bash autocompletion broken when using SetOutput()

[thediveo]

• go.mod: github.com/spf13/cobra v1.8.1
• Ubuntu 24.10
• bash "version 5.2.32(1)-release (x86_64-pc-linux-gnu)"

Noticed the problem both in my failing unit tests as well as on the CLI itself. For testing and as an example I use my https://github.com/thediveo/enumflag/tree/master/test/enumflag-testing. Building enumflag-test and then in the CLI first entering the binary name and then TAB-TAB yields:

/tmp/test $ ./enumflag-testing 
:4
Completion ended with directive
completion                       (Generate the autocompletion script for the specified shell)
help                             (Help about any command)
test

I see this same problem also in an Ubuntu 24.04.1LTS-based devcontainer with bash "version 5.2.21(1)-release (x86_64-pc-linux-gnu)".

Maybe #2213 might be related?

[marckhouzam]

This is because you use SetOutput() which is deprecated. This function redirects both the output and error streams, and the completion logic prints stuff to the error stream, which is why you are seeing it on your screen.

cobra/command.go

Lines 284 to 285 in 0745e55

	// Deprecated: Use SetOut and/or SetErr instead
	func (c *Command) SetOutput(output io.Writer) {

You should not redirect the error stream to stdout for the __complete command.

[thediveo]

many thanks for the quick help!

[marckhouzam]

You weren’t the first to hit this problem 😀