running npm run lintfix will address all of the lint issues. I'm still looking at the PR, but I'm liking the es6 updates.

Looks like you can install bsdtar by adding this to the .github/workflows/ci:

➜  haraka git:(master) ✗ git diff
diff --git a/.github/workflows/ci-test.yml b/.github/workflows/ci-test.yml
index 6eaff2ef..ef4d0d29 100644
--- a/.github/workflows/ci-test.yml
+++ b/.github/workflows/ci-test.yml
@@ -36,6 +36,9 @@ jobs:
       with:
         node-version: ${{ matrix.node-version }}
 
+    - name: Install bsdtar
+      run: sudo apt-get install -y bsdtar
+
     - name: Install
       run: npm install
 

The only thing I've found is that it might be already included https://docs.microsoft.com/en-us/virtualization/community/team-blog/2017/20171219-tar-and-curl-come-to-windows

find_bsdtar_path() will need to be updated to find the path inside windows. Sadly I've no access to windows for couple years to check this

Well, I'm okay with you just putting in a prehook in the attachment plugin tests, and if you can't find bsdtar, then skip the tests.

I use Windows and I can tell you the following:

• bsdtar is included by default only in Windows Server 2019 or higher and Windows 10 v1809 (October 2018 update) or higher
• bsdtar is called just "tar" on Windows
• It is located in the primary System32 folder (i.e., C:\Windows\System32). This location would typically be in the PATH by default.
• It is known to work on older versions of Windows by copying the exe's, but there is no official way to get it on older versions, to my knowledge.

I've tried two blind tests but execution with absolute and relative path was failing, see:
https://github.com/haraka/Haraka/runs/5814356719?check_suite_focus=true#step:5:700
https://github.com/haraka/Haraka/runs/5814251741?check_suite_focus=true#step:5:690

(I'll do requested change tomorrow)

windows tests conversation moved here and deleted from this PR

Sorry, been out of office. Thanks Matt!