first commit

scripts/ensure-rust-toolchain.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+SOURCE_DIR=${1:?usage: ensure-rust-toolchain.sh SOURCE_DIR}
+[[ -r "$SOURCE_DIR/Cargo.toml" ]] || { echo "missing Cargo.toml: $SOURCE_DIR" >&2; exit 1; }
+metadata=$(python3.11 - "$SOURCE_DIR" <<'PY'
+import pathlib, re, sys, tomllib
+root=pathlib.Path(sys.argv[1])
+manifest=tomllib.loads((root/'Cargo.toml').read_text())
+minimum=manifest.get('package',{}).get('rust-version','')
+pinned=''
+p=root/'rust-toolchain.toml'
+if p.exists(): pinned=tomllib.loads(p.read_text()).get('toolchain',{}).get('channel','')
+if minimum and not re.fullmatch(r'[0-9]+\.[0-9]+(?:\.[0-9]+)?', minimum): raise SystemExit('unsupported rust-version')
+if pinned and not (pinned=='stable' or re.fullmatch(r'[0-9]+\.[0-9]+(?:\.[0-9]+)?', pinned)): raise SystemExit('unsupported rust-toolchain channel')
+print(minimum)
+print(pinned)
+PY
+)
+mapfile -t requested <<< "$metadata"
+minimum=${requested[0]:-}
+channel=${requested[1]:-stable}
+[[ -n "$channel" ]] || channel=stable
+if ! rustup run "$channel" rustc --version >/dev/null 2>&1; then
+  echo "installing Rust toolchain $channel" >&2
+  rustup toolchain install "$channel" --profile minimal >&2
+fi
+installed=$(rustup run "$channel" rustc --version | awk '{print $2}')
+if [[ -n "$minimum" ]]; then
+  lowest=$(printf '%s\n%s\n' "$installed" "$minimum" | sort -V | head -n1)
+  if [[ "$lowest" != "$minimum" ]]; then
+    echo "Rust $installed does not satisfy project MSRV $minimum" >&2
+    exit 1
+  fi
+fi
+printf '%s\n' "$channel"