nix develop: Request one output of bashInteractive

[alexshpilkin]

Fixes #6500 (the nix develop implementation bug part per my description there, I’m assuming the nix why-depends doc / semantics part will get its own bug)

I really tried to make a test this time, but while I can verify interactively that the problem was present and is now gone, I just can’t seem to get the test suite to either succeed here or to fail on master. FWIW, the simplest thing I tried was

diff --git a/tests/nix-shell.sh b/tests/nix-shell.sh                                                                                                           
index 3241d7a0f..96d6cf063 100644                                                                                                                              
--- a/tests/nix-shell.sh                                                                                                                                       
+++ b/tests/nix-shell.sh                                                                                                                                       
@@ -85,7 +85,7 @@ output=$($TEST_ROOT/spaced\ \\\'\"shell.shebang.rb abc ruby)                                                                                 
 [ "$output" = '-e load(ARGV.shift) -- '"$TEST_ROOT"'/spaced \'\''"shell.shebang                                                                               
.rb abc ruby' ]                                                                                                                                                
                                                                                                                                                               
 # Test 'nix develop'.                                                                                                                                         
-nix develop -f "$shellDotNix" shellDrv -c bash -c '[[ -n $stdenv ]]'                                                                                          
+nix develop -f "$shellDotNix" shellDrv -c bash -c '[[ -n $stdenv ]]' |& grep -qv error                                                                        
                                       
 # Ensure `nix develop -c` preserves stdin                                                                                                                     
 echo foo | nix develop -f "$shellDotNix" shellDrv -c cat | grep -q foo                                                                                        

but that seems to succeed on master for some reason (?!..).

[Artturin]

works

$ nix develop "nixpkgs#bash"
error (ignored): error: argument 'flake:nixpkgs#bashInteractive' should evaluate to one store path

[artturin@artturinlinux:~/nixgits/my-nixpkgs]$
exit
$ nix run "github:alexshpilkin/nix/fix-6500" -- develop "nixpkgs#bash"

[artturin@artturinlinux:~/nixgits/my-nixpkgs]$
exit

[edolstra]

The problem is that this will break if bashInteractive ever changes its outputs (e.g. moves bash to a bin output).

[alexshpilkin]

It will also break if bashInteractive is ever renamed, and there’s a big fat warning comment about that in Nixpkgs, so I assumed that would be okay? The warning should probably be extended to mention the output name as well, of course.

[edolstra]

A more future-proof fix is to use toStorePaths() instead of toStorePath(), and look in each output for a bin/bash.

[thufschmitt]

@edolstra would it make sense to merge this as-it-is and add the proper fix later? This is a rather big breakage and it’s really sad to keep master in this state

[edolstra]

Thanks, I've fixed it in a different way in #6518.

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/tweag-nix-dev-update-30/19112/1