install_command only accepts a single command, but the documentation says that I can “provide arbitrary commands” to it

[oakkitten]

The documentation for install_command says,

Note: You can also provide arbitrary commands to the install_command. (...)

I don't think this is correct. Given this config,

[tox]
skip_install = true
skipsdist = true
envlist = foo

[testenv]
install_command =
    echo '!!!!!!!!!!!!!!!!!!!!!!! install 1' {packages}
    echo '!!!!!!!!!!!!!!!!!!!!!!! install 2' {packages}
commands =
    echo '!!!!!!!!!!!!!!!!!!!!!!! test' {envname}
allowlist_externals =
    echo
deps =
    zoo

tox 3 will only execute the first command:

$ python -m tox -rvv
...
[1190] /mnt/c/Users/s/tox_install_command_test$ /usr/bin/echo '!!!!!!!!!!!!!!!!!!!!!!! install 1' zoo
!!!!!!!!!!!!!!!!!!!!!!! install 1 zoo
foo finish: getenv /mnt/c/Users/s/tox_install_command_test/.tox/foo after 17.95 seconds
...

and tox 4 will execute what appears to be the two commands glued together as one, but only replacing the first {packages}

$ python -m tox -rvv
...
foo: 20300 W install_deps> echo '!!!!!!!!!!!!!!!!!!!!!!! install 1' zoo echo '!!!!!!!!!!!!!!!!!!!!!!! install 2' '{packages}' [tox/tox_env/api.py:398]
!!!!!!!!!!!!!!!!!!!!!!! install 1 zoo echo !!!!!!!!!!!!!!!!!!!!!!! install 2 {packages}
foo: 20324 I exit 0 (0.01 seconds) /mnt/c/Users/s/tox_install_command_test> echo '!!!!!!!!!!!!!!!!!!!!!!! install 1' zoo echo '!!!!!!!!!!!!!!!!!!!!!!! install 2' '{packages}' pid=1269 [tox/execute/api.py:275]
...

I suppose that tox should:

• Change the documentation so that it doesn't say that I can use command“s” in install_command;
• Produce an error if I try, instead of ignoring lines or gluing them together.

Also, tox might:

• Support multiple installation commands via install_commands (note the ”s”), and only require {packages} to be passed to one of them;
• Deprecate install_command in favor of the above.

See logs: tox3.txt, tox4.txt.

[oakkitten]

Also, suppose you want to have different install_command for different envs, you might do something like this, which works:

$ cat tox.ini
[tox]
skip_install = true
skipsdist = true
envlist = woo-{foo,bar,baz3}

[testenv]
install_command =
    foo: echo installing {packages} foo!!!
    bar: echo installing {packages} bar!!!
    baz3: echo installing {packages} baz3!!!
allowlist_externals =
    echo
deps =
    zoo
$ python -m tox -rvv | grep 'install_deps>'
woo-foo: 21282 W install_deps> echo installing zoo 'foo!!!' [tox/tox_env/api.py:398]
woo-bar: 41848 W install_deps> echo installing zoo 'bar!!!' [tox/tox_env/api.py:398]
woo-baz3: 64244 W install_deps> echo installing zoo 'baz3!!!' [tox/tox_env/api.py:398]

But if you try going multiline, things become weird fast:

$ cat tox.ini
[tox]
skip_install = true
skipsdist = true
envlist = woo-{foo,bar,baz3}

[testenv]
install_command =
    foo: echo installing {packages} foo!!!
    bar: echo installing {packages} bar!!! \
        hello
    baz3: echo installing {packages} baz3!!!
allowlist_externals =
    echo
deps =
    zoo
$ python -m tox -rvv | grep 'install_deps>'
woo-foo: 19778 W install_deps> echo installing zoo 'foo!!!' hello [tox/tox_env/api.py:398]
woo-bar: 39174 W install_deps> echo installing zoo 'bar!!!' hello [tox/tox_env/api.py:398]
woo-baz3: 59575 W install_deps> hello echo installing zoo 'baz3!!!' [tox/tox_env/api.py:398]

$ cat tox.ini
[tox]
skip_install = true
skipsdist = true
envlist = woo-{foo,bar,baz3}

[testenv]
install_command =
    foo: echo installing {packages} foo!!!
    bar: echo installing {packages} bar!!!
    baz3: echo installing {packages} baz3!!! '\
        ' hello
allowlist_externals =
    echo
deps =
    zoo
$ python -m tox -rvv | grep 'install_deps>'
woo-foo: 20250 W install_deps> echo installing zoo 'foo!!!' ''"'"' hello' [tox/tox_env/api.py:398]
woo-bar: 40360 W install_deps> echo installing zoo 'bar!!!' ''"'"' hello' [tox/tox_env/api.py:398]
woo-baz3: 62490 W install_deps> echo installing zoo 'baz3!!!' '' hello [tox/tox_env/api.py:398]

The documentation doesn't suggest that this is supposed to work in the first place, so this part is not a bug per se. I'm only mentioning this as this behavior might be indicative of an issue elsewhere.

[gaborbernat]

I think here the documentation is where the issue is. The install_command was designed and always only allowed one command to be specified. And I'd keep that behaviour. If you want to call multiple ones you should create a shim python script that forwards our one call to multiple ones.

[oakkitten]

May I ask why not allow multiple commands? Besides, wouldn't reusing the logic from commands simplify things? Anyway, in the case of a single command, it would be nice to have an error of sorts if the user does try to put multiple.

[gaborbernat]

May I ask why not allow multiple commands?

To limit complexity in tox. 1 command is enough 99% of time and when it's not can be worked around the users.

Anyway, in the case of a single command, it would be nice to have an error of sorts if the user does try to put multiple.

I believe this should happen in tox 4 🤔

[oakkitten]

To limit complexity in tox.

But if you reused the logic from commands, wouldn't it reduce complexity?

I believe this should happen in tox 4 🤔

While I didn't test with main, the snippets above use 4.0.0b1.

[gaborbernat]

But if you reused the logic from commands, wouldn't it reduce complexity?

Those two are handled conceptually differently and I'd not overload them. You introduce a lot of complexity there, what if the first command fails and the second succeeds. Again, if you must you can achieve this by writing a custom plugin. The core tox will not support this thought.

[oakkitten]

With commands, if the first command fails, the second isn't run. I would expect exactly the same behavior from install_command. I am not sure how these are conceptually different.

But I guess since install_command is deprecated it's not worth discussing it. (When will it be removed? I don't think that documentation mentions that it's deprecated.)