Apply alias rewrites to arrays (#4958)

[#2489](#2489) introduced
automatic aliasing rules to support `@interfaceObject`.

These rules now properly apply to lists.

.changesets/fix_watcher_raccoon_meat_crop.md

@@ -0,0 +1,8 @@
+### Apply alias rewrites to arrays ([PR #TODO](https://github.com/apollographql/router/pull/4958))
+
+
+[#2489](https://github.com/apollographql/router/pull/2489) introduced automatic aliasing rules to support `@interfaceObject`.
+
+These rules now properly apply to lists.
+
+By [@o0ignition0o](https://github.com/o0ignition0o) in https://github.com/apollographql/router/pull/4958

apollo-router/src/query_planner/rewrites.rs

@@ -73,6 +73,16 @@ impl DataRewrite {
                                 obj.insert(renamer.rename_key_to.clone(), value);
                             }
                         }
+
+                        if let Some(arr) = selected.as_array_mut() {
+                            for item in arr {
+                                if let Some(obj) = item.as_object_mut() {
+                                    if let Some(value) = obj.remove(k.as_str()) {
+                                        obj.insert(renamer.rename_key_to.clone(), value);
+                                    }
+                                }
+                            }
+                        }
                     });
                 }
             }
@@ -92,3 +102,117 @@ pub(crate) fn apply_rewrites(
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use serde_json_bytes::json;
+
+    use super::*;
+
+    // The schema is not used for the tests
+    // but we need a valid one
+    const SCHEMA: &str = r#"
+       schema
+         @core(feature: "https://specs.apollo.dev/core/v0.1"),
+         @core(feature: "https://specs.apollo.dev/join/v0.1")
+       {
+         query: Query
+       }
+       directive @core(feature: String!) repeatable on SCHEMA
+       directive @join__graph(name: String!, url: String!) on ENUM_VALUE
+
+       enum join__Graph {
+           FAKE @join__graph(name:"fake" url: "http://localhost:4001/fake")
+       }
+
+       type Query {
+         i: [I]
+       }
+
+       interface I {
+         x: Int
+       }
+
+       type A implements I {
+         x: Int
+       }
+
+       type B {
+         y: Int
+       }
+    "#;
+
+    #[test]
+    fn test_key_renamer_object() {
+        let mut data = json!({
+            "data": {
+                "__typename": "TestType",
+                "testField__alias_0": {
+                    "__typename": "TestField",
+                    "field":"thisisatest"
+                }
+            }
+        });
+
+        let dr = DataRewrite::KeyRenamer(DataKeyRenamer {
+            path: "data/testField__alias_0".into(),
+            rename_key_to: "testField".to_string(),
+        });
+
+        dr.maybe_apply(
+            &Schema::parse_test(SCHEMA, &Default::default()).unwrap(),
+            &mut data,
+        );
+
+        assert_eq!(
+            json! {{
+                "data": {
+                    "__typename": "TestType",
+                    "testField": {
+                        "__typename": "TestField",
+                        "field":"thisisatest"
+                    }
+                }
+            }},
+            data
+        );
+    }
+
+    #[test]
+    fn test_key_renamer_array() {
+        let mut data = json!(
+            {
+                "data": [{
+                    "__typename": "TestType",
+                    "testField__alias_0": {
+                        "__typename": "TestField",
+                        "field":"thisisatest"
+                    }
+                }]
+            }
+        );
+
+        let dr = DataRewrite::KeyRenamer(DataKeyRenamer {
+            path: "data/testField__alias_0".into(),
+            rename_key_to: "testField".to_string(),
+        });
+
+        dr.maybe_apply(
+            &Schema::parse_test(SCHEMA, &Default::default()).unwrap(),
+            &mut data,
+        );
+
+        assert_eq!(
+            json! {{
+                "data": [{
+                    "__typename": "TestType",
+                    "testField": {
+                        "__typename": "TestField",
+                        "field":"thisisatest"
+                    }
+                }]
+            }},
+            data
+        );
+    }
+}