Gather the sources to build an opam project

opam-sources.sh

#!/usr/bin/env bash

# Instructions. You need:
# - a working opam environment
# - an opam file in your current directory (to describe your project)
# - possibly some packages path-pinned in the current switch
#
# Run the scripts, and then check the contents of sources/

set -eu

NAME=$(hexdump -n 2 -e '/2 "%u"' /dev/urandom)

CURRENT_SWITCH=$(opam switch show)

OPAMVAR_ocaml_version=$(opam config var ocaml-version)
OPAMVAR_compiler=$(opam config var compiler)
OPAMVAR_preinstalled=$(opam config var preinstalled)
OPAMVAR_os=$(opam config var os)

export OPAMVAR_ocaml_version
export OPAMVAR_compiler
export OPAMVAR_preinstalled
export OPAMVAR_os

echo "OPAMROOT=$(opam config var root)"
echo "ocaml-version=${OPAMVAR_ocaml_version}"
echo "compiler=${OPAMVAR_compiler}"
echo "preinstalled=${OPAMVAR_preinstalled}"
echo "os=${OPAMVAR_os}"

OUTPUT=/tmp/pkgs-${NAME}.json
export OPAMYES=1

# create a new switch
opam switch "${NAME}" -A system

# pin the package
opam pin add "${NAME}.pkg" . -n

# ask the solver to install the package, and parse the JSON result
unset OPAMYES
export OPAMNO=1
opam install "${NAME}" --dry-run --json="${OUTPUT}"
ALL_PACKAGES=$(jq '.[] | map(select(.install)) | map( [.install.name, .install.version] | join(".")) | join(" ")' "${OUTPUT}")

opam unpin "${NAME}" -y
opam switch "${CURRENT_SWITCH}"

# create and populate sources/
rm -rf sources
mkdir -p sources

CURRENT_DIR=$(pwd)
cd sources

BASE_PKGS="base-threads base-unix base-bigarray base-bytes"

for pkg in ${BASE_PKGS} ${ALL_PACKAGES//\"}; do
    echo "Adding ${pkg}"
    # check if it is a local pin
    if [ "${pkg}" != "${NAME}.pkg" ]; then
	pinned=$(opam info "${pkg}" -f pinned)
	case "${pinned}" in
	    "") opam source "${pkg}";;
	    "path")
		localPath=$(opam info "${pkg}" -f upstream-url)
		ln -s "${localPath}" "${pkg}";;
	    *) echo "Error: opam info ${pkg} -f pinned"; exit 1;;
	esac
    fi
done

cd "${CURRENT_DIR}"
opam switch remove "${NAME}"