XINCGer/Unity3DTraining · error · DescriptorValidationException

" " is already defined (as something other than a package)…

Error message

"{name}" is already defined (as something other than a package) in file "{old.File.Name}".

What it means

DescriptorPool.AddPackage throws DescriptorValidationException when building a FileDescriptor if the package name being registered collides with an existing symbol (message, enum, service, field, etc.) of the same fully-qualified name in the pool. A name can only refer to a package if nothing else has already claimed it. This mirrors protobuf's C++ descriptor validation rules.

Solutions

1. Rename the conflicting declaration: either the package in one .proto file or the message/enum/service with the same fully-qualified name.
2. Check every loaded file in the pool for a type whose fully-qualified name equals the package name in the failing file.
3. Regenerate code after renaming so descriptors are consistent.
4. If files are loaded dynamically, load the package-declaring file first or into a separate pool to avoid cross-file collisions.

Example fix

// before (file A)
message foo { ... } // fully-qualified: foo
// file B
package foo.bar; // collides with message foo
// after
message FooMsg { ... } // no collision with package foo

// Before building a FileDescriptor, collect every type FQN already in the pool
// and check the new file's package against them:
bool collides = existingTypeFqns.Contains(newFileProto.Package);

try
{
    var fd = FileDescriptor.BuildFromByteString(bytes, dependencies);
}
catch (DescriptorValidationException ex) when (ex.Message.Contains("as something other than a package"))
{
    // surface the conflicting file/name to schema maintainers
}

When it happens

Trigger: Calling FileDescriptor.BuildFromByteString/FromGeneratedCode for a .proto file whose 'package' declaration has the same fully-qualified name as a message, enum, or service already registered in the same descriptor pool — e.g. package foo.bar while a message foo.bar already exists from a previously loaded file.

Common situations: Merging multiple .proto files into one pool where one file's package path coincidentally matches another file's message name; renaming/moving declarations so a package path now shadows an existing type; generated-code registration order issues after schema refactoring.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• " " is already defined in file " ".
• Missing name.
• " " is not a valid identifier.
• Field number has already been used in " " by field " ".
• " " is not defined.

AI-assisted analysis of XINCGer/Unity3DTraining@016f98412e (2026-09-12). Data as JSON: /api/errors/89e76d4166b6c48f. Report an issue: GitHub.

Appendix: source

Thrown at NetWorkAndResources/Socket_Protobuff/Assets/Plugins/Google.Protobuf/Reflection/DescriptorPool.cs:139

        {
            int dotpos = fullName.LastIndexOf('.');
            String name;
            if (dotpos != -1)
            {
                AddPackage(fullName.Substring(0, dotpos), file);
                name = fullName.Substring(dotpos + 1);
            }
            else
            {
                name = fullName;
            }

            IDescriptor old;
            if (descriptorsByName.TryGetValue(fullName, out old))
            {
                if (!(old is PackageDescriptor))
                {
                    throw new DescriptorValidationException(file,
                                                            "\"" + name +
                                                            "\" is already defined (as something other than a " +
                                                            "package) in file \"" + old.File.Name + "\".");
                }
            }
            descriptorsByName[fullName] = new PackageDescriptor(name, fullName, file);
        }

        /// <summary>
        /// Adds a symbol to the symbol table.
        /// </summary>
        /// <exception cref="DescriptorValidationException">The symbol already existed
        /// in the symbol table.</exception>
        internal void AddSymbol(IDescriptor descriptor)
        {
            ValidateSymbolName(descriptor);
            String fullName = descriptor.FullName;

View on GitHub (pinned to 016f98412e)