tox-backticks

tox-backticks allows use of backticks within setenv to run commands to populate environment variables that can then be accessed using {env:var}.

[testenv:simple]
setenv =
  FOO=`python -c 'import sys; sys.stdout.write("foo")'`
commands =
  python -c 'assert "{env:FOO}" == "foo"'

Commands within the backticks follow the standard tox rules, where it must be an executable installed into the venv, or be an executable permitted using whitelist_externals.

To reduce the impact on the tox syntax, the backticks must enclose the entire setenv line. Due to this choice, this plugin will only break existing tox usage where a user wanted an environment variable which started and ended with a literal backtick, deemed rather unlikely and judged to be foolish anyway. If that is truely needed, the following approach allows literal backticks at start and end.

[testenv:literal_ignored] setenv = BACKTICK=` INNERBACKTICK=``{env:BACKTICK} commands = python -c 'assert "{env:INNERBACKTICKS}" == "```"'

To use backticks for a part of a variable, use multiple setenv. The order of setenv is irrelevant.

[testenv:nested_reversed]
setenv =
  BAR=`{env:FOO} -c 'import sys; sys.stdout.write("foo")'`
  FOO=`python -c 'import sys; sys.stdout.write("python")'`
commands =
  python -c 'assert "{env:BAR}" == "foo"'

Tox will report an error if multiple setenv are recursively defined, preventing the correct order from being established.

See tests/tox.ini for samples.

Contributing

Please do not create an issue requesting using backticks within commands. While it can result in a neater tox.ini, the same effect can be achieved using setenv and testenv that depend on other testenv.

If you can find a way to correctly intercept and process backticks between each command execution of a testenv with multiple commands, I will be keen to merge a patch as long as the new functionality is disabled by default. i.e. the backticks in the second command must be able to use state created by the first command, otherwise backticks in commands is useless.

The next problem with backticks within commands is that literal backticks within in the commands, which is why it must be off by default, at least initially. One non-intrusive semantics is to allow commands of form

export VAR=`do_stuff`

That line is useless in tox, as it wouldnt have any effect, and is easily parsable.