From 5b46753e1f1df52948517f2d24ddd1df56d9e5e1 Mon Sep 17 00:00:00 2001
From: VenishPaneliya <141703684+VenishPaneliya@users.noreply.github.com>
Date: Thu, 20 Aug 2026 16:09:54 +0530
Subject: [PATCH] Keep the sub-app's deprecated flag in add_typer()

add_typer() declared `deprecated` as a plain False while every other
setting in the same signature uses the Default() sentinel, including
`hidden` on the line above it.

solve_typer_info_defaults() relies on that sentinel to tell "the caller
passed this to add_typer()" apart from "the caller said nothing". A bare
False is not a DefaultPlaceholder, so Priority 1 always matched and the
callback and sub-app instance were never consulted: a sub-app that marked
itself deprecated lost the flag as soon as it was added to a parent.

Passing deprecated=True to add_typer() directly already worked, and the
sibling `hidden` propagates correctly, so only the default was wrong.

Typer.command() also uses a bare False, but it builds a CommandInfo, which
never goes through solve_typer_info_defaults(), so it is left as is.
---
 tests/test_deprecation.py | 35 +++++++++++++++++++++++++++++++++++
 typer/main.py             |  2 +-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/tests/test_deprecation.py b/tests/test_deprecation.py
index 8f21bbf34f..c331385ad7 100644
--- a/tests/test_deprecation.py
+++ b/tests/test_deprecation.py
@@ -1,7 +1,10 @@
 import pytest
 import typer
+import typer.core
 from typer.testing import CliRunner
 
+from tests.utils import needs_rich
+
 runner = CliRunner()
 
 
@@ -23,3 +26,35 @@ def cmd(
         match="The 'is_flag' and 'flag_value' parameters are not supported by Typer"
     ):
         add_command()
+
+
+@pytest.mark.parametrize(
+    ("use_rich", "expected"),
+    [
+        pytest.param(False, "(DEPRECATED)"),
+        pytest.param(True, "(deprecated)", marks=needs_rich),
+    ],
+)
+def test_add_typer_keeps_sub_app_deprecated(
+    monkeypatch: pytest.MonkeyPatch, use_rich: bool, expected: str
+) -> None:
+    """A sub-app that marks itself deprecated stays deprecated once added.
+
+    ``add_typer()`` has to leave its own ``deprecated`` default as a
+    ``Default()`` placeholder, otherwise it reads as an explicit argument and
+    overrides the value the sub-app set on itself.
+    """
+    monkeypatch.setattr(typer.core, "HAS_RICH", use_rich)
+
+    app = typer.Typer()
+    sub_app = typer.Typer(deprecated=True)
+
+    @sub_app.command()
+    def sub_command() -> None:
+        """Sub command."""  # pragma: no cover
+
+    app.add_typer(sub_app, name="sub")
+
+    result = runner.invoke(app, ["--help"])
+    assert result.exit_code == 0
+    assert expected in result.output
diff --git a/typer/main.py b/typer/main.py
index 700648da66..05f7143844 100644
--- a/typer/main.py
+++ b/typer/main.py
@@ -1073,7 +1073,7 @@ def add_typer(
                 Mark this command as deprecated in the help outputs. `False` by default.
                 """
             ),
-        ] = False,
+        ] = Default(False),
         # Rich settings
         rich_help_panel: Annotated[
             str | None,