Feat/add rust toolchain (#1235)

* feature: update rust-toolchain

* add(ci): action that updates `rust-toolchain`

We purposefully keep our version a little behind the newest releases,
to give people the time to update. Now this is unambigious and we can
use all the features our current toolchain allows.

1 files changed, 68 insertions, 0 deletions

diff --git a/assets/scripts/update-toolchain.sh b/assets/scripts/update-toolchain.sh
new file mode 100755
index 000000000..fe027659f
--- /dev/null
+++ b/assets/scripts/update-toolchain.sh
@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+set -euo pipefail
+# dependencies: bash, curl, jq
+#
+# Updates a rust-toolchain file in relation to the official rust releases.
+
+# How many minor versions delta there should be,
+# will automatically advance patch versions.
+MINOR_DELTA=2
+RUST_TOOLCHAIN_VERSION=$(grep -oP 'channel = "\K[^"]+' "./rust-toolchain")
+#RUST_TOOLCHAIN_FILE=../../rust-toolchain
+RUST_TOOLCHAIN_FILE=./rust-toolchain
+
+# update with new version number
+update_channel(){
+printf \
+"
+# This file is updated by \`update-toolchain.sh\`
+# We aim to be around 1-2 rust releases behind in order
+# to get people the time to update their toolchains properly.
+# By enforcing this, we can also make full use of the features
+# provided by the current channel.
+
+"
+sed -e "/channel/s/\".*\"/\"$1\"/" "${RUST_TOOLCHAIN_FILE}"
+}
+
+get_last_no_releases() {
+    curl --silent "https://api.github.com/repos/rust-lang/rust/releases" | \
+        jq '.[range(20)].tag_name' | sed -e 's/\"//g'
+}
+
+function parse_semver() {
+    local token="$1"
+    local major=0
+    local minor=0
+    local patch=0
+
+    if grep -E '^[0-9]+\.[0-9]+\.[0-9]+' <<<"$token" >/dev/null 2>&1 ; then
+        local n=${token//[!0-9]/ }
+        local a=(${n//\./ })
+        major=${a[0]}
+        minor=${a[1]}
+        patch=${a[2]}
+    fi
+
+    echo "$major $minor $patch"
+}
+function get_string_arrary() {
+    IFS=' ' read  -r -a array <<< "$1";
+    echo "${array["${2}"]}"
+}
+
+RUST_TOOLCHAIN_VERSION="$(parse_semver $(echo $RUST_TOOLCHAIN_VERSION))"
+TARGET_TOOLCHAIN_MINOR_VERSION=$(($(get_string_arrary "${RUST_TOOLCHAIN_VERSION}" 1) - MINOR_DELTA))
+
+LATEST=0
+for i in $(get_last_no_releases);do
+    SEMVER=($(parse_semver "$i"))
+    if [ "$LATEST" != "${SEMVER[1]}" ];then
+        MINOR_DELTA=$((MINOR_DELTA - 1))
+    fi
+    LATEST="${SEMVER[1]}"
+    if [ -1 == "${MINOR_DELTA}" ];then
+        echo "$(update_channel "$i")"> ${RUST_TOOLCHAIN_FILE}
+        exit
+    fi
+done