build: get different rebar3 based on different OTP versions

.tool-versions

@@ -0,0 +1,11 @@
+## The Official Releases using OTP 26 since EMQX v5.5.0
+## See also
+## https://github.com/emqx/emqx/releases/tag/v5.5.0
+# erlang 26.2.1-2
+# elixir 1.15.7-otp-26
+
+## Keep using OTP 25.3.2 for docker image
+## see also
+## https://github.com/emqx/emqx/blob/v5.6.0/build#L400-L401
+erlang 25.3.2-2
+elixir 1.15.7-otp-25

Makefile

@@ -1,22 +1,25 @@
+export BUILD_WITHOUT_QUIC ?= true
+export BUILD_WITHOUT_ROCKSDB ?= true
+
 ## shallow clone for speed
+export REBAR_GIT_CLONE_OPTIONS += --depth=1
 
-BUILD_WITHOUT_QUIC ?= true
-export BUILD_WITHOUT_QUIC
-BUILD_WITHOUT_ROCKSDB ?= true
-export BUILD_WITHOUT_ROCKSDB
+## Feature Used in rebar plugin emqx_plugrel
+## The Feature have not enabled by default on OTP25
+export ERL_FLAGS ?= -enable-feature maybe_expr
 
-REBAR ?= $(or $(shell which rebar3 2>/dev/null),$(CURDIR)/rebar3)
-REBAR_VERSION ?= 3.19.0-emqx-1
+REBAR = $(CURDIR)/rebar3
+SCRIPTS = $(CURDIR)/scripts
 
 .PHONY: all
 all: compile
 
-.PHONY: get-rebar3
-get-rebar3:
-	@$(CURDIR)/get-rebar3 $(REBAR_VERSION)
+.PHONY: ensure-rebar3
+ensure-rebar3:
+	@$(SCRIPTS)/ensure-rebar3.sh
 
 $(REBAR):
-	$(MAKE) get-rebar3
+	$(MAKE) ensure-rebar3
 
 .PHONY: compile
 compile: $(REBAR)

scripts/ensure-rebar3.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+[ "${DEBUG:-0}" -eq 1 ] && set -x
+
+OTP_VSN="${OTP_VSN:-$(./scripts/get-otp-vsn.sh)}"
+case ${OTP_VSN} in
+    25*)
+        VERSION="3.19.0-emqx-9"
+        ;;
+    26*)
+        VERSION="3.20.0-emqx-1"
+        ;;
+    *)
+        echo "Unsupported Erlang/OTP version $OTP_VSN"
+        exit 1
+        ;;
+esac
+
+# ensure dir
+cd -P -- "$(dirname -- "${BASH_SOURCE[0]}")/.."
+
+DOWNLOAD_URL='https://github.com/emqx/rebar3/releases/download'
+
+download() {
+    echo "downloading rebar3 ${VERSION}"
+    curl -f -L "${DOWNLOAD_URL}/${VERSION}/rebar3" -o ./rebar3
+}
+
+# get the version number from the second line of the escript
+# because command `rebar3 -v` tries to load rebar.config
+# which is slow and may print some logs
+version() {
+    head -n 2 ./rebar3 | tail -n 1 | tr ' ' '\n' | grep -E '^.+-emqx-.+'
+}
+
+if [ -f 'rebar3' ] && [ "$(version)" = "$VERSION" ]; then
+    exit 0
+fi
+
+download
+chmod +x ./rebar3

scripts/get-otp-vsn.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+erl -noshell -eval '{ok, Version} = file:read_file(filename:join([code:root_dir(), "releases", erlang:system_info(otp_release), "OTP_VERSION"])), io:fwrite(Version), halt().'