GitHub Actions: Required property is missing: shell

Introduction

I am currently to crate a composite GitHub Actions that build a JavaDoc from Java project and publish it automatically to a static page with GitHub Page.

Problematic

But I got this error when I try to run it:

Current runner version: '2.287.1'
Operating System
Virtual Environment
Virtual Environment Provisioner
GITHUB_TOKEN Permissions
Secret source: Actions
Prepare workflow directory
Prepare all required actions
Getting action download info
Download action repository 'MathieuSoysal/Javadoc-publisher.yml@v2.0.2' (SHA:878c07f835dd9bcbb8800090d109c91b0f0d4581)
Error: MathieuSoysal/Javadoc-publisher.yml/v2.0.2/action.yml (Line: 29, Col: 5): Required property is missing: shell
Error: MathieuSoysal/Javadoc-publisher.yml/v2.0.2/action.yml (Line: 29, Col: 5): Required property is missing: shell
Error: GitHub.DistributedTask.ObjectTemplating.TemplateValidationException: The template is not valid. MathieuSoysal/Javadoc-publisher.yml/v2.0.2/action.yml (Line: 29, Col: 5): Required property is missing: shell
   at GitHub.DistributedTask.ObjectTemplating.TemplateValidationErrors.Check()
   at GitHub.Runner.Worker.ActionManifestManager.ConvertRuns(IExecutionContext executionContext, TemplateContext templateContext, TemplateToken inputsToken, String fileRelativePath, MappingToken outputs)
   at GitHub.Runner.Worker.ActionManifestManager.Load(IExecutionContext executionContext, String manifestFile)
Error: Fail to load MathieuSoysal/Javadoc-publisher.yml/v2.0.2/action.yml

Affected code:

name: Deploy Javadoc
description: 'Automatically  generate your Javadoc from your maven project and deploy it with GitHub Page on javadoc branch.'
branding:
  icon: 'book-open'
  color: 'white'
inputs:
  java-version:  # version of java
    description: 'Java version inside your project'
    required: true
    default: '17'
  GITHUB_TOKEN: # GitHub Token
    description: 'The GitHub token the GitHub repository'
    required: true
  javadoc-branch: # branch where the javadoc is hosted
    description: 'Branch where the javadoc is hosted'
    required: true
    default: javadoc
 
runs:
  using: "composite"
  steps:
  - uses: actions/checkout@v2
    with:
      fetch-depth: 0
  - uses: actions/setup-java@v2
    with:
      java-version: ${{ inputs.java-version }}
      distribution: 'adopt'
  - name: Generate Javadoc
    run: mvn org.apache.maven.plugins:maven-javadoc-plugin:3.3.1:aggregate
  - name: Deploy 🚀
    uses: JamesIves/github-pages-deploy-action@4.1.8
    with:
      GITHUB_TOKEN: ${{ inputs.GITHUB_TOKEN }}
      BRANCH: ${{ inputs.javadoc-branch }}
      CLEAN: true
      FOLDER: target/site/apidocs
      TARGET_FOLDER: javadoc

Code that execute the GitHub Actions in question:

name: Deploy Javadoc

on:
  push:
    branches:
      - master

jobs:
  publish:
    runs-on: ubuntu-latest
    steps:
      - name: Deploy JavaDoc 🚀
        uses: MathieuSoysal/Javadoc-publisher.yml@v2.0.3
        with:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          javadoc-branch: javadoc
          java-version: 17

Question

Anyone have an idea to solve this problem?

When using composite actions, you have to specify the shell.

As you don’t specify a runner type in composite actions, you need to specify the shell instead for each action.

In your case, the problem is in this step, you need to add shell: bash here:

- name: Generate Javadoc
  shell: bash
  run: mvn org.apache.maven.plugins:maven-javadoc-plugin:3.3.1:aggregate

Docs: https://docs.github.com/en/actions/creating-actions/creating-a-composite-action#creating-an-action-metadata-file