Revert "Clarify mutable objects usage"

This reverts commit 9f02d0a3e5a5ffc82256391c244b1af38e41ef78.

It turns out that this does introduce a behavioral change in existing
users of ConfigurationData, which it wasn't supposed to (it was supposed
to preserve behavior there, and add a new *warning* for
EnvironmentVariables).

This breaks projects such as pulseaudio, libvirt, and probably more.
Roll back the change and try again after 1.5.0 is released.

Fixes: #13372

1 files changed, 10 insertions, 16 deletions

diff --git a/mesonbuild/interpreter/interpreterobjects.py b/mesonbuild/interpreter/interpreterobjects.py
index 32f05bafb..d5c1efaa8 100644
--- a/mesonbuild/interpreter/interpreterobjects.py
+++ b/mesonbuild/interpreter/interpreterobjects.py
@@ -284,7 +284,6 @@ class EnvironmentVariablesHolder(ObjectHolder[mesonlib.EnvironmentVariables], Mu
 
     def __init__(self, obj: mesonlib.EnvironmentVariables, interpreter: 'Interpreter'):
         super().__init__(obj, interpreter)
-        MutableInterpreterObject.__init__(self)
         self.methods.update({'set': self.set_method,
                              'unset': self.unset_method,
                              'append': self.append_method,
@@ -309,14 +308,12 @@ class EnvironmentVariablesHolder(ObjectHolder[mesonlib.EnvironmentVariables], Mu
     @typed_kwargs('environment.set', ENV_SEPARATOR_KW)
     def set_method(self, args: T.Tuple[str, T.List[str]], kwargs: 'EnvironmentSeparatorKW') -> None:
         name, values = args
-        self.check_used(self.interpreter, fatal=False)
         self.held_object.set(name, values, kwargs['separator'])
 
     @FeatureNew('environment.unset', '1.4.0')
     @typed_pos_args('environment.unset', str)
     @noKwargs
     def unset_method(self, args: T.Tuple[str], kwargs: TYPE_kwargs) -> None:
-        self.check_used(self.interpreter, fatal=False)
         self.held_object.unset(args[0])
 
     @typed_pos_args('environment.append', str, varargs=str, min_varargs=1)
@@ -324,7 +321,6 @@ class EnvironmentVariablesHolder(ObjectHolder[mesonlib.EnvironmentVariables], Mu
     def append_method(self, args: T.Tuple[str, T.List[str]], kwargs: 'EnvironmentSeparatorKW') -> None:
         name, values = args
         self.warn_if_has_name(name)
-        self.check_used(self.interpreter, fatal=False)
         self.held_object.append(name, values, kwargs['separator'])
 
     @typed_pos_args('environment.prepend', str, varargs=str, min_varargs=1)
@@ -332,7 +328,6 @@ class EnvironmentVariablesHolder(ObjectHolder[mesonlib.EnvironmentVariables], Mu
     def prepend_method(self, args: T.Tuple[str, T.List[str]], kwargs: 'EnvironmentSeparatorKW') -> None:
         name, values = args
         self.warn_if_has_name(name)
-        self.check_used(self.interpreter, fatal=False)
         self.held_object.prepend(name, values, kwargs['separator'])
 
 
@@ -343,7 +338,6 @@ class ConfigurationDataHolder(ObjectHolder[build.ConfigurationData], MutableInte
 
     def __init__(self, obj: build.ConfigurationData, interpreter: 'Interpreter'):
         super().__init__(obj, interpreter)
-        MutableInterpreterObject.__init__(self)
         self.methods.update({'set': self.set_method,
                              'set10': self.set10_method,
                              'set_quoted': self.set_quoted_method,
@@ -355,31 +349,32 @@ class ConfigurationDataHolder(ObjectHolder[build.ConfigurationData], MutableInte
                              })
 
     def __deepcopy__(self, memo: T.Dict) -> 'ConfigurationDataHolder':
-        obj = ConfigurationDataHolder(copy.deepcopy(self.held_object), self.interpreter)
+        return ConfigurationDataHolder(copy.deepcopy(self.held_object), self.interpreter)
+
+    def is_used(self) -> bool:
+        return self.held_object.used
+
+    def __check_used(self) -> None:
         if self.is_used():
-            # Copies of used ConfigurationData used to be immutable. It is now
-            # allowed but we need this flag to print a FeatureNew warning if
-            # that happens.
-            obj.mutable_feature_new = True
-        return obj
+            raise InterpreterException("Can not set values on configuration object that has been used.")
 
     @typed_pos_args('configuration_data.set', str, (str, int, bool))
     @typed_kwargs('configuration_data.set', _CONF_DATA_SET_KWS)
     def set_method(self, args: T.Tuple[str, T.Union[str, int, bool]], kwargs: 'kwargs.ConfigurationDataSet') -> None:
-        self.check_used(self.interpreter)
+        self.__check_used()
         self.held_object.values[args[0]] = (args[1], kwargs['description'])
 
     @typed_pos_args('configuration_data.set_quoted', str, str)
     @typed_kwargs('configuration_data.set_quoted', _CONF_DATA_SET_KWS)
     def set_quoted_method(self, args: T.Tuple[str, str], kwargs: 'kwargs.ConfigurationDataSet') -> None:
-        self.check_used(self.interpreter)
+        self.__check_used()
         escaped_val = '\\"'.join(args[1].split('"'))
         self.held_object.values[args[0]] = (f'"{escaped_val}"', kwargs['description'])
 
     @typed_pos_args('configuration_data.set10', str, (int, bool))
     @typed_kwargs('configuration_data.set10', _CONF_DATA_SET_KWS)
     def set10_method(self, args: T.Tuple[str, T.Union[int, bool]], kwargs: 'kwargs.ConfigurationDataSet') -> None:
-        self.check_used(self.interpreter)
+        self.__check_used()
         # bool is a subclass of int, so we need to check for bool explicitly.
         # We already have typed_pos_args checking that this is either a bool or
         # an int.
@@ -442,7 +437,6 @@ class ConfigurationDataHolder(ObjectHolder[build.ConfigurationData], MutableInte
     @noKwargs
     def merge_from_method(self, args: T.Tuple[build.ConfigurationData], kwargs: TYPE_kwargs) -> None:
         from_object = args[0]
-        self.check_used(self.interpreter)
         self.held_object.values.update(from_object.values)