[gentoo-dev] [PATCH 1/3 v2] cargo.eclass: Add cargo_env helper and use it in compile, test, install

[James Le Cuirot <chewi@gentoo.org>]

Rust packages have a tendency to rebuild parts during test and install.
It is not clear whether this can be addressed. We were therefore relying
on some environment variables set during the compile phase for
cross-compiling to work in the later phases. This is not ideal,
especially if you need to build for multiple targets.

These environment variables can also be useful in other contexts, such
as the build runner in app-misc/anki.

This change moves the setting of these variables into a separate helper
that is now used in all these phases and can be used by ebuilds too. The
variables are now kept local to each invocation of this helper,
preventing leakage.

Signed-off-by: James Le Cuirot <chewi@gentoo.org>
---
 eclass/cargo.eclass | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/eclass/cargo.eclass b/eclass/cargo.eclass
index 7db34efb4e174..b6d5fe21f0a7b 100644
--- a/eclass/cargo.eclass
+++ b/eclass/cargo.eclass
@@ -523,26 +523,23 @@ cargo_src_configure() {
 	[[ ${ECARGO_ARGS[@]} ]] && einfo "Configured with: ${ECARGO_ARGS[@]}"
 }

-# @FUNCTION: cargo_src_compile
+# @FUNCTION: cargo_env
+# @USAGE: Command with its arguments
 # @DESCRIPTION:
-# Build the package using cargo build.
-cargo_src_compile() {
-	debug-print-function ${FUNCNAME} "$@"
-
-	[[ ${_CARGO_GEN_CONFIG_HAS_RUN} ]] || \
-		die "FATAL: please call cargo_gen_config before using ${FUNCNAME}"
-
+# Run the given command under an environment needed for performing tasks with
+# Cargo such as building.
+cargo_env() {
 	filter-lto
 	tc-export AR CC CXX PKG_CONFIG

 	if tc-is-cross-compiler; then
-		export CARGO_BUILD_TARGET=$(rust_abi)
+		declare -x CARGO_BUILD_TARGET=$(rust_abi)
 		local TRIPLE=${CARGO_BUILD_TARGET//-/_}
-		export CARGO_TARGET_"${TRIPLE^^}"_LINKER=$(tc-getCC)
+		declare -x CARGO_TARGET_"${TRIPLE^^}"_LINKER=$(tc-getCC)

 		# Set vars for cc-rs crate.
 		tc-export_build_env
-		export \
+		declare -x \
 			HOST_AR=$(tc-getBUILD_AR)
 			HOST_CC=$(tc-getBUILD_CC)
 			HOST_CXX=$(tc-getBUILD_CXX)
@@ -550,9 +547,21 @@ cargo_src_compile() {
 			HOST_CXXFLAGS=${BUILD_CXXFLAGS}
 	fi

+	"${@}"
+}
+
+# @FUNCTION: cargo_src_compile
+# @DESCRIPTION:
+# Build the package using cargo build.
+cargo_src_compile() {
+	debug-print-function ${FUNCNAME} "$@"
+
+	[[ ${_CARGO_GEN_CONFIG_HAS_RUN} ]] || \
+		die "FATAL: please call cargo_gen_config before using ${FUNCNAME}"
+
 	set -- cargo build $(usex debug "" --release) ${ECARGO_ARGS[@]} "$@"
 	einfo "${@}"
-	"${@}" || die "cargo build failed"
+	cargo_env "${@}" || die "cargo build failed"
 }

 # @FUNCTION: cargo_src_install
@@ -573,7 +582,7 @@ cargo_src_install() {
 		$(usex debug --debug "") \
 		${ECARGO_ARGS[@]} "$@"
 	einfo "${@}"
-	"${@}" || die "cargo install failed"
+	cargo_env "${@}" || die "cargo install failed"

 	rm -f "${ED}/usr/.crates.toml" || die
 	rm -f "${ED}/usr/.crates2.json" || die
@@ -590,7 +599,7 @@ cargo_src_test() {

 	set -- cargo test $(usex debug "" --release) ${ECARGO_ARGS[@]} "$@"
 	einfo "${@}"
-	"${@}" || die "cargo test failed"
+	cargo_env "${@}" || die "cargo test failed"
 }

 fi
--
2.45.2