options: Handle updates to choices in options

Currently if you change the `choices` field in the meson_options.txt
file, no update will be done until `meson setup --wipe` is called. Now
if the choices change then the options will be properly merged.

If the currently select value is still valid it is guaranteed to be
kept, if it is now invalid the new default value will be used and a
warning will be printed.

Fixes #7386

1 files changed, 15 insertions, 5 deletions

diff --git a/mesonbuild/coredata.py b/mesonbuild/coredata.py
index 4be828b..e3b3b01 100644
--- a/mesonbuild/coredata.py
+++ b/mesonbuild/coredata.py
@@ -689,14 +689,24 @@ class CoreData:
     def get_external_link_args(self, for_machine: MachineChoice, lang):
         return self.compiler_options[for_machine][lang]['link_args'].value
 
-    def merge_user_options(self, options: T.Dict[str, T.Union[str, bool, int]]) -> None:
+    def merge_user_options(self, options: T.Dict[str, UserOption[T.Any]]) -> None:
         for (name, value) in options.items():
             if name not in self.user_options:
                 self.user_options[name] = value
-            else:
-                oldval = self.user_options[name]
-                if type(oldval) != type(value):
-                    self.user_options[name] = value
+                continue
+
+            oldval = self.user_options[name]
+            if type(oldval) != type(value):
+                self.user_options[name] = value
+            elif oldval.choices != value.choices:
+                # If the choices have changed, use the new value, but attempt
+                # to keep the old options. If they are not valid keep the new
+                # defaults but warn.
+                self.user_options[name] = value
+                try:
+                    value.set_value(oldval.value)
+                except MesonException as e:
+                    mlog.warning('Old value(s) of {} are no longer valid, resetting to default ({}).'.format(name, value.value))
 
     def is_cross_build(self, when_building_for: MachineChoice = MachineChoice.HOST) -> bool:
         if when_building_for == MachineChoice.BUILD: