support/download/go-post-process: implement Go vendoring support

This commit introduces the download post-process script
support/download/go-post-process, and hooks it into the Go package
infrastructure.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Skiff fixup:

 - run "go mod init" just before "go mod vendor"
 - this fixes the case when go.mod does not exist
 - use -modcacherw to fix "make clean" permissions errors
 - proposal was e-mailed to the buildroot mailing list

Signed-off-by: Christian Stewart <christian@paral.in>

Signed-off-by: Christian Stewart <christian@paral.in>

package/pkg-download.mk

@@ -112,6 +112,7 @@ define DOWNLOAD
 		-o '$($(2)_DL_DIR)/$(notdir $(1))' \
 		$(if $($(2)_DOWNLOAD_POST_PROCESS),-p '$($(2)_DOWNLOAD_POST_PROCESS)') \
 		$(if $($(2)_GIT_SUBMODULES),-r) \
+		$(if $($(2)_GOMOD),-g '$($(2)_GOMOD)') \
 		$(foreach uri,$(call DOWNLOAD_URIS,$(1),$(2)),-u $(uri)) \
 		$(QUIET) \
 		-- \

package/pkg-golang.mk

@@ -42,12 +42,13 @@ define inner-golang-package
 
 $(2)_BUILD_OPTS += \
 	-ldflags "$$($(2)_LDFLAGS)" \
+	-modcacherw \
 	-tags "$$($(2)_TAGS)" \
 	-trimpath \
 	-p $(PARALLEL_JOBS)
 
 # Target packages need the Go compiler on the host.
-$(2)_DEPENDENCIES += host-go
+$(2)_DOWNLOAD_DEPENDENCIES += host-go
 
 $(2)_BUILD_TARGETS ?= .
 
@@ -72,6 +73,11 @@ $(2)_SRC_SOFTWARE = $$(word 2,$$(subst /, ,$$(call notdomain,$$($(2)_SITE))))
 # If the go.mod file does not exist, one is written with this root path.
 $(2)_GOMOD ?= $$($(2)_SRC_DOMAIN)/$$($(2)_SRC_VENDOR)/$$($(2)_SRC_SOFTWARE)
 
+$(2)_DOWNLOAD_POST_PROCESS = go
+$(2)_DL_ENV = \
+	$(HOST_GO_COMMON_ENV) \
+	GOPROXY=direct
+
 # Generate a go.mod file if it doesn't exist. Note: Go is configured
 # to use the "vendor" dir and not make network calls.
 define $(2)_GEN_GOMOD

support/download/dl-wrapper

@@ -17,19 +17,20 @@
 # We want to catch any unexpected failure, and exit immediately.
 set -e
 
-export BR_BACKEND_DL_GETOPTS=":hc:d:o:n:N:H:ru:qf:e"
+export BR_BACKEND_DL_GETOPTS=":hc:d:g:o:n:N:H:ru:qf:e"
 
 main() {
     local OPT OPTARG
     local backend output hfile recurse quiet rc
     local -a uris
 
     # Parse our options; anything after '--' is for the backend
-    while getopts ":c:d:D:o:n:N:H:rf:u:qp:" OPT; do
+    while getopts ":c:d:D:g:o:n:N:H:rf:u:qp:" OPT; do
         case "${OPT}" in
         c)  cset="${OPTARG}";;
         d)  dl_dir="${OPTARG}";;
         D)  old_dl_dir="${OPTARG}";;
+        g)  gomod_init="${OPTARG}";;
         o)  output="${OPTARG}";;
         n)  raw_base_name="${OPTARG}";;
         N)  base_name="${OPTARG}";;
@@ -138,6 +139,7 @@ main() {
 
         if [ -n "${post_process}" ] ; then
                 ${OLDPWD}/support/download/${post_process}-post-process \
+                         -g "${gomod_init}" \
                          -o "${tmpf}" \
                          -n "${raw_base_name}"
         fi

support/download/go-post-process

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+
+set -e
+
+. $(dirname $0)/post-process-helpers
+
+# Parse our options
+while getopts "n:g:o:" OPT; do
+        case "${OPT}" in
+        g)  gomod_init="${OPTARG}";;
+        o)  output="${OPTARG}";;
+        n)  base_name="${OPTARG}";;
+        :)  error "option '%s' expects a mandatory argument\n" "${OPTARG}";;
+        \?) error "unknown option '%s'\n" "${OPTARG}";;
+        esac
+done
+
+# Already vendored tarball, nothing to do
+if tar tf ${output} | grep -q "^[^/]*/vendor" ; then
+	exit 0
+fi
+
+unpack ${base_name} ${output}
+
+# Do the Go vendoring
+pushd ${base_name} > /dev/null
+# modcacherw option leaves directories in the module cache at their default
+# permissions rather than making them read-only.
+if [ ! -f go.mod ] && [ -n "${gomod_init}" ]; then
+    go mod init -modcacherw ${gomod_init}
+fi
+go mod vendor -modcacherw -v
+popd > /dev/null
+
+repack ${base_name} ${output}