Merge pull request #8512 from bonzini/feature-methods

Utility methods for feature objects

7 files changed, 99 insertions, 5 deletions

diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md
index 103f4d8..111a6f0 100644
--- a/docs/markdown/Reference-manual.md
+++ b/docs/markdown/Reference-manual.md
@@ -2818,6 +2818,31 @@ The following methods are defined for all [`feature` options](Build-options.md#f
 - `enabled()`: returns whether the feature was set to `'enabled'`
 - `disabled()`: returns whether the feature was set to `'disabled'`
 - `auto()`: returns whether the feature was set to `'auto'`
+- `allowed()` *(since 0.59.0)*: returns whether the feature was set to `'enabled'` or `'auto'`
+- `disable_auto_if(value)` *(since 0.59.0)*: returns the feature, with
+  `'auto'` converted to `'disabled'` if value is true.
+
+  | Feature / Condition | True      | False |
+  | ------------------- | ----      | ----- |
+  | Enabled             | Enabled   | Enabled |
+  | Disabled            | Disabled  | Disabled |
+  | Auto                | Disabled  | Auto |
+
+- `require(value, error_message: '')` *(since 0.59.0)*: returns
+  the object itself if the value is true; an error if the object is
+  `'enabled'` and the value is false; a disabled feature if the object
+  is `'auto'` or `'disabled'` and the value is false.
+
+`require` is useful to restrict the applicability of `'auto'` features,
+for example based on other features or on properties of the host machine:
+
+```
+if get_option('directx').require(host_machine.system() == 'windows',
+       error_message: 'DirectX only available on Windows').allowed() then
+  src += ['directx.c']
+  config.set10('HAVE_DIRECTX', 1)
+endif
+```
 
 ### `generator` object
 
diff --git a/mesonbuild/interpreter/interpreterobjects.py b/mesonbuild/interpreter/interpreterobjects.py
index 61720c8..e87feb9 100644
--- a/mesonbuild/interpreter/interpreterobjects.py
+++ b/mesonbuild/interpreter/interpreterobjects.py
@@ -66,29 +66,71 @@ class FeatureOptionHolder(InterpreterObject, ObjectHolder[coredata.UserFeatureOp
     def __init__(self, env: 'Environment', name: str, option: coredata.UserFeatureOption):
         InterpreterObject.__init__(self)
         ObjectHolder.__init__(self, option)
-        if option.is_auto():
+        if option and option.is_auto():
             # TODO: we need to case here because options is not a TypedDict
             self.held_object = T.cast(coredata.UserFeatureOption, env.coredata.options[OptionKey('auto_features')])
         self.name = name
         self.methods.update({'enabled': self.enabled_method,
                              'disabled': self.disabled_method,
+                             'allowed': self.allowed_method,
                              'auto': self.auto_method,
+                             'require': self.require_method,
+                             'disable_auto_if': self.disable_auto_if_method,
                              })
 
+    @property
+    def value(self):
+        return 'disabled' if not self.held_object else self.held_object.value
+
+    def as_disabled(self):
+        return FeatureOptionHolder(None, self.name, None)
+
     @noPosargs
     @permittedKwargs({})
     def enabled_method(self, args, kwargs):
-        return self.held_object.is_enabled()
+        return self.value == 'enabled'
 
     @noPosargs
     @permittedKwargs({})
     def disabled_method(self, args, kwargs):
-        return self.held_object.is_disabled()
+        return self.value == 'disabled'
+
+    @noPosargs
+    @permittedKwargs({})
+    def allowed_method(self, args, kwargs):
+        return not self.value == 'disabled'
 
     @noPosargs
     @permittedKwargs({})
     def auto_method(self, args, kwargs):
-        return self.held_object.is_auto()
+        return self.value == 'auto'
+
+    @permittedKwargs({'error_message'})
+    def require_method(self, args, kwargs):
+        if len(args) != 1:
+            raise InvalidArguments('Expected 1 argument, got %d.' % (len(args), ))
+        if not isinstance(args[0], bool):
+            raise InvalidArguments('boolean argument expected.')
+        error_message = kwargs.pop('error_message', '')
+        if error_message and not isinstance(error_message, str):
+            raise InterpreterException("Error message must be a string.")
+        if args[0]:
+            return self
+
+        if self.value == 'enabled':
+            prefix = 'Feature {} cannot be enabled'.format(self.name)
+            prefix = prefix + ': ' if error_message else ''
+            raise InterpreterException(prefix + error_message)
+        return self.as_disabled()
+
+    @permittedKwargs({})
+    def disable_auto_if_method(self, args, kwargs):
+        if len(args) != 1:
+            raise InvalidArguments('Expected 1 argument, got %d.' % (len(args), ))
+        if not isinstance(args[0], bool):
+            raise InvalidArguments('boolean argument expected.')
+        return self if self.value != 'auto' or not args[0] else self.as_disabled()
+
 
