From 3e746f43bcd64ae5d72a894ad210f85590b9f112 Mon Sep 17 00:00:00 2001
From: Robert Ross <robert@firehydrant.io>
Date: Tue, 19 Dec 2023 10:20:30 -0500
Subject: [PATCH] Add ForceUppercaseEnums option on unmarshalling options

For systems that send in lowercase enums such as in API requests, this option is helpful to first uppercase the encoded value before doing a lookup for the enum by name.
---
 encoding/protojson/decode.go      | 13 +++++++--
 encoding/protojson/decode_test.go | 45 ++++++++++++++++++++-----------
 2 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/encoding/protojson/decode.go b/encoding/protojson/decode.go
index 503390627..5e1c12909 100644
--- a/encoding/protojson/decode.go
+++ b/encoding/protojson/decode.go
@@ -40,6 +40,10 @@ type UnmarshalOptions struct {
 	// If DiscardUnknown is set, unknown fields and enum name values are ignored.
 	DiscardUnknown bool
 
+	// If ForceUppercaseEnums is set, enum values are first uppercased
+	// before being looked up by name.
+	ForceUppercaseEnums bool
+
 	// Resolver is used for looking up types when unmarshaling
 	// google.protobuf.Any messages or extension fields.
 	// If nil, this defaults to using protoregistry.GlobalTypes.
@@ -331,7 +335,7 @@ func (d decoder) unmarshalScalar(fd protoreflect.FieldDescriptor) (protoreflect.
 		}
 
 	case protoreflect.EnumKind:
-		if v, ok := unmarshalEnum(tok, fd, d.opts.DiscardUnknown); ok {
+		if v, ok := unmarshalEnum(tok, fd, d.opts.DiscardUnknown, d.opts.ForceUppercaseEnums); ok {
 			return v, nil
 		}
 
@@ -476,11 +480,16 @@ func unmarshalBytes(tok json.Token) (protoreflect.Value, bool) {
 	return protoreflect.ValueOfBytes(b), true
 }
 
-func unmarshalEnum(tok json.Token, fd protoreflect.FieldDescriptor, discardUnknown bool) (protoreflect.Value, bool) {
+func unmarshalEnum(tok json.Token, fd protoreflect.FieldDescriptor, discardUnknown bool, forceUppercaseEnums bool) (protoreflect.Value, bool) {
 	switch tok.Kind() {
 	case json.String:
 		// Lookup EnumNumber based on name.
 		s := tok.ParsedString()
+
+		if forceUppercaseEnums {
+			s = strings.ToUpper(s)
+		}
+
 		if enumVal := fd.Enum().Values().ByName(protoreflect.Name(s)); enumVal != nil {
 			return protoreflect.ValueOfEnum(enumVal.Number()), true
 		}
diff --git a/encoding/protojson/decode_test.go b/encoding/protojson/decode_test.go
index 417da1dea..b9fd99908 100644
--- a/encoding/protojson/decode_test.go
+++ b/encoding/protojson/decode_test.go
@@ -2474,22 +2474,35 @@ func TestUnmarshal(t *testing.T) {
 			},
 		},
 	}, {
-		desc:         "weak fields",
-		inputMessage: &testpb.TestWeak{},
-		inputText:    `{"weak_message1":{"a":1}}`,
-		wantMessage: func() *testpb.TestWeak {
-			m := new(testpb.TestWeak)
-			m.SetWeakMessage1(&weakpb.WeakImportMessage1{A: proto.Int32(1)})
-			return m
-		}(),
-		skip: !flags.ProtoLegacy,
-	}, {
-		desc:         "weak fields; unknown field",
-		inputMessage: &testpb.TestWeak{},
-		inputText:    `{"weak_message1":{"a":1}, "weak_message2":{"a":1}}`,
-		wantErr:      `unknown field "weak_message2"`, // weak_message2 is unknown since the package containing it is not imported
-		skip:         !flags.ProtoLegacy,
-	}}
+		desc: "ForceUppercaseEnums: lowercase value with enum",
+		umo: protojson.UnmarshalOptions{
+			ForceUppercaseEnums: true,
+		},
+		inputMessage: &pb3.Enums{},
+		inputText: `{
+		"sEnum": "one"
+	}`,
+		wantMessage: &pb3.Enums{
+			SEnum: pb3.Enum_ONE,
+		},
+	},
+		{
+			desc:         "weak fields",
+			inputMessage: &testpb.TestWeak{},
+			inputText:    `{"weak_message1":{"a":1}}`,
+			wantMessage: func() *testpb.TestWeak {
+				m := new(testpb.TestWeak)
+				m.SetWeakMessage1(&weakpb.WeakImportMessage1{A: proto.Int32(1)})
+				return m
+			}(),
+			skip: !flags.ProtoLegacy,
+		}, {
+			desc:         "weak fields; unknown field",
+			inputMessage: &testpb.TestWeak{},
+			inputText:    `{"weak_message1":{"a":1}, "weak_message2":{"a":1}}`,
+			wantErr:      `unknown field "weak_message2"`, // weak_message2 is unknown since the package containing it is not imported
+			skip:         !flags.ProtoLegacy,
+		}}
 
 	for _, tt := range tests {
 		tt := tt