,
+    // exercising the shared VID generator: colliding VIDs would cause a DB
+    // constraint violation.
     {
         ctx.start_and_sync_to(test_ptr(4)).await;
 
-        let content = "EXAMPLE_3";
+        let query_res = ctx
+            .query(&format!(
+                r#"{{ fileEntity(id: "{}") {{ id, content }} }}"#,
+                hash_2.clone()
+            ))
+            .await
+            .unwrap();
+        assert_json_eq!(
+            query_res,
+            Some(object! { fileEntity: object!{ id: hash_2.clone(), content: "EXAMPLE_2" } })
+        );
+
         let query_res = ctx
             .query(&format!(
                 r#"{{ fileEntity(id: "{}") {{ id, content }} }}"#,
@@ -687,7 +701,7 @@ async fn file_data_sources() {
             .unwrap();
         assert_json_eq!(
             query_res,
-            Some(object! { fileEntity: object!{ id: hash_3.clone(), content: content } })
+            Some(object! { fileEntity: object!{ id: hash_3.clone(), content: "EXAMPLE_3" } })
         );
     }