 class RunProcess(InterpreterObject):
 
diff --git a/run_unittests.py b/run_unittests.py
index 21bb30e..6f5ec58 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -6719,7 +6719,7 @@ class LinuxlikeTests(BasePlatformTests):
         self.assertEqual(libhello_nolib.get_compile_args(), [])
         self.assertEqual(libhello_nolib.get_pkgconfig_variable('foo', {}), 'bar')
         self.assertEqual(libhello_nolib.get_pkgconfig_variable('prefix', {}), self.prefix)
-        self.assertEqual(libhello_nolib.get_pkgconfig_variable('escaped_var', {}), 'hello\ world')
+        self.assertEqual(libhello_nolib.get_pkgconfig_variable('escaped_var', {}), r'hello\ world')
         self.assertEqual(libhello_nolib.get_pkgconfig_variable('unescaped_var', {}), 'hello world')
 
         cc = env.detect_c_compiler(MachineChoice.HOST)
diff --git a/test cases/common/192 feature option/meson.build b/test cases/common/192 feature option/meson.build
index ef3fa22..b5e26fa 100644
--- a/test cases/common/192 feature option/meson.build
+++ b/test cases/common/192 feature option/meson.build
@@ -8,18 +8,33 @@ disabled_opt = get_option('disabled')
 assert(not feature_opts.enabled(), 'Should be auto option')
 assert(not feature_opts.disabled(), 'Should be auto option')
 assert(feature_opts.auto(), 'Should be auto option')
+assert(feature_opts.allowed(), 'Should be auto option')
 
 assert(required_opt.enabled(), 'Should be enabled option')
 assert(not required_opt.disabled(), 'Should be enabled option')
 assert(not required_opt.auto(), 'Should be enabled option')
+assert(required_opt.allowed(), 'Should be enabled option')
+assert(required_opt.require(true, error_message: 'xyz').enabled(), 'Should be enabled option')
+assert(required_opt.disable_auto_if(true).enabled(), 'Should be enabled option')
+assert(required_opt.disable_auto_if(false).enabled(), 'Should be enabled option')
 
 assert(not optional_opt.enabled(), 'Should be auto option')
 assert(not optional_opt.disabled(), 'Should be auto option')
 assert(optional_opt.auto(), 'Should be auto option')
+assert(optional_opt.allowed(), 'Should be auto option')
+assert(optional_opt.require(true).auto(), 'Should be auto option')
+assert(optional_opt.require(false, error_message: 'xyz').disabled(), 'Should be disabled auto option')
+assert(optional_opt.disable_auto_if(true).disabled(), 'Should be disabled auto option')
+assert(optional_opt.disable_auto_if(false).auto(), 'Should be auto option')
 
 assert(not disabled_opt.enabled(), 'Should be disabled option')
 assert(disabled_opt.disabled(), 'Should be disabled option')
 assert(not disabled_opt.auto(), 'Should be disabled option')
+assert(not disabled_opt.allowed(), 'Should be disabled option')
+assert(disabled_opt.require(true).disabled(), 'Should be disabled option')
+assert(disabled_opt.require(false, error_message: 'xyz').disabled(), 'Should be disabled option')
+assert(disabled_opt.disable_auto_if(true).disabled(), 'Should be disabled option')
+assert(disabled_opt.disable_auto_if(false).disabled(), 'Should be disabled option')
 
 dep = dependency('threads', required : required_opt)
 assert(dep.found(), 'Should find required "threads" dep')
diff --git a/test cases/failing/111 feature require/meson.build b/test cases/failing/111 feature require/meson.build
new file mode 100644
index 0000000..d976ae8
--- /dev/null
+++ b/test cases/failing/111 feature require/meson.build
@@ -0,0 +1,2 @@
+project('no fallback', 'c')
+foo = get_option('reqfeature').require(false, error_message: 'frobnicator not available')
diff --git a/test cases/failing/111 feature require/meson_options.txt b/test cases/failing/111 feature require/meson_options.txt
new file mode 100644
index 0000000..d6f2ce6
--- /dev/null
+++ b/test cases/failing/111 feature require/meson_options.txt
@@ -0,0 +1,2 @@
+option('reqfeature', type : 'feature', value : 'enabled', description : 'A required feature')
+
diff --git a/test cases/failing/111 feature require/test.json b/test cases/failing/111 feature require/test.json
new file mode 100644
index 0000000..7c4640d
--- /dev/null
+++ b/test cases/failing/111 feature require/test.json
@@ -0,0 +1,8 @@
+{
+  "stdout": [
+    {
+      "match": "re",
+      "line": ".*/meson\\.build:2:0: ERROR: Feature reqfeature cannot be enabled: frobnicator not available"
+    }
+  ]
+}