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Validation and prompts ​

Use requires to catch missing inputs before a task runs. Add enum when only certain values are allowed, and enable interactive prompts when users should be able to fill in missing values at the terminal.

Require an input ​

Declare inputs in requires.vars, then pass them on the command line:

yaml
version: '3'

tasks:
  release:
    requires:
      vars: [VERSION]
    cmds:
      - echo "Preparing release {{.VERSION}}"

Run task release VERSION=1.2.3 to print the message. Without VERSION, Task fails and identifies the missing input. Task variables and values inherited from the process environment can satisfy the requirement.

A variable set to an empty string counts as present. To reject an empty value, use an enum of nonempty strings or a precondition.

Restrict allowed values ​

Use name and enum to require a string from a fixed list:

yaml
version: '3'

tasks:
  deploy:
    requires:
      vars:
        - name: ENV
          enum: [dev, staging, prod]
    cmds:
      - echo "Deploying to {{.ENV}}"

task deploy ENV=staging succeeds. task deploy ENV=preview fails before running the command. Enum validation applies to string variables, including strings inherited from the environment.

Ask for missing input ​

Run task --interactive deploy with the example above to choose the missing ENV from a menu. Required variables without an enum use a text input instead.

To enable this behavior by default, set it in your Task configuration:

~/.taskrc.yml
yaml
interactive: true

For a task with both kinds of input:

yaml
version: '3'

tasks:
  deploy:
    requires:
      vars:
        - name: ENVIRONMENT
          enum: [dev, staging, prod]
        - VERSION
    cmds:
      - echo "Deploying {{.VERSION}} to {{.ENVIRONMENT}}"

task --interactive deploy asks for an environment and a version. Values already supplied through the CLI, environment, or Taskfile do not prompt:

shell
task deploy ENVIRONMENT=prod VERSION=1.0.0

Prompts require a terminal. In CI or another non-interactive environment, missing variables cause an error; supply all required values explicitly.

Reuse allowed values ​

Define a shared list and reference it from an enum:

yaml
version: '3'

vars:
  ALLOWED_ENVS: [dev, staging, prod]

tasks:
  deploy:
    requires:
      vars:
        - name: ENV
          enum:
            ref: .ALLOWED_ENVS
    cmds:
      - echo "Deploying to {{.ENV}}"

References can also transform values. Given a config.json file containing {"allowed_environments": ["dev", "prod"]}, this reads the list from it:

yaml
version: '3'

vars:
  CONFIG:
    sh: cat config.json

tasks:
  deploy:
    requires:
      vars:
        - name: ENV
          enum:
            ref: ( .CONFIG | fromJson ).allowed_environments
    cmds:
      - echo "Deploying to {{.ENV}}"

For newline-separated command output, convert it to a list before using it as an enum. This example uses the entries in an existing services/ directory:

yaml
version: '3'

vars:
  AVAILABLE_SERVICES:
    sh: ls services/

tasks:
  deploy:
    requires:
      vars:
        - name: SERVICE
          enum:
            ref: .AVAILABLE_SERVICES | splitLines | compact
    cmds:
      - echo "Deploying {{.SERVICE}}"

Related guide

A prompt for input fills in a value. A confirmation prompt asks whether execution should proceed, even if all input values are already present.