composer2nix

composer2nix is a tool that can be used to generate Nix expressions for PHP composer packages.

Nix integration makes it possible to use the Nix package manager (as opposed to composer) to deploy PHP packages including all their required dependencies.

In addition, generated Nix composer packages support convenient integration of PHP applications with NixOS services, such as NixOS' Apache HTTP service.

Prerequisites

This package requires the following packages to be installed:

Nix package manager
The Nix prefetch scripts. They can be installed from Nix packages by running:

$ nix-env -f '<nixpkgs>' -iA nix-prefetch-scripts

Consult the Nix documentation for detailed installation instructions.

Installation

This package can be installed with both composer and the Nix package manager. To install it with composer, run:

$ composer global require svanderburg/composer2nix

To install this package with Nix, clone the Git repository and run:

$ nix-env -f release.nix -iA package.x86_64-linux

Building a development version

A development version can be deployed by checking out the Git repository and running:

$ nix-env -f release.nix -iA package.x86_64-linux

The above command installs the development composer2nix executable into the Nix profile of the user.

Alternatively, you can use composer directly to install the project dependencies:

$ composer install

Usage

You need a project providing a composer.json and (if applicable) a composer.lock configuration file.

Running the following command generates Nix expressions from the composer configuration files:

$ composer2nix

The above command produces three expressions: php-packages.nix containing the dependencies, composer-env.nix the build infrastructure and default.nix that can be used to compose the package from its dependencies.

Running the following command-line instruction deploys the package with Nix including its dependencies:

$ nix-build

Deploying a web application project

We can use composer2nix to automate the deployment of a web application project as part of a NixOS configuration.

For example, we can create the following trivial PHP web application (index.php) that uses the dompdf library to generate a PDF file from an HTML page:

<?php
require 'vendor/autoload.php';

use Dompdf\Dompdf;

$dompdf = new Dompdf();
$dompdf->loadHtml('hello world');

$dompdf->setPaper('A4', 'landscape');
$dompdf->render();

$dompdf->stream();
?>

We can write the following composer.json configuration file to configure the dompdf dependency:

{
    "name": "exampleapp/exampleapp",

    "require": {
        "dompdf/dompdf": "^0.8.0"
    }
}

With the following commmand we can let composer deploy the dependencies (and pinpoint the used versions in a composer.lock file):

$ composer install

Instead, we can also use composer2nix:

$ composer2nix

The above command generates Nix expressions that can be used to deploy the web application and its dependencies.

We can use Nix to build a bundle of our web application including its dependencies:

$ nix-build
$ ls result/
index.php  vendor/

(As may be observed, the vendor/ folder contains all dependency artifacts).

We can attach the generated package to a document root of the Apache server in a NixOS configuration:

{pkgs, config, ...}:

let
  myexampleapp = import /home/sander/myexampleapp {
    inherit pkgs;
  };
in
{
  time.timeZone = "UTC";

  services.httpd = {
    enable = true;
    adminAddr = "admin@localhost";
    enablePHP = true;
    documentRoot = myexampleapp;
  };

  ...
}

We can deploy the above NixOS configuration as follows:

$ nixos-rebuild switch

If the above command succeeds, we have a running system with the Apache webserver serving our web application.

Deploying a command-line utility project

In addition to web applications, we can also deploy command-line utility projects implemented in PHP.

For example, for the composer2nix project, we can generate a CLI-specific expression by adding the --executable parameter:

$ composer2nix --executable

We can install the composer2nix executable in our Nix profile by running:

$ nix-env -f default.nix -i

Deploying third-party end user packages

Aside from deploying development projects, we may also want to deploy third party end-user packages, typically command-line tools.

We can use composer2nix to automatically generate expressions from a third party package that comes from Packagist, such as phpunit:

$ composer2nix -p phpunit/phpunit

After generating the expressions, we can deploy phpunit in our Nix profile, by running:

$ nix-env -f default.nix -iA phpunit-phpunit

And after installing the package with Nix, we should be able to run:

$ phpunit --version

By default, composer2nix attempts to download the latest version of a package. We can also add a parameter that specifies the version we want to use:

$ composer2nix -p phpunit/phpunit --package-version 6.2.0

The above command-line instruction deploys phpunit version 6.2.0.

The --package-version parameter supports any version specifier supported by composer, including version ranges.

Advanced features

composer2nix supports a number of less commonly used advanced features.

Disabling the deployment of development dependencies

By default composer (and as a result, also composer2nix) will include all development dependencies. However, in production environments you typically want to exclude them to reduce the amount of disk space consumed and the deployment times.

By overriding the expression (e.g. creating a file named: override.nix) and appending the noDev = true; parameter, we can disable development dependencies:

{pkgs ? import <nixpkgs> {
  inherit system;
}, system ? builtins.currentSystem}:

let
  phpPackage = import ./default.nix {
    inherit pkgs system;
    noDev = true; # Disable development dependencies
  };
in
phpPackage

We can deploy the above package with the following command-line instruction:

$ nix-build override.nix

Removing composer artifacts

By default, when deploying a composer package with Nix it will also include the composer configuration files (composer.json and composer.lock) in the package.

However, for production scenarios, such as deploying a web application, you typically do not need these files. It is also possible to remove these composer configuration files:

{pkgs ? import <nixpkgs> {
  inherit system;
}, system ? builtins.currentSystem}:

let
  phpPackage = import ./default.nix {
    inherit pkgs system;
  };
in
phpPackage.override {
  removeComposerArtifacts = true; # Remove composer configuration files
}

Running post installation instructions

For some packages, we may want to run additional command line instructions after the packaging process completes, such as running unit tests.

By creating an override Nix expression that invokes the generated build function and providing a postInstall hook, we can specify additional command-line instructions to run:

{pkgs ? import <nixpkgs> {
  inherit system;
}, system ? builtins.currentSystem}:

let
  phpPackage = import ./default.nix {
    inherit pkgs system;
  };
in
phpPackage.override {
  postInstall = ''
    php vendor/bin/phpunit tests
  '';
}

In the above code fragment, we invoke phpunit to run all our unit tests.

Adding unspecified dependencies

Some packages may also require non-PHP package dependencies. Since these dependencies are not specified in a composer configuration file, their deployments may typically fail in a Nix builder environment, because they cannot be implicitly found.

By overriding the generated package expression, we can supply these missing dependencies ourselves:

{pkgs ? import <nixpkgs> {
  inherit system;
}, system ? builtins.currentSystem}:

let
  phpPackage = import ./default.nix {
    inherit pkgs system;
  };
in
phpPackage.override {
  buildInputs = [ pkgs.graphviz ];
  postInstall = ''
    php vendor/bin/phpdocumentor -d src -t out
  '';
}

The above expression overrides the generated PHP package by supplying graphviz as an extra dependency. This package is particularly useful when it is desired to use phpdocumentor -- it uses graphviz to generate class diagrams. If this tool is not present in the build environment, class diagrams will not be generated.

Symlinking dependencies

By default, composer2nix makes copies of all packages that end up in the vendor/ folder. This is the default option, because some packages load the autoload.php relative from its resolved location, such as phpunit and may not work properly if a dependency is a symlink.

It is also possible to symlink all dependencies as opposed to copying them which makes deployments faster and more space efficient:

$ composer2nix --symlink-dependencies

Limitations

This tool is still in the prototype stage. As a result, it may have some issues. Furthermore, support for fossil repositories is currently completely absent.

License

The contents of this package is available under the MIT license