5 files changed, 82 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+                    mlog.warning('Old value(s) of {} are no longer valid, resetting to default ({}).'.format(name, value.value))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:
diff --git a/run_unittests.py b/run_unittests.py
index 0385404..881b781 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -3325,6 +3325,46 @@ int main(int argc, char **argv) {
         self.setconf("-Dfree_array_opt=['a,b', 'c,d']", will_build=False)
         self.opt_has('free_array_opt', ['a,b', 'c,d'])
 
+    def test_options_with_choices_changing(self) -> None:
+        """Detect when options like arrays or combos have their choices change."""
+        testdir = Path(os.path.join(self.unit_test_dir, '84 change option choices'))
+        options1 = str(testdir / 'meson_options.1.txt')
+        options2 = str(testdir / 'meson_options.2.txt')
+
+        # Test that old options are changed to the new defaults if they are not valid
+        real_options = str(testdir / 'meson_options.txt')
+        self.addCleanup(os.unlink, real_options)
+
+        shutil.copy(options1, real_options)
+        self.init(str(testdir))
+        shutil.copy(options2, real_options)
+
+        self.build()
+        opts = self.introspect('--buildoptions')
+        for item in opts:
+            if item['name'] == 'combo':
+                self.assertEqual(item['value'], 'b')
+                self.assertEqual(item['choices'], ['b', 'c', 'd'])
+            elif item['name'] == 'arr':
+                self.assertEqual(item['value'], ['b'])
+                self.assertEqual(item['choices'], ['b', 'c', 'd'])
+
+        self.wipe()
+
+        # When the old options are valid they should remain
+        shutil.copy(options1, real_options)
+        self.init(str(testdir), extra_args=['-Dcombo=c', '-Darray=b,c'])
+        shutil.copy(options2, real_options)
+        self.build()
+        opts = self.introspect('--buildoptions')
+        for item in opts:
+            if item['name'] == 'combo':
+                self.assertEqual(item['value'], 'c')
+                self.assertEqual(item['choices'], ['b', 'c', 'd'])
+            elif item['name'] == 'arr':
+                self.assertEqual(item['value'], ['b', 'c'])
+                self.assertEqual(item['choices'], ['b', 'c', 'd'])
+
     def test_subproject_promotion(self):
         testdir = os.path.join(self.unit_test_dir, '12 promote')
         workdir = os.path.join(self.builddir, 'work')
diff --git a/test cases/unit/84 change option choices/meson.build b/test cases/unit/84 change option choices/meson.build
new file mode 100644
index 0000000..d056d65
--- /dev/null
+++ b/test cases/unit/84 change option choices/meson.build
@@ -0,0 +1 @@
+project('change option choices')
diff --git a/test cases/unit/84 change option choices/meson_options.1.txt b/test cases/unit/84 change option choices/meson_options.1.txt
new file mode 100644
index 0000000..d0326a5
--- /dev/null
+++ b/test cases/unit/84 change option choices/meson_options.1.txt
@@ -0,0 +1,13 @@
+option(
+    'combo',
+    type : 'combo',
+    choices : ['a', 'b', 'c'],
+    value : 'a',
+)
+
+option(
+    'array',
+    type : 'array',
+    choices : ['a', 'b', 'c'],
+    value : ['a'],
+)
diff --git a/test cases/unit/84 change option choices/meson_options.2.txt b/test cases/unit/84 change option choices/meson_options.2.txt
new file mode 100644
index 0000000..4684673
--- /dev/null
+++ b/test cases/unit/84 change option choices/meson_options.2.txt
@@ -0,0 +1,13 @@
+option(
+    'combo',
+    type : 'combo',
+    choices : ['b', 'c', 'd'],
+    value : 'b',
+)
+
+option(
+    'array',
+    type : 'array',
+    choices : ['b', 'c', 'd'],
+    value : ['b'],
+)