Fix duplicate-header crash

validata_core/__init__.py

@@ -192,6 +192,7 @@ def repair_core(dataset: tablib.Dataset, schema_field_names):
     last_nonempty_header_col = None
     first_nonempty_header_col = None
     empty_header_cols = []
+    duplicate_header_map = {}
 
     for i, head in enumerate(dataset.headers):
 
@@ -214,11 +215,19 @@ def repair_core(dataset: tablib.Dataset, schema_field_names):
             append_col(rejected_cols_dataset, dataset.get_col(i), head)
             continue
 
-        # Move duplicate columns in a special dataset
+        # Rename and move duplicate columns in a special dataset
         if head in column_names_dict:
+            ver = duplicate_header_map.get(head) or 1
+            fixed_head = '{}~{}'.format(head, ver)
+            duplicate_header_map[head] = ver + 1
             report.append(goodtables.Error(code='duplicate-header',
-                                           message_substitutions={'column-number': i+1, 'column-name': head}))
-            append_col(rejected_cols_dataset, dataset.get_col(i), head)
+                                           message_substitutions={
+                                               'column-name': head,
+                                               'fixed-column-name': fixed_head,
+                                               # not used by Validata but needed to avoid
+                                               # a KeyError in message substitution
+                                               'column_numbers': ''}))
+            append_col(rejected_cols_dataset, dataset.get_col(i), fixed_head)
 
         # Normal case
         else: