The Coq derivation is overridable through the `coq.override overrides`, where overrides is an attribute set which contains the arguments to override. We recommend overriding either of the following
*`version` (optional, defaults to the latest version of Coq selected for nixpkgs, see `pkgs/top-level/coq-packages` to witness this choice), which follows the conventions explained in the `coqPackages` section below,
*`customOCamlPackage` (optional, defaults to `null`, which lets Coq choose a version automatically), which can be set to any of the ocaml packages attribute of `ocaml-ng` (such as `ocaml-ng.ocamlPackages_4_10` which is the default for Coq 8.11 for example).
*`coq-version` (optional, defaults to the short version e.g. "8.10"), is a version number of the form "x.y" that indicates which Coq's version build behavior to mimic when using a source which is not a release. E.g. `coq.override { version = "d370a9d1328a4e1cdb9d02ee032f605a9d94ec7a"; coq-version = "8.10"; }`.
The recommended way of defining a derivation for a Coq library, is to use the `coqPackages.mkCoqDerivation` function, which is essentially a specialization of `mkDerivation` taking into account most of the specifics of Coq libraries. The following attributes are supported:
* if it is a known released version string, i.e. from the `release` attribute below, the according release is picked, and the `version` attribute of the resulting derivation is set to this release string,
* if it is a majorMinor `"x.y"` prefix of a known released version (as defined above), then the latest `"x.y.z"` known released version is selected (for the ordering given by `versionAtLeast`),
* if it is a path or a string representing an absolute path (i.e. starting with `"/"`), the provided path is selected as a source, and the `version` attribute of the resulting derivation is set to `"dev"`,
* if it is a string of the form `owner:branch` then it tries to download the `branch` of owner `owner` for a project of the same name using the same vcs, and the `version` attribute of the resulting derivation is set to `"dev"`, additionally if the owner is not provided (i.e. if the `owner:` prefix is missing), it defaults to the original owner of the package (see below),
* if it is a string of the form `"#N"`, and the domain is github, then it tries to download the current head of the pull request `#N` from github,
*`defaultVersion` (optional). Coq libraries may be compatible with some specific versions of Coq only. The `defaultVersion` attribute is used when no `version` is provided (or if `version = null`) to select the version of the library to use by default, depending on the context. This selection will mainly depend on a `coq` version number but also possibly on other packages versions (e.g. `mathcomp`). If its value ends up to be `null`, the package is marked for removal in end-user `coqPackages` attribute set.
*`release` (optional, defaults to `{}`), lists all the known releases of the library and for each of them provides an attribute set with at least a `sha256` attribute (you may use the shell command `nix-prefetch-url --unpack <archive-url>` to find it, where `<archive-url>` is for example `https://github.com/owner/repo/archive/version.tar.gz`), each attribute set of the list of releases also takes optional overloading arguments for the fetcher as below (i.e.`domain`, `owner`, `repo`, `rev` assuming the default fetcher is used) and optional overrides for the result of the fetcher (i.e. `version` and `src`).
*`fetcher` (optional, default to a generic fetching mechanism supporting github or gitlab based infrastructures), is a function that takes at least an `owner`, a `repo`, a `rev`, and a `sha256` and returns an attribute set with a `version` and `src`.
*`repo` (optional, defaults to the value of `pname`),
*`owner` (optional, defaults to `"coq-community"`).
*`domain` (optional, defaults to `"github.com"`), domains including the strings `"github"` or `"gitlab"` in their names are automatically supported, otherwise, one must change the `fetcher` argument to support them (cf `pkgs/development/coq-modules/heq/default.nix` for an example),
*`releaseRev` (optional, defaults to `(v: v)`), provides a default mapping from release names to revision hashes/branch names/tags,
*`displayVersion` (optional), provides a way to alter the computation of `name` from `pname`, by explaining how to display version numbers,
*`namePrefix` (optional), provides a way to alter the computation of `name` from `pname`, by explaining which dependencies must occur in `name`,
*`extraBuildInputs` (optional), by default `buildInputs` just contains `coq`, this allows to add more build inputs,
*`mlPlugin` (optional, defaults to `false`). Some extensions (plugins) might require OCaml and sometimes other OCaml packages. Standard dependencies can be added by setting the current option to `true`. For a finer grain control, the `coq.ocamlPackages` attribute can be used in `extraBuildInputs` to depend on the same package set Coq was built against.
*`enableParallelBuilding` (optional, defaults to `true`), since it is activated by default, we provide a way to disable it.
*`extraInstallFlags` (optional), allows to extend `installFlags` which initializes the variable `COQMF_COQLIB` so as to install in the proper subdirectory. Indeed Coq libraries should be installed in `$(out)/lib/coq/${coq.coq-version}/user-contrib/`. Such directories are automatically added to the `$COQPATH` environment variable by the hook defined in the Coq derivation.
*`setCOQBIN` (optional, defaults to `true`), by default, the environment variable `$COQBIN` is set to the current Coq's binary, but one can disable this behavior by setting it to `false`,
*`useMelquiondRemake` (optional, default to `null`) is an attribute set, which, if given, overloads the `preConfigurePhases`, `configureFlags`, `buildPhase`, and `installPhase` attributes of the derivation for a specific use in libraries using `remake` as set up by Guillaume Melquiond for `flocq`, `gappalib`, `interval`, and `coquelicot` (see the corresponding derivation for concrete examples of use of this option). For backward compatibility, the attribute `useMelquiondRemake.logpath` must be set to the logical root of the library (otherwise, one can pass `useMelquiondRemake = {}` to activate this without backward compatibility).
*`dropAttrs`, `keepAttrs`, `dropDerivationAttrs` are all optional and allow to tune which attribute is added or removed from the final call to `mkDerivation`.
It also takes other standard `mkDerivation` attributes, they are added as such, except for `meta` which extends an automatically computed `meta` (where the `platform` is the same as `coq` and the homepage is automatically computed).
Here is a simple package example. It is a pure Coq library, thus it depends on Coq. It builds on the Mathematical Components library, thus it also takes some `mathcomp` derivations as `extraBuildInputs`.
