Versions
- Automating versions
- Requiring the new versions

Versions

This section explains how different versions of a given package can be created, first starting with manually changing the version attribute in the conanfile.py recipe, and then introducing the set_version() method as a mechanism to automate the definition of the package version.

Note

This section uses very simple, empty recipes without building any code, so without build(), package(), etc., to illustrate the versioning with the simplest possible recipes, and allowing the examples to run easily and to be very fast and simple. In real life, the recipes would be full-blown recipes as seen in previous sections of the tutorial, building actual libraries and packages.

Let’s start with a very simple recipe:

conanfile.py

from conan import ConanFile
class pkgRecipe(ConanFile):
    name = "pkg"
    version = "1.0"
    # The recipe would export files and package them, but not really
    # necessary for the purpose of this part of the tutorial
    # exports_sources = "include/*"
    # def package(self):
    #    ...

That we can create pkg/1.0 package with:

$ conan create .
...
pkg/1.0 .
...
$ conan list "pkg/*"
Local Cache
  pkg
    pkg/1.0

If we now did some changes to the source files of this library, this would be a new version, and we could change the conanfile.py version to version = "1.1" and create the new pkg/1.1 version:

# Make sure you modified conanfile.py to version=1.1
$ conan create .
...
pkg/1.1 .
...
$ conan list "pkg/*"
Local Cache
  pkg
    pkg/1.0
    pkg/1.1

As we can see, now we see in our cache both pkg/1.0 and pkg/1.1. The Conan cache can store any number of different versions and configurations for the same pkg package.

Automating versions

Instead of manually changing the version in conanfile.py, it is possible to automate it with 2 different approaches.

First it is possible to provide the version directly in the command line. In the example above, we could remove the version attribute from the recipe and do:

# Make sure you removed the version attribute in conanfile.py
$ conan create . --version=1.2
...
pkg/1.2 .
...
$ conan list "pkg/*"
Local Cache
  pkg
    pkg/1.0
    pkg/1.1
    pkg/1.2

The other possibility is to use the set_version() method to define the version dynamically, for example, if the version already exists in the source code or in a text file, or it should be deduced from the git version.

Let’s assume that we have a version.txt file in the repo, that contains just the version string 1.3. Then, this can be done:

conanfile.py

from conan import ConanFile
from conan.tools.files import  load
class pkgRecipe(ConanFile):
    name = "pkg"
    def set_version(self):
        self.version = load(self, "version.txt")

# No need to specify the version in CLI arg or in recipe attribute
$ conan create .
...
pkg/1.3 .
...
$ conan list "pkg/*"
Local Cache
  pkg
    pkg/1.0
    pkg/1.1
    pkg/1.2
    pkg/1.3

It is also possible to combine the command line version definition, falling back to reading from file if the command line argument is not provided with the following syntax:

conanfile.py

def set_version(self):
    # if self.version is already defined from CLI --version arg, it will
    # not load version.txt
    self.version = self.version or load(self, "version.txt")

# This will create the "1.4" version even if the version.txt file contains "1.3"
$ conan create . --version=1.4
...
pkg/1.4 .
...
$ conan list "pkg/*"
Local Cache
  pkg
    pkg/1.0
    pkg/1.1
    pkg/1.2
    pkg/1.3
    pkg/1.4

Likewise, it is possible to obtain the version from a Git tag:

conanfile.py

from conan import ConanFile
from conan.tools.scm import Git
class pkgRecipe(ConanFile):
    name = "pkg"
    def set_version(self):
        git = Git(self)
        tag = git.run("describe --tags")
        self.version = tag

# assuming this is a git repo, and it was tagged to 1.5
$ git init .
$ git add .
$ git commit -m "initial commit"
$ git tag 1.5
$ conan create .
    ...
    pkg/1.5 .
    ...
    $ conan list "pkg/*"
    Local Cache
      pkg
        pkg/1.0
        pkg/1.1
        pkg/1.2
        pkg/1.3
        pkg/1.4
        pkg/1.5

Note

Best practices

We could try to use something like the branch name or the commit as the version number. However this might have some disadvantages, for example, when this package is being required, it will need a explicit requires = "pkg/commit" in every other package recipe requiring this one, and it might be difficult to update consumers consistently, and to know if a newer or older dependency is being used.

Requiring the new versions

When a new package version is created, if other package recipes requiring this one contain a explicit requires, pinning the exact version like:

app/conanfile.py

from conan import ConanFile
class AppRecipe(ConanFile):
    name = "app"
    version = "1.0"
    requires = "pkg/1.0"

Then, installing or creating the app recipe will keep requiring and using the pkg/1.0 version and not the newer ones. To start using the new pkg versions, it is necessary to explicitly update the requires like:

app/conanfile.py

from conan import ConanFile
class AppRecipe(ConanFile):
    name = "app"
    version = "1.0"
    requires = "pkg/1.5"

This process, while it achieves very good reproducibility and traceability, can be a bit tedious if we are managing a large dependency graph and we want to move forward to use the latest dependencies versions faster and with less manual intervention. To automate this, the version-ranges explained in the next section can be used.