test query on relationship using nested key

CHANGELOG.md

@@ -15,6 +15,7 @@ described by [ndc-spec](https://hasura.github.io/ndc-spec/). Version 0.2 makes
 a number of improvements to the spec, and enables features that were previously
 not possible. Highlights of those new features include:
 
+- relationships can use a nested object field on the target side as a join key
 - grouping result documents, and aggregating on groups of documents (pending implementation in the mongo connector)
 - queries on fields of nested collections (document fields that are arrays of objects)
 - filtering on scalar values inside array document fields - previously it was possible to filter on fields of objects inside arrays, but not on scalars

crates/integration-tests/src/tests/local_relationship.rs

@@ -1,6 +1,9 @@
 use crate::{connector::Connector, graphql_query, run_connector_query};
 use insta::assert_yaml_snapshot;
-use ndc_test_helpers::{asc, field, query, query_request, relation_field, relationship};
+use ndc_test_helpers::{
+    asc, binop, exists, field, query, query_request, related, relation_field,
+    relationship, target, value,
+};
 
 #[tokio::test]
 async fn joins_local_relationships() -> anyhow::Result<()> {
@@ -210,3 +213,33 @@ async fn joins_on_field_names_that_require_escaping() -> anyhow::Result<()> {
     );
     Ok(())
 }
+
+#[tokio::test]
+async fn joins_relationships_on_nested_key() -> anyhow::Result<()> {
+    assert_yaml_snapshot!(
+        run_connector_query(
+            Connector::TestCases,
+            query_request()
+                .collection("departments")
+                .query(
+                    query()
+                        .predicate(exists(
+                            related!("schools_departments"),
+                            binop("_eq", target!("name"), value!("West Valley"))
+                        ))
+                        .fields([
+                            relation_field!("departments" => "schools_departments", query().fields([
+                              field!("name")
+                            ]))
+                        ])
+                        .order_by([asc!("_id")])
+                )
+                .relationships([(
+                    "schools_departments",
+                    relationship("schools", [("_id", &["departments", "math_department_id"])])
+                )])
+        )
+        .await?
+    );
+    Ok(())
+}

crates/integration-tests/src/tests/snapshots/integration_tests__tests__local_relationship__joins_relationships_on_nested_key.snap

@@ -0,0 +1,8 @@
+---
+source: crates/integration-tests/src/tests/local_relationship.rs
+expression: "run_connector_query(Connector::TestCases,\nquery_request().collection(\"departments\").query(query().predicate(exists(related!(\"schools_departments\"),\nbinop(\"_eq\", target!(\"name\"),\nvalue!(\"West Valley\")))).fields([relation_field!(\"departments\" =>\n\"schools_departments\",\nquery().fields([field!(\"name\")]))]).order_by([asc!(\"_id\")])).relationships([(\"schools_departments\",\nrelationship(\"schools\",\n[(\"_id\", &[\"departments\", \"math_department_id\"])]))])).await?"
+---
+- rows:
+    - departments:
+        rows:
+          - name: West Valley