## A.41 library(prolog_pack): A package manager for Prolog

See also
  - Installed packages can be inspected using `?- doc_browser.`
  - `library(build/tools)`
To be done
  - Version logic
  - Find and resolve conflicts
  - Upgrade git packages
  - Validate git packages
  - Test packages: run tests from directory‘test'.

The `library(prolog_pack)` provides the SWI-Prolog package manager. This library lets you inspect installed packages, install packages, remove packages, etc. It is complemented by the built-in attach_packs/0 that makes installed packages available as libraries.

To make changes to a package:

- Clone the git repo,t go into the repo and run: `?- pack_install(.).` This builds the pack locally and creates a symlink to make it available.
- `?- pack_rebuild(package_name).` This runs‘make distclean`and` make` with the right environment. It will also write a file `buildendv.sh` that you can source to get the environment for running a normal `make` (this is done only if there is a `configure` step; i.e., if there is a `configure.in` or `configure`.
- The build process also supports `cmake`.

Once you have made the changes, you should edit the `pack.pl` file to change the `version` item. After updating the git repo, issue a `pack_install(package_name, [upgrade(true), test(true), rebuild(make)])` to cause the repository to refresh. You can simulate the full installation process by removing all the build files in the package (including any in submodules), running pack_install/1, and then running pack_install using a `file://` URL.

[det]pack_list_installed
  List currently installed packages. Unlike pack_list/1, only locally installed packages are displayed and no connection is made to the internet.
  See also
    Use pack_list/1 to find packages.
pack_info(+Pack)
  Print more detailed information about Pack.
[det]pack_search(+Query)
[det]pack_list(+Query)
  Query package server and installed packages and display results. Query is matches case-insensitively against the name and title of known and installed packages. For each matching package, a single line is displayed that provides:

  - Installation status

    - p: package, not installed
    - i: installed package; up-to-date with public version
    - U: installed package; can be upgraded
    - A: installed package; newer than publically available
    - l: installed package; not on server

  - Name@Version
  - Name@Version(ServerVersion)
  - Title

  Hint: `?- pack_list('').` lists all packages.

  The predicates pack_list/1 and pack_search/1 are synonyms. Both contact the package server at http://www.swi-prolog.org to find available packages.

  See also
    pack_list_installed/0 to list installed packages without contacting the server.
[det]pack_install(+Spec:atom)
  Install a package. Spec is one of

  - A package name. This queries the package repository at http://www.swi-prolog.org
  - Archive file name
  - HTTP URL of an archive file name. This URL may contain a star (*) for the version. In this case pack_install asks for the directory content and selects the latest version.
  - GIT URL (not well supported yet)
  - A local directory name given as `file://` URL
  - `'.'`, in which case a relative symlink is created to the current directory (all other options for Spec make a copy of the files).

  After resolving the type of package, pack_install/2 is used to do the actual installation.

[det]pack_install(+Name, +Options)
  Install package Name. Processes the options below. Default options as would be used by pack_install/1 are used to complete the provided Options.
  url(+URL)
    Source for downloading the package
  package_directory(+Dir)
    Directory into which to install the package.
  global(+Boolean)
    If `true`, install in the XDG common application data path, making the pack accessible to everyone. If `false`, install in the XDG user application data path, making the pack accessible for the current user only. If the option is absent, use the first existing and writable directory. If that doesn't exist find locations where it can be created and prompt the user to do so.
  insecure(+Boolean)
    When `true` (default `false`), do not perform any checks on SSL certificates when downloading using `https`.
  interactive(+Boolean)
    Use default answer without asking the user if there is a default action.
  silent(+Boolean)
    If `true` (default false), suppress informational progress messages.
  upgrade(+Boolean)
    If `true` (default `false`), upgrade package if it is already installed.
  rebuild(Condition)
    Rebuild the foreign components. Condition is one of `if_absent` (default, do nothing if the directory with foreign resources exists), `make` (run `make`) or `true` (run‘make distclean` followed by the default configure and build steps).
  test(Boolean)
    If `true` (default), run the pack tests.
  git(+Boolean)
    If `true` (default `false` unless URL ends with =.git=), assume the URL is a GIT repository.
  link(+Boolean)
    Can be used if the installation source is a local directory and the file system supports symbolic links. In this case the system adds the current directory to the pack registration using a symbolic link and performs the local installation steps.

  Non-interactive installation can be established using the option `interactive(false)`. It is adviced to install from a particular trusted URL instead of the plain pack name for unattented operation.

[det]pack_url_file(+URL, -File)
  True if File is a unique id for the referenced pack and version. Normally, that is simply the base name, but GitHub archives destroy this picture. Needed by the pack manager.
[det]pack_rebuild(+Pack)
  Rebuild possible foreign components of Pack.
[det]pack_rebuild
  Rebuild foreign components of all packages.
[semidet]pack_upgrade(+Pack)
  Try to upgrade the package Pack.
  To be done
    Update dependencies when updating a pack from git?
[det]pack_remove(+Name)
  Remove the indicated package.
[nondet]pack_property(?Pack, ?Property)
  True when Property is a property of an installed Pack. This interface is intended for programs that wish to interact with the package manager. Defined properties are:
  directory(Directory)
    Directory into which the package is installed
  version(Version)
    Installed version
  title(Title)
    Full title of the package
  author(Author)
    Registered author
  download(URL)
    Official download URL
  readme(File)
    Package `README` file (if present)
  todo(File)
    Package `TODO` file (if present)
[det]pack_attach(+Dir, +Options)
  Attach a single package in Dir. The Dir is expected to contain the file `pack.pl` and a `prolog` directory. Options processed:
  duplicate(+Action)
    What to do if the same package is already installed in a different directory. Action is one of
    warning
      Warn and ignore the package
    keep
      Silently ignore the package
    replace
      Unregister the existing and insert the new package
  search(+Where)
    Determines the order of searching package library directories. Default is `last`, alternative is `first`.
  See also
    attach_packs/2 to attach multiple packs from a directory.