From 8dc0d5956391f7e43a217649314f0e2e1a5f0d96 Mon Sep 17 00:00:00 2001
From: Matt Toohey <mtoohey@block.xyz>
Date: Tue, 5 Mar 2024 16:22:51 +1100
Subject: [PATCH] fix: lowercase request and response fields should produce an
 error (#1016)

Fixes #848
---
 go-runtime/compile/schema.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/go-runtime/compile/schema.go b/go-runtime/compile/schema.go
index 1904b1a380..40ca38f2f6 100644
--- a/go-runtime/compile/schema.go
+++ b/go-runtime/compile/schema.go
@@ -10,6 +10,7 @@ import (
 	"reflect"
 	"strings"
 	"sync"
+	"unicode"
 
 	"golang.org/x/tools/go/ast/astutil"
 	"golang.org/x/tools/go/packages"
@@ -417,6 +418,11 @@ func visitStruct(pctx *parseContext, node ast.Node, tnode types.Type) (*schema.D
 			return nil, fmt.Errorf("field %s: %w", f.Name(), err)
 		}
 
+		// Check if field is exported
+		if len(f.Name()) > 0 && unicode.IsLower(rune(f.Name()[0])) {
+			return nil, fmt.Errorf("params field %s must be exported by starting with an uppercase letter", f.Name())
+		}
+
 		// Extract the JSON tag and split it to get just the field name
 		tagContent := reflect.StructTag(s.Tag(i)).Get(aliasFieldTag)
 		tagParts := strings.Split(tagContent, ",")