[Buildroot] [PATCH v1 1/3] package/pkg-cargo: add support to bundle a custom Cargo.lock file

[Thomas Devoogdt]

E.g. https://github.com/lu-zero/cargo-c/releases/tag/v0.10.15

Cargo-c releases a separate Cargo.lock file, but doesn't bundle
one in its normal .tar.gz code source target.

We can't use extra downloads/patches/... as cargo is a vendored
package, which is done quite early in the chain.

This patch allows us to define a custom Cargo.lock source.
Both a local bundled file and remote (only wget) file can be linked.

Usage:

<PKG>_CARGO_LOCK_FILE = <PKG>_PKGDIR/Cargo.lock

<PKG>_CARGO_LOCK_FILE = https://.../Cargo.lock

Signed-off-by: Thomas Devoogdt <thomas at devoogdt.com>
---
Superseeds https://patchwork.ozlabs.org/project/buildroot/patch/20250324173246.100112-1-guillaume.chaye@zeetim.com/.
---
 package/pkg-cargo.mk                |  5 +++++
 support/download/cargo-post-process | 14 +++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/package/pkg-cargo.mk b/package/pkg-cargo.mk
index 47a6353f25..626e5ea472 100644
--- a/package/pkg-cargo.mk
+++ b/package/pkg-cargo.mk
@@ -195,6 +195,11 @@ ifneq ($$($(2)_SUBDIR),)
 $(2)_DOWNLOAD_POST_PROCESS_OPTS += -m$$($(2)_SUBDIR)/Cargo.toml
 endif
 
+# Allow to download a custom Cargo.lock file.
+ifneq ($$($(3)_CARGO_LOCK_FILE),)
+$(2)_DOWNLOAD_POST_PROCESS_OPTS += -l$$($(3)_CARGO_LOCK_FILE)
+endif
+
 # Because we append vendored info, we can't rely on the values being empty
 # once we eventually get into the generic-package infra. So, we duplicate
 # the heuristics here
diff --git a/support/download/cargo-post-process b/support/download/cargo-post-process
index b0e59ad74d..7913724fe2 100755
--- a/support/download/cargo-post-process
+++ b/support/download/cargo-post-process
@@ -11,11 +11,12 @@ if [ "${BR_CARGO_MANIFEST_PATH}" ]; then
 fi
 
 manifest=Cargo.toml
-while getopts "n:o:m:" OPT; do
+while getopts "n:o:m:l:" OPT; do
     case "${OPT}" in
     o)  output="${OPTARG}";;
     n)  base_name="${OPTARG}";;
     m)  manifest="${OPTARG}";;
+    l)  lockfile="${OPTARG}";;
     :)  error "option '%s' expects a mandatory argument\n" "${OPTARG}";;
     \?) error "unknown option '%s'\n" "${OPTARG}";;
     esac
@@ -31,6 +32,17 @@ post_process_unpack "${base_name}" "${output}"
 # Do the Cargo vendoring
 pushd "${base_name}" > /dev/null
 
+# Copy the custom lockfile path if given
+# TODO: use --lockfile-path once stable
+if [ -n "${lockfile}" ] ; then
+    rm -f "${lockfile}"
+    if [ -f "${lockfile}" ] ; then
+        cp "${lockfile}" Cargo.lock
+    else
+        ${WGET} "${lockfile}" -O Cargo.lock
+    fi
+fi
+
 # Create the local .cargo/config.toml with vendor info
 mkdir -p .cargo/
 mkdir -p "${CARGO_HOME}"
-- 
2.43.0