uasyncio: StreamReader.readline: Handle partial reads.

Now it will return a complete line regardless if it may take several
partial reads to do that. Test included.

uasyncio/test_readline.py

@@ -0,0 +1,30 @@
+from uasyncio import StreamReader
+
+class MockSock:
+
+    def __init__(self, data_list):
+        self.data = data_list
+
+    def readline(self):
+        try:
+            return self.data.pop(0)
+        except IndexError:
+            return b""
+
+
+mock = MockSock([
+    b"line1\n",
+    b"parts ", b"of ", b"line2\n",
+    b"unterminated",
+])
+
+
+def func():
+    sr = StreamReader(mock)
+    assert await sr.readline() == b"line1\n"
+    assert await sr.readline() == b"parts of line2\n"
+    assert await sr.readline() == b"unterminated"
+    assert await sr.readline() == b""
+
+for i in func():
+    pass

uasyncio/uasyncio/__init__.py

@@ -92,19 +92,20 @@ class StreamReader:
     def readline(self):
         if __debug__:
             log.debug("StreamReader.readline()")
-#        if DEBUG and __debug__:
-#            log.debug("StreamReader.readline(): after IORead: %s", s)
+        buf = b""
         while True:
             yield IORead(self.s)
             res = self.s.readline()
-            if res is not None:
-                break
-            log.warn("Empty read")
+            assert res is not None
             if not res:
                 yield IOReadDone(self.s)
+                break
+            buf += res
+            if buf[-1] == 0x0a:
+                break
         if DEBUG and __debug__:
-            log.debug("StreamReader.readline(): res: %s", res)
-        return res
+            log.debug("StreamReader.readline(): %s", buf)
+        return buf
 
     def aclose(self):
         yield IOReadDone(self.s)