upb: implement Dart public imports

PiperOrigin-RevId: 625324587

upb/reflection/def.hpp

@@ -515,6 +515,10 @@ class FileDefPtr {
     return FieldDefPtr(upb_FileDef_TopLevelExtension(ptr_, index));
   }
 
+  bool resolves(const char* path) const {
+    return upb_FileDef_Resolves(ptr_, path);
+  }
+
   explicit operator bool() const { return ptr_ != nullptr; }
 
   friend bool operator==(FileDefPtr lhs, FileDefPtr rhs) {

upb/reflection/file_def.c

@@ -170,6 +170,17 @@ const upb_MiniTableExtension* _upb_FileDef_ExtensionMiniTable(
   return f->ext_layouts[i];
 }
 
+// Note: Import cycles are not allowed so this will terminate.
+bool upb_FileDef_Resolves(const upb_FileDef* f, const char* path) {
+  if (!strcmp(f->name, path)) return true;
+
+  for (int i = 0; i < upb_FileDef_PublicDependencyCount(f); i++) {
+    const upb_FileDef* dep = upb_FileDef_PublicDependency(f, i);
+    if (upb_FileDef_Resolves(dep, path)) return true;
+  }
+  return false;
+}
+
 static char* strviewdup(upb_DefBuilder* ctx, upb_StringView view) {
   char* ret = upb_strdup2(view.data, view.size, _upb_DefBuilder_Arena(ctx));
   if (!ret) _upb_DefBuilder_OomErr(ctx);

upb/reflection/file_def.h

@@ -51,6 +51,9 @@ int upb_FileDef_TopLevelMessageCount(const upb_FileDef* f);
 const upb_FileDef* upb_FileDef_WeakDependency(const upb_FileDef* f, int i);
 int upb_FileDef_WeakDependencyCount(const upb_FileDef* f);
 
+// Returns whether |symbol| is transitively included by |f|
+bool upb_FileDef_Resolves(const upb_FileDef* f, const char* symbol);
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif