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The current approach of determining dub dependencies is by specifying
a name and, optionally, a version. Dub will then be called to generate
a json summary of the package and code in meson will parse that and
extract relevant information. This can be insufficient because dub
packages can provide multiple configurations for multiple use-cases,
examples include providing a configuration for an executable and a
configuration for a library. As a practical example, the dub package
itself provides an application configuration and multiple library
configurations, the json description of dub will, by default, be for
the application configuration which will make dub as a library
unusable in meson.
This can be solved without modifying the meson build interface by
having dub describe the entire local project and collecting
dependencies information from that. This way dub will generate
information based on the project's 'dub.json' file, which is free to
require dependencies in any way accepted by dub, by specifying
configurations, by modifying compilation flags etc. This is all
transparent to meson as dub's main purpose is to provide a path to the
library file generated by the dependency in addition to other
command-line arguments for the compiler.
This change will, however, require that projects that want to build
with meson also provided a 'dub.json' file in which dependency
information is recorded. Failure to do so will not break existing
projects that didn't use a 'dub.json', but they will be limited to
what the previous implementation offered. Projects that already have a
'dub.json' should be fine, so long as the file is valid and the
information in it matches the one in 'meson.build'. For example for a
'dependency()' call in 'meson.build' that dependency must exist in
'dub.json', otherwise the call will now fail when it worked
previously.
Using a 'dub.json' also has as a consequence that the version of the
dependencies that are found are the ones specified in
'dub.selections.json', which can be helpful for projects that already
provide a 'dub.json' in addition to 'meson.build' to de-duplicate code.
In terms of other code changes:
- multiple version requirements for a dub dependency now work, though
they can only be used when a 'dub.json' is present in which case the
version of dependencies is already pinned by 'dub.selections.json'
- the 'd/11 dub' test case has been changed to auto-generate the
'dub.json' config outside of the source directory, as the
auto-generated file triggers warning when parsed by dub, which upsets
the new code as the warnings interfere with the legitimate output.
Signed-off-by: Andrei Horodniceanu <a.horodniceanu@proton.me>
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