aiorepl: Add tab completion support.

Use micropython.repl_autocomplete() to provide tab completion matching
the native REPL behavior: single match inserts the completion, multiple
matches prints candidates and redraws the prompt, tab after whitespace
inserts 4 spaces for indentation. Falls back gracefully on ports without
MICROPY_HELPER_REPL.

Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

Author: pi-anl

micropython/aiorepl/README.md

@@ -94,7 +94,7 @@ Ctrl-D at the asyncio REPL command prompt will terminate the current event loop,
 
 The following features are unsupported:
 
-* Tab completion is not supported (also unsupported in `python -m asyncio`).
+* Tab completion requires `micropython.repl_autocomplete` (available when firmware is built with `MICROPY_HELPER_REPL`, which is the default for most ports).
 * Multi-line continuation. However you can do single-line definitions of functions, see demo above.
 * Exception tracebacks. Only the exception type and message is shown, see demo above.
 * Emacs shortcuts (e.g. Ctrl-A, Ctrl-E, to move to start/end of line).

micropython/aiorepl/aiorepl.py

@@ -106,6 +106,7 @@ async def task(g=None, prompt="--> "):
         hist_n = 0  # Number of history entries.
         c = 0  # ord of most recent character.
         t = 0  # timestamp of most recent character.
+        _autocomplete = getattr(micropython, "repl_autocomplete", None)
         while True:
             hist_b = 0  # How far back in the history are we currently.
             sys.stdout.write(prompt)
@@ -187,6 +188,31 @@ async def task(g=None, prompt="--> "):
                     elif c == CHAR_CTRL_E:
                         sys.stdout.write("paste mode; Ctrl-C to cancel, Ctrl-D to finish\n===\n")
                         paste = True
+                    elif c == 0x09 and not paste:
+                        # Tab key.
+                        cursor_pos = len(cmd) - curs
+                        if cursor_pos > 0 and cmd[cursor_pos - 1] <= " ":
+                            # Insert 4 spaces for indentation after whitespace.
+                            compl = "    "
+                        elif _autocomplete and cursor_pos > 0:
+                            compl = _autocomplete(cmd[:cursor_pos])
+                        else:
+                            compl = ""
+                        if compl:
+                            # Insert completion at cursor.
+                            if curs:
+                                cmd = "".join((cmd[:-curs], compl, cmd[-curs:]))
+                                sys.stdout.write(cmd[-curs - len(compl) :])
+                                sys.stdout.write("\x1b[{}D".format(curs))
+                            else:
+                                sys.stdout.write(compl)
+                                cmd += compl
+                        elif compl is None:
+                            # Multiple matches printed by autocomplete, redraw line.
+                            sys.stdout.write(prompt)
+                            sys.stdout.write(cmd)
+                            if curs:
+                                sys.stdout.write("\x1b[{}D".format(curs))
                     elif c == 0x1B:
                         # Start of escape sequence.
                         key = await s.read(2)

micropython/aiorepl/manifest.py

@@ -1,5 +1,5 @@
 metadata(
-    version="0.2.2",
+    version="0.3.0",
     description="Provides an asynchronous REPL that can run concurrently with an asyncio, also allowing await expressions.",
 )
 

micropython/aiorepl/test_autocomplete.py

@@ -0,0 +1,43 @@
+# Test tab completion logic used by aiorepl.
+import sys
+import micropython
+
+try:
+    micropython.repl_autocomplete
+except AttributeError:
+    print("SKIP")
+    raise SystemExit
+
+# Test the autocomplete API contract that aiorepl depends on.
+
+# Single completion: keyword "import"
+result = micropython.repl_autocomplete("impo")
+print(repr(result))
+
+# No match: returns empty string
+result = micropython.repl_autocomplete("xyz_no_match_zzz")
+print(repr(result))
+
+# Multiple matches: returns None (candidates printed to stdout by C code).
+# Create two globals sharing a prefix so autocomplete finds multiple matches.
+import __main__
+
+__main__.tvar_alpha = 1
+__main__.tvar_beta = 2
+result = micropython.repl_autocomplete("tvar_")
+del __main__.tvar_alpha
+del __main__.tvar_beta
+print("multiple:", repr(result))
+
+# Test the whitespace-before-cursor logic used for tab-as-indentation.
+# This validates the condition: cursor_pos > 0 and cmd[cursor_pos - 1] <= " "
+test_cases = [
+    ("x ", True),  # space before cursor
+    ("x", False),  # non-whitespace before cursor
+    ("\n", True),  # newline counts as whitespace
+    ("", False),  # empty line (cursor_pos == 0)
+]
+for cmd, expected in test_cases:
+    cursor_pos = len(cmd)
+    is_whitespace = cursor_pos > 0 and cmd[cursor_pos - 1] <= " "
+    print(cmd.encode(), is_whitespace == expected)

micropython/aiorepl/test_autocomplete.py.exp

@@ -0,0 +1,9 @@
+'rt '
+''
+
+tvar_alpha      tvar_beta
+multiple: None
+b'x ' True
+b'x' True
+b'\n' True
+b'' True