golang: Move module cache into DL_DIR

This also adds a config option GOLANG_MOD_CACHE_WORLD_READABLE; if
enabled, chmod is run after a Go package build to make all
files/directories in the module cache world-readable.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

lang/golang/golang-build.sh

@@ -0,0 +1,48 @@
+#!/bin/sh
+
+log() {
+	# shellcheck disable=SC2039
+	local IFS=" "
+	printf '%s\n' "$*"
+}
+
+log_error() {
+	# shellcheck disable=SC2039
+	local IFS=" "
+	printf 'Error: %s\n' "$*" >&2
+}
+
+cache_cleanup() {
+	if ! [ -d "$GO_MOD_CACHE_DIR" ]; then
+		return 0
+	fi
+
+	# in case go is called without -modcacherw
+	find "$GO_MOD_CACHE_DIR" -type d -not -perm -u+w -exec chmod u+w '{}' +
+
+	if [ -n "$CONFIG_GOLANG_MOD_CACHE_WORLD_READABLE" ]; then
+		find "$GO_MOD_CACHE_DIR"      -type d -not -perm -go+rx -exec chmod go+rx '{}' +
+		find "$GO_MOD_CACHE_DIR" -not -type d -not -perm -go+r  -exec chmod go+r  '{}' +
+	fi
+
+	return 0
+}
+
+
+if [ "$#" -lt 1 ]; then
+	log_error "Missing command"
+	exit 1
+fi
+
+command="$1"
+shift 1
+
+case "$command" in
+	cache_cleanup)
+		cache_cleanup
+		;;
+	*)
+		log_error "Invalid command \"$command\""
+		exit 1
+		;;
+esac

lang/golang/golang-package.mk

@@ -186,6 +186,7 @@ GO_PKG_TARGET_VARS= \
 GO_PKG_BUILD_VARS= \
 	GOPATH=$(GO_PKG_BUILD_DIR) \
 	GOCACHE=$(GO_PKG_CACHE_DIR) \
+	GOMODCACHE=$(GO_MOD_CACHE_DIR) \
 	GOENV=off
 
 GO_PKG_DEFAULT_VARS= \
@@ -226,7 +227,7 @@ GoPackage/has_binaries=$(call GoPackage/is_dir_not_empty,$(GO_PKG_BUILD_BIN_DIR)
 define GoPackage/Build/Configure
 	( \
 		cd $(PKG_BUILD_DIR) ; \
-		mkdir -p $(GO_PKG_BUILD_DIR)/bin $(GO_PKG_BUILD_DIR)/src $(GO_PKG_CACHE_DIR) ; \
+		mkdir -p $(GO_PKG_BUILD_DIR)/bin $(GO_PKG_BUILD_DIR)/src $(GO_PKG_CACHE_DIR) $(GO_MOD_CACHE_DIR) ; \
 		\
 		files=$$$$($(FIND) ./ \
 			-type d -a \( -path './.git' -o -path './$(GO_PKG_WORK_DIR_NAME)' \) -prune -o \
@@ -303,9 +304,12 @@ define GoPackage/Build/Compile
 	( \
 		cd $(GO_PKG_BUILD_DIR) ; \
 		export $(GO_PKG_VARS) ; \
+		if [ -f "$(PKG_BUILD_DIR)/go.mod" ] ; then \
+			modargs="$(GO_MOD_ARGS)" ; \
+		fi ; \
 		\
 		echo "Finding targets" ; \
-		targets=$$$$(go list $(GO_PKG_BUILD_PKG)) ; \
+		targets=$$$$(go list $$$$modargs $(GO_PKG_BUILD_PKG)) ; \
 		for pattern in $(GO_PKG_EXCLUDES); do \
 			targets=$$$$(echo "$$$$targets" | grep -v "$$$$pattern") ; \
 		done ; \
@@ -319,7 +323,7 @@ define GoPackage/Build/Compile
 		\
 		if [ "$(strip $(GO_PKG_SOURCE_ONLY))" != 1 ]; then \
 			echo "Building targets" ; \
-			go install $(GO_PKG_INSTALL_ARGS) $(1) $$$$targets ; \
+			go install $(GO_PKG_INSTALL_ARGS) $$$$modargs $(1) $$$$targets ; \
 			retval=$$$$? ; \
 			echo ; \
 			\
@@ -328,9 +332,9 @@ define GoPackage/Build/Compile
 				echo ; \
 			fi ; \
 			\
-			echo "Cleaning module download cache (golang/go#27455)" ; \
-			go clean -modcache ; \
-			echo ; \
+			if [ "$$$$retval" -ne 0 ]; then \
+				$(call Go/CacheCleanup) ; \
+			fi ; \
 		fi ; \
 		exit $$$$retval ; \
 	)
@@ -362,6 +366,7 @@ endef
 ifneq ($(strip $(GO_PKG)),)
   Build/Configure=$(call GoPackage/Build/Configure)
   Build/Compile=$(call GoPackage/Build/Compile)
+  Hooks/Compile/Post+=Go/CacheCleanup
   Build/InstallDev=$(call GoPackage/Build/InstallDev,$(1))
 endif
 

lang/golang/golang-values.mk

@@ -219,3 +219,20 @@ ifneq ($(filter $(GO_OS_ARCH),$(GO_PIE_SUPPORTED_OS_ARCH)),)
   GO_TARGET_PIE_SUPPORTED:=1
   GO_TARGET_PIE_INSTALL_SUFFIX:=$(call go_pie_install_suffix,$(GO_OS_ARCH))
 endif
+
+
+# General build info
+
+GO_MOD_CACHE_DIR:=$(DL_DIR)/go-mod-cache
+
+GO_MOD_ARGS= \
+	-modcacherw
+
+GO_GENERAL_BUILD_CONFIG_VARS= \
+	CONFIG_GOLANG_MOD_CACHE_WORLD_READABLE="$(CONFIG_GOLANG_MOD_CACHE_WORLD_READABLE)" \
+	GO_MOD_CACHE_DIR="$(GO_MOD_CACHE_DIR)"
+
+define Go/CacheCleanup
+	$(GENERAL_BUILD_CONFIG_VARS) \
+	$(SHELL) $(GO_INCLUDE_DIR)/golang-build.sh cache_cleanup
+endef

lang/golang/golang/Config.in

@@ -12,4 +12,8 @@ config GOLANG_EXTERNAL_BOOTSTRAP_ROOT
 
 	  Leave blank to compile the default bootstrap Go.
 
+config GOLANG_MOD_CACHE_WORLD_READABLE
+	bool "Ensure Go module cache is world-readable"
+	default n
+
 endmenu