This is a GitHub Action that uses (by default) coqorg/coq Docker images, which in turn is based on coqorg/base, a Docker image with a Debian environment.

For more details about these images, see the docker-coq wiki.

The docker-coq-action provides built-in support for opam builds.

coq is built on-top of ocaml and so coq projects use ocaml's package manager (opam) to build themselves. This GitHub Action supports opam out of the box. If your project does not already have a coq-….opam file, you might generate one such file by using the corresponding template gathered in coq-community/templates.

This .opam file can then serve as a basis for submitting releases in coq/opam-coq-archive, and related guidelines (including the required .opam metadata) are available in https://coq.inria.fr/opam-packaging.html.

More details can be found in the opam documentation.

Assuming the Git repository contains a folder/coq-proj.opam file, it will run (by default) the following commands:

opam config list; opam repo list; opam list
sudo apt-get update -y -q
opam pin add -n -y -k path coq-proj folder
opam update -y
opam install --confirm-level=unsafe-yes -j 2 coq-proj --deps-only
opam list
opam install -y -v -j 2 coq-proj
opam list
opam remove coq-proj

The apt-get command and the --confirm-level=unsafe-yes opam option are necessary for automatic installation of system packages that may be required by coq-proj.opam, as described in the opam 2.1 release notes.

Using a GitHub Action in your GitHub repository amounts to committing a file .github/workflows/your-workflow-name.yml, e.g. .github/workflows/build.yml, containing (among others), a snippet such as:

runs-on: ubuntu-latest  # container actions require GNU/Linux
strategy:
  matrix:
    coq_version:
      - '8.16'
      - dev
    ocaml_version: ['default']
  fail-fast: false  # don't stop jobs if one fails
steps:
  - uses: actions/checkout@v2
  - uses: coq-community/docker-coq-action@v1
    with:
      opam_file: 'folder/coq-proj.opam'
      coq_version: ${{ matrix.coq_version }}
      ocaml_version: ${{ matrix.ocaml_version }}

Each field can be customized, see below for the documentation of those specific to the docker-coq-action, or the GitHub Actions official documentation for the standard fields involved in workflows.

For details, see also:

• the action.yml file (containing the metadata processed by the GitHub Actions platform itself, as well as some comments, albeit more terse than the documentation below);
• the accompanying coq-demo example repo;
• the two workflows coq-demo.yml and python-demo.yml that both serve as docker-coq-action's CI test-suite and provide some examples of use.

The Git repo of docker-coq-action uses master as developing branch and v1 as release branch; and the corresponding tags v1.x.y follow semantic versioning.

We develop docker-coq-action with a special focus on backward compatibility, so that if your workflow just uses coq-community/docker-coq-action@v1, you will be able to benefit from new features, while expecting no breaking change.

However, we recall that the version of any GitHub Action can just as well be referenced by a tag or a commit SHA.

Contrary to some custom practice of GitHub Actions maintainers, we do not change to which commit a tag points once it is published. As a result, the latest stable version denoted by the short Git reference v1 is implemented as a release branch, not as a tag. Anyway, if you do not trust the maintainers of a given GitHub Action, it is always safer to reference a commit SHA.

Optional

The path of the .opam file (or a directory), relative to the repo root.

Default: "." (if the argument is omitted or an empty string).

Note-1: relying on the value of this INPUT_OPAM_FILE variable, the following two variables are exported when running the custom_script:

if [ -z "$INPUT_OPAM_FILE" ] || [ -d "$INPUT_OPAM_FILE" ]; then
    WORKDIR=""
    PACKAGE=${INPUT_OPAM_FILE:-.}
else
    WORKDIR=$(dirname "$INPUT_OPAM_FILE")
    PACKAGE=$(basename "$INPUT_OPAM_FILE" .opam)
fi

Note-2: if this value is a directory (e.g., .), relying on the custom_script default value, the action will install all the *.opam packages stored in this directory.

Optional

The version of Coq. E.g., "8.10".

Default: "latest" (= latest stable version).

Append the -native suffix if the version is >= 8.13 (or dev) and you are interested in the image that contains the coq-native package. E.g., "8.13-native", "latest-native", "dev-native".

