test: don't allow interface{} types

generated_test.go

@@ -0,0 +1,37 @@
+package rootly
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"testing"
+)
+
+func TestNoInterfaceTypeAliases(t *testing.T) {
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, "schema.gen.go", nil, 0)
+	if err != nil {
+		t.Fatalf("failed to parse schema.gen.go: %v", err)
+	}
+
+	for _, decl := range f.Decls {
+		genDecl, ok := decl.(*ast.GenDecl)
+		if !ok || genDecl.Tok != token.TYPE {
+			continue
+		}
+		for _, spec := range genDecl.Specs {
+			typeSpec, ok := spec.(*ast.TypeSpec)
+			if !ok || !typeSpec.Assign.IsValid() {
+				continue
+			}
+
+			t.Run(typeSpec.Name.Name+" should not be an interface{}", func(t *testing.T) {
+				iface, ok := typeSpec.Type.(*ast.InterfaceType)
+
+				if ok && iface.Methods.NumFields() == 0 {
+					t.Fail()
+				}
+			})
+		}
+	}
+}