[lldb] Fix typed commands not shown on the screen

The issue is that in python3.14,
`fcntl.ioctl` now throws a buffer overflow error
when the buffer is too small (see python/cpython#132919).
This caused the Python interpreter to fail terminal detection and not
properly echo user commands back to the screen.

Fix by dropping the custom terminal size check entirely and using the
built-in `sys.stdin.isatty()` instead.

Fixes llvm#173302

Author: da-viper

lldb/packages/Python/lldbsuite/test/lldbpexpect.py

@@ -10,6 +10,7 @@
 
 
 @skipIfRemote
+@skipIfWindows
 @add_test_categories(["pexpect"])
 class PExpectTest(TestBase):
     NO_DEBUG_INFO_TESTCASE = True

lldb/source/Interpreter/embedded_interpreter.py

@@ -1,8 +1,6 @@
 import sys
 import builtins
 import code
-import lldb
-import traceback
 
 try:
     import readline
@@ -31,19 +29,6 @@ def is_libedit():
 
 g_run_one_line_str = None
 
-
-def get_terminal_size(fd):
-    try:
-        import fcntl
-        import termios
-        import struct
-
-        hw = struct.unpack("hh", fcntl.ioctl(fd, termios.TIOCGWINSZ, "1234"))
-    except:
-        hw = (0, 0)
-    return hw
-
-
 class LLDBExit(SystemExit):
     pass
 
@@ -74,50 +59,21 @@ def readfunc_stdio(prompt):
 def run_python_interpreter(local_dict):
     # Pass in the dictionary, for continuity from one session to the next.
     try:
-        fd = sys.stdin.fileno()
-        interacted = False
-        if get_terminal_size(fd)[1] == 0:
-            try:
-                import termios
-
-                old = termios.tcgetattr(fd)
-                if old[3] & termios.ECHO:
-                    # Need to turn off echoing and restore
-                    new = termios.tcgetattr(fd)
-                    new[3] = new[3] & ~termios.ECHO
-                    try:
-                        termios.tcsetattr(fd, termios.TCSADRAIN, new)
-                        interacted = True
-                        code.interact(
-                            banner="Python Interactive Interpreter. To exit, type 'quit()', 'exit()'.",
-                            readfunc=readfunc_stdio,
-                            local=local_dict,
-                        )
-                    finally:
-                        termios.tcsetattr(fd, termios.TCSADRAIN, old)
-            except:
-                pass
-            # Don't need to turn off echoing
-            if not interacted:
-                code.interact(
-                    banner="Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.",
-                    readfunc=readfunc_stdio,
-                    local=local_dict,
-                )
-        else:
-            # We have a real interactive terminal
-            code.interact(
-                banner="Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.",
-                readfunc=readfunc,
-                local=local_dict,
-            )
+        banner = "Python Interactive Interpreter. To exit, type 'quit()', 'exit()'."
+        input_func = readfunc_stdio
+
+        is_atty = sys.stdin.isatty()
+        if is_atty:
+            banner = "Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D."
+            input_func = readfunc
+
+        code.interact(banner=banner, readfunc=input_func, local=local_dict)
     except LLDBExit:
         pass
     except SystemExit as e:
         if e.code:
             print("Script exited with code %s" % e.code)
 
-
 def run_one_line(local_dict, input_string):
     global g_run_one_line_str
     try:

lldb/test/API/terminal/TestPythonInterpreterEcho.py

@@ -0,0 +1,62 @@
+"""
+Test that typing python expression in the terminal is echoed back to stdout.
+"""
+
+from lldbsuite.test.decorators import skipIfAsan
+from lldbsuite.test.lldbpexpect import PExpectTest
+
+
+@skipIfAsan
+class PythonInterpreterEchoTest(PExpectTest):
+    PYTHON_PROMPT = ">>> "
+
+    def verify_command_echo(
+        self, command: str, expected_output: str = "", is_regex: bool = False
+    ):
+        assert self.child != None
+        child = self.child
+        self.assertIsNotNone(self.child, "expected a running lldb process.")
+
+        child.sendline(command)
+
+        # Build pattern list: match whichever comes first (output or prompt)
+        # This prevents waiting for a timeout if there's no match
+        pattern = []
+        match_expected = expected_output and len(expected_output) > 0
+
+        if match_expected:
+            pattern.append(expected_output)
+        pattern.append(self.PYTHON_PROMPT)
+
+        expect_func = child.expect if is_regex else child.expect_exact
+        match_idx = expect_func(pattern)
+        if match_expected:
+            self.assertEqual(
+                match_idx, 0, "Expected output `{expected_output}` in stdout."
+            )
+
+        self.assertIsNotNone(self.child.before, "Expected output before prompt")
+        self.assertIsInstance(self.child.before, bytes)
+        echoed_text: str = self.child.before.decode("ascii").strip()
+        self.assertEqual(
+            command, echoed_text, f"Command '{command}' should be echoed to stdout."
+        )
+
+        if match_expected:
+            child.expect_exact(self.PYTHON_PROMPT)
+
+    def test_python_interpreter_echo(self):
+        """Test that that the user typed commands is echoed to stdout"""
+
+        self.launch(use_colors=False, dimensions=(100, 100))
+
+        # enter the python interpreter
+        self.verify_command_echo(
+            "script --language python --", expected_output="Python.*\\.", is_regex=True
+        )
+        self.child_in_script_interpreter = True
+
+        self.verify_command_echo("val = 300")
+        self.verify_command_echo(
+            "print('result =', 300)", expected_output="result = 300"
+        )