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Information for external library / Coq plugin authors

You are encouraged to consider submitting your project for addition to Coq's CI. This means that:

  • Any time that a proposed change is breaking your project, Coq developers and contributors will send you patches to adapt it or will explain how to adapt it and work with you to ensure that you manage to do it.

On the condition that:

  • At the time of the submission, your project works with Coq's master branch.

  • Your project is publicly available in a git repository and we can easily send patches to you (e.g. through pull / merge requests).

  • You react in a timely manner to discuss / integrate those patches. When seeking your help for preparing such patches, we will accept that it takes longer than when we are just requesting to integrate a simple (and already fully prepared) patch.

  • You do not push, to the branches that we test, commits that haven't been first tested to compile with the corresponding branch(es) of Coq.

    For that, we recommend setting a CI system for you project, see supported CI images for Coq below.

  • You maintain a reasonable build time for your project, or you provide a "lite" target that we can use.

  • You keep points-of-contact up to date.

In case you forget to comply with these last four conditions, we would reach out to you and give you a 30-day grace period during which your project would be moved into our "allow failure" category. At the end of the grace period, in the absence of progress, the project would be removed from our CI.

Timely merging of overlays

A pitfall of the current CI setup is that when a breaking change is merged in Coq upstream, CI for your contrib will be broken until you merge the corresponding pull request with the fix for your contribution.

As of today, you have to worry about synchronizing with Coq upstream every once in a while; we hope we will improve this in the future by using coqbot; meanwhile, a workaround is to give merge permissions to someone from the Coq team as to help with these kind of merges.

OCaml and plugin-specific considerations

Projects that link against Coq's OCaml API [most of them are known as "plugins"] do have some special requirements:

  • Coq's OCaml API is not stable. We hope to improve this in the future but as of today you should expect to have to merge a fair amount of "overlays", usually in the form of Pull Requests from Coq developers in order to keep your plugin compatible with Coq master.

    In order to alleviate the load, you can delegate the merging of such compatibility pull requests to Coq developers themselves, by granting access to the plugin repository or by using bots such as Bors that allow for automatic management of Pull Requests.

  • Plugins in the CI should compile with the OCaml flags that Coq uses. In particular, warnings that are considered fatal by the Coq developers must be also fatal for plugin CI code.

Add your project by submitting a pull request

Add a new ci-mydev.sh script to dev/ci; set the corresponding variables in ci-basic-overlay.sh; add the corresponding target to Makefile.ci and a new job to .gitlab-ci.yml so that this new target is run. Have a look at #17241 for an example. Do not hesitate to submit an incomplete pull request if you need help to finish it.

Some important points:

  • Mention one or a few points of contact in ci-basic-overlay.sh.

  • Let $job be the name of the new job as used for the name of the added script file dev/ci/ci-$job.sh. Then the added target in Makefile.ci must be named ci-$job and the added job in .gitlab-ci.yml must be named library:$job or plugin:$job. $job must be a valid shell variable name, typically this means replacing dashs (-) with underscores (_).

  • Let $project be the name of your project as used for the first argument to project in ci-basic-overlay.sh. Usually this is the same as $job in the above bullet. It must also be a valid shell variable name. In some cases a script will handle multiple source repositories and so will need multiple $project, see for instance script verdi_raft.

  • If you wish to run a test suite for your project which takes non-negligible time, it may be useful to run the test suite in a separate Makefile.ci target and GitLab job, using a separate shell script. In terms of the above bullet points this means a $project used in multiple $jobs. See for instance mathcomp and mathcomp_test.

  • When declaring the job in .gitlab-ci.yml you must choose the opam switch by using extends: .ci-template or extends: .ci-template-flambda.

    The first one uses the minimum version of OCaml supported by Coq. The second one uses the highest version of OCaml supported by Coq, with flambda enabled (currently it actually uses OCaml 4.14.1 as 5.0 has significant performance issues). See also the corresponding Dockerfiles to find out what specific packages are available in each switch.

    If your job depends on other jobs, you must use the same opam switch. If you wish to depend on jobs currently declared in separate switches, please open a draft pull request and the Coq developers will decide which jobs should change switches. If you need an exception to this rule for some other reason, please discuss with the Coq developers.

  • Job dependencies are declared in 2 places: Makefile.ci using the usual Makefile syntax, and .gitlab-ci.yml using needs. If you only depend on Coq itself the implicit needs from the template suffices. Otherwise the needs list must include build:base or build:edge+flambda (depending on the switch you chose). See for instance the declaration for library:ci-analysis.

  • If you depend on more than Coq itself you must specify the stage: build-2 if all your dependencies depend only on Coq itself, otherwise build-3+ (the number is the max depth of the dependency chain, with Coq itself at 0 and the default from the template at 1).

  • If needed you can disable native compilation by doing export COQEXTRAFLAGS='-native-compiler no' before the build commands in the script file. If any of your dependencies disable native compilation you must do the same.

You may also be interested in having your project tested in our performance benchmark. Currently this is done by providing a .dev OPAM package in https://github.com/coq/opam-coq-archive and opening an issue at https://github.com/coq/coq/issues.

Recommended branching policy.

It is sometimes the case that you will need to maintain a branch of your project for particular Coq versions. This is in fact very likely if your project includes a Coq ML plugin.

For such projects, we recommend a branching convention that mirrors Coq's branching policy. Then, you would have a master branch that follows Coq's master, a v8.8 branch that works with Coq's v8.8 branch and so on.

This convention will be supported by tools in the future to make some developer commands work more seamlessly.

Supported CI images for Coq

The Coq developers and contributors provide official Docker and Nix images for testing against Coq master. Using these images is highly recommended: