clockworklabs/SpacetimeDB · error

Failed to generate table due to validation errors

Error message

Failed to generate table due to validation errors

What it means

Panic in SpacetimeDB's Unreal Engine C++ binding generator (`spacetime generate --lang cpp` etc.). When generating code for each module view, the generator builds a `TableSchema::from_view_def_for_codegen(...)` and calls `.validated()`; if the view's schema collects any validation errors, `expect` panics and aborts codegen. It means the module's view definition itself is structurally invalid from the schema validator's perspective.

Source

Thrown at crates/codegen/src/unrealcpp.rs:1152

            let schema = TableSchema::from_module_def(module, table, (), 0.into())
                .validated()
                .expect("table schema should validate");
            let table_cpp_content = generate_table_cpp(self.module_prefix, module, table, self.module_name, &schema);
            let table_cpp_filename = format!(
                "Source/{}/Private/ModuleBindings/Tables/{}Table.g.cpp",
                self.module_name,
                format_args!("{module_prefix}{}", table.name.deref().to_case(Case::Pascal))
            );
            files.push(OutputFile {
                filename: table_cpp_filename,
                code: table_cpp_content,
            });
        }
        for view in module.views() {
            let tbl = TableDef::from(view.clone());
            let schema = TableSchema::from_view_def_for_codegen(module, view)
                .validated()
                .expect("Failed to generate table due to validation errors");
            let view_cpp_content = generate_table_cpp(self.module_prefix, module, &tbl, self.module_name, &schema);
            let view_cpp_filename = format!(
                "Source/{}/Private/ModuleBindings/Tables/{}Table.g.cpp",
                self.module_name,
                format_args!("{module_prefix}{}", view.name.deref().to_case(Case::Pascal))
            );
            files.push(OutputFile {
                filename: view_cpp_filename,
                code: view_cpp_content,
            });
        }

        files
    }
}

// Helper function to generate table .cpp implementation files
fn generate_table_cpp(

View on GitHub (pinned to 6dee26c6ef)

Solutions

1. Re-run `spacetime build` / validation on the module to surface the underlying validation error messages before codegen (the panic message itself hides the error list).
2. Inspect recently added views in the module and remove or fix the one that fails validation (often an unsupported type or bad projection).
3. Check SpacetimeDB release notes for schema-validation changes and update the module SDK (`spacetime` CLI + `spacetimedb-std`) to matching versions.
4. If the view is optional for your game client, delete it from the module and regenerate to confirm it is the culprit, then re-add incrementally.

Example fix

// module (before): view with a type Unreal codegen cannot validate
view BadView { projection: SomeUnsupportedType }

// module (after): project a supported scalar/product type
view BadView { projection: String }

// Before codegen, validate every table/view schema the same way codegen does
use spacetimedb_schema::table::TableSchema;
for view in module.views() {
    if let Err(errors) = TableSchema::from_view_def_for_codegen(module, view).validated() { /* fix errors before generate */ }
}

When it happens

Trigger: Running codegen for Unreal C++ bindings against a module whose `view` definition fails `TableSchema` validation — e.g. a view projecting unsupported types, mismatched column/index definitions, or a view referencing elements the schema validator rejects. The sibling loop over tables uses the same pattern, so a bad table can also surface here when `TableDef::from(view)` is built.

Common situations: Upgrading SpacetimeDB CLI or module SDK versions where view validation rules tightened; hand-editing a `.satellite`/module schema; adding a new view with exotic types (e.g. certain sum types or nested structures) that Unreal codegen cannot map; mixing old generated bindings with a new module.

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

• table schema should validate for query builder codegen
• view schema should validate for query builder codegen
• table should exist in the database for AddConstraint
• expected ModuleDef to contain key, but it does not
• `table_id` must not be `TableId::SENTINEL` in `{row_level_se

AI-assisted analysis of clockworklabs/SpacetimeDB@6dee26c6ef (2026-08-20). Data as JSON: /api/errors/b89aa6ed87426831. Report an issue: GitHub.