Add a FLATTEN_RECORD_LIST formula

sandbox/grist/functions/lookup.py

@@ -26,6 +26,18 @@ def COLUMNS(range):
   """Returns the number of columns in a specified array or range."""
   raise NotImplementedError()
 
+def FLATTEN_RECORDS_LIST(list_of_records, dedup=False):
+    """Returns a flat list of records"""
+    if type(list_of_records) is not list:
+        raise TypeError("Unexpected Argument, waiting of a list of Records")
+    if len(list_of_records) == 0:
+        return list_of_records
+    flatten_list = [el for val in list_of_records for el in val]
+    el_type = {el.__class__.__name__ for el in flatten_list}
+    if list(el_type)[0] != 'Record':
+        return FLATTEN_RECORDS_LIST(flatten_list, dedup)
+    return list(set(flatten_list)) if dedup else flatten_list
+
 @unimplemented
 def GETPIVOTDATA(value_name, any_pivot_table_cell, original_column_1, pivot_item_1=None, *args):
   """Extracts an aggregated value from a pivot table that corresponds to the specified row and column headings."""