Add 'override-requirements' global option

docs/markdown/Build-options.md

@@ -76,6 +76,14 @@ d = dependency('foo', required : get_option('foo_option'))
 app = executable('myapp', 'main.c', dependencies : [d])
 ```
 
+If the value of a `requirement` option is set to `not-required`, that value is
+overriden by the global `override_requirements` option (which defaults to
+`not-required`). This is intended to be used by packagers who want to have full
+control on which dependencies are required and which are disabled, and not rely
+on build-deps being installed (at the right version) to get a feature enabled.
+They could set `override_requirements=required` to enable all features and
+disabled only the few they explicitly don't want, if any.
+
 This type is available since version 0.46.0
 
 ## Using build options

mesonbuild/coredata.py

@@ -159,10 +159,9 @@ def validate_value(self, value, user_input=True):
         return newvalue
 
 class UserRequirementOption(UserComboOption):
+    static_choices = ['required', 'not-required', 'disabled']
     def __init__(self, name, description, value, yielding=None):
-        super().__init__(name, description,
-            ['required', 'not-required', 'disabled'],
-            value, yielding)
+        super().__init__(name, description, self.static_choices, value, yielding)
 
 
 # This class contains all data that must persist over multiple
@@ -356,6 +355,8 @@ def get_builtin_option_choices(optname):
             return None
         elif builtin_options[optname][0] == UserBooleanOption:
             return [True, False]
+        elif builtin_options[optname][0] == UserRequirementOption:
+            return UserRequirementOption.static_choices
         else:
             return builtin_options[optname][2]
     else:
@@ -408,6 +409,7 @@ def get_builtin_option_default(optname, prefix='', noneIfSuppress=False):
     'backend':         [UserComboOption, 'Backend to use.', backendlist, 'ninja'],
     'stdsplit':        [UserBooleanOption, 'Split stdout and stderr in test logs.', True],
     'errorlogs':       [UserBooleanOption, "Whether to print the logs from failing tests.", True],
+    'override_requirements': [UserRequirementOption, "Override value of all 'not-required' requirements user options.", 'not-required'],
 }
 
 # Special prefix-dependent defaults for installation directories that reside in

mesonbuild/interpreter.py

@@ -257,9 +257,11 @@ def merge_from_method(self, args, kwargs):
             self.held_object.values[k] = v
 
 class RequirementHolder(InterpreterObject):
-    def __init__(self, value):
+    def __init__(self, value, interp):
         super().__init__()
         self.value = value
+        if self.value == 'not-required':
+            self.value = interp.coredata.get_builtin_option('override_requirements')
         self.methods.update({'get_value': self.get_value_method})
 
     @permittedMethodKwargs({})
@@ -1960,7 +1962,7 @@ def get_option(self, nodes, args, kwargs):
     def func_get_option(self, nodes, args, kwargs):
         opt = self.get_option(nodes, args, kwargs)
         if isinstance(opt, coredata.UserRequirementOption):
-            return RequirementHolder(opt.value)
+            return RequirementHolder(opt.value, self)
         return getattr(opt, 'value', opt)
 
     @noKwargs

mesonbuild/mconf.py

@@ -138,7 +138,8 @@ def print_conf(self):
         print('  Build dir ', self.build.environment.build_dir)
         print('\nCore options:\n')
         carr = []
-        for key in ['buildtype', 'warning_level', 'werror', 'strip', 'unity', 'default_library']:
+        for key in ['buildtype', 'warning_level', 'werror', 'strip', 'unity',
+                    'default_library', 'override_requirements']:
             carr.append({'name': key,
                          'descr': coredata.get_builtin_option_description(key),
                          'value': self.coredata.get_builtin_option(key),

mesonbuild/mesonmain.py

@@ -66,6 +66,7 @@ def create_parser():
     add_builtin_argument(p, 'warnlevel', dest='warning_level')
     add_builtin_argument(p, 'stdsplit', action='store_false')
     add_builtin_argument(p, 'errorlogs', action='store_false')
+    add_builtin_argument(p, 'override-requirements')
     p.add_argument('--cross-file', default=None,
                    help='File describing cross compilation environment.')
     p.add_argument('-D', action='append', dest='projectoptions', default=[], metavar="option",