shellcheck-markdown.yml

---
name: Shellcheck code in Markdown

on: [push]

concurrency:
  # cancel any in-progress job or run
  # https://github.com/kdeldycke/workflows/commit/8bee3ba877
  # https://docs.github.com/actions/using-jobs/using-concurrency
  group: ${{ github.ref }}
  cancel-in-progress: true

jobs:
  build:
    runs-on: ubuntu-latest
    defaults:
      run:
        shell: bash
    steps:
      - uses: actions/checkout@v4
      - name: Run shellcheck
        run: |
          # test shell syntax of Markdown code snippets
          # https://github.com/dylanaraps/pure-sh-bible/commit/9d54e96011

          set +o allexport
          set -o noclobber
          set -o noglob
          set -o nounset
          set -o verbose
          trap 'printf "shellcheck complete\n"' EXIT INT

          # Extract code blocks from the README.
          while read -r line; do
            test "${code-}" = '1' &&
              test "${line-}" != '```' &&
              printf '%s\n' "${line-}"

            case "${line-}" in
            '```sh' | '```bash' | '```zsh' | '```shell')
              code='1'
              ;;
            '```')
              code=''
              ;;
            *) ;;

            esac
          done < <(
            # Markdown filename extensions
            # https://github.com/github/linguist/blob/116d46aacc/lib/linguist/languages.yml#L3221-L3231
            command find -- . \
              -name '*.md' -o \
              -name '*.markdown' -o \
              -name '*.mdown' -o \
              -name '*.mdwn' -o \
              -name '*.mdx' -o \
              -name '*.mkd' -o \
              -name '*.mkdn' -o \
              -name '*.mkdown' -o \
              -name '*.ronn' -o \
              -name '*.scd' -o \
              -name '*.workbook'
          ) >'./codesnippets_code'

          # Print the code blocks.
          while read -r line; do
            printf '%s\n' "${line-}"
          done <'./codesnippets_code'

          # Run shellcheck on the extracted code blocks
          # and this test script itself.

          # SC1071: allow shell directives outside sh, bash, ksh, dash
          # SC1090: allow linking to a dynamic location
          # SC1091: allow linking to, but not following, linked scripts
          # SC2123: allow `PATH=...`
          # SC2312: allow masking of return values
          command shellcheck \
            --exclude="SC1071,SC1090,SC1091,SC2123,SC2312" \
            --wiki-link-count="$(command getconf UINT_MAX)" \
            --check-sourced \
            --enable=all \
            --source-path=/dev/null \
            --external-sources \
            --include="" \
            --shell=bash \
            --severity=style \
            --norc \
            --color=always \
            -- \
            ./codesnippets_code \
            "$0" ||
            exit 1
...