dev-lang/go: add system-bootstrap use flag

If a previous version of dev-lang/go is installed, you can use this use
flag to skip downloading the bootstrap archives and bootstrap the new
version using the already-installed version.

For the initial installation of dev-lang/go, we have to download all of
the bootstrap archives to make the go ebuild work under crossdev. For
this reason, system-bootstrap cannot be turned on by default.

Bug: https://bugs.gentoo.org/671394
closes: https://bugs.gentoo.org/684652
Copyright: Sony Interactive Entertainment Inc.
Package-Manager: Portage-2.3.62, Repoman-2.3.12
Signed-off-by: William Hubbs <williamh@gentoo.org>

3 files changed, 30 insertions, 15 deletions

diff --git a/dev-lang/go/go-1.11.9.ebuild b/dev-lang/go/go-1.11.9.ebuild
index 8fafeb455ba2..a53df7c09567 100644
--- a/dev-lang/go/go-1.11.9.ebuild
+++ b/dev-lang/go/go-1.11.9.ebuild
@@ -48,20 +48,20 @@ case ${PV}  in
 	esac
 esac
 
-# If gccgo is not being used to build Go, there is no way to know the
-# architecture or operating system of the build machine, so we need to
-# download all of our bootstrap archives to allow this ebuild to work
-# under crossdev.
+# If gccgo or a previously installed version of dev-lang/go is not being
+# used to build Go, there is no way to know the architecture or operating system
+# of the build machine, so we need to download all of our bootstrap
+# archives to allow this ebuild to work under crossdev.
 #
 # https://bugs.gentoo.org/671394
-SRC_URI+="!gccgo? ( ${BOOTSTRAP_URI} )"
+SRC_URI+="!gccgo? ( !system-bootstrap? ( ${BOOTSTRAP_URI} ) )"
 
 DESCRIPTION="A concurrent garbage collected and typesafe programming language"
 HOMEPAGE="https://golang.org"
 
 LICENSE="BSD"
 SLOT="0/${PV}"
-IUSE="gccgo"
+IUSE="gccgo system-bootstrap"
 
 BDEPEND="gccgo? ( >=sys-devel/gcc-5[go] )"
 RDEPEND="!<dev-go/go-tools-0_pre20150902"
@@ -151,6 +151,9 @@ pkg_pretend()
 	if [[ $(go_tuple) != $(go_tuple ${CTARGET}) ]]; then
 		die "CHOST CTARGET pair unsupported: CHOST=${CHOST} CTARGET=${CTARGET}"
 	fi
+	[[ ${MERGE_TYPE} != binary ]] &&
+		use system-bootstrap && ! has_version "dev-lang/go" &&
+		die "dev-lang/go must be installed to use the system-bootstrap use flag"
 }
 
 src_unpack()
@@ -160,7 +163,7 @@ src_unpack()
 	else
 		unpack "go${MY_PV}.src.tar.gz"
 	fi
-	use gccgo ||
+	use gccgo || use system-bootstrap ||
 		unpack "go-$(go_os ${CBUILD})-$(go_arch ${CBUILD})-${BOOTSTRAP_VERSION}.tbz"
 }
 
@@ -176,6 +179,8 @@ src_compile()
 		[[ -x ${go_binary} ]] ||
 			die "go-$(gcc-major-version): command not found"
 		ln -s "${go_binary}" "${GOROOT_BOOTSTRAP}/bin/go" || die
+	elif use system-bootstrap; then
+		export GOROOT_BOOTSTRAP="${EPREFIX}"/usr/lib/go
 	fi
 	export GOROOT_FINAL="${EPREFIX}"/usr/lib/go
 	export GOROOT="$(pwd)"
diff --git a/dev-lang/go/go-1.12.4.ebuild b/dev-lang/go/go-1.12.4.ebuild
index 8fafeb455ba2..a53df7c09567 100644
--- a/dev-lang/go/go-1.12.4.ebuild
+++ b/dev-lang/go/go-1.12.4.ebuild
@@ -48,20 +48,20 @@ case ${PV}  in
 	esac
 esac
 
-# If gccgo is not being used to build Go, there is no way to know the
-# architecture or operating system of the build machine, so we need to
-# download all of our bootstrap archives to allow this ebuild to work
-# under crossdev.
+# If gccgo or a previously installed version of dev-lang/go is not being
+# used to build Go, there is no way to know the architecture or operating system
+# of the build machine, so we need to download all of our bootstrap
+# archives to allow this ebuild to work under crossdev.
 #
 # https://bugs.gentoo.org/671394
-SRC_URI+="!gccgo? ( ${BOOTSTRAP_URI} )"
+SRC_URI+="!gccgo? ( !system-bootstrap? ( ${BOOTSTRAP_URI} ) )"
 
 DESCRIPTION="A concurrent garbage collected and typesafe programming language"
 HOMEPAGE="https://golang.org"
 
 LICENSE="BSD"
 SLOT="0/${PV}"
-IUSE="gccgo"
+IUSE="gccgo system-bootstrap"
 
 BDEPEND="gccgo? ( >=sys-devel/gcc-5[go] )"
 RDEPEND="!<dev-go/go-tools-0_pre20150902"
@@ -151,6 +151,9 @@ pkg_pretend()
 	if [[ $(go_tuple) != $(go_tuple ${CTARGET}) ]]; then
 		die "CHOST CTARGET pair unsupported: CHOST=${CHOST} CTARGET=${CTARGET}"
 	fi
+	[[ ${MERGE_TYPE} != binary ]] &&
+		use system-bootstrap && ! has_version "dev-lang/go" &&
+		die "dev-lang/go must be installed to use the system-bootstrap use flag"
 }
 
 src_unpack()
@@ -160,7 +163,7 @@ src_unpack()
 	else
 		unpack "go${MY_PV}.src.tar.gz"
 	fi
-	use gccgo ||
+	use gccgo || use system-bootstrap ||
 		unpack "go-$(go_os ${CBUILD})-$(go_arch ${CBUILD})-${BOOTSTRAP_VERSION}.tbz"
 }
 
@@ -176,6 +179,8 @@ src_compile()
 		[[ -x ${go_binary} ]] ||
 			die "go-$(gcc-major-version): command not found"
 		ln -s "${go_binary}" "${GOROOT_BOOTSTRAP}/bin/go" || die
+	elif use system-bootstrap; then
+		export GOROOT_BOOTSTRAP="${EPREFIX}"/usr/lib/go
 	fi
 	export GOROOT_FINAL="${EPREFIX}"/usr/lib/go
 	export GOROOT="$(pwd)"
diff --git a/dev-lang/go/metadata.xml b/dev-lang/go/metadata.xml
index f981de1f10bc..8d9af604ec98 100644
--- a/dev-lang/go/metadata.xml
+++ b/dev-lang/go/metadata.xml
@@ -11,6 +11,11 @@
 		channels and a clean syntax.  
 	</longdescription>
 	<use>
-		<flag name="gccgo">Enable bootstrapping using gccgo</flag>
+		<flag name="gccgo">
+			Bootstrap using <pkg>sys-devel/gcc</pkg>[go]
+		</flag>
+		<flag name="system-bootstrap">
+			Bootstrap using previously installed <pkg>dev-lang/go</pkg>
+		</flag>
 	</use>
 </pkgmetadata>