feat(quick-1): add enum/repeated query param test cases and helper functions

- Add Region enum, SearchAdvancedRequest, EmptyRequest to query_params.proto
- Add SearchAdvanced and GetDefaults RPCs to QueryParamService
- Add TSEnumUnspecifiedValue helper for enum zero-value detection
- Update TSZeroCheckForField to handle EnumKind and repeated fields
- Add "enum" case to TSZeroCheck for fallback path

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: SebastienMelki

internal/httpgen/testdata/proto/query_params.proto

@@ -44,6 +44,22 @@ service QueryParamService {
       method: HTTP_METHOD_GET
     };
   }
+
+  // Advanced search with enum + repeated params
+  rpc SearchAdvanced(SearchAdvancedRequest) returns (SearchResponse) {
+    option (sebuf.http.config) = {
+      path: "/search/advanced"
+      method: HTTP_METHOD_GET
+    };
+  }
+
+  // RPC with empty request message
+  rpc GetDefaults(EmptyRequest) returns (SearchResponse) {
+    option (sebuf.http.config) = {
+      path: "/defaults"
+      method: HTTP_METHOD_GET
+    };
+  }
 }
 
 message SearchWithTypesRequest {
@@ -83,6 +99,25 @@ message GetWithFiltersRequest {
   int32 limit = 3 [(sebuf.http.query) = { name: "limit" }];
 }
 
+enum Region {
+  REGION_UNSPECIFIED = 0;
+  REGION_AMERICAS = 1;
+  REGION_EUROPE = 2;
+  REGION_ASIA = 3;
+}
+
+message SearchAdvancedRequest {
+  // Enum query param (bugs #1 and #2)
+  Region region = 1 [(sebuf.http.query) = { name: "region" }];
+  // Repeated string query param (bugs #3 and #4)
+  repeated string countries = 2 [(sebuf.http.query) = { name: "countries" }];
+  // Normal string for baseline
+  string keyword = 3 [(sebuf.http.query) = { name: "keyword" }];
+}
+
+// Empty request message (bug #6)
+message EmptyRequest {}
+
 message SearchResponse {
   repeated string results = 1;
   int32 total = 2;

internal/tscommon/types.go

@@ -71,6 +71,24 @@ func TSScalarTypeForField(field *protogen.Field) string {
 	}
 }
 
+// TSEnumUnspecifiedValue returns the first enum value (UNSPECIFIED variant) as a quoted string.
+// For enum fields, this is the zero-value equivalent used in TS zero checks.
+func TSEnumUnspecifiedValue(field *protogen.Field) string {
+	if field.Desc.Kind() != protoreflect.EnumKind || field.Enum == nil {
+		return `""`
+	}
+	values := field.Enum.Values
+	if len(values) == 0 {
+		return `""`
+	}
+	// Check for custom enum_value annotation on the first value
+	customValue := annotations.GetEnumValueMapping(values[0])
+	if customValue != "" {
+		return fmt.Sprintf(`"%s"`, customValue)
+	}
+	return fmt.Sprintf(`"%s"`, string(values[0].Desc.Name()))
+}
+
 // TSZeroCheck returns the TypeScript zero-value check expression for a query param.
 // Uses the proto field kind (not TS type) to determine the appropriate check.
 // For int64/uint64 fields, this returns the STRING encoding check; use TSZeroCheckForField
@@ -89,6 +107,10 @@ func TSZeroCheck(fieldKind string) string {
 		"uint64", "fixed64":
 		// Default: 64-bit integers are encoded as strings in proto3 JSON
 		return ` !== "0"`
+	case "enum":
+		// Without field context, we cannot determine the UNSPECIFIED value;
+		// fall back to bool-style truthy check
+		return ""
 	default:
 		return ` !== ""`
 	}
@@ -97,17 +119,24 @@ func TSZeroCheck(fieldKind string) string {
 // TSZeroCheckForField returns the TypeScript zero-value check expression for a field,
 // checking encoding annotations for int64/uint64 fields.
 func TSZeroCheckForField(field *protogen.Field) string {
+	// Repeated fields use length check (truthy check pattern)
+	if field.Desc.IsList() {
+		return ""
+	}
+
 	kind := field.Desc.Kind()
 
 	// Check for int64/uint64 encoding annotation
-	//exhaustive:ignore - only int64 kinds need special handling, default covers all others
+	//exhaustive:ignore - only int64/enum kinds need special handling, default covers all others
 	switch kind {
 	case protoreflect.Int64Kind, protoreflect.Sint64Kind, protoreflect.Sfixed64Kind,
 		protoreflect.Uint64Kind, protoreflect.Fixed64Kind:
 		if annotations.IsInt64NumberEncoding(field) {
 			return " !== 0" // NUMBER encoding: numeric zero check
 		}
 		return ` !== "0"` // Default (STRING/UNSPECIFIED): string zero check
+	case protoreflect.EnumKind:
+		return " !== " + TSEnumUnspecifiedValue(field)
 	default:
 		// All other types use the base helper
 		return TSZeroCheck(kind.String())