opts: Allow string concatenation (fixes #7199)

mesonbuild/optinterpreter.py

@@ -177,6 +177,13 @@ class OptionInterpreter:
             if not isinstance(res, bool):
                 raise OptionException('Token after "not" is not a a boolean')
             return not res
+        elif isinstance(arg, mparser.ArithmeticNode):
+            l = self.reduce_single(arg.left)
+            r = self.reduce_single(arg.right)
+            if not (arg.operation == 'add' and isinstance(l, str) and isinstance(r, str)):
+                raise OptionException('Only string concatenation with the "+" operator is allowed')
+            FeatureNew.single_use('string concatenation in meson_options.txt', '0.55.0', self.subproject)
+            return l + r
         else:
             raise OptionException('Arguments may only be string, int, bool, or array of those.')
 

test cases/common/43 options/meson_options.txt

@@ -1,7 +1,7 @@
-option('testoption', type : 'string', value : 'optval', description : 'An option to do something')
+option('testoption', type : 'string', value : 'optval', description : 'An option ' + 'to do something')
 option('other_one', type : 'boolean', value : not (not (not (not false))))
-option('combo_opt', type : 'combo', choices : ['one', 'two', 'combo'], value : 'combo')
+option('combo_opt', type : 'co' + 'mbo', choices : ['one', 'two', 'combo'], value : 'combo')
 option('array_opt', type : 'array', choices : ['one', 'two', 'three'], value : ['one', 'two'])
 option('free_array_opt', type : 'array')
 option('integer_opt', type : 'integer', min : 0, max : -(-5), value : 3)
-option('neg_int_opt', type : 'integer', min : -5, max : 5, value : -3)
+option('neg' + '_' + 'int' + '_' + 'opt', type : 'integer', min : -5, max : 5, value : -3)