If the coq_version value contains the -native suffix, the ocaml_version value is ignored (as coq-native images only come with a single OCaml version). Still, a warning is raised if ocaml_version is nonempty and different from "default".

Optional

The version of OCaml.

Default: "default" (= Docker-Coq's default OCaml version for the given Coq version).

Among "default", "4.02", "4.05", "4.07-flambda", "4.08-flambda", "4.09-flambda", "4.10-flambda", "4.11-flambda", "4.12-flambda", "4.13-flambda", "4.14-flambda"…

Warning! not all OCaml versions are available with all Coq versions.

The supported compilers w.r.t. each version of Coq are documented in the OCaml-versions policy section of the docker-coq wiki.

Optional

The bash snippet to run before install

Default:

startGroup "Print opam config"
  opam config list; opam repo list; opam list
endGroup

See custom_script and startGroup/endGroup for more details.

Optional

The bash snippet to install the opam PACKAGE dependencies.

Default:

startGroup "Install dependencies"
  sudo apt-get update -y -q
  opam pin add -n -y -k path $PACKAGE $WORKDIR
  opam update -y
  opam install --confirm-level=unsafe-yes -j 2 $PACKAGE --deps-only
endGroup

where $PACKAGE and $WORKDIR are set from the opam_file variable.

See custom_script and startGroup/endGroup for more details.

Optional

The bash snippet to run after install (if successful).

Default:

startGroup "List installed packages"
  opam list
endGroup

See custom_script and startGroup/endGroup for more details.

Optional

The bash snippet to run before script.

Default: "" (empty string).

See custom_script and startGroup/endGroup for more details.

Optional

The bash snippet to install the opam PACKAGE.

Default:

startGroup "Build"
  opam install -y -v -j 2 $PACKAGE
  opam list
endGroup

where $PACKAGE is set from the opam_file variable.

See custom_script and startGroup/endGroup for more details.

Optional

The bash snippet to run after script (if successful).

Default: "" (empty string).

See custom_script and startGroup/endGroup for more details.

Optional

The bash snippet to uninstall the opam PACKAGE.

Default:

startGroup "Uninstallation test"
  opam remove $PACKAGE
endGroup

where $PACKAGE is set from the opam_file variable.

See custom_script and startGroup/endGroup for more details.

Optional

The main script run in the container; may be overridden; but overriding more specific parts of the script is preferred.

Default:

{{before_install}}
{{install}}
{{after_install}}
{{before_script}}
{{script}}
{{after_script}}
{{uninstall}}

Note-1: the semantics of this variable is a standard Bash script, that is evaluated within the workflow container after replacing the "mustache" placeholders with the value of their variable counterpart. For example, {{uninstall}} will be replaced with the value of the uninstall variable (the default value of which being the string opam remove $PACKAGE).

Note-2: this option is named custom_script rather than run or so to discourage changing its recommended, default value for building a regular opam project, while keeping the flexibility to be able to change it.

Note-3: if you decide to override the custom_script value anyway, you can just as well rely on the "mustache interpolation" of {{before_install}} … {{uninstall}}, and customize the underlying values.

Optional

The name of the Docker image to pull.

Default: unset

If this variable is unset, its value is computed from the values of keywords coq_version and ocaml_version.

If you use the standard docker-coq images, we recommend to directly use keywords coq_version and ocaml_version.

If you use another registry such as that of docker-mathcomp images, you can benefit from that keyword by writing a configuration such as:

runs-on: ubuntu-latest
strategy:
  matrix:
    image:
      - mathcomp/mathcomp:1.10.0-coq-8.10
      - mathcomp/mathcomp:1.10.0-coq-8.11
      - mathcomp/mathcomp:1.11.0-coq-dev
      - mathcomp/mathcomp-dev:coq-dev
  fail-fast: false  # don't stop jobs if one fails
steps:
  - uses: actions/checkout@v2
  - uses: coq-community/docker-coq-action@v1
    with:
      opam_file: 'folder/coq-proj.opam'
      custom_image: ${{ matrix.image }}

Optional

A space-separated list of env variables to export to the custom_script.

Default: "", i.e., no additional variable is exported.

Note-1: The values of the variables to export may be defined by using the env keyword.

