EntityResolver input type fix

fixes 99designs#2326 - when using `@entityResolver(multi: true)` the InputType of
the entity resolver may be in a different package (usually `model`).
The fix is to pull the types.Type of the resolver input, and use
templates.CurrentImports.LookupType in order to render it correctly
(possibly adding another import)

plugin/federation/entity.go

@@ -1,7 +1,10 @@
 package federation
 
 import (
+	"go/types"
+
 	"github.com/99designs/gqlgen/codegen/config"
+	"github.com/99designs/gqlgen/codegen/templates"
 	"github.com/99designs/gqlgen/plugin/federation/fieldset"
 	"github.com/vektah/gqlparser/v2/ast"
 )
@@ -17,9 +20,14 @@ type Entity struct {
 }
 
 type EntityResolver struct {
-	ResolverName string      // The resolver name, such as FindUserByID
-	KeyFields    []*KeyField // The fields declared in @key.
-	InputType    string      // The Go generated input type for multi entity resolvers
+	ResolverName  string      // The resolver name, such as FindUserByID
+	KeyFields     []*KeyField // The fields declared in @key.
+	InputType     types.Type  // The Go generated input type for multi entity resolvers
+	InputTypeName string
+}
+
+func (e *EntityResolver) LookupInputType() string {
+	return templates.CurrentImports.LookupType(e.InputType)
 }
 
 type KeyField struct {

plugin/federation/federation.go

@@ -134,12 +134,12 @@ func (f *federation) InjectSourceLate(schema *ast.Schema) *ast.Source {
 				if entityResolverInputDefinitions != "" {
 					entityResolverInputDefinitions += "\n\n"
 				}
-				entityResolverInputDefinitions += "input " + r.InputType + " {\n"
+				entityResolverInputDefinitions += "input " + r.InputTypeName + " {\n"
 				for _, keyField := range r.KeyFields {
 					entityResolverInputDefinitions += fmt.Sprintf("\t%s: %s\n", keyField.Field.ToGo(), keyField.Definition.Type.String())
 				}
 				entityResolverInputDefinitions += "}"
-				resolvers += fmt.Sprintf("\t%s(reps: [%s!]!): [%s]\n", r.ResolverName, r.InputType, e.Name)
+				resolvers += fmt.Sprintf("\t%s(reps: [%s!]!): [%s]\n", r.ResolverName, r.InputTypeName, e.Name)
 			} else {
 				resolverArgs := ""
 				for _, keyField := range r.KeyFields {
@@ -234,6 +234,23 @@ func (f *federation) GenerateCode(data *codegen.Data) error {
 		}
 	}
 
+	// fill in types for resolver inputs
+	//
+	for _, entity := range f.Entities {
+		if !entity.Multi {
+			continue
+		}
+
+		for _, resolver := range entity.Resolvers {
+			obj := data.Inputs.ByName(resolver.InputTypeName)
+			if obj == nil {
+				return fmt.Errorf("input object %s not found", resolver.InputTypeName)
+			}
+
+			resolver.InputType = obj.Type
+		}
+	}
+
 	return templates.Render(templates.Options{
 		PackageName:     data.Config.Federation.Package,
 		Filename:        data.Config.Federation.Filename,
@@ -327,9 +344,9 @@ func (f *federation) setEntities(schema *ast.Schema) {
 				}
 
 				e.Resolvers = append(e.Resolvers, &EntityResolver{
-					ResolverName: resolverName,
-					KeyFields:    keyFields,
-					InputType:    resolverFieldsToGo + "Input",
+					ResolverName:  resolverName,
+					KeyFields:     keyFields,
+					InputTypeName: resolverFieldsToGo + "Input",
 				})
 			}
 

plugin/federation/federation.gotpl

@@ -133,7 +133,7 @@ func (ec *executionContext) __resolve_entities(ctx context.Context, representati
 				{{ if and .Resolvers .Multi -}}
 				case "{{.Def.Name}}":
 					{{range $i, $_ := .Resolvers -}}
-						_reps := make([]*{{.InputType}}, len(reps))
+						_reps := make([]*{{.LookupInputType}}, len(reps))
 
 						for i, rep := range reps {
 							{{ range $i, $keyField := .KeyFields -}}
@@ -143,7 +143,7 @@ func (ec *executionContext) __resolve_entities(ctx context.Context, representati
 								}
 							{{end}}
 
-							_reps[i] = &{{.InputType}} {
+							_reps[i] = &{{.LookupInputType}} {
 							{{ range $i, $keyField := .KeyFields -}}
 								{{$keyField.Field.ToGo}}: id{{$i}},
 							{{end}}