fix: generic index access constraint case (#542) (#2421)

* Add test for #542

* fix: generic index access constraint case (#542)

---------

Co-authored-by: Neal Granger <[email protected]>

Author: amake

src/NodeParser/IndexedAccessTypeNodeParser.ts

@@ -79,7 +79,10 @@ export class IndexedAccessTypeNodeParser implements SubNodeParser {
                         return objectType;
                     }
 
-                    throw new LogicError(node, `Invalid index "${type.getValue()}" in type "${objectType.getId()}"`);
+                    // When the indexed property does not exist (e.g. constrained generics with
+                    // narrower instantiations), treat it as never so optional properties are dropped
+                    // instead of throwing.
+                    return new NeverType();
                 }
 
                 throw new LogicError(node, `No additional properties in type "${objectType.getId()}"`);

test/valid-data/generic-indexed-access-constraint/index.test.ts

@@ -0,0 +1,4 @@
+import { assertValidSchema } from "../../utils";
+import { test } from "node:test";
+
+test("generic-indexed-access-constraint", assertValidSchema("generic-indexed-access-constraint", "MyObject"));

test/valid-data/generic-indexed-access-constraint/main.ts

@@ -0,0 +1,6 @@
+export interface MyGeneric<T extends { a?: string; b: number }> {
+    a?: T["a"];
+    b: T["b"];
+}
+
+export interface MyObject extends MyGeneric<{ b: number }> {}

test/valid-data/generic-indexed-access-constraint/schema.json

@@ -0,0 +1,18 @@
+{
+  "$ref": "#/definitions/MyObject",
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "MyObject": {
+      "additionalProperties": false,
+      "properties": {
+        "b": {
+          "type": "number"
+        }
+      },
+      "required": [
+        "b"
+      ],
+      "type": "object"
+    }
+  }
+}