Fix importer fewer columns than expected Traceback (#277)

Now when an importer spec is modified to have a column
reference that is out of range for the source data, an
error is shown. If such importer spec is executed an
error will also be thrown and logged.

Re spine-tools/Spine-Toolbox#2333

spinedb_api/import_mapping/generator.py

@@ -83,6 +83,7 @@ def get_mapped_data(
     rows = list(data_source)
     if not rows:
         return mapped_data, errors
+    column_count = len(max(rows, key=lambda x: len(x) if x else 0))
     if column_convert_fns is None:
         column_convert_fns = {}
     if row_convert_fns is None:
@@ -92,7 +93,7 @@ def get_mapped_data(
     for mapping in mappings:
         read_state = {}
         mapping = deepcopy(mapping)
-        mapping.polish(table_name, data_header)
+        mapping.polish(table_name, data_header, column_count)
         mapping_errors = check_validity(mapping)
         if mapping_errors:
             errors += mapping_errors

spinedb_api/import_mapping/import_mapping.py

@@ -135,22 +135,44 @@ def read_start_row(self, row):
             raise ValueError(f"row must be >= 0 ({row})")
         self._read_start_row = row
 
-    def polish(self, table_name, source_header, for_preview=False):
+    def check_for_invalid_column_refs(self, header, table_name):
+        """Checks that the mappings column refs are not out of range for the source table
+
+        Args:
+            header (list): The header of the table as a list
+            table_name (str): The name of the source table
+
+        Returns:
+            str: Error message if a column ref exceeds the column count of the source table,
+            empty string otherwise
+        """
+        if self.child is not None:
+            error = self.child.check_for_invalid_column_refs(header, table_name)
+            if error:
+                return error
+        if isinstance(self.position, int) and self.position >= len(header) > 0:
+            msg = f"Column ref {self.position + 1} is out of range for the source table \"{table_name}\""
+            return msg
+        return ""
+
+    def polish(self, table_name, source_header, column_count=0, for_preview=False):
         """Polishes the mapping before an import operation.
         'Expands' transient ``position`` and ``value`` attributes into their final value.
 
         Args:
             table_name (str)
             source_header (list(str))
+            column_count (int, optional)
+            for_preview (bool, optional)
         """
-        self._polish_for_import(table_name, source_header)
+        self._polish_for_import(table_name, source_header, column_count)
         if for_preview:
             self._polish_for_preview(source_header)
 
-    def _polish_for_import(self, table_name, source_header):
+    def _polish_for_import(self, table_name, source_header, column_count):
         # FIXME: Polish skip columns
         if self.child is not None:
-            self.child._polish_for_import(table_name, source_header)
+            self.child._polish_for_import(table_name, source_header, column_count)
         if isinstance(self.position, str):
             # Column mapping with string position, we need to find the index in the header
             try:
@@ -185,6 +207,9 @@ def _polish_for_import(self, table_name, source_header):
             except IndexError:
                 msg = f"'{self.value}' is not a valid index in header '{source_header}'"
                 raise InvalidMappingComponent(msg)
+        if isinstance(self.position, int) and self.position >= column_count > 0:
+            msg = f"Column ref {self.position + 1} is out of range for the source table \"{table_name}\""
+            raise InvalidMappingComponent(msg)
 
     def _polish_for_preview(self, source_header):
         if self.position == Position.header and self.value is not None:

spinedb_api/spine_io/importers/reader.py

@@ -16,7 +16,7 @@
 
 from itertools import islice
 
-from spinedb_api.exception import ConnectorError
+from spinedb_api.exception import ConnectorError, InvalidMappingComponent
 from spinedb_api.import_mapping.generator import get_mapped_data, identity
 from spinedb_api.import_mapping.import_mapping_compat import parse_named_mapping_spec
 from spinedb_api import DateTime, Duration, ParameterValueFormatError
@@ -151,7 +151,7 @@ def get_mapped_data(
                     row_convert_fns,
                     unparse_value,
                 )
-            except (ConnectorError, ParameterValueFormatError) as error:
+            except (ConnectorError, ParameterValueFormatError, InvalidMappingComponent) as error:
                 errors.append(str(error))
                 continue
             for key, value in data.items():