fix implementation type generation for fragment on a union

docs/CHANGELOG.md

@@ -30,6 +30,7 @@ When releasing a new version:
 ### Bug fixes:
 - The presence of negative pointer directives, i.e., `# @genqlient(pointer: false)` are now respected even in the when `optional: pointer` is set in the configuration file.
 - Made name collisions between query/mutation arguments and local function variables less likely.
+- Fix generation issue related to golang type implementation of complex graphql union fragments
 
 ## v0.6.0
 

generate/convert.go

@@ -701,6 +701,17 @@ func fragmentMatches(containingTypedef, fragmentTypedef *ast.Definition) bool {
 			return true
 		}
 	}
+
+	// Handle the special case where the fragment is on a union, then the
+	// fragment can match any of the types in the union.
+	if fragmentTypedef.Kind == ast.Union {
+		for _, typeName := range fragmentTypedef.Types {
+			if typeName == containingTypedef.Name {
+				return true
+			}
+		}
+	}
+
 	return false
 }
 

generate/testdata/queries/ComplexNamedFragments.graphql

@@ -47,3 +47,34 @@ fragment ContentFields on Content {
 query ComplexNamedFragments {
   ... on Query { ...QueryFragment }
 }
+
+## two fragments of different types with fields containing the same inline named fragment of a union
+fragment SimpleLeafContent on LeafContent {
+  ... on Article {
+    id
+  }
+  ... on Video {
+    id
+  }
+}
+
+fragment UserLastContent on User {
+  lastContent {
+    ... SimpleLeafContent
+  }
+}
+
+fragment TopicNewestContent on Topic {
+  newestContent {
+    ... SimpleLeafContent
+  }
+}
+
+query ComplexNamedFragmentsWithInlineUnion {
+  user {
+    ...UserLastContent
+  }
+  root {
+    ...TopicNewestContent
+  }
+}

generate/testdata/queries/schema.graphql

@@ -69,6 +69,8 @@ type User {
   pokemon: [Pokemon!]
   greeting: Clip
   birthdate: Date
+
+  lastContent: LeafContent
 }
 
 """An audio clip, such as of a user saying hello."""
@@ -141,6 +143,8 @@ type Topic implements Content {
   schoolGrade: String
   next: Topic
   related: [Topic!]
+
+  newestContent: LeafContent
 }
 
 input RecursiveInput {