From b8ccc25c26247d3005c97727271e6b06459a53ff Mon Sep 17 00:00:00 2001
From: Camden Cheek <camden@ccheek.com>
Date: Sat, 19 Oct 2024 16:48:40 -0600
Subject: [PATCH] support leading pipe in union definition

---
 internal/schema/schema.go      |  3 +++
 internal/schema/schema_test.go | 36 ++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/internal/schema/schema.go b/internal/schema/schema.go
index 84bb6fe1..03bdfb83 100644
--- a/internal/schema/schema.go
+++ b/internal/schema/schema.go
@@ -488,6 +488,9 @@ func parseUnionDef(l *common.Lexer) *ast.Union {
 
 	union.Directives = common.ParseDirectives(l)
 	l.ConsumeToken('=')
+	if l.Peek() == '|' {
+		l.ConsumeToken('|')
+	}
 	union.TypeNames = []string{l.ConsumeIdent()}
 	for l.Peek() == '|' {
 		l.ConsumeToken('|')
diff --git a/internal/schema/schema_test.go b/internal/schema/schema_test.go
index 73cc6d41..594afb46 100644
--- a/internal/schema/schema_test.go
+++ b/internal/schema/schema_test.go
@@ -1124,6 +1124,42 @@ func TestInterfaceImplementsInterface(t *testing.T) {
 				return nil
 			},
 		},
+		{
+			name: "Unions can be defined with a leading pipe",
+			sdl: `
+			type Named {
+				name: String!
+			}
+			type Numbered {
+				num: Int!
+			}
+			union Item1 =
+				| Named
+				| Numbered
+			union Item2 = | Named | Numbered
+			`,
+			validateSchema: func(s *ast.Schema) error {
+				for _, itemName := range []string{"Item1", "Item2"} {
+					typ, ok := s.Types[itemName].(*ast.Union)
+					if !ok {
+						return fmt.Errorf("type %q not found", "Item")
+					}
+					if len(typ.UnionMemberTypes) != 2 {
+						return fmt.Errorf("Expected 2 possible types, but instead got %d types", len(typ.UnionMemberTypes))
+					}
+					posible := map[string]struct{}{
+						"Named":    {},
+						"Numbered": {},
+					}
+					for _, pt := range typ.UnionMemberTypes {
+						if _, ok := posible[pt.Name]; !ok {
+							return fmt.Errorf("Unexpected possible type %q", pt.Name)
+						}
+					}
+				}
+				return nil
+			},
+		},
 	} {
 		t.Run(tt.name, func(t *testing.T) {
 			s, err := schema.ParseSchema(tt.sdl, tt.useStringDescriptions)