Experimental 'genvslite' WIP. (#11049)

* Capture all compile args from the first round of ninja backend generation for all languages used in building the targets so that these args, defines, and include paths can be applied to the .vcxproj's intellisense fields for all buildtypes/configurations.

Solution generation is now set up for mutiple build configurations (buildtypes) when using '--genvslite'.

All generated vcxprojs invoke the same high-level meson compile to build all targets;  there's no selective target building (could add this later).  Related to this, we skip pointlessly generating vcxprojs for targets that aren't buildable (BuildTarget-derived), which aren't of interest to the user anyway.

When using --genvslite, no longer inject '<ProjectReference ...>' dependencies on which a generated .vcxproj depends because that imposes a forced visual studio build dependency, which we don't want, since we're essentially bypassing VS's build in favour of running 'meson compile ...'.

When populating the vcxproj's shared intellisense defines, include paths, and compiler options fields, we choose the most frequent src file language, since this means more project src files can simply reference the project shared fields and fewer files of non-primary language types need to populate their full set of intellisense fields.  This makes for smaller .vcxproj files.

Paths for generated source/header/etc files, left alone, would be added to solution projects relative to the '..._vs' build directory, where they're never generated;  they're generated under the respective '..._[debug/opt/release]' ninja build directories that correspond to the solution build configuration. Although VS doesn't allow conditional src/header listings in vcxprojs (at least not in a simple way that I'm aware of), we can ensure these generated sources get adjusted to at least reference locations under one of the concrete build directories (I've chosen '..._debug') under which they will be generated.

Testing with --genvslite has revealed that, in some cases, the presence of 'c:\windows\system32;c:\windows' on the 'Path' environment variable (via the make-style project's ExecutablePath element) is critical to getting the 'meson compile ...' build to succeed.  Not sure whether this is some 'find and guess' implicit defaults behaviour within meson or within the MSVC compiler that some projects may rely on. Feels weird but not sure of a better solution than forcibly adding these to the Path environment variable (the Executable Path property of the project).

Added a new windows-only test to windowstests.py ('test_genvslite') to exercise the --genvslite option along with checking that the 'msbuild' command invokes the 'meson compile ...' of the build-type-appropriate-suffixed temporary build dir and checks expected program output.

Check and report error if user specifies a non-ninja backend with a 'genvslite' setup, since that conflicts with the stated behaviour of genvslite.  Also added this test case to 'WindowsTests.test_genvslite'

I had problems tracking down some problematic environment variable behaviour, which appears to need a work-around. See further notes on VSINSTALLDIR, in windowstests.py, test_genvslite.
'meson setup --help' clearly states that positional arguments are ... [builddir] [sourcedir].  However, BasePlatformTests.init(...) was passing these in the order [sourcedir] [builddir].  This was producing failures, saying, "ERROR: Neither directory contains a build file meson.build." but when using the correct ordering, setup now succeeds.

Changed regen, run_tests, and run_install utility projects to be simpler makefile projects instead, with commands to invoke the appropriate '...meson.py --internal regencheck ...' (or install/test) on the '[builddir]_[buildtype]' as appropriate for the curent VS configuration.  Also, since the 'regen.vcxproj' utility didn't work correctly with '--genvslite' setup build dirs, and getting it to fully work would require more non-trivial intrusion into new parts of meson (i.e. '--internal regencheck', '--internal regenerate', and perhaps also 'setup --reconfigure'), for now, the REGEN project is replaced with a simpler, lighter-weight RECONFIGURE utility proj, which is unlinked from any solution build dependencies and which simply runs 'meson setup --reconfigure [builddir]_[buildtype] [srcdir]' on each of the ninja-backend build dirs for each buildtype.
Yes, although this will enable the building/compiling to be correctly configured, it can leave the solution/vcxprojs stale and out-of-date, it's simple for the user to 'meson setup --genvslite ...' to fully regenerate an updated, correct solution again. However, I've noted this down as a 'fixme' to consider implementing the full regen behaviour for the genvslite case.

* Review feedback changes -
- Avoid use of 'captured_compile_args_per_buildtype_and_target' as an 'out' param.
- Factored a little msetup.py, 'run(...)' macro/looping setup steps, for genvslite, out into a 'run_genvslite_setup' func.

* Review feedback:  Fixed missing spaces between multi-line strings.

* 'backend_name' assignment gets immediately overwritten in 'genvslite' case so moved it into else/non-genvslite block.

* Had to bump up 'test cases/unit/113 genvslites/...' up to 114; it collided with a newly added test dir again.

* Changed validation of 'capture' and 'captured_compile_args_...' to use MesonBugException instead of MesonException.

* Changed some function param and closing brace indentation.

1 files changed, 11 insertions, 0 deletions

diff --git a/docs/markdown/snippets/gen_vslite.md b/docs/markdown/snippets/gen_vslite.md
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+## Added a new '--genvslite' option for use with 'meson setup ...'
+
+To facilitate a more usual visual studio work-flow of supporting and switching between
+multiple build configurations (buildtypes) within the same solution, among other
+[reasons](https://github.com/mesonbuild/meson/pull/11049), use of this new option
+has the effect of setting up multiple ninja back-end-configured build directories,
+named with their respective buildtype suffix.  E.g. 'somebuilddir_debug',
+'somebuilddir_release', etc. as well as a '_vs'-suffixed directory that contains the
+generated multi-buildtype solution.  Building/cleaning/rebuilding in the solution
+now launches the meson build (compile) of the corresponding buildtype-suffixed build
+directory, instead of using Visual Studio's native engine.
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