Unhelpful error message when writing malformed data to $GITHUB_ENV

Describe the bug When writing a particular string to $GITHUB_ENV, the runner throws a nullref, i.e. Object reference not set to an instance of an object.

To Reproduce See https://github.community/t/nullref-when-writing-to-github-env-from-python/221606 . The following python code reproduces the issue.

import environ
with open(environ['GITHUB_ENV'], 'a') as f:
  subcomment = """\
Please verify the following diffs:
- [ ] All articles ran in 0:00:56.697371: [en](https://wiki.tf/d/3106540) [ar](https://wiki.tf/d/3106518) [cs](https://wiki.tf/d/3106519) [da](https://wiki.tf/d/3106520) [de](https://wiki.tf/d/3106521) [es](https://wiki.tf/d/3106522) [fi](https://wiki.tf/d/3106523) [fr](https://wiki.tf/d/3106524) [hu](https://wiki.tf/d/3106525) [it](https://wiki.tf/d/3106526) [ja](https://wiki.tf/d/3106527) [ko](https://wiki.tf/d/3106528) [nl](https://wiki.tf/d/3106529) [no](https://wiki.tf/d/3106530) [pl](https://wiki.tf/d/3106531) [pt](https://wiki.tf/d/3106532) [pt-br](https://wiki.tf/d/3106533) [ro](https://wiki.tf/d/3106534) [ru](https://wiki.tf/d/3106535) [sv](https://wiki.tf/d/3106536) [tr](https://wiki.tf/d/3106537) [zh-hans](https://wiki.tf/d/3106538) [zh-hant](https://wiki.tf/d/3106539)
- [ ] Wanted templates ran in 0:00:37.264911: [en](https://wiki.tf/d/3106541)"""
  f.write('GITHUB_COMMENT<<EOF')
  f.write(subcomment)
  f.write('EOF')

Expected behavior The bug here is about a lack of newline after the EOF marker. So, I would expect an error which says something like “malformed EOF marker”, or “EOF marker too long”. A very precient error might say “EOF marker missing newline”.

Runner Version and Platform

Runner version 2.285.1, Ubuntu 20.04.3

What’s not working?

https://github.com/jbzdarkid/TFWiki-scripts/runs/4728629242?check_suite_focus=true

Job Log Output

2022-01-06T15:26:24.2881206Z ##[group]Run python master.py pull_request
2022-01-06T15:26:24.2882292Z python master.py pull_request
2022-01-06T15:26:24.2930406Z shell: /usr/bin/bash -e {0}
2022-01-06T15:26:24.2930893Z env:
2022-01-06T15:26:24.2931483Z   pythonLocation: /opt/hostedtoolcache/Python/3.8.12/x64
2022-01-06T15:26:24.2932252Z   LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.8.12/x64/lib
2022-01-06T15:26:24.2933714Z   WIKI_USERNAME: ***
2022-01-06T15:26:24.2934234Z   WIKI_PASSWORD: ***
2022-01-06T15:26:24.2934678Z ##[endgroup]
2022-01-06T15:26:24.4627453Z ##[error]Unable to process file command 'env' successfully.
2022-01-06T15:26:24.4642131Z ##[error]Object reference not set to an instance of an object.
2022-01-06T15:26:24.4820362Z ##[group]Run peter-evans/find-comment@v1
2022-01-06T15:26:24.4820930Z with:
2022-01-06T15:26:24.4821305Z   issue-number: 13
2022-01-06T15:26:24.4821857Z   comment-author: github-actions[bot]
2022-01-06T15:26:24.4822902Z   token: ***
2022-01-06T15:26:24.4823414Z   repository: jbzdarkid/TFWiki-scripts
2022-01-06T15:26:24.4823954Z   direction: first
2022-01-06T15:26:24.4824355Z env:
2022-01-06T15:26:24.4824913Z   pythonLocation: /opt/hostedtoolcache/Python/3.8.12/x64
2022-01-06T15:26:24.4825643Z   LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.8.12/x64/lib
2022-01-06T15:26:24.4826209Z ##[endgroup]

[ruvceskistefan]

Hi @jbzdarkid, I created a PR that will close the described issue. Thanks again for your contribution and further explanation of the bug!

[ruvceskistefan]

Okay, now I see. I thought the problem was specifically the lack of a new line after the EOF marker and that the subcomment string itself is not important. Thanks for the clarification, I am working on solving the problem.