Default-empty vectors of enums (#6505)

* disable clippy

* Vector of enum default

* swift and tests

* git clang format

* Rewrite enum parser checks

* Remove Voids from more_defaults

* vector enum swift

* remove vector accessor from swift

* clang format

Co-authored-by: Casper Neo <cneo@google.com>

1 files changed, 25 insertions, 17 deletions

diff --git a/src/idl_parser.cpp b/src/idl_parser.cpp
index f20b6f9a..69fa9d13 100644
--- a/src/idl_parser.cpp
+++ b/src/idl_parser.cpp
@@ -910,24 +910,32 @@ CheckedError Parser::ParseField(StructDef &struct_def) {
   }
 
   if (type.enum_def) {
-    // The type.base_type can only be scalar, union, array or vector.
-    // Table, struct or string can't have enum_def.
-    // Default value of union and vector in NONE, NULL translated to "0".
-    FLATBUFFERS_ASSERT(IsInteger(type.base_type) ||
-                       (type.base_type == BASE_TYPE_UNION) || IsVector(type) ||
-                       IsArray(type));
-    if (IsVector(type)) {
-      // Vector can't use initialization list.
-      FLATBUFFERS_ASSERT(field->value.constant == "0");
+    // Verify the enum's type and default value.
+    const std::string &constant = field->value.constant;
+    if (type.base_type == BASE_TYPE_UNION) {
+      if (constant != "0") { return Error("Union defaults must be NONE"); }
+    } else if (IsVector(type)) {
+      if (constant != "0" && constant != "[]") {
+        return Error("Vector defaults may only be `[]`.");
+      }
+    } else if (IsArray(type)) {
+      if (constant != "0") {
+        return Error("Array defaults are not supported yet.");
+      }
     } else {
-      // All unions should have the NONE ("0") enum value.
-      auto in_enum = field->IsOptional() ||
-                     type.enum_def->attributes.Lookup("bit_flags") ||
-                     type.enum_def->FindByValue(field->value.constant);
-      if (false == in_enum)
-        return Error("default value of " + field->value.constant +
-                     " for field " + name + " is not part of enum " +
-                     type.enum_def->name);
+      if (!IsInteger(type.base_type)) {
+        return Error("Enums must have integer base types");
+      }
+      // Optional and bitflags enums may have default constants that are not
+      // their specified variants.
+      if (!field->IsOptional() &&
+          type.enum_def->attributes.Lookup("bit_flags") == nullptr) {
+        if (type.enum_def->FindByValue(constant) == nullptr) {
+          return Error("default value of `" + constant + "` for " + "field `" +
+                       name + "` is not part of enum `" + type.enum_def->name +
+                       "`.");
+        }
+      }
     }
   }