From 73f276c5dbe33cd619d9f55ca05d14affa3aab8f Mon Sep 17 00:00:00 2001
From: Martin Burchell <mb2353@cam.ac.uk>
Date: Fri, 15 May 2020 15:22:14 +0100
Subject: [PATCH] Handle EmptyData error from pandas read_csv

---
 redcap/project.py    | 25 +++++++++++++++++--------
 test/test_project.py | 18 ++++++++++++++++++
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/redcap/project.py b/redcap/project.py
index c0ba925..977ede2 100755
--- a/redcap/project.py
+++ b/redcap/project.py
@@ -176,7 +176,6 @@ def export_fem(self, arms=None, format='json', df_kwargs=None):
         """
         ret_format = format
         if format == 'df':
-            from pandas import read_csv
             ret_format = 'csv'
         pl = self.__basepl('formEventMapping', format=ret_format)
 
@@ -189,9 +188,9 @@ def export_fem(self, arms=None, format='json', df_kwargs=None):
             return response
         elif format == 'df':
             if not df_kwargs:
-                return read_csv(StringIO(response))
-            else:
-                return read_csv(StringIO(response), **df_kwargs)
+                df_kwargs = {}
+
+            return self.read_csv(StringIO(response), **df_kwargs)
 
     def export_metadata(self, fields=None, forms=None, format='json',
             df_kwargs=None):
@@ -219,7 +218,6 @@ def export_metadata(self, fields=None, forms=None, format='json',
         """
         ret_format = format
         if format == 'df':
-            from pandas import read_csv
             ret_format = 'csv'
         pl = self.__basepl('metadata', format=ret_format)
         to_add = [fields, forms]
@@ -235,7 +233,7 @@ def export_metadata(self, fields=None, forms=None, format='json',
         elif format == 'df':
             if not df_kwargs:
                 df_kwargs = {'index_col': 'field_name'}
-            return read_csv(StringIO(response), **df_kwargs)
+            return self.read_csv(StringIO(response), **df_kwargs)
 
     def delete_records(self, records):
         """
@@ -329,7 +327,6 @@ def export_records(self, records=None, fields=None, forms=None,
         """
         ret_format = format
         if format == 'df':
-            from pandas import read_csv
             ret_format = 'csv'
         pl = self.__basepl('record', format=ret_format)
         fields = self.backfill_fields(fields, forms)
@@ -360,10 +357,22 @@ def export_records(self, records=None, fields=None, forms=None,
                 else:
                     df_kwargs = {'index_col': self.def_field}
             buf = StringIO(response)
-            df = read_csv(buf, **df_kwargs)
+            df = self.read_csv(buf, **df_kwargs)
             buf.close()
             return df
 
+    def read_csv(self, buf, **df_kwargs):
+        """Wrapper around pandas read_csv that handles EmptyDataError"""
+        from pandas import DataFrame, read_csv
+        from pandas.errors import EmptyDataError
+
+        try:
+            df = read_csv(buf, **df_kwargs)
+        except EmptyDataError:
+            df = DataFrame()
+
+        return df
+
     def metadata_type(self, field_name):
         """If the given field_name is validated by REDCap, return it's type"""
         return self.__meta_metadata(field_name,
diff --git a/test/test_project.py b/test/test_project.py
index 83f7c2e..94ddf8a 100644
--- a/test/test_project.py
+++ b/test/test_project.py
@@ -615,6 +615,24 @@ def test_import_dataframe(self):
         self.assertIn('count', response)
         self.assertNotIn('error', response)
 
+    def test_export_records_handles_empty_data_error(self):
+        self.reg_proj._call_api = mock.Mock()
+        self.reg_proj._call_api.return_value = "\n", {}
+        df = self.reg_proj.export_records(format='df')
+        self.assertTrue(df.empty)
+
+    def test_export_fem_handles_empty_data_error(self):
+        self.reg_proj._call_api = mock.Mock()
+        self.reg_proj._call_api.return_value = "\n", {}
+        df = self.reg_proj.export_fem(format='df')
+        self.assertTrue(df.empty)
+
+    def test_export_metadata_handles_empty_data_error(self):
+        self.reg_proj._call_api = mock.Mock()
+        self.reg_proj._call_api.return_value = "\n", {}
+        df = self.reg_proj.export_metadata(format='df')
+        self.assertTrue(df.empty)
+
     @responses.activate
     def test_date_formatting(self):
         """Test date_format parameter"""