From 10431ca36fd3e647fa3e52479223a41c316b133d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Henrique=20Ferreira=20de=20Freitas?=
 <joaohf@gmail.com>
Date: Mon, 1 May 2023 10:56:50 -0300
Subject: [PATCH] Introduce rebar3_external plugin to handle leveldb source
 code

Currently [1], rebar3 does not support adding hooks for 'get-deps'. That
is why the compile rule in c_src/Makefile has also to call get_deps
makefile rule in order to fetch leveldb source code. The whole process
works but can be improved.

This change introduces a plugin called rebar3_external which deals with
external source code like leveldb source code. That way rebar3 can
perform dependency manager without relies on makefiles or scripts.

The intend is to have leveldb source code managed by rebar3. So, one
could easily upgrade it just bumping the leveldb version in the
rebar3.config file.

1: https://github.com/erlang/rebar3/issues/2784
---
 c_src/Makefile | 26 +++++++++-----------------
 rebar.config   | 20 +++++++++++++++-----
 rebar.lock     |  6 +++++-
 3 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/c_src/Makefile b/c_src/Makefile
index c6d70f55..55251af9 100644
--- a/c_src/Makefile
+++ b/c_src/Makefile
@@ -1,4 +1,4 @@
-LEVELDB_VSN ?= "2.0.38"
+LEVELDB_SRC := $(REBAR_DEPS_DIR)/leveldb/c_src
 C_SRC_DIR := $(shell pwd)
 PROJECT_DIR := $(abspath $(C_SRC_DIR)/..)
 TARGET_DIR := $(PROJECT_DIR)/priv/
@@ -11,8 +11,8 @@ TOOLS = \
 	sst_scan
 
 LDFLAGS := $(LDFLAGS) -lsnappy -lpthread
-CFLAGS := $(CFLAGS) -I. -I $(C_SRC_DIRC_SRC_DIR)/leveldb/include -fPIC
-CXXFLAGS := $(CXXFLAGS) -I. -I $(C_SRC_DIR)/leveldb/include -fPIC
+CFLAGS := $(CFLAGS) -I. -I $(LEVELDB_SRC)/include -fPIC
+CXXFLAGS := $(CXXFLAGS) -I. -I $(LEVELDB_SRC)/include -fPIC
 TEST_CXXFLAGS := $(CXXFLAGS) -Wno-narrowing
 
 ifeq ($(shell uname -s), Darwin)
@@ -33,25 +33,17 @@ ifeq ($(shell uname -s), Darwin)
 	TEST_CXXFLAGS += -Wno-c++11-narrowing
 endif
 
-get-deps:
-	git config --global --add safe.directory /__w/eleveldb/eleveldb
-	echo "ubuntu-latest image with otp-22, are you happy now?"
-	if [ ! -d leveldb ]; then \
-	    git clone --depth=1 --branch=$(LEVELDB_VSN) https://github.com/basho/leveldb && \
-	    (cd leveldb && git submodule update --depth 1 --init); \
-	fi
-
-compile: get-deps ldb
-	for tool in $(TOOLS); do cp leveldb/$$tool $(TARGET_DIR); done
+compile: ldb
+	for tool in $(TOOLS); do cp $(LEVELDB_SRC)/$$tool $(TARGET_DIR); done
 
 ldb:
 	@echo "Building LevelDB..."
-	$(MAKE) LDFLAGS="" -C leveldb all
-	$(MAKE) LDFLAGS="$(LDFLAGS)" -C leveldb tools
+	$(MAKE) LDFLAGS="" -C $(LEVELDB_SRC) all
+	$(MAKE) LDFLAGS="$(LDFLAGS)" -C $(LEVELDB_SRC) tools
 
 clean:
-	$(MAKE) -C leveldb clean
+	$(MAKE) -C $(LEVELDB_SRC) clean
 	for tool in $(TOOLS); do rm -f $(TARGET_DIR)$$tool; done
 
 test: compile
-	$(MAKE) LDFLAGS="$(LDFLAGS)" CXXFLAGS="$(TEST_CXXFLAGS)" CFLAGS="$(CFLAGS)" -C leveldb test
+	$(MAKE) LDFLAGS="$(LDFLAGS)" CXXFLAGS="$(TEST_CXXFLAGS)" CFLAGS="$(CFLAGS)" -C $(LEVELDB_SRC) test
diff --git a/rebar.config b/rebar.config
index 409c8147..5667b477 100644
--- a/rebar.config
+++ b/rebar.config
@@ -3,7 +3,19 @@
 
 {eunit_opts, [verbose]}.
 
-{plugins, [{eqc_rebar, {git, "https://github.com/Quviq/eqc-rebar", {branch, "master"}}}, pc]}.
+{plugins, [
+    {eqc_rebar, {git, "https://github.com/Quviq/eqc-rebar", {branch, "master"}}},
+    pc,
+    rebar3_external
+]}.
+
+{deps, [
+    {leveldb,
+        {external, {git, "https://github.com/basho/leveldb", {tag, "2.0.38"}}, "c_src", [
+            {description, "leveldb: A key-value store"},
+            {vsn, "2.0.38"}
+        ]}}
+]}.
 
 {provider_hooks, [
     {post, [
@@ -32,13 +44,11 @@
 
 {port_env, [
     %% Make sure to set -fPIC when compiling leveldb
-    {"CXXFLAGS", "$CXXFLAGS -Wall -O3 -fPIC -I c_src/leveldb/include -I c_src/leveldb"},
-    {"LDFLAGS", "$LDFLAGS c_src/leveldb/libleveldb.a -lsnappy -lstdc++"}
+    {"CXXFLAGS", "$CXXFLAGS -Wall -O3 -fPIC -I $REBAR_DEPS_DIR/leveldb/c_src/include -I $REBAR_DEPS_DIR/leveldb/c_src"},
+    {"LDFLAGS", "$LDFLAGS $REBAR_DEPS_DIR/leveldb/c_src/libleveldb.a -lsnappy -lstdc++"}
 ]}.
 
 {pre_hooks, [
-    {"(linux|darwin|solaris)", 'get-deps', "./make -C c_src get-deps"},
-    {"(freebsd|netbsd|openbsd)", 'get-deps', "gmake -C c_src get-deps"},
     {"(linux|darwin|solaris)", compile, "make -C c_src compile"},
     {"(freebsd|netbsd|openbsd)", compile, "gmake -C c_src compile"},
     {"(linux|darwin|solaris)", eunit, "make -C c_src test"},
diff --git a/rebar.lock b/rebar.lock
index 57afcca0..5d53b5d5 100644
--- a/rebar.lock
+++ b/rebar.lock
@@ -1 +1,5 @@
-[].
+[{<<"leveldb">>,
+  {external,{git,"https://github.com/basho/leveldb",{tag,"2.0.38"}},
+            "c_src",
+            [{description,"leveldb: A key-value store"},{vsn,"2.0.38"}]},
+  0}].