Add parallel dependency compilation env variable (#13)

Projects using this Feature will benefit from the recommended setting of
this new environment variable to half the available CPUs.


https://elixir-lang.org/blog/2025/10/16/elixir-v1-19-0-released/#parallel-compilation-of-dependencies

Author: jgarber623-cargosense

src/elixir-project/devcontainer-feature.json

@@ -1,6 +1,6 @@
 {
   "id": "elixir-project",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "name": "elixir-project",
   "description": "An opinionated, batteries-included Dev Container Feature for Elixir projects.",
   "documentationURL": "https://github.com/CargoSense/devcontainer-features/tree/main/src/elixir-project",

src/elixir-project/scripts/onCreateCommand.sh

@@ -11,10 +11,12 @@ BASHRC_DIR="${HOME}/.bashrc.d"
 mkdir -p "${BASHRC_DIR}"
 chmod 700 "${BASHRC_DIR}"
 
-# Configure environment variables that rely on `CONTAINER_WORKSPACE_FOLDER`
+# Configure environment variables that rely on `CONTAINER_WORKSPACE_FOLDER` and
+# set dependency compilation parallelism (new in Elixir v1.19)
 cat << EOF > "${BASHRC_DIR}/elixir-project.bashrc"
 export HISTFILE="${CONTAINER_WORKSPACE_FOLDER}/.bash_history"
 export ERL_AFLAGS="-kernel shell_history enabled -kernel shell_history_path '\\"${CONTAINER_WORKSPACE_FOLDER}/.iex_history\\"'"
+export MIX_OS_DEPS_COMPILE_PARTITION_COUNT="\$(( "\$(nproc --all)" / 2 ))"
 EOF
 
 chmod +x "${BASHRC_DIR}/elixir-project.bashrc"

test/elixir-project/test.sh

@@ -7,7 +7,7 @@ set -e
 source dev-container-features-test-lib
 
 # Feature-specific tests
-check "environment" bash -c "env | grep ERL_AFLAGS"
+check "environment" bash -c "env | grep ERL_AFLAGS && env | grep MIX_OS_DEPS_COMPILE_PARTITION_COUNT"
 check "gitignore" grep -xF .bash_history .gitignore
 
 # Report result