Note-2: Regarding the naming of these variables:

• Only use ASCII letters, _ and digits, i.e., matching the [a-zA-Z_][a-zA-Z0-9_]* regexp.
• Avoid reserved identifiers (namely: HOME, CI, and strings starting with GITHUB_, ACTIONS_, RUNNER_, or INPUT_).

Here is a minimal working example of this feature:

runs-on: ubuntu-latest
steps:
  - uses: actions/checkout@v2
  - uses: coq-community/docker-coq-action@v1
    with:
      opam_file: 'folder/coq-proj.opam'
      coq_version: 'dev'
      ocaml_version: 'default'
      export: 'OPAMWITHTEST'  # space-separated list of variables
    env:
      OPAMWITHTEST: 'true'

Here, setting the OPAMWITHTEST environment variable is useful to run the unit tests (specified using opam's with-test clause) after the package build.

The default value of fields {{before_install}}, {{install}}, {{after_install}}, {{script}}, and {{uninstall}} involves the bash functions startGroup (taking 1 argument: startGroup "Group title") and endGroup.

These bash functions are defined in timegroup.sh and have the following features:

• they create foldable groups in the GitHub Actions logs (see the online doc),
• and they compute the elapsed time for the considered group;
• these groups cannot be nested,
• and if an endGroup has been forgotten, it is implicitly and automatically inserted at the next startGroup (albeit it is better to make each endGroup explicit, for readability).

Here is an example of script along with the output log so obtained:

ex_var="ex_value"
# […]

startGroup "Toy example"
  echo "ex_var=$ex_var"
endGroup

• Folded version:

  

• Unfolded version:

  

Beware that the following script is buggy:

script: |
  startGroup "Build project"
    make -j2 && make test && make install
  endGroup

Because if make test fails, it won't make the CI fail.

bash -c 'set -e; false && true; echo $?; echo this should not be run'
# → 1
# → this should not be run

bash -c 'set -e; false; true; echo $?; echo this should not be run'
# (no output)

bash -c 'set -e; ( false && true ); echo $?; echo this should not be run'
# (no output)

Instead, you should write one of the following variants:

• using semicolons:

  script: |
    startGroup "Build project"
      make -j2 ; make test ; make install
    endGroup

• using newlines:

  script: |
    startGroup "Build project"
      make -j2
      make test
      make install
    endGroup

• using && but within a subshell:

  script: |
    startGroup "Build project"
      ( make -j2 && make test && make install )
    endGroup

If you use the docker-coq images, the container user has UID=GID=1000 while the GitHub Actions workdir has (UID=1001, GID=116). This is not an issue when relying on opam to build the Coq project. Otherwise, you may want to use sudo in the container to change the permissions. You may also install additional Debian packages (see the dedicated section below).

Typically, this would lead to a workflow specification like this:

runs-on: ubuntu-latest
strategy:
  matrix:
    image:
      - 'coqorg/coq:dev'
  fail-fast: false  # don't stop jobs if one fails
steps:
  - uses: actions/checkout@v2
  - uses: coq-community/docker-coq-action@v1
    with:
      opam_file: 'folder/coq-proj.opam'
      custom_image: ${{ matrix.image }}
      before_script: |
        startGroup "Workaround permission issue"
          sudo chown -R coq:coq .  # <--
        endGroup
      script: |
        startGroup "Build project"
          make -j2
        endGroup
      uninstall: |
        startGroup "Clean project"
          make clean
        endGroup
  - name: Revert permissions
    # to avoid a warning at cleanup time
    if: ${{ always() }}
    run: sudo chown -R 1001:116 .  # <--

For more details, see the CI setup / Remarks section in the docker-coq wiki.

The docker-coq-action and its "child" Docker image (specified by the custom_image field) run inside a container, which implies the associated filesystem is isolated from the runner.

However, the GitHub workspace directory is made available in the container (using a so-called bind-mount) and set as the current working directory.

As a result:

• all the files installed outside of this GitHub workspace directory (such as opam packages installed in /home/coq/.opam) are "lost" when docker-coq-action terminates;
• all the files put in the GitHub workspace directory (or in a sub-directory) are kept;
  so it is possible to create artifacts, then use an action such as actions/upload-artifact@v2 in a subsequent step.

