build(rust): declare rust-version 1.88; rustup setup for the server

rust/Cargo.toml

@@ -3,7 +3,10 @@ resolver = "3"
 members = ["collector"]
 
 [workspace.package]
+# 1.88: edition 2024 let-chains, and dependencies (home, icu_*) need it. Distro
+# cargo packages are older: install the toolchain with rustup (rust/README.md).
 edition = "2024"
+rust-version = "1.88"
 license = "MIT"
 publish = false
 repository = "https://git.b4l.co.th/B4L/Northern-Thailand-Ping-River-Monitor"

rust/README.md

@@ -72,12 +72,21 @@ Linux needs `pkg-config` and `libssl-dev`.
 
 ### Deploy
 
-On the server, after `git pull` (the Python side of the switch ships in the
-same commit):
+Needs Rust >= 1.88. Distro `cargo` packages are older (`resolver 3 is not
+valid` / `edition 2024` errors), so install the toolchain once with rustup:
 
 ```bash
-cargo build --release --locked --manifest-path rust/Cargo.toml   # as a normal user,
-                                                                  # or BIN=<CI artifact>
+apt-get install -y build-essential pkg-config libssl-dev curl
+curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile minimal
+. "$HOME/.cargo/env"        # puts ~/.cargo/bin before /usr/bin/cargo
+cargo --version             # >= 1.88
+```
+
+Then on the server, after `git pull` (the Python side of the switch ships in
+the same commit):
+
+```bash
+cargo build --release --locked --manifest-path rust/Cargo.toml   # or BIN=<CI artifact>
 sudo bash scripts/install_collector.sh             # install + dry run, nothing switched
 sudo bash scripts/install_collector.sh --cutover   # Rust collects from now on
 sudo bash scripts/install_collector.sh --rollback  # back to Python collection

rust/collector/Cargo.toml

@@ -3,6 +3,7 @@ name = "ping-collector"
 version = "0.1.0"
 description = "Ping River Monitor data collector: RID gauges, HII/ThaiWater, RID dams, Open-Meteo rain -> PostgreSQL"
 edition.workspace = true
+rust-version.workspace = true
 license.workspace = true
 publish.workspace = true
 repository.workspace = true

scripts/install_collector.sh

@@ -12,7 +12,8 @@
 # linux-x86_64" CI artifact) or from rust/target/release/ping-collector, built
 # beforehand as a normal user:
 #   cargo build --release --locked --manifest-path rust/Cargo.toml
-# (needs rustup, pkg-config and libssl-dev).
+# (needs Rust >= 1.88 from rustup -- distro cargo is too old -- plus pkg-config
+# and libssl-dev; see rust/README.md).
 set -euo pipefail
 
 APP_DIR="${APP_DIR:-/opt/thailand-water-monitor}"