gh-133390: Support SQL keyword completion for sqlite3 CLI (GH-133393) (GH-135292)

Co-authored-by: Tan Long <tanloong@foxmail.com>

Lib/sqlite3/_completer.py

@@ -0,0 +1,42 @@
+from contextlib import contextmanager
+
+try:
+    from _sqlite3 import SQLITE_KEYWORDS
+except ImportError:
+    SQLITE_KEYWORDS = ()
+
+_completion_matches = []
+
+
+def _complete(text, state):
+    global _completion_matches
+
+    if state == 0:
+        text_upper = text.upper()
+        _completion_matches = [c for c in SQLITE_KEYWORDS if c.startswith(text_upper)]
+    try:
+        return _completion_matches[state] + " "
+    except IndexError:
+        return None
+
+
+@contextmanager
+def completer():
+    try:
+        import readline
+    except ImportError:
+        yield
+        return
+
+    old_completer = readline.get_completer()
+    try:
+        readline.set_completer(_complete)
+        if readline.backend == "editline":
+            # libedit uses "^I" instead of "tab"
+            command_string = "bind ^I rl_complete"
+        else:
+            command_string = "tab: complete"
+        readline.parse_and_bind(command_string)
+        yield
+    finally:
+        readline.set_completer(old_completer)