16fa3b9f07
This PR makes it possible to select only a subset of virtual dependencies from a spec that _may_ provide more. To select providers, a syntax to specify edge attributes is introduced:
```
hdf5 ^[virtuals=mpi] mpich
```
With that syntax we can concretize specs like:
```console
$ spack spec strumpack ^[virtuals=mpi] intel-parallel-studio+mkl ^[virtuals=lapack] openblas
```
On `develop` this would currently fail with:
```console
$ spack spec strumpack ^intel-parallel-studio+mkl ^openblas
==> Error: Spec cannot include multiple providers for virtual 'blas'
Requested 'intel-parallel-studio' and 'openblas'
```
In package recipes, virtual specs that are declared in the same `provides` directive need to be provided _together_. This means that e.g. `openblas`, which has:
```python
provides("blas", "lapack")
```
needs to provide both `lapack` and `blas` when requested to provide at least one of them.
## Additional notes
This capability is needed to model compilers. Assuming that languages are treated like virtual dependencies, we might want e.g. to use LLVM to compile C/C++ and Gnu GCC to compile Fortran. This can be accomplished by the following[^1]:
```
hdf5 ^[virtuals=c,cxx] llvm ^[virtuals=fortran] gcc
```
[^1]: We plan to add some syntactic sugar around this syntax, and reuse the `%` sigil to avoid having a lot of boilerplate around compilers.
Modifications:
- [x] Add syntax to interact with edge attributes from spec literals
- [x] Add concretization logic to be able to cherry-pick virtual dependencies
- [x] Extend semantic of the `provides` directive to express when virtuals need to be provided together
- [x] Add unit-tests and documentation
18 lines
545 B
Python
18 lines
545 B
Python
# Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
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# Spack Project Developers. See the top-level COPYRIGHT file for details.
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#
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# SPDX-License-Identifier: (Apache-2.0 OR MIT)
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from spack.package import *
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class OpenblasWithLapack(Package):
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"""Dummy version of OpenBLAS that also provides LAPACK, for testing."""
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homepage = "http://www.openblas.net"
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url = "http://github.com/xianyi/OpenBLAS/archive/v0.2.15.tar.gz"
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version("0.2.15", md5="b1190f3d3471685f17cfd1ec1d252ac9")
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provides("lapack", "blas")
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