package/pkg-golang: new package infrastructure

This patch adds a new infrastructure for golang based packages.

Signed-off-by: Angelo Compagnucci <angelo@amarulasolutions.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
[Arnout:
 - Rewrap comments to 80 columns.
 - Create a global definition of GO_TARGET_ENV.
 - <PKG>_GO_ENV is appended to the default env instead of replacing it.
 - Add a note to inner-golang-package that only target is supported.
]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/Makefile.in

@@ -452,3 +452,4 @@ include package/pkg-kconfig.mk
 include package/pkg-rebar.mk
 include package/pkg-kernel-module.mk
 include package/pkg-waf.mk
+include package/pkg-golang.mk

package/pkg-golang.mk

@@ -0,0 +1,130 @@
+################################################################################
+# Golang package infrastructure
+#
+# This file implements an infrastructure that eases development of package .mk
+# files for Go packages. It should be used for all packages that are written in
+# go.
+#
+# See the Buildroot documentation for details on the usage of this
+# infrastructure
+#
+#
+# In terms of implementation, this golang infrastructure requires the .mk file
+# to only specify metadata information about the package: name, version,
+# download URL, etc.
+#
+# We still allow the package .mk file to override what the different steps are
+# doing, if needed. For example, if <PKG>_BUILD_CMDS is already defined, it is
+# used as the list of commands to perform to build the package, instead of the
+# default golang behavior. The package can also define some post operation
+# hooks.
+#
+################################################################################
+
+GO_BIN = $(HOST_DIR)/bin/go
+
+# We pass an empty GOBIN, otherwise "go install: cannot install
+# cross-compiled binaries when GOBIN is set"
+GO_TARGET_ENV = \
+	$(HOST_GO_TARGET_ENV) \
+	GOBIN= \
+	CGO_ENABLED=$(HOST_GO_CGO_ENABLED)
+
+################################################################################
+# inner-golang-package -- defines how the configuration, compilation and
+# installation of a Go package should be done, implements a few hooks to tune
+# the build process for Go specificities and calls the generic package
+# infrastructure to generate the necessary make targets
+#
+#  argument 1 is the lowercase package name
+#  argument 2 is the uppercase package name, including a HOST_ prefix for host
+#             packages
+#  argument 3 is the uppercase package name, without the HOST_ prefix for host
+#             packages
+#  argument 4 is the type (target or host)
+#
+# NOTE Only type target is supported at the moment
+################################################################################
+
+define inner-golang-package
+
+$(2)_WORKSPACE ?= _gopath
+
+ifeq ($(BR2_STATIC_LIBS),y)
+$(2)_LDFLAGS += -extldflags '-static'
+endif
+
+$(2)_BUILD_OPTS += -ldflags "$$($(2)_LDFLAGS)"
+$(2)_BUILD_OPTS += -tags "$$($(2)_TAGS)"
+
+# Target packages need the Go compiler on the host.
+$(2)_DEPENDENCIES += host-go
+
+$(2)_BUILD_TARGETS ?= .
+
+$(2)_INSTALL_BINS ?= $(1)
+
+# The go build/install command installs the binaries inside
+# gopath/bin/linux_GOARCH/ when cross compilation is enabled. We set this
+# variable here to be used by packages if needed.
+$(2)_BINDIR = $$($(2)_WORKSPACE)/bin/linux_$$(GO_GOARCH)
+
+# Source files in Go should be extracted in a precise folder in the hierarchy
+# of GOPATH. It usually resolves around domain/vendor/software. By default, we
+# derive domain/vendor/software from the upstream URL of the project, but we
+# allow $(2)_SRC_SUBDIR to be overridden if needed.
+$(2)_SRC_DOMAIN = $$(call domain,$($(2)_SITE))
+$(2)_SRC_VENDOR = $$(word 1,$$(subst /, ,$$(call notdomain,$($(2)_SITE))))
+$(2)_SRC_SOFTWARE = $$(word 2,$$(subst /, ,$$(call notdomain,$($(2)_SITE))))
+
+$(2)_SRC_SUBDIR ?= $$($(2)_SRC_DOMAIN)/$$($(2)_SRC_VENDOR)/$$($(2)_SRC_SOFTWARE)
+$(2)_SRC_PATH = $$(@D)/$$($(2)_WORKSPACE)/src/$$($(2)_SRC_SUBDIR)
+
+# Configure step. Only define it if not already defined by the package .mk
+# file.
+ifndef $(2)_CONFIGURE_CMDS
+define $(2)_CONFIGURE_CMDS
+	mkdir -p $$(@D)/$$($(2)_WORKSPACE)/bin
+	mkdir -p $$(dir $$($(2)_SRC_PATH))
+	ln -sf $$(@D) $$($(2)_SRC_PATH)
+endef
+endif
+
+# Build step. Only define it if not already defined by the package .mk file. We
+# use the install command instead of build command here because the install
+# command just moves the package binaries into <workspace>/bin/linux_GOARCH/.
+# This leverages the go build infrastructure for building and installing
+# multiple binaries.
+ifndef $(2)_BUILD_CMDS
+define $(2)_BUILD_CMDS
+	$$(foreach d,$$($(2)_BUILD_TARGETS),\
+		cd $$($(2)_SRC_PATH); \
+		$$(GO_TARGET_ENV) \
+			GOPATH="$$(@D)/$$($(2)_WORKSPACE)" \
+			$$($(2)_GO_ENV) \
+			$$(GO_BIN) install -v $$($(2)_BUILD_OPTS) ./$$(d)
+	)
+endef
+endif
+
+# Target installation step. Only define it if not already defined by the
+# package .mk file.
+ifndef $(2)_INSTALL_TARGET_CMDS
+define $(2)_INSTALL_TARGET_CMDS
+	$$(foreach d,$$($(2)_INSTALL_BINS),\
+		$(INSTALL) -D -m 0755 $$(@D)/$$($(2)_BINDIR)/$$(d) $(TARGET_DIR)/usr/bin/$$(d)
+	)
+endef
+endif
+
+# Call the generic package infrastructure to generate the necessary make
+# targets
+$(call inner-generic-package,$(1),$(2),$(3),$(4))
+
+endef # inner-golang-package
+
+################################################################################
+# golang-package -- the target generator macro for Go packages
+################################################################################
+
+golang-package = $(call inner-golang-package,$(pkgname),$(call UPPERCASE,$(pkgname)),$(call UPPERCASE,$(pkgname)),target)