Set minimal required `just` version for a justfile

[nyurik]

just is rapidly evolving, frequently adding new features. justfiles are frequently shared between users, and those users may have different Just versions installed, which means in some cases some newer features might not be available in the older just versions.

We need a way to specify the minimum required version for just, similar to how cmake and many other similar tools do it. The actual syntax is up for a discussion:

Naming is hard

Some ideas...

set mjv := '1.32.0'
set minimum-just := '1.32.0'
set require-just-at-least := '1.32.0'
set min-required-just := '1.32.0'
set min-just-version := '1.32.0'

[hustcer]

set min-just-version := '1.32.0'

[casey]

This is actually quite a tricky problem. Let's say there's a new function foo() in just 1.50.0, so when using it, you put set minimum-just-version := '1.50.0':

set minimum-just-version := '1.50.0'

foo:
  echo {{ foo() }}

However, a call to a new function in just 1.49.0 is a compilation error, so when you're producing an error message, you do not have a Justfile whose settings you can inspect for a minimum-just-version to produce a better error message.

This is a somewhat trivial example, because a missing function error could be deferred until the end of compilation, so you did have a Justfile you could get the minimum just version from, however in the case of, for example, new grammatical constructs, there's no way you can parse the justfile at all, so you can't extract the minimum just version to improve the error message.

There are a few solutions, but none of them seem very nice:

• Have a separatefile, like .justversion, which is a file which only contains the minimum version, and refer to that when an error happens.
• Try to grep through the file if you get an error, and just search for a line that matches set min-just-version := '.*'
• Have a special form for directives embedded in comments, so they don't depend on parsing anything else #! just-version 1.50.0

I'm not convinced though that any of these are worth it though.

[Spatenheinz]

Just a thought,
Would it make sense to only allow the minimum version as the very first tokens of a Justfile, but still as optional?

[casey]

Just a thought, Would it make sense to only allow the minimum version as the very first tokens of a Justfile, but still as optional?

This is possible, although I'd like to avoid adding special case parsing logic just for this feature.

[windl1n]

what if add version into filename? like

.a.b.c.justfile
a.b.c@justfile

which can be created by just --init
and in justfile, when add new function,

[min(a.b.c)]
foo:
  ...

i think not all func need to work at the same version

[nyurik]

lets not, min version is a small implementation detail, and most users of the repo shouldn't be aware of it. First non-comment line could work ok though

[nyurik]

As a simpler temporary solution we could also use a function that returns current just's version as described in #2616

[private]
validate_just:
    if [ {{semver_matches(just_version(), ">1.38")}} != 'true' ]; then \
        echo "Your just runner is too old, please update" ;\
        exit 1 ;\
    fi

foo: validate_just
    echo "running foo"

[andyn-ff]

FWIW I think this would be really valuable. One of the most frequently 'wtf' moments I see as our team is starting to adopt just more is where someone uses new recipe annotations, for example, and other haven't updated their just version in a while and they get an immediate failure when they try to run any recipe (because the Justfile can't be parsed). It would be a huge help to have an error message for this that tells the user what they can do to fix it. Rather than "I've got no idea what this syntax means", which looks like an error on the Justfile-contributor's part, it would be really lovely to report "You need to update just in order to use this Justfile".

[ashi009]

Just put this on the top of your justfile:

PLEASE_RUN_BREW_UPGRADE_JUST := `min_version=1.45.0; [[ "$(printf '%s\n' "${min_version}" "$(just --version | cut -d' ' -f2)" | sort -V | head -n1)" == "${min_version}" ]]`

just will eagerly evaluate the expression, and fail the execution if exiting with non zero value. Above uses sort -V which is supported on most OS (including macOS.)

$ just
error: Backtick failed with exit code 1
  ——▶ justfile:14:33
   │
14 │ PLEASE_RUN_BREW_UPGRADE_JUST := `min_version=1.45.0; [[ "$(printf '%s\n' "${min_version}" "$(just --version | cut -d' ' -f2)" | sort -V | head -n1)" == "${min_version}" ]]`
   │                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This is fully backward compatible and anyone who reads the error message, should have a sense to update their just runner.

Even if just added a new func/keyword/conffile to assert the version, people with historical just runner will not be able to get any useful information from the backtrace.

[nyurik]

wouldn't work on windows i guess...

[nyurik]

Note that merging #2892 would solve this issue, albeit a bit more verbose than needed:

_required_just_ver := if semver_matches(just_version(), '>=1.43.0') == 'true' {
  'yes'
} else {
  error('just version 1.43.0 or greater is required, found ' + just_version())
}

[laniakea64]

Note that merging #2892 would solve this issue, albeit a bit more verbose than needed:

_required_just_ver := if semver_matches(just_version(), '>=1.43.0') == 'true' {
  'yes'
} else {
  error('just version 1.43.0 or greater is required, found ' + just_version())
}

😕 I was not able to get this error to show when making up fictitious unimplemented syntaxes or functions in the justfile?

[nyurik]

I am not sure i understood what you mean