8.4 Escrevendo manifestos

guix commands let you specify package lists on the command line. This is convenient, but as the command line becomes longer and less trivial, it quickly becomes more convenient to have that package list in what we call a manifest. A manifest is some sort of a “bill of materials” that defines a package set. You would typically come up with a code snippet that builds the manifest, store it in a file, say manifest.scm, and then pass that file to the -m (or --manifest) option that many guix commands support. For example, here’s what a manifest for a simple package set might look like:

;; Manifest for three packages.
(specifications->manifest '("gcc-toolchain" "make" "git"))

Once you have that manifest, you can pass it, for example, to guix package to install just those three packages to your profile (veja -m option of guix package):

guix package -m manifest.scm

... or you can pass it to guix shell (veja -m option of guix shell) to spawn an ephemeral environment:

guix shell -m manifest.scm

... or you can pass it to guix pack in pretty much the same way (veja -m option of guix pack). You can store the manifest under version control, share it with others so they can easily get set up, etc.

But how do you write your first manifest? To get started, maybe you’ll want to write a manifest that mirrors what you already have in a profile. Rather than start from a blank page, guix package can generate a manifest for you (veja guix package --export-manifest):

# Write to 'manifest.scm' a manifest corresponding to the
# default profile, ~/.guix-profile.
guix package --export-manifest > manifest.scm

Or maybe you’ll want to “translate” command-line arguments into a manifest. In that case, guix shell can help (veja guix shell --export-manifest):

# Write a manifest for the packages specified on the command line.
guix shell --export-manifest gcc-toolchain make git > manifest.scm

In both cases, the --export-manifest option tries hard to generate a faithful manifest; in particular, it takes package transformation options into account (veja Opções de transformação de pacote).

Nota: Manifests are symbolic: they refer to packages of the channels currently in use (veja Canais). In the example above, gcc-toolchain might refer to version 11 today, but it might refer to version 13 two years from now.

If you want to “pin” your software environment to specific package versions and variants, you need an additional piece of information: the list of channel revisions in use, as returned by guix describe. Veja Replicando Guix, for more information.

Once you’ve obtained your first manifest, perhaps you’ll want to customize it. Since your manifest is code, you now have access to all the Guix programming interfaces!

Let’s assume you want a manifest to deploy a custom variant of GDB, the GNU Debugger, that does not depend on Guile, together with another package. Building on the example seen in the previous section (veja Definindo variantes de pacote), you can write a manifest along these lines:

(use-modules (guix packages)
             (gnu packages gdb)               ;for 'gdb'
             (gnu packages version-control))  ;for 'git'

;; Define a variant of GDB without a dependency on Guile.
(define gdb-sans-guile
  (package
    (inherit gdb)
    (inputs (modify-inputs (package-inputs gdb)
              (delete "guile")))))

;; Return a manifest containing that one package plus Git.
(packages->manifest (list gdb-sans-guile git))

Note that in this example, the manifest directly refers to the gdb and git variables, which are bound to a package object (veja package Reference), instead of calling specifications->manifest to look up packages by name as we did before. The use-modules form at the top lets us access the core package interface (veja Definindo pacotes) and the modules that define gdb and git (veja Módulos de pacote). Seamlessly, we’re weaving all this together—the possibilities are endless, unleash your creativity!

The data type for manifests as well as supporting procedures are defined in the (guix profiles) module, which is automatically available to code passed to -m. The reference follows.

Data Type: manifest

Data type representing a manifest.

It currently has one field:

entries

This must be a list of manifest-entry records—see below.

Data Type: manifest-entry

Data type representing a manifest entry. A manifest entry contains essential metadata: a name and version string, the object (usually a package) for that entry, the desired output (veja Pacotes com múltiplas saídas), and a number of optional pieces of information detailed below.

Most of the time, you won’t build a manifest entry directly; instead, you will pass a package to package->manifest-entry, described below. In some unusual cases though, you might want to create manifest entries for things that are not packages, as in this example:

;; Manually build a single manifest entry for a non-package object.
(let ((hello (program-file "hello" #~(display "Hi!"))))
  (manifest-entry
    (name "foo")
    (version "42")
    (item
     (computed-file "hello-directory"
                     #~(let ((bin (string-append #$output "/bin")))
                         (mkdir #$output) (mkdir bin)
                          (symlink #$hello
                                   (string-append bin "/hello")))))))

The available fields are the following:

name

version

Name and version string for this entry.

item

A package or other file-like object (veja file-like objects).

output (default: "out")

Output of item to use, in case item has multiple outputs (veja Pacotes com múltiplas saídas).

dependencies (default: '())

List of manifest entries this entry depends on. When building a profile, dependencies are added to the profile.

Typically, the propagated inputs of a package (veja propagated-inputs) end up having a corresponding manifest entry in among the dependencies of the package’s own manifest entry.

search-paths (default: '())

The list of search path specifications honored by this entry (veja Caminhos de pesquisa).

properties (default: '())

List of symbol/value pairs. When building a profile, those properties get serialized.

This can be used to piggyback additional metadata—e.g., the transformations applied to a package (veja Opções de transformação de pacote).

parent (default: (delay #f))

A promise pointing to the “parent” manifest entry.

This is used as a hint to provide context when reporting an error related to a manifest entry coming from a dependencies field.

Procedure: concatenate-manifests lst

Concatenate the manifests listed in lst and return the resulting manifest.

Procedure: package->manifest-entry package [output] [#:properties]

Return a manifest entry for the output of package package, where output defaults to "out", and with the given properties. By default properties is the empty list or, if one or more package transformations were applied to package, it is an association list representing those transformations, suitable as an argument to options->transformation (veja options->transformation).

The code snippet below builds a manifest with an entry for the default output and the send-email output of the git package:

(use-modules (gnu packages version-control))

(manifest (list (package->manifest-entry git)
                (package->manifest-entry git "send-email")))

Procedure: packages->manifest packages

Return a list of manifest entries, one for each item listed in packages. Elements of packages can be either package objects or package/string tuples denoting a specific output of a package.

Using this procedure, the manifest above may be rewritten more concisely:

(use-modules (gnu packages version-control))

(packages->manifest (list git `(,git "send-email")))

Procedure: package->development-manifest package [system] [#:target]

Return a manifest for the development inputs of package for system, optionally when cross-compiling to target. Development inputs include both explicit and implicit inputs of package.

Like the -D option of guix shell (veja guix shell -D), the resulting manifest describes the environment in which one can develop package. For example, suppose you’re willing to set up a development environment for Inkscape, with the addition of Git for version control; you can describe that “bill of materials” with the following manifest:

(use-modules (gnu packages inkscape)          ;for 'inkscape'
             (gnu packages version-control))  ;for 'git'

(concatenate-manifests
 (list (package->development-manifest inkscape)
       (packages->manifest (list git))))

In this example, the development manifest that package->development-manifest returns includes the compiler (GCC), the many supporting libraries (Boost, GLib, GTK, etc.), and a couple of additional development tools—these are the dependencies guix show inkscape lists.

Last, the (gnu packages) module provides higher-level facilities to build manifests. In particular, it lets you look up packages by name—see below.

Procedure: specifications->manifest specs

Given specs, a list of specifications such as "emacs@25.2" or "guile:debug", return a manifest. Specs have the format that command-line tools such as guix install and guix package understand (veja Invocando guix package).

As an example, it lets you rewrite the Git manifest that we saw earlier like this:

(specifications->manifest '("git" "git:send-email"))

Notice that we do not need to worry about use-modules, importing the right set of modules, and referring to the right variables. Instead, we directly refer to packages in the same way as on the command line, which can often be more convenient.