fix return value for detecting yarn workspace plugin

Author: Danielle Adams

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## main
 - Prune devDependencies with Yarn 2 ([#891](https://github.com/heroku/heroku-buildpack-nodejs/pull/891))
 - Add 10.x, 12.x, and 14.x to inventory ([902](https://github.com/heroku/heroku-buildpack-nodejs/pull/902))
+- Fix yarn workspace plugin detection ([#905](https://github.com/heroku/heroku-buildpack-nodejs/pull/905))
 
 ## v183 (2020-02-03)
 - Update node version to 14 ([#885](https://github.com/heroku/heroku-buildpack-nodejs/pull/885))

lib/dependencies.sh

@@ -175,6 +175,7 @@ yarn_prune_devdependencies() {
  cd "$build_dir" || return
 
  if has_yarn_workspace_plugin_installed "$build_dir"; then
+ echo "Running 'yarn workspaces focus --all --production'"
  meta_set "workspace-plugin-present" "true"
 
  # The cache is removed beforehand because the command is running an install on devDeps, and

lib/yarn-2.sh

@@ -28,7 +28,15 @@ has_yarn_cache() {
 has_yarn_workspace_plugin_installed() {
  local build_dir="$1"
  local plugin_paths=$(get_yarn_plugin_paths "$build_dir")
- [[ ! -n $plugin_paths ]] && echo "$plugin_paths" | grep plugin-workspace-tools
+ local path
+
+ if [[ -n $plugin_paths ]]; then
+ path=$(echo "$plugin_paths" | grep plugin-workspace-tools)
+ else
+ path=""
+ fi
+
+ [[ ! "$path" == "" ]]
 }
 
 get_yarn_plugin_paths() {

test/run

@@ -679,6 +679,7 @@ testYarn2() {
  assertCaptured "The buildpack won't cache the dependencies in .yarn/cache."
  assertCaptured "Running 'yarn install' with yarn.lock"
  assertCaptured "Version 3.9.7" # tsc output
+ assertCaptured "Running 'yarn workspaces focus --all --production'"
  assertCapturedSuccess
 }