From a1a05e80ecf3d6a6775e17494a426317b4a19813 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= <essen@ninenines.eu>
Date: Tue, 1 Oct 2024 14:59:45 +0200
Subject: Initial beam-cache implementation

When switching between normal build and running tests
it takes a while for modules to be rebuilt. With the
beam-cache the files are saved and can be restored
when switching between contexts. This greatly speeds
up the context switching.
---
 CHANGELOG.asciidoc |  4 ++++
 build.config       |  3 +++
 core/beam-cache.mk | 42 ++++++++++++++++++++++++++++++++++++++++++
 core/erlc.mk       |  2 +-
 core/test.mk       |  7 +++++--
 5 files changed, 55 insertions(+), 3 deletions(-)
 create mode 100644 core/beam-cache.mk

diff --git a/CHANGELOG.asciidoc b/CHANGELOG.asciidoc
index 6a38a21..c6b759b 100644
--- a/CHANGELOG.asciidoc
+++ b/CHANGELOG.asciidoc
@@ -49,3 +49,7 @@
             `CACHE_DEPS=1` to enable.
 
 2023/05/16: Remove support for HiPE and ErlLLVM.
+
+2024/10/01: Initial beam-cache implementation. This is used
+            to cache beam files when switching from/to test
+            builds.
diff --git a/build.config b/build.config
index b363ef0..5ef60f8 100644
--- a/build.config
+++ b/build.config
@@ -6,11 +6,14 @@
 # Core modules.
 core/core
 core/kerl
+
+# Index and dependencies.
 index/*
 core/index
 core/deps
 
 # Core modules, continued.
+core/beam-cache
 core/erlc
 core/docs
 core/rel
diff --git a/core/beam-cache.mk b/core/beam-cache.mk
new file mode 100644
index 0000000..d0f1d3c
--- /dev/null
+++ b/core/beam-cache.mk
@@ -0,0 +1,42 @@
+# Copyright (c) 2024, Loïc Hoguin <essen@ninenines.eu>
+# This file is part of erlang.mk and subject to the terms of the ISC License.
+
+.PHONY: beam-cache-restore-app beam-cache-restore-test clean-beam-cache distclean-beam-cache
+
+BEAM_CACHE_DIR ?= $(ERLANG_MK_TMP)/beam-cache
+PROJECT_BEAM_CACHE_DIR = $(BEAM_CACHE_DIR)/$(PROJECT)
+
+clean:: clean-beam-cache
+
+clean-beam-cache:
+	$(verbose) rm -rf $(PROJECT_BEAM_CACHE_DIR)
+
+distclean:: distclean-beam-cache
+
+$(PROJECT_BEAM_CACHE_DIR):
+	$(verbose) mkdir -p $(PROJECT_BEAM_CACHE_DIR)
+
+distclean-beam-cache:
+	$(gen_verbose) rm -rf $(BEAM_CACHE_DIR)
+
+beam-cache-restore-app: | $(PROJECT_BEAM_CACHE_DIR)
+	$(verbose) rm -rf $(PROJECT_BEAM_CACHE_DIR)/ebin-test
+ifneq ($(wildcard ebin/),)
+	$(verbose) mv ebin/ $(PROJECT_BEAM_CACHE_DIR)/ebin-test
+endif
+ifneq ($(wildcard $(PROJECT_BEAM_CACHE_DIR)/ebin-app),)
+	$(gen_verbose) mv $(PROJECT_BEAM_CACHE_DIR)/ebin-app ebin/
+else
+	$(verbose) $(MAKE) --no-print-directory clean-app
+endif
+
+beam-cache-restore-test: | $(PROJECT_BEAM_CACHE_DIR)
+	$(verbose) rm -rf $(PROJECT_BEAM_CACHE_DIR)/ebin-app
+ifneq ($(wildcard ebin/),)
+	$(verbose) mv ebin/ $(PROJECT_BEAM_CACHE_DIR)/ebin-app
+endif
+ifneq ($(wildcard $(PROJECT_BEAM_CACHE_DIR)/ebin-test),)
+	$(gen_verbose) mv $(PROJECT_BEAM_CACHE_DIR)/ebin-test ebin/
+else
+	$(verbose) $(MAKE) --no-print-directory clean-app
+endif
diff --git a/core/erlc.mk b/core/erlc.mk
index b8555b7..8f9abc2 100644
--- a/core/erlc.mk
+++ b/core/erlc.mk
@@ -53,7 +53,7 @@ ifneq ($(wildcard src/),)
 
 # Targets.
 
-app:: $(if $(wildcard ebin/test),clean) deps
+app:: $(if $(wildcard ebin/test),beam-cache-restore-app) deps
 	$(verbose) $(MAKE) --no-print-directory $(PROJECT).d
 	$(verbose) $(MAKE) --no-print-directory app-build
 
diff --git a/core/test.mk b/core/test.mk
index 8054abc..8967fd1 100644
--- a/core/test.mk
+++ b/core/test.mk
@@ -45,14 +45,17 @@ define compile_test_erl
 endef
 
 ERL_TEST_FILES = $(call core_find,$(TEST_DIR)/,*.erl)
+
 $(ERLANG_MK_TMP)/$(PROJECT).last-testdir-build: $(ERL_TEST_FILES) $(MAKEFILE_LIST)
-	$(eval FILES_TO_COMPILE := $(if $(filter $(MAKEFILE_LIST),$?),$(filter $(ERL_TEST_FILES),$^),$?))
+# When we have to recompile files in src/ the .d file always gets rebuilt.
+# Therefore we want to ignore it when rebuilding test files.
+	$(eval FILES_TO_COMPILE := $(if $(filter $(filter-out $(PROJECT).d,$(MAKEFILE_LIST)),$?),$(filter $(ERL_TEST_FILES),$^),$(filter $(ERL_TEST_FILES),$?)))
 	$(if $(strip $(FILES_TO_COMPILE)),$(call compile_test_erl,$(FILES_TO_COMPILE)) && touch $@)
 endif
 
 test-build:: IS_TEST=1
 test-build:: ERLC_OPTS=$(TEST_ERLC_OPTS)
-test-build:: $(if $(wildcard src),$(if $(wildcard ebin/test),,clean)) $(if $(IS_APP),,deps test-deps)
+test-build:: $(if $(wildcard src),$(if $(wildcard ebin/test),,beam-cache-restore-test)) $(if $(IS_APP),,deps test-deps)
 # We already compiled everything when IS_APP=1.
 ifndef IS_APP
 ifneq ($(wildcard src),)
-- 
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