Here is an example job for this use case, which also takes into account the previously-mentioned permissions workaround:

runs-on: ubuntu-latest
strategy:
  matrix:
    image:
      - 'coqorg/coq:dev'
  fail-fast: false  # don't stop jobs if one fails
    steps:
      - uses: coq-community/docker-coq-action@v1
        with:
          opam_file: 'folder/coq-proj.opam'
          custom_image: ${{ matrix.image }}
          before_script: |
            startGroup "Workaround permission issue"
              sudo chown -R coq:coq .
            endGroup
          script: |
            startGroup "Build project"
              coq_makefile -f _CoqProject -o Makefile
              make -j2
            endGroup
          after_script: |
            set -o pipefail  # recommended if the script uses pipes

            startGroup "Build artifacts"
              mkdir -v -p artifacts
              opam list > artifacts/opam_list.txt
              make test 2>&1 | tee artifacts/make_test.txt
            endGroup
          uninstall: ''
      - name: Revert permissions
        # to avoid a warning at cleanup time
        if: ${{ always() }}
        run: sudo chown -R 1001:116 .
      - uses: actions/upload-artifact@v2
        with:
          name: example-artifact
          path: artifacts/
          if-no-files-found: error  # 'warn' or 'ignore' are also available, defaults to `warn`
          retention-days: 8

If you use docker-coq-action with a Docker-Coq image (the default when the custom_image field is omitted), the image is based on Debian stable and the container user (UID=GID=1000) has sudo rights, so you can rely on apt-get to install additional Debian packages.

This use case is illustrated by the following job that installs the emacs and tree packages:

runs-on: ubuntu-latest
strategy:
  matrix:
    image:
      - 'coqorg/coq:dev'
  fail-fast: false  # don't stop jobs if one fails
steps:
  - uses: actions/checkout@v2
  - uses: coq-community/docker-coq-action@v1
    with:
      opam_file: 'folder/coq-proj.opam'
      custom_image: ${{ matrix.image }}
      before_script: |
        startGroup "Install APT dependencies"
          cat /etc/os-release  # Print the Debian OS version
          # sudo apt-get update -y -q # this mandatory command is already run in install step by default
          sudo DEBIAN_FRONTEND=noninteractive apt-get install -y -q --no-install-recommends \
            emacs \
            tree  # for instance
            # Alphabetical order is recommended for long package lists to ease review and update
        endGroup
      after_script: |
        startGroup "Post-test"
          emacs --version
          tree
        endGroup

The code run in the docker-coq-action container relies on the following invocation to display a customized prompt before each command:

export PS4='+ \e[33;1m($0 @ line $LINENO) \$\e[0m '; set -ex

As a result, due to the set -x option, the value of each variable is exposed in the log.

For example, the script:

startGroup "Risky example"
  TOKEN=$(uuidgen -r)
  curl -fsS -X POST -F token="$TOKEN" https://example.com >/dev/null
endGroup

will produce a log such as:

Hence the following two remarks:

1. If need be, it is possible to temporarily disable the trace feature in your script, surrounding the lines at stake by (set +x, set -x).
   Your script would thus look like:

   set +x
   
   #...some code with no trace...
   
   set -x

   or, to get some even less verbose output:

   { set +x; } 2>/dev/null
   
   #...some code with no trace...
   
   set -x

2. Fortunately, this trace feature cannot make repository secrets ${{ secrets.STH }} leak, as GitHub Actions automatically redact them in the log.
   Regarding secrets obtained by other means, e.g. from a command-line program, it is recommended to perform the three actions below in a previous run: step:

   • store the "locally-created secret" in an environment variable:

     SOME_TOKEN="..."

   • immediately mark the variable as masked:

     echo "::add-mask::$SOME_TOKEN"

   • register the variable to make it available for subsequent steps:

     printf "%s\n" "SOME_TOKEN=$(printf "%q" "$SOME_TOKEN")" >> $GITHUB_ENV

   A comprehensive example of this approach is available in PR erikmd/docker-coq-github-action-demo#12.

   For completeness, note that masking inputs involved in workflow_dispatch may require some jq-based workaround, as mentioned in issue actions/runner#643.