ujson: do not eat trailing whitespace

Ujson should only worry about whitespace before JSON.  This becomes apparent when you are using MP stream protocol to read directly from input buffers.

When you attempt to read(1) on a UART (and possibly other protocols) you have to wait for either the byte or the timeout.

Fixes:
- Waiting for a timeout after you have completed reading a correct and complete JSON off the input.
- Raising an OSError after reading a correct and complete JSON off the input.
- Eating more data than semantically owned off the input buffer.
- Blocking to start parsing JSON until the entire JSON body has been loaded into a potentially large, contiguous Python object.

Code you would write before:
```
line = board_busio_uart_port.read_line()
json_dict = json.loads(line)
```
or reaching for fixed buffers and swapping them around in Python.

Code that did not work before that does now:
```
json_dict = json.load(board_busio_uart_port)
```

- This removes the need for intermediate copies of data when reading JSON from micropython stream protocol inputs.
- It also increases total application speed by parsing JSON concurrently with receiving on boards that read from UART via DMA.
- It simplifies code that users write while improving their apps.

1 files changed, 4 insertions, 0 deletions

diff --git a/shared-bindings/busio/UART.c b/shared-bindings/busio/UART.c
index f231924d5..883b4630f 100644
--- a/shared-bindings/busio/UART.c
+++ b/shared-bindings/busio/UART.c
@@ -39,6 +39,9 @@
 #include "py/stream.h"
 #include "supervisor/shared/translate.h"
 
+#define STREAM_DEBUG(...) (void)0
+// #define STREAM_DEBUG(...) mp_printf(&mp_plat_print __VA_OPT__(,) __VA_ARGS__)
+
 
 //| .. currentmodule:: busio
 //|
@@ -219,6 +222,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(busio_uart___exit___obj, 4, 4, busio_
 
 // These three methods are used by the shared stream methods.
 STATIC mp_uint_t busio_uart_read(mp_obj_t self_in, void *buf_in, mp_uint_t size, int *errcode) {
+    STREAM_DEBUG("busio_uart_read stream %d\n", size);
     busio_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
     check_for_deinit(self);
     byte *buf = buf_in;