#55 Fixed the empty input bug

Author: ahsimb

doc/changes/unreleased.md

@@ -6,4 +6,8 @@ Code name: tbd
 
 ### Bugs
 
-n/a
+* #55: Not possible to create StandaloneMockContext with empty input list
+
+### Features
+
+* #56: Made script_code_wrapper_function parameter of the MockMetaData optional.

exasol_udf_mock_python/mock_context.py

@@ -1,4 +1,5 @@
 from typing import List, Tuple, Iterator, Iterable, Any, Optional, Union
+from collections.abc import Sized
 from functools import wraps
 
 import pandas as pd
@@ -133,24 +134,30 @@ def emit(self, *args) -> None:
         self._current_context.emit(*args)
 
 
-def get_scalar_input(inp: Any) -> Iterable[Tuple[Any, ...]]:
+def get_scalar_input(inp: Any) -> Iterable[Iterable[Any]]:
     """
     Figures out if the SCALAR parameters are provided as a scalar value or a tuple
     and also if there is a wrapping container around.
-    Unless the parameters are already in a wrapping container returns parameters as a tuple wrapped
-    into a one-item list, e.g [(param1[, param2, ...)]. Otherwise, returns the original input.
+    Unless the parameters are already in a wrapping Sized container, returns parameters as an iterable
+    wrapped into a one-item list, e.g [(param1, [param2, ...])]. Otherwise, returns the original input.
 
     :param  inp:        Input parameters.
     """
 
-    if isinstance(inp, Iterable) and not isinstance(inp, str):
-        row1 = next(iter(inp))
-        if isinstance(row1, Iterable) and not isinstance(row1, str):
-            return inp
-        else:
-            return [inp]
-    else:
-        return [(inp,)]
+    if inp is not None:
+        if (not isinstance(inp, Iterable)) or isinstance(inp, str):
+            return [(inp,)]
+        try:
+            row1 = next(iter(inp))
+            if (not isinstance(row1, Iterable)) or isinstance(row1, str):
+                return [inp]
+            elif not isinstance(inp, Sized):
+                return list(inp)
+            else:
+                return inp
+        except StopIteration:
+            pass
+    return [tuple()]
 
 
 class StandaloneMockContext(UDFContext):

exasol_udf_mock_python/mock_meta_data.py

@@ -42,7 +42,8 @@ def __init__(
         self._current_user = current_user
         self._current_schema = current_schema
         self._scope_user = scope_user
-        self._script_code = self._extract_script_code(script_code_wrapper_function)
+        self._script_code = (None if script_code_wrapper_function is None
+                             else self._extract_script_code(script_code_wrapper_function))
         self._connection_id = connection_id
         self._database_name = database_name
         self._database_version = database_version

pyproject.toml

@@ -19,7 +19,7 @@ keywords = ['exasol', 'udf', 'mock', 'testing']
 [tool.poetry.dependencies]
 python = "^3.8"
 pandas = "^1.4"
-numpy =  "^1.22"
+numpy =  ">=1.26.0"
 dill = ">=0.3.7"
 
 [tool.poetry.dev-dependencies]

tests/test_mock_context_standalone.py

@@ -63,6 +63,21 @@ def test_attr_scalar(context_scalar_return):
     assert context_scalar_return.t == 5
 
 
+@pytest.mark.parametrize('inp', [None, [], [[]]])
+def test_context_empty_input(inp):
+    meta_data = MockMetaData(
+        script_code_wrapper_function=udf_wrapper,
+        input_type='SCALAR',
+        input_columns=[],
+        output_type='RETURNS',
+        output_columns=[Column('t', int, 'INTEGER')]
+    )
+    _ = StandaloneMockContext(inp, meta_data)
+    # There is nothing to test here apart from successful creation of the
+    # context object. This internally has some checks that need to be passed.
+    pass
+
+
 def test_next(context_set_emits):
     assert context_set_emits.next()
     assert context_set_emits.t1 == 6