This adds two new methods, that are conceptually related in the same way
that `enable_auto_if` and `disable_auto_if` are. They are different
however, in that they will always replace an `auto` value with an
`enabled` or `disabled` value, or error if the feature is in the
opposite state (calling `feature(disabled).enable_if(true)`, for
example). This matters when the feature will be passed to
dependency(required : …)`, which has different behavior when passed an
enabled feature than an auto one.
The `disable_if` method will be controversial, I'm sure, since it
can be expressed via `feature.require()` (`feature.require(not
condition) == feature.disable_if(condition)`). I have two defences of
this:
1) `feature.require` is difficult to reason about, I would expect
require to be equivalent to `feature.enable_if(condition)`, not to
`feature.disable_if(not condition)`.
2) mixing `enable_if` and `disable_if` in the same call chain is much
clearer than mixing `require` and `enable_if`:
```meson
get_option('feat') \
.enable_if(foo) \
.disable_if(bar) \
.enable_if(opt)
```
vs
```meson
get_option('feat') \
.enable_if(foo) \
.require(not bar) \
.enable_if(opt)
```
In the first chain it's immediately obvious what is happening, in the
second, not so much, especially if you're not familiar with what
`require` means.
It's always been strange to me we don't have an opposite method of the
`disable_auto_if` method, but I've been pressed to find a case where we
_need_ one, because `disable_auto_if` can't be logically contorted to
work. I finally found the case where they're not equivalent: when you
don't want to convert to a boolean:
```meson
f = get_option('feat').disable_auto_if(not foo)
g = get_option('feat').enable_auto_if(foo)
dep1 = dependency('foo', required : f)
dep2 = dependency('foo', required : g)
```
Add a method to downgrade an option to disabled if it is not used.
This is useful to avoid unnecessary search for dependencies;
for example
dep = dependency('dep', required: get_option('feature').disable_auto_if(not foo))
can be used instead of the more verbose and complex
if get_option('feature').auto() and not foo then
dep = dependency('', required: false)
else
dep = dependency('dep', required: get_option('feature'))
endif
or to avoid unnecessary dependency searches:
dep1 = dependency('dep1', required: get_option('foo'))
# dep2 is only used together with dep1
dep2 = dependency('dep2', required: get_option('foo').disable_auto_if(not dep1.found()))
```
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a method to perform a logical AND on a feature object. The method
also takes care of raising an error if 'enabled' is ANDed with false.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This method simplifies the conversion of Feature objects to booleans.
Often, one has to use the "not" operator in order to treat "auto"
and "enabled" the same way.
"allowed()" also works well in conjunction with the require method that
is introduced in the next patch. For example,
if get_option('foo').require(host_machine.system() == 'windows').allowed() then
src += ['foo.c']
config.set10('HAVE_FOO', 1)
endif
can be used instead of
if host_machine.system() != 'windows'
if get_option('foo').enabled()
error('...')
endif
endif
if not get_option('foo').disabled() then
src += ['foo.c']
config.set10('HAVE_FOO', 1)
endif
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
D lang compilers have an option -release (or similar) which turns off
asserts, contracts, and other runtime type checking. This patch wires
that up to the b_ndebug flag.
Fixes#7082
This is a special type of option to be passed to most 'required' keyword
arguments. It adds a 3rd state to the traditional boolean value to cause
those methods to always return not-found even if the dependency could be
found.
Since integrators doesn't want enabled features to be a surprise there
is a global option "auto_features" to enable or disable all
automatic features.
Dylan Baker
Paolo Bonzini
Jussi Pakkanen
Xavier Claessens