Drone-runner-docker environment can't set empty strings

Drone Bugs
1

Our org upgraded from the very legacy drone-agent to drone-runner-docker 1.8 and found that the new runner is unable to set empty env vars in the environment block (only recourse is to use unset or export in commands before execution). This seems unintended since setting

environment:
  foo:

reads to be very explicitly setting an existing environment variable in the docker image to be empty upon execution. I also tested with drone-runner-kube 1.0.0-rc3 and it setting empty env vars does work with ‘’ or “” (but not null). Is there a reason why this functionality doesn’t exist for drone-runner-docker / could that be added?

Below is a sample pipeline to reproduce using docker and kubernetes runners.

---
kind: pipeline
type: docker
name: docker
steps:
  # outputs 20.10.14
  - name: test-empty-string-1
    image: docker
    pull: if-not-exists
    commands:
      - echo $DOCKER_VERSION

  # outputs 20.10.14
  - name: test-empty-string-2
    image: docker
    pull: if-not-exists
    environment:
      DOCKER_VERSION: null
    commands:
      - echo $DOCKER_VERSION

  # outputs 20.10.14
  - name: test-empty-string-3
    image: docker
    pull: if-not-exists
    environment:
      DOCKER_VERSION: ""
    commands:
      - echo $DOCKER_VERSION

  # outputs asdf
  - name: test-empty-string-4
    image: docker
    pull: if-not-exists
    environment:
      DOCKER_VERSION: asdf
    commands:
      - echo $DOCKER_VERSION

  # outputs 20.10.14
  - name: test-empty-string-5
    image: docker
    pull: if-not-exists
    environment:
      DOCKER_VERSION: ''
    commands:
      - echo $DOCKER_VERSION
---
kind: pipeline
type: kubernetes
name: kubernetes
steps:
  # outputs 20.10.14
  - name: test-empty-string-1
    image: docker
    pull: if-not-exists
    commands:
      - echo $DOCKER_VERSION

  # outputs 20.10.14
  - name: test-empty-string-2
    image: docker
    pull: if-not-exists
    environment:
      DOCKER_VERSION: null
    commands:
      - echo $DOCKER_VERSION

  # outputs empty string
  - name: test-empty-string-3
    image: docker
    pull: if-not-exists
    environment:
      DOCKER_VERSION: ""
    commands:
      - echo $DOCKER_VERSION

  # outputs asdf
  - name: test-empty-string-4
    image: docker
    pull: if-not-exists
    environment:
      DOCKER_VERSION: asdf
    commands:
      - echo $DOCKER_VERSION

  # outputs empty string
  - name: test-empty-string-5
    image: docker
    pull: if-not-exists
    environment:
      DOCKER_VERSION: ''
    commands:
      - echo $DOCKER_VERSION