More robust parsing of worksheets with handling:

- handle the case of empty worksheet.
- handle the case of worksheet with no data.

redash/query_runner/google_spreadsheets.py

@@ -79,9 +79,52 @@ def _value_eval_list(value):
     return value_list
 
 
-class GoogleSpreadsheet(BaseQueryRunner):
-    HEADER_INDEX = 0
+HEADER_INDEX = 0
 
+
+class WorksheetNotFoundError(Exception):
+    def __init__(self, worksheet_num, worksheet_count):
+        message = "Worksheet number {} not found. Spreadsheet has {} worksheets. Note that the worksheet count is zero based.".format(worksheet_num, worksheet_count)
+        super(WorksheetNotFoundError, self).__init__(message)
+
+
+def parse_worksheet(worksheet):
+    if not worksheet:
+        return {'columns': [], 'rows': []}
+
+    column_names = []
+    columns = []
+
+    for j, column_name in enumerate(worksheet[HEADER_INDEX]):
+        column_names.append(column_name)
+        columns.append({
+            'name': column_name,
+            'friendly_name': column_name,
+            'type': TYPE_STRING
+        })
+
+    if len(worksheet) > 1:
+        for j, value in enumerate(worksheet[HEADER_INDEX+1]):
+            columns[j]['type'] = _guess_type(value)
+
+    rows = [dict(zip(column_names, _value_eval_list(row))) for row in worksheet[HEADER_INDEX + 1:]]
+    data = {'columns': columns, 'rows': rows}
+
+    return data
+
+
+def parse_spreadsheet(spreadsheet, worksheet_num):
+    worksheets = spreadsheet.worksheets()
+    worksheet_count = len(worksheets)
+    if worksheet_num >= worksheet_count:
+        raise WorksheetNotFoundError(worksheet_num, worksheet_count)
+
+    worksheet = worksheets[worksheet_num].get_all_values()
+
+    return parse_worksheet(worksheet)
+
+
+class GoogleSpreadsheet(BaseQueryRunner):
     @classmethod
     def annotate_query(cls):
         return False
@@ -129,19 +172,9 @@ class GoogleSpreadsheet(BaseQueryRunner):
         try:
             spreadsheet_service = self._get_spreadsheet_service()
             spreadsheet = spreadsheet_service.open_by_key(key)
-            worksheets = spreadsheet.worksheets()
-            all_data = worksheets[worksheet_num].get_all_values()
-            column_names = []
-            columns = []
-            for j, column_name in enumerate(all_data[self.HEADER_INDEX]):
-                column_names.append(column_name)
-                columns.append({
-                    'name': column_name,
-                    'friendly_name': column_name,
-                    'type': _guess_type(all_data[self.HEADER_INDEX + 1][j])
-                })
-            rows = [dict(zip(column_names, _value_eval_list(row))) for row in all_data[self.HEADER_INDEX + 1:]]
-            data = {'columns': columns, 'rows': rows}
+
+            data = parse_spreadsheet(spreadsheet, worksheet_num)
+
             json_data = json.dumps(data, cls=JSONEncoder)
             error = None
         except gspread.SpreadsheetNotFound:

tests/query_runner/test_google_spreadsheets.py

@@ -1,7 +1,11 @@
 # -*- coding: utf-8 -*-
 
 from unittest import TestCase
+
+from mock import Mock, MagicMock
+
 from redash.query_runner.google_spreadsheets import _guess_type, _value_eval_list, TYPE_STRING, TYPE_BOOLEAN
+from redash.query_runner.google_spreadsheets import parse_worksheet, parse_spreadsheet, WorksheetNotFoundError
 
 
 class TestGuessType(TestCase):
@@ -26,3 +30,32 @@ class TestValueEvalList(TestCase):
         values = ['true', 'false', 'True', 'False', 'TRUE', 'FALSE']
         converted_values = [True, False, True, False, True, False]
         self.assertEqual(converted_values, _value_eval_list(values))
+
+
+class TestParseSpreadsheet(TestCase):
+    def test_returns_meaningful_error_for_missing_worksheet(self):
+        spreadsheet = MagicMock()
+
+        spreadsheet.worksheets = MagicMock(return_value=[])
+        self.assertRaises(WorksheetNotFoundError, parse_spreadsheet, spreadsheet, 0)
+
+        spreadsheet.worksheets = MagicMock(return_value=[1, 2])
+        self.assertRaises(WorksheetNotFoundError, parse_spreadsheet, spreadsheet, 2)
+
+
+empty_worksheet = []
+only_headers_worksheet = [['Column A', 'Column B']]
+regular_worksheet = [['String Column', 'Boolean Column', 'Number Column'], ['A', 'TRUE', '1'], ['B', 'FALSE', '2'], ['C', 'TRUE', '3'], ['D', 'FALSE', '4']]
+
+
+# The following test that the parse function doesn't crash. They don't test correct output.
+class TestParseWorksheet(TestCase):
+    def test_parse_empty_worksheet(self):
+        parse_worksheet(empty_worksheet)
+
+    def test_parse_only_headers_worksheet(self):
+        parse_worksheet(only_headers_worksheet)
+
+    def test_parse_regular_worksheet(self):
+        parse_worksheet(regular_worksheet)
+