Improve config error checking

subsetter/config_model.py

@@ -1,6 +1,6 @@
 from typing import Dict, List, Literal, Optional, Union
 
-from pydantic import BaseModel, ConfigDict, Field
+from pydantic import BaseModel, ConfigDict, Field, model_validator
 from typing_extensions import Annotated
 
 from subsetter.common import DatabaseConfig, SQLKnownOperator, SQLLiteralType
@@ -30,6 +30,19 @@ class ExtraFKConfig(ForbidBaseModel):
         dst_table: str
         dst_columns: List[str]
 
+        @model_validator(mode="after")
+        def check_columns_match(self):
+            col_count = len(self.src_columns)
+            if not col_count:
+                raise ValueError("src_columns cannot be empty")
+            if len(self.dst_columns) != col_count:
+                raise ValueError("src_columns and dst_columns must be the same length")
+            if len(set(self.src_columns)) != col_count:
+                raise ValueError("each column in src_columns must be unique")
+            if len(set(self.dst_columns)) != col_count:
+                raise ValueError("each column in src_columns must be unique")
+            return self
+
     class ColumnConstraint(ForbidBaseModel):
         column: str
         operator: SQLKnownOperator

subsetter/planner.py

@@ -138,22 +138,56 @@ def _solve_order(self) -> List[str]:
 
     def _add_extra_fks(self) -> None:
         """Add in additional foreign keys requested."""
-        for extra_fk in self.config.extra_fks:
+        for index, extra_fk in enumerate(self.config.extra_fks):
             src_schema, src_table_name = parse_table_name(extra_fk.src_table)
             dst_schema, dst_table_name = parse_table_name(extra_fk.dst_table)
             table = self.meta.tables.get((src_schema, src_table_name))
             if table is None:
                 LOGGER.warning(
-                    "Found no source table %s.%s referenced in add_extra_fks",
+                    "Found no source table %s.%s referenced in extra_fks[%d]",
                     src_schema,
                     src_table_name,
+                    index,
                 )
                 continue
-            if (dst_schema, dst_table_name) not in self.meta.tables:
+
+            src_missing_cols = {
+                col
+                for col in extra_fk.src_columns
+                if col not in table.table_obj.columns
+            }
+            if src_missing_cols:
+                LOGGER.warning(
+                    "Columns %s do not exist in %s.%s referenced in extra_fks[%d]",
+                    src_missing_cols,
+                    src_schema,
+                    src_table_name,
+                    index,
+                )
+                continue
+
+            dst_table = self.meta.tables.get((dst_schema, dst_table_name))
+            if dst_table is None:
+                LOGGER.warning(
+                    "Found no destination table %s.%s referenced in add_extra_fks[%d]",
+                    dst_schema,
+                    dst_table_name,
+                    index,
+                )
+                continue
+
+            dst_missing_cols = {
+                col
+                for col in extra_fk.dst_columns
+                if col not in dst_table.table_obj.columns
+            }
+            if dst_missing_cols:
                 LOGGER.warning(
-                    "Found no destination table %s.%s referenced in add_extra_fks",
+                    "Columns %s do not exist in %s.%s referenced in extra_fks[%d]",
+                    dst_missing_cols,
                     dst_schema,
                     dst_table_name,
+                    index,
                 )
                 continue