chain=True silently ignored since 0.26.0 (vendored Click) — API misleadingly documents it as supported

[okurz]

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Example Code

import typer
from typer.testing import CliRunner

app = typer.Typer(chain=True)

@app.command()
def a():
    print("A")

@app.command()
def b():
    print("B")

result = CliRunner().invoke(app, ["a", "b"])
print(f"exit_code: {result.exit_code}")
print(result.output)

Description

Observation

Since version 0.26.0 (which vendored Click and restructured TyperGroup under PR #1774), setting chain=True on a Typer app is silently accepted but has no effect. Chained command invocations fail with Got unexpected extra argument(s).

However, the chain parameter is still fully exposed on the public API (on Typer(), add_typer(), and TyperInfo), and its docstring misleadingly states that it is:

"**Note**: you probably shouldn't use this parameter, it is inherited from Click and supported for compatibility ... Allow passing more than one subcommand argument."

Since command chaining is no longer supported after the Click vendoring refactor, passing chain=True explicitly should fail with a clear RuntimeError rather than failing silently at runtime, and the misleading docstrings should be corrected.

Relating to the attached minimum reproducer:
Expected Behavior (e.g. Typer 0.25.1)
Both commands are executed sequentially:
A
B
exit_code: 0
Actual Behavior (Typer 0.26.0 - 0.26.8)
Silent failure of the chain; Click throws an "unexpected extra argument" usage error on the second command:

Usage: root a [OPTIONS]
Try 'root a --help' for help.
╭─ Error ──────────────────────────────────────────────────────────────────────╮
│ Got unexpected extra argument(s) (b)                                         │
╰──────────────────────────────────────────────────────────────────────────────╯
exit_code: 2

Proposed Solution / PR Preview

I have prepared a patch in my fork to:

1. Detect explicit truthy chain (not the Default(False) placeholder) in TyperInfo.__init__ and raise a clear, helpful RuntimeError on instantiation.
2. Correct the three outdated docstrings in main.py to state chaining is unsupported and will raise an error. Alternatively remove it completely.
3. Optional: Add pytest safety checks for this guard.

Operating System

Linux

Operating System Details

openSUSE Slowroll

Project Version

0.26.0 through 0.26.8 (including master)

Python Version

3.13.13

Additional Context

No response

[svlandeg]

Thanks, we'll fix this in a future refactor, this argument will become unsupported as already indicated in the API docstring.