Simplify the json_stream() utility

The previous implementation was generic over the kind of decoder
and separator. However, the only use was with JSON decoder and
newline-based splitting.

Signed-off-by: Francesco Zardi <frazar0@hotmail.it>

docker/utils/json_stream.py

@@ -1,4 +1,3 @@
-import json
 import json.decoder
 
 from ..errors import StreamParseError
@@ -37,30 +36,12 @@ def json_stream(stream):
     This handles streams which are inconsistently buffered (some entries may
     be newline delimited, and others are not).
     """
-    return split_buffer(stream, json_splitter, json_decoder.decode)
-
-
-def line_splitter(buffer, separator='\n'):
-    index = buffer.find(str(separator))
-    if index == -1:
-        return None
-    return buffer[:index + 1], buffer[index + 1:]
-
-
-def split_buffer(stream, splitter=None, decoder=lambda a: a):
-    """Given a generator which yields strings and a splitter function,
-    joins all input, splits on the separator and yields each chunk.
-    Unlike string.split(), each chunk includes the trailing
-    separator, except for the last one if none was found on the end
-    of the input.
-    """
-    splitter = splitter or line_splitter
     buffered = ''
 
     for data in stream_as_text(stream):
         buffered += data
         while True:
-            buffer_split = splitter(buffered)
+            buffer_split = json_splitter(buffered)
             if buffer_split is None:
                 break
 
@@ -69,6 +50,13 @@ def split_buffer(stream, splitter=None, decoder=lambda a: a):
 
     if buffered:
         try:
-            yield decoder(buffered)
+            yield json_decoder.decode(buffered)
         except Exception as e:
             raise StreamParseError(e) from e
+
+
+def line_splitter(buffer: str, separator='\n'):
+    index = buffer.find(str(separator))
+    if index == -1:
+        return None
+    return buffer[:index + 1], buffer[index + 1:]