We are pleased to announce that Conan 1.39 has been released and brings some significant new features and bug fixes. One of the most important features is the new syntax for aliases that we have backported from 2.0 to 1.39. We have added a new --require-override argument to define dependency overrides directly on the command line. Also, for the new toolchains and generators, you can set the new win_bash property in the ConanFile to enable running commands in a bash shell in Windows. We have a new VCVars generator that creates a batch script that will activate the Visual Studio Developer Command Prompt. Finally, the new Environment model comes with several improvements.

Aliases syntax from 2.0 backported to 1.39

Current alias syntax is problematic as they are impossible to distinguish from any other requirement. Because of this, we have introduced a new explicit syntax for Conan 2.0 that we are now backporting to 1.39. Porting this syntax to the current Conan version will also make the transition of recipes smoother.

The new syntax adds () characters (in a similar way that the [] brackets do for version ranges definition) to indicate that we are requiring an alias:

class MyPkg(ConanFile):
    # With the previous syntax youn can't know if it's an alias upfront:
    # requires = "boost/latest@mycompany/stable"

    # New experimental syntax is explicit:
    requires = "boost/(latest)@mycompany/stable"

If you want to read the original proposal for the new aliases syntax, please check the pull request in the Conan 2.0 Tribe GitHub repository.

New –require-override CLI argument

The conan install command has a new --require-override argument. Setting this argument is equivalent to declaring overrides=True when adding a require. This can be very convenient to test things during development, but for production it is better to update the conanfiles to explicitly reflect in code which specific versions upstream are used.

You can use it like:

conan install mypkg/1.0@ --require-override=zlib/1.2.11

That is equivalent to declare this in the conanfile.py:

self.requires("zlib/1.2.11", override=True)

New self.win_bash mechanism

There’s a new self.win_bash attribute for the ConanFile that supersedes the “classic” self.run(…, win_bash=True) to run commands inside a Windows subsystem. Setting self.win_bash to True will run all the self.run() commands in the ConanFile inside a bash shell. Also, this will only happen for Windows so there’s no need to check the platform in recipes.

All the new Autotools, AutotoolsToolchain, AutotoolsDeps, and PkgConfigDeps will work automatically when self.win_bash=True is set.

The new subsystem model is explicit and there’s no more auto-detection. To set the path to bash.exe and the type of subsystem, please use these new configuration variables:

tools.microsoft.bash:subsystem: msys2, cygwin, msys or wsl.
tools.microsoft.bash:path: C:/Path/To/Bash.exe

New conan.tools.microsoft.VCVars generator

We have also added a new VCVars generator that generates a file called conanvcvars.bat that activates the Visual Studio developer command prompt according to the current settings by wrapping the vcvarsall Microsoft bash script.

You can use it in your conanfile.py

class MyPkg(ConanFile):
    generators = "VCVars"

or conafile.txt

[generators]
VCVars

Note that this generator runs the conanvcvars.bat script by default. This can be controlled setting the auto_activate argument in the generate method. Please read more about this in the documentation.

Several improvements in the new Environment model

Now Environment objects implement remove and items methods. Also, a unique environment launcher named conanenv.bat/sh is now generated to aggregate all the environment generators (VirtualRunEnv, VirtualBuildEnv, AutotoolsToolchain, and AutotoolsDeps) so you can easily activate all of them with just one command.


Besides the items listed above, there were some minor bug fixes you may wish to read about. If so, please refer to the changelog for the complete list.

We hope you enjoy this release, and look forward to your feedback.