[feature request] opam dichotomic search for upper/lower bound of a given dependency of a given package

[UnixJunkie]

Hello,

Cc @mseri I think there is definitively a feature that would save some time to users:

• the ability to search automatically for the lower (or upper) bound version constraint of a given dependency of a given package.

I.e. in my current opam switch (i.e. for some fixed OCaml version), I might want to know the version constraints of one (or maybe all) of the dependencies of a given package (which might be pinned to its development version).

I think being able to search automatically for the lower bound might be useful for opam package maintainers.
Maybe, for several dependencies of one package, the search can be done in parallel.

Regards,
F.

[dra27]

It's possibly doable with some existing commands, e.g. opam list dependency --coinstallable-with package.version --all-versions will give the list all versions of dependency of package.version which can be installed and the bounds could be extracted from that (and then repeat over the existing dependencies).

It's not (yet) totally clear what the feature looks like - is there some more context we could see?

[kit-ty-kate]

Is what you want something like that?

#!/bin/bash

set -e

result=()

add() {
  local i=0
  local isset=false

  for line in "${result[@]}" ; do
    local name=$(echo "$line" | cut '-d ' -f1)

    if test "$name" = "$1" ; then
      result[$i]="$line $2"
      isset=true
    fi

    i=$(($i + 1))
  done

  if test "$isset" = "false" ; then
    result+=("$1 $2")
  fi
}

deps=$(opam list --required-by "$1" --all-versions -s)

last=
lastv=
for pkg in $deps ; do
  name=$(echo "$pkg" | cut -d. -f1)
  version=$(echo "$pkg" | cut -d. -f2-)

  if test "$name" != "$last" ; then
    if test "$last" != "" ; then
      add "$last" "$lastv"
    fi

    add "$name" "$version"
  fi

  last=$name
  lastv=$version
done

if test "$last" != "" ; then
  add "$last" "$lastv"
fi

for line in "${result[@]}" ; do
  name=$(echo "$line" | cut '-d ' -f1)
  lower=$(echo "$line" | cut '-d ' -f2)
  upper=$(echo "$line" | cut '-d ' -f3)

  if test "$lower" = "$upper" ; then
    constraint="{= \"$lower\"}"
  else
    constraint="{>= \"$lower\" & <= \"$upper\"}"
  fi

  echo "\"$name\" $constraint"
done

(to call with ./script.sh <your package>)

[UnixJunkie]

@dra27 the context is just you want to add a new version (or a new opam package) in opam-repository.
To do so nowadays, you need to specify at least a lower-bound version for all (or at least several) of those dependencies.
@kate I will give it a try. Maybe such script should be hosted somewhere under version control.