Pre-commands

MegaLinter can run custom commands before running linters (for example, installing a plugin required by one of the linters you use).

Example in .mega-linter.yml config file

PRE_COMMANDS:
  - command: npm install eslint-plugin-whatever
    cwd: root        # Will be run at the root of the MegaLinter Docker image
    secured_env: true  # True by default. If set to false, no global variables will be hidden (for example, if you need GITHUB_TOKEN)
    run_before_linters: True # Will be run before the execution of the linters themselves; required for npm/pip commands that cannot be run in parallel
  - command: echo "pre-test command has been called"
    cwd: workspace   # Will be run at the root of the workspace (usually your repository root)
    continue_if_failed: False  # Will stop the process if the command fails (return code > 0)
  - command: pip install flake8-cognitive-complexity
    venv: flake8 # Will be run within the flake8 Python virtualenv. There is one virtualenv per Python-based linter, with the same name
  - command: export MY_OUTPUT_VAR="my output var" && export MY_OUTPUT_VAR2="my output var2"
    output_variables: ["MY_OUTPUT_VAR","MY_OUTPUT_VAR2"] # Will collect the values of output variables and update MegaLinter's own ENV context
  - command: echo "Some command called before loading MegaLinter plugins"
    cwd: workspace   # Will be run at the root of the workspace (usually your repository root)
    continue_if_failed: False  # Will stop the process if the command fails (return code > 0)
    tag: before_plugins # Tag indicating that the command will be run before loading plugins
  - command: echo "Some command called after running MegaLinter linters"
    run_after_linters: True # Will be run after the execution of the linters themselves

Note: to keep them lightweight, MegaLinter images do not embed a compilation toolchain. If a pre-command needs to compile native code (e.g. a pip package distributed only as source), install the toolchain first within your pre-command: apk add --no-cache gcc make musl-dev.

Property	Description	Default value
command	Command line to run	Mandatory
cwd	Directory where to run the command (workspace or root)	root
run_before_linters	If set to true, runs the command before the execution of the linters themselves, required for npm/pip commands that cannot be run in parallel	false
run_after_linters	If set to true, runs the command after the execution of the linters themselves	false
secured_env	Apply filtering of secured environment variables before calling the command (default true). Be careful if you disable it!	true
continue_if_failed	If set to false, stop the MegaLinter process in case of command failure	true
venv	If set, runs the command in the related Python venv
output_variables	ENV variables to read from output after running the commands, and store in MegaLinter's ENV context so they can be reused in subsequent commands	[]
tag	Tag defining at which command entry point the command will be run (available tags: before_plugins)