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

Lib/sqlite3/__main__.py

@@ -12,6 +12,8 @@ from code import InteractiveConsole
 from textwrap import dedent
 from _colorize import get_theme, theme_no_color
 
+from ._completer import completer
+
 
 def execute(c, sql, suppress_errors=True, theme=theme_no_color):
     """Helper that wraps execution of SQL code.
@@ -136,12 +138,9 @@ def main(*args):
             execute(con, args.sql, suppress_errors=False, theme=theme)
         else:
             # No SQL provided; start the REPL.
-            console = SqliteInteractiveConsole(con, use_color=True)
-            try:
-                import readline  # noqa: F401
-            except ImportError:
-                pass
-            console.interact(banner, exitmsg="")
+            with completer():
+                console = SqliteInteractiveConsole(con, use_color=True)
+                console.interact(banner, exitmsg="")
     finally:
         con.close()
 

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)