Add ListTarget and associated test case

streaming_form_data/targets.py

@@ -84,6 +84,47 @@ def value(self):
         return b"".join(self._values)
 
 
+class ListTarget(BaseTarget):
+    """ListTarget stores the input in an in-memory list of bytes,
+    which is then joined into the final value and appended to an in-memory
+    list of byte strings when each value is finished.
+
+    This is usefull for situations where more than one value may be submitted for
+    the same argument.
+    """
+
+    def __init__(self, _type=bytes, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        self._temp_value = []
+        self._values = []
+        self._type = _type
+
+    def on_data_received(self, chunk: bytes):
+        self._temp_value.append(chunk)
+
+    def on_finish(self):
+        value = b"".join(self._temp_value)
+        self._temp_value = []
+
+        if self._type == str:
+            value = value.decode("UTF-8")
+        elif self._type == bytes:
+            pass  # already is bytes, no need to do anything
+        else:
+            value = self._type(value)
+
+        self._values.append(value)
+
+    @property
+    def value(self):
+        return self._values
+
+    @property
+    def finished(self):
+        return self._finished
+
+
 class FileTarget(BaseTarget):
     """FileTarget writes (streams) the input to an on-disk file."""
 

tests/test_targets.py

@@ -11,6 +11,7 @@
     DirectoryTarget,
     NullTarget,
     ValueTarget,
+    ListTarget,
     S3Target,
     CSVTarget,
 )
@@ -82,6 +83,38 @@ def test_value_target_total_size_validator():
         target.data_received(b"world")
 
 
+def test_list_target_basic():
+    target = ListTarget()
+
+    assert target.value == []
+
+    target.multipart_filename = None
+
+    target.start()
+    assert target.multipart_filename is None
+    assert target.value == []
+
+    # Send and finish multiple values
+    target.data_received(b"Cat")
+    target.finish()
+    target.data_received(b"Dog")
+    target.finish()
+    target.data_received(b"Big")
+    target.data_received(b" ")
+    target.data_received(b"Goldfish")
+    target.finish()
+
+    assert target.multipart_filename is None
+    assert target.value == [b"Cat", b"Dog", b"Big Goldfish"]
+
+
+def test_list_target_not_set():
+    target = ListTarget()
+
+    assert target.multipart_filename is None
+    assert target.value == []
+
+
 def test_file_target_basic():
     filename = os.path.join(tempfile.gettempdir(), "file.txt")