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Configurations

DUB combines build options and requirements from two sources when building:

  • Configuration, through the --config=... switch
  • Build type, through the --build=... switch

While technically the two things are often very similar, semantically it makes sense to split them into two distinct categories. While build types often generically apply to any configuration and adjust how it is run, configurations rather represent different possible options and configurations of your project that may be chosen between.

Using dub build --print-configs it's possible to list the available configurations and which one is the default.

Default configuration

When no configurations are defined in the package recipe, a default configuration is generated:

  • if the package target type is set explicitly to "executable", a default configuration --config=application will be generated and used by default. If the main source file is not set in the recipe, it is defaulted.
  • if the package target type is set explicitly to "none", no configurations will be generated
  • if the package target type is "autodetect" (default or set explicitly) then:
    • if a default main file exists, the target type is set to "executable", the mainSourceFile is set to that path and the --config=application configuration as described above is added
    • additionally in either way there will be a --config=library configuration that is the same as the recipe, not setting any main source file.

In the usual case with a minimal dub recipe and an app.d file this means the configurations --config=application and --config=library will be available, allowing the package to both be used as application (when just running dub build or dub run in the folder) or as automatically a library when depending on it, excluding the app.d file.

Otherwise if there are configurations defined in the recipe, no default configurations will be created and the first available (matching platform) configuration will be picked for building.

So for regular builds this matching order is used:

  1. if the --config CLI flag is set, that configuration is used
  2. if configurations are defined in the recipe:
    1. the first configuration is picked
  3. if no configurations are defined in the recipe:
    1. if target type is "executable", the auto-generated --config=application is picked
    2. if target type is "autodetect" or unset:
      1. if a default main file exists, the auto-generated --config=application is picked
      2. if no default main file exists, the auto-generated --config=library is picked

If no configuration is found (default on targetType "none"), the test is skipped for the package.

When testing a package (dub-test(1)) the following steps are checked in order, with the first matching one being the used configuration.

  1. if the --config CLI flag is set, that configuration is used
  2. if the --main-file CLI flag is set, the first configuration that is not targetType "executable" is picked
  3. if a "unittest" configuration is defined, it is used
  4. if it exists, the first configuration that is not targetType "executable" is picked
  5. if it exists, the first configuration is picked

If no configuration is found (default on targetType "none"), the test is skipped for the package.

Last update: August 15, 2022
Created: August 5, 2022