We are bringing Conan 1.13 release and here you have a new edition of the highlighted features you may find handy in this new version. Let’s check them out!

Recipe and package revisions

Some releases ago we started to include some of the changes needed to adapt the Conan internals to work with the new revisions concept, that is an implicit way of creating revisions of the same version of a package without having to bump the version explicitly.

The motivation to include this concept in packages an recipes was mainly driven by the fact that in most of the situations when developing a Conan package, the recipe conanfile.py follows a different development cycle. An example of this could be a recipe adding support for building in another OS. Adding this change would probably not require any change in the library itself nor in the build system, however, to reflect that change you would need to upload the recipe to a remote with the same reference (e.g. lib/1.1.2@user/channel) and overwrite the previous version.

This has problems for the traceability of packages (you lose the old version -in fact “revision”-) and have no way to go back to previous state. Some users already noticed it when using Conan in production and started to append the commit or just a number at the end of the library version, something like lib/1.1.2-<commit-hash>@user/channel. Although this solved the traceability issue, this has the disadvantage of having to bump the version on every other recipe depending on the updated one.

We have realized that to make it work properly, this behavior should be implemented as part of the Conan model and that’s why this release includes the first experimental version of Conan working with revisions!

Revisions explained

The current Conan model uses references to talk about a recipe associated to a scope created with a user and a channel <package_name>/<version>@<user_name>/<channel> and a package ID which is a hash of the settings options and requirements used to identify the binary packages.

Normally to indicate a binary package of a package you would need something like: <package_name>/<version>@<user_name>/<channel>:<package_id>

This model has not changed and you will still be able to use this package reference in the commands and recipes. However, we have added two more levels:

  • Recipe revision (RREV): A unique ID using the latest VCS hash or a checksum of the recipe manifest (conanfile.py with files exported if any).
  • Package revision (PREV): A unique ID using the checksum of the package manifest (all files stored in a binary package).

This means that now you can point to an exact revision of a binary package writing the reference and package ID together with the recipe and package revisions: <package_name>/<version>@<user_name>/<channel>#<RREV>:<package_id>#<PREV>

Working with revisions

The concept of revisions is mostly server side, where all the recipe revisions and package revisions will be stored. In the client side (in the Conan cache) we can only have one revision at a time.

To try and work with revisions in the client, you would need to opt in setting CONAN_REVISIONS_ENABLED=1 in the environment or enabling that in the configuration file:

$ conan config set general.revisions_enabled=True

You would also need a conan_server updated to 1.13 and it will be fully supported in upcoming versions of JFrog Artifactory soon.

Now, every time a recipe is exported or a package is created, it will get a new revision:

$ conan create . user/channel
Exporting package recipe
IrrXML/1.2@user/channel: Folder: C:\Users\danimtb\.conan\data\IrrXML\1.2\user\channel\export
IrrXML/1.2@user/channel: Using git commit as the recipe revision: 681d7e590d2da0a164166f737a49cf32c735ee6c
    IrrXML/1.2@user/channel from local cache - Cache
    IrrXML/1.2@user/channel:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7 - Build
IrrXML/1.2@user/channel: Package '6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7' created

You can search the packages created as usual but also the recipe revision just created:

$ conan search IrrXML/1.2@user/channel --revisions

Revisions for 'IrrXML/1.2@user/channel':
681d7e590d2da0a164166f737a49cf32c735ee6c (No time)

The “(No time)” output is just a reference to get when it was exported, however this time will come from the server. If the commit of the repo where the recipe is living changes, there will be a new revision created that will replace the current one in the client. However, you can upload it to the server and you will have different revisions:

$ conan search IrrXML/1.2@user/channel --revisions --remote server

Revisions for 'IrrXML/1.2@user/channel' at remote 'conan-local':
72389507bbaab233bb3bad798432c19a05752ae7 (2019-03-11 14:26:25 UTC)
681d7e590d2da0a164166f737a49cf32c735ee6c (2019-03-11 13:42:50 UTC)

Now, anyone installing or performing a conan install --update will automatically get the latest revision from the server. Moreover, they can also target target a specific recipe revision:

$ conan install IrrXML/1.2@user/channel#681d7e590d2da0a164166f737a49cf32c735ee6c --remote server --update
[==================================================] 372B/372B
IrrXML/1.2@user/channel: WARN: The package IrrXML/1.2@user/channel:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7 doesn't belong to the installed recipe revision, removing folder
Installing package: IrrXML/1.2@user/channel
    IrrXML/1.2@user/channel from 'conan-local' - Download
    IrrXML/1.2@user/channel:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7 - Download

Read more about revisions in the documentation and don’t forget that we are open to any feedback.

Package ID versioning mode

From the beginning Conan has always used Semantic Versioning for requirements version to calculate the package ID has for every binary package. That means that a package libA/1.2.3 which is a dependency of libB/1.0.0 will change the binary hash of libB only if the major part of the version is changed. Otherwise it will hash to the same package ID.

Let’s check it:

  • libA/1.2.3


    from conans import ConanFile
    class LibA(ConanFile):
    $ conan create conanfile.py libA/1.2.3@user/channel
    $ conan create conanfile.py libA/1.3.3@user/channel
    $ conan create conanfile.py libA/2.0.0@user/channel
  • libB/1.0.0:


    from conans import ConanFile
    class LibB(ConanFile):
        name = "libB"
        version = "1.0.0"
        requires = "libA/1.2.3@user/channel"
    $ conan info .
        ID: 5ab84d6acfe1f23c4fae0ab88f26e3a396351ac9
        BuildID: None
        Remote: None
        Recipe: Cache
        Revision: 7ee2bfe571d258167c9356f2d7f503b3
        Binary: Cache
        Binary remote: None
        Creation date: 2019-03-11 16:09:47
        Required by:
            conanfile.py (libB/1.0.0@None/None)
    conanfile.py (libB/1.0.0@None/None)
      ID: 8a4d75100b721bfde375a978c780bf3880a22bab
      BuildID: None

    You can see that the binary ID generated for libB would be 8a4d75100b721bfde375a978c780bf3880a22bab. If we change the requirement to libA/1.3.3@user/channel we will get the same ID for libA. However, if we change the requirement to the major version libA/2.0.0@user/channel this will be reflected as a new package ID for libB, in this case f1fc64edd1a6c2fb7d41b78ecf5972a0e7a85df8.

    $ conan info .
        ID: 5ab84d6acfe1f23c4fae0ab88f26e3a396351ac9
        BuildID: None
        Remote: None
        Recipe: Cache
        Revision: 233bc35f1c94fcf2a2f18420d0d2bb45
        Binary: Cache
        Binary remote: None
        Creation date: 2019-03-11 16:19:42
        Required by:
            conanfile.py (libB/1.2.3@None/None)
    conanfile.py (libB/1.2.3@None/None)
        ID: f1fc64edd1a6c2fb7d41b78ecf5972a0e7a85df8
        BuildID: None

This was the only default behavior allowed until Conan 1.13, now you can change this default in your configuration file conan.conf:

default_package_id_mode = full_package_mode

Following the previous example but using the default package ID mode to full_package_mode, will indicate a new libB binary for any change on the version of libA.

Any of the modes described in Defining Package ABI compatibility section from the documentation can be used and setting this will come handy to anyone who wants to have fine control over the package ID generation and the compatibility of binaries regarding its dependencies.

Update on editable packages

In latest release we also brought editable packages as a way to map a custom layout of a project to consume the binaries of a package without the need of exporting them to the cache.

In this release we have enhanced this feature with useful changes:

  • Layout files now allow the usage of Jinja templating for settings and options:

    {% if options.shared %}
    {% else %}
    {% endif %}
  • Command has been renamed to conan editable with the corresponding subcommands conan editable add, conan editable remove to put a package in this editable mode or remove it.

  • Now you can show all the packages that are configured as editable too:

    $ conan editable list
      Path: C:\Users\danimtb\test
      Layout: None

Check the docs for more info about editable packages.

New implementation for Workspaces

The workspaces feature is back with a new implementation on top of the editables. The use case for this feature was the fact of working simultaneously on more than one package. Making changes on any dependency will require to issue a Conan command to make the changes available in the cache to be consumed by a downstream package.

The Conan workspaces allow to have more than one package in user folders and directly use other packages from user folders too without the need to put them in the local cache. Furthermore, it enables incremental builds on large projects containing multiple packages.

Basically, you define a workspace YAML file with the layout of your projects:


        path: say
        path: hello
        path: chat
layout: layout_gcc
workspace_generator: cmake
root: chat/0.1@user/testing

And you indicate a general editable layout file or set a specific one for each package as well as the root consumer package you are building for.

Finally a workspace generator that will be the wrapper for all the packages in the workspace. Similar to the concept of Visual Studio with the projects (editable packages) that can be included in a global solution (workspace). Currently the only supported generator is CMake, although a Visual Studio one could be feasible.

We have introduced a specific command and subcommand for workspaces, conan workspace install, that will use the aforementioned workspace file to set the libraries into editable mode and generate the workspace generator file conanworkspace.cmake to be used:

$ conan workspace install ../cmake/conanws_gcc.yml

    chat/0.1@user/testing from user folder - Editable
    hello/0.1@user/testing from user folder - Editable
    say/0.1@user/testing from user folder - Editable
    chat/0.1@user/testing:586bfc45a254754b47be1e6553aab648a85e425b - Editable
    hello/0.1@user/testing:98ce62312cb8b844c4a47cba2e495294a7e3e4ba - Editable
    say/0.1@user/testing:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7 - Editable

say/0.1@user/testing: Generator cmake created conanbuildinfo.cmake
say/0.1@user/testing: Generated conaninfo.txt
say/0.1@user/testing: Generated graphinfo
say/0.1@user/testing: Generated conanbuildinfo.txt
hello/0.1@user/testing: Generator cmake created conanbuildinfo.cmake
hello/0.1@user/testing: Generated conaninfo.txt
hello/0.1@user/testing: Generated graphinfo
hello/0.1@user/testing: Generated conanbuildinfo.txt
chat/0.1@user/testing: Generator cmake created conanbuildinfo.cmake
chat/0.1@user/testing: Generated conaninfo.txt
chat/0.1@user/testing: Generated graphinfo
chat/0.1@user/testing: Generated conanbuildinfo.txt

Take a look at the workspaces documentation to learn more things like changing the layout of packages, having more than one root or how to use multi configuration (Release/Debug) packages.

In case you want to learn more about the changes in this release, check the full list of features and fixes in the changelog with the link to the Pull Request with the implementation and discussion details and don’t forget to update.

Finally, if you find a bug or want to start a new discussion, please do not hesitate to open a new issue here. Many thanks!