feature nix: add option useAttrPath to use packages attribute path (#787)

* add option `useAttrPath` to support `nix-env -iA`

* add test and fix problem

* change to useAttributePath

* bump the version

* update test

src/nix/devcontainer-feature.json

 {
     "id": "nix",
-    "version": "1.1.3",
+    "version": "1.2.0",
     "name": "Nix Package Manager",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/nix",
     "description": "Installs the Nix package manager and optionally a set of packages.",
@@ -21,6 +21,11 @@
             "default": "",
             "description": "Optional comma separated list of Nix packages to install in profile."
         },
+        "useAttributePath": {
+            "type": "boolean",
+            "default": false,
+            "description": "Enable this option to use exact attribute path of the package in the Nixpkgs repository, aligning with the nix-env -iA command."
+        },
         "flakeUri": {
             "type": "string",
             "default": "",

src/nix/install.sh

@@ -8,6 +8,7 @@ cd "${FEATURE_DIR}"
 VERSION="${VERSION:-"latest"}"
 MULTIUSER="${MULTIUSER:-"true"}"
 PACKAGES="${PACKAGES//,/ }"
+USEATTRIBUTEPATH="${USEATTRIBUTEPATH:-"false"}"
 FLAKEURI="${FLAKEURI:-""}"
 EXTRANIXCONFIG="${EXTRANIXCONFIG:-""}"
 USERNAME="${USERNAME:-"${_REMOTE_USER:-"automatic"}"}"

src/nix/post-install-steps.sh

@@ -2,10 +2,29 @@
 set -e
 echo "(*) Executing post-installation steps..."
 
+# if not starts with "nixpkgs." add it as prefix to package name
+add_nixpkgs_prefix() {
+  local packages=$1
+  local -a addr
+  IFS=' ' read -ra addr <<<"$packages"
+  for i in "${!addr[@]}"; do
+    if [[ ${addr[i]} != nixpkgs.* ]]; then
+      addr[i]="nixpkgs.${addr[i]}"
+    fi
+  done
+  IFS=' ' echo "${addr[*]}"
+}
+
 # Install list of packages in profile if specified.
 if [ ! -z "${PACKAGES}" ] && [ "${PACKAGES}" != "none" ]; then
+  if [ "${USEATTRIBUTEPATH}" = "true" ]; then
+    PACKAGES=$(add_nixpkgs_prefix "$PACKAGES")
+    echo "Installing packages \"${PACKAGES}\" in profile..."
+    nix-env -iA ${PACKAGES}
+  else
     echo "Installing packages \"${PACKAGES}\" in profile..."
     nix-env --install ${PACKAGES}
+  fi
 fi
 
 # Install Nix flake in profile if specified

test/nix/packages-use-attr-path.sh

+#!/bin/bash
+set -e
+
+# Optional: Import test library bundled with the devcontainer CLI
+source dev-container-features-test-lib
+
+uid="$(id -u)"
+echo "Current user UID is ${uid}."
+if [ "${uid}" != "1000" ]; then
+    echo "Current user UID was adjusted."
+fi
+set +e
+vscode_uid="$(id -u vscode)"
+set -e
+if [ "${vscode_uid}" != "" ]; then
+    echo "User vscode UID is ${vscode_uid}."
+    if [ "${vscode_uid}" != "1000" ]; then
+        echo "User vscode UID was adjusted."
+    fi
+fi
+nix_uid="$(stat /nix -c "%u")"
+echo "/nix UID is ${nix_uid}."
+
+cat /etc/os-release
+
+# Feature-specific tests
+# The 'check' command comes from the dev-container-features-test-lib.
+check "nix-env" type nix-env
+check "vim_installed" type vim
+check "node_installed" type node
+check "yarn_installed" type yarn
+
+# Report result
+# If any of the checks above exited with a non-zero exit code, the test will fail.
+reportResults &2>1

test/nix/scenarios.json

@@ -81,6 +81,17 @@
             }
         }
     },
+    "packages-use-attr-path": {
+        "image": "mcr.microsoft.com/devcontainers/base:ubuntu",
+        "remoteUser": "vscode",
+        "features": {
+            "nix": {
+                "packages": "nodePackages.nodejs,nixpkgs.vim,nixpkgs.yarn",
+                "useAttributePath": true
+            }
+        }
+    },
+
     "flake": {
         "image": "mcr.microsoft.com/devcontainers/base:ubuntu",
         "remoteUser": "vscode",