From 90105be71c8fc71322ebae47a5d26407c99d8fdf Mon Sep 17 00:00:00 2001
From: Ivan Willig <iwillig@gmail.com>
Date: Fri, 7 Feb 2025 11:47:24 -0500
Subject: [PATCH] Support leading Pipes in Union Synatx

This change adds support for leading pipe values in union
definitions. This was added to GraphQL in 2017.

This should address issue #465.

Co-authored-by: Toby Crawley <toby@tcrawley.org>
---
 resources/com/walmartlabs/lacinia/schema.g4   |  2 +-
 .../lacinia/parser/schema_test.clj            | 26 ++++++++++++-------
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/resources/com/walmartlabs/lacinia/schema.g4 b/resources/com/walmartlabs/lacinia/schema.g4
index ce9d110b..9818e146 100644
--- a/resources/com/walmartlabs/lacinia/schema.g4
+++ b/resources/com/walmartlabs/lacinia/schema.g4
@@ -118,7 +118,7 @@ unionExtDef
   ;
 
 unionTypes
-  : (anyName '|')* anyName
+  : '|'? ( anyName '|')* anyName
   ;
 
 enumDef
diff --git a/test/com/walmartlabs/lacinia/parser/schema_test.clj b/test/com/walmartlabs/lacinia/parser/schema_test.clj
index 2a3ddd12..729e1e95 100644
--- a/test/com/walmartlabs/lacinia/parser/schema_test.clj
+++ b/test/com/walmartlabs/lacinia/parser/schema_test.clj
@@ -181,17 +181,25 @@
          (parse-string "interface Flow { ebb : String }"))))
 
 (deftest schema-union
-  (is (= {:unions
-          {:Matter
-           {:members [:Solid :Liquid :Gas :Plasma :INPUT_OBJECT]}}}
-         (parse-string "union Matter = Solid | Liquid | Gas | Plasma | INPUT_OBJECT")))
+
+  (testing "basic union type"
+    (is (= {:unions
+            {:Matter
+             {:members [:Solid :Liquid :Gas :Plasma :INPUT_OBJECT]}}}
+           (parse-string "union Matter = Solid | Liquid | Gas | Plasma | INPUT_OBJECT"))))
+
+  (testing "leading pipe chars in union"
+    (is (= {:unions
+            {:Matter
+             {:members [:Solid :Liquid :Gas :Plasma :INPUT_OBJECT]}}}
+           (parse-string "union Matter = | Solid | Liquid | Gas | Plasma | INPUT_OBJECT"))))
 
   (testing "extensions"
-   (is (= {:unions
-           {:Matter
-            {:members [:Solid :Liquid :Gas :Plasma :INPUT_OBJECT]}}}
-          (parse-string (str "union Matter = Solid\n"
-                             "extend union Matter = Liquid | Gas | Plasma | INPUT_OBJECT"))))))
+    (is (= {:unions
+            {:Matter
+             {:members [:Solid :Liquid :Gas :Plasma :INPUT_OBJECT]}}}
+           (parse-string (str "union Matter = Solid\n"
+                              "extend union Matter = Liquid | Gas | Plasma | INPUT_OBJECT"))))))
 
 (deftest schema-field-args
   (is (= {:objects