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

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

Lib/test/test_sqlite3/test_cli.py

@@ -1,14 +1,22 @@
 """sqlite3 CLI tests."""
 import sqlite3
+import sys
+import textwrap
 import unittest
+import unittest.mock
+import os
 
 from sqlite3.__main__ import main as cli
+from test.support.import_helper import import_module
 from test.support.os_helper import TESTFN, unlink
+from test.support.pty_helper import run_pty
 from test.support import (
     captured_stdout,
     captured_stderr,
     captured_stdin,
     force_not_colorized_test_class,
+    requires_subprocess,
+    verbose,
 )
 
 
@@ -200,5 +208,108 @@ class InteractiveSession(unittest.TestCase):
             self.assertIn('\x1b[1;35mOperationalError (SQLITE_ERROR)\x1b[0m: '
                           '\x1b[35mnear "sel": syntax error\x1b[0m', err)
 
+
+@requires_subprocess()
+@force_not_colorized_test_class
+class Completion(unittest.TestCase):
+    PS1 = "sqlite> "
+
+    @classmethod
+    def setUpClass(cls):
+        _sqlite3 = import_module("_sqlite3")
+        if not hasattr(_sqlite3, "SQLITE_KEYWORDS"):
+            raise unittest.SkipTest("unable to determine SQLite keywords")
+
+        readline = import_module("readline")
+        if readline.backend == "editline":
+            raise unittest.SkipTest("libedit readline is not supported")
+
+    def write_input(self, input_, env=None):
+        script = textwrap.dedent("""
+            import readline
+            from sqlite3.__main__ import main
+
+            readline.parse_and_bind("set colored-completion-prefix off")
+            main()
+        """)
+        return run_pty(script, input_, env)
+
+    def test_complete_sql_keywords(self):
+        # List candidates starting with 'S', there should be multiple matches.
+        input_ = b"S\t\tEL\t 1;\n.quit\n"
+        output = self.write_input(input_)
+        self.assertIn(b"SELECT", output)
+        self.assertIn(b"SET", output)
+        self.assertIn(b"SAVEPOINT", output)
+        self.assertIn(b"(1,)", output)
+
+        # Keywords are completed in upper case for even lower case user input.
+        input_ = b"sel\t\t 1;\n.quit\n"
+        output = self.write_input(input_)
+        self.assertIn(b"SELECT", output)
+        self.assertIn(b"(1,)", output)
+
+    @unittest.skipIf(sys.platform.startswith("freebsd"),
+                    "Two actual tabs are inserted when there are no matching"
+                    " completions in the pseudo-terminal opened by run_pty()"
+                    " on FreeBSD")
+    def test_complete_no_match(self):
+        input_ = b"xyzzy\t\t\b\b\b\b\b\b\b.quit\n"
+        # Set NO_COLOR to disable coloring for self.PS1.
+        output = self.write_input(input_, env={**os.environ, "NO_COLOR": "1"})
+        lines = output.decode().splitlines()
+        indices = (
+            i for i, line in enumerate(lines, 1)
+            if line.startswith(f"{self.PS1}xyzzy")
+        )
+        line_num = next(indices, -1)
+        self.assertNotEqual(line_num, -1)
+        # Completions occupy lines, assert no extra lines when there is nothing
+        # to complete.
+        self.assertEqual(line_num, len(lines))
+
+    def test_complete_no_input(self):
+        from _sqlite3 import SQLITE_KEYWORDS
+
+        script = textwrap.dedent("""
+            import readline
+            from sqlite3.__main__ import main
+
+            # Configure readline to ...:
+            # - hide control sequences surrounding each candidate
+            # - hide "Display all xxx possibilities? (y or n)"
+            # - hide "--More--"
+            # - show candidates one per line
+            readline.parse_and_bind("set colored-completion-prefix off")
+            readline.parse_and_bind("set colored-stats off")
+            readline.parse_and_bind("set completion-query-items 0")
+            readline.parse_and_bind("set page-completions off")
+            readline.parse_and_bind("set completion-display-width 0")
+            readline.parse_and_bind("set show-all-if-ambiguous off")
+            readline.parse_and_bind("set show-all-if-unmodified off")
+
+            main()
+        """)
+        input_ = b"\t\t.quit\n"
+        output = run_pty(script, input_, env={**os.environ, "NO_COLOR": "1"})
+        try:
+            lines = output.decode().splitlines()
+            indices = [
+                i for i, line in enumerate(lines)
+                if line.startswith(self.PS1)
+            ]
+            self.assertEqual(len(indices), 2)
+            start, end = indices
+            candidates = [l.strip() for l in lines[start+1:end]]
+            self.assertEqual(candidates, sorted(SQLITE_KEYWORDS))
+        except:
+            if verbose:
+                print(' PTY output: '.center(30, '-'))
+                print(output.decode(errors='replace'))
+                print(' end PTY output '.center(30, '-'))
+            raise
+
+
+
 if __name__ == "__main__":
     unittest.main()