Raise error if schema is an empty string

Author: erindru

sqlmesh/dbt/loader.py

@@ -73,16 +73,28 @@ def sqlmesh_config(
     if threads is not None:
         # the to_sqlmesh() function on TargetConfig maps self.threads -> concurrent_tasks
         profile.target.threads = threads
-        
+
     gateway_kwargs = {}
     if infer_state_schema_name:
         profile_name = context.profile_name
+
         # Note: we deliberately isolate state based on the target *schema* and not the target name.
         # It is assumed that the project will define a target, eg 'dev', and then in each users own ~/.dbt/profiles.yml the schema
         # for the 'dev' target is overriden to something user-specific, rather than making the target name itself user-specific.
         # This means that the schema name is the indicator of isolated state, not the target name which may be re-used across multiple schemas.
         target_schema = profile.target.schema_
-        gateway_kwargs["state_schema"] = f"sqlmesh_state_{profile_name}_{target_schema}"
+
+        # dbt-core doesnt allow schema to be undefined, but it does allow an empty string, and then just
+        # fails at runtime when `CREATE SCHEMA ""` doesnt work
+        if not target_schema:
+            raise ConfigError(
+                f"Target '{profile.target_name}' does not specify a schema.\n"
+                "A schema is required in order to infer where to store SQLMesh state"
+            )
+
+        inferred_state_schema_name = f"sqlmesh_state_{profile_name}_{target_schema}"
+        logger.info("Inferring state schema: %s", inferred_state_schema_name)
+        gateway_kwargs["state_schema"] = inferred_state_schema_name
 
     return Config(
         loader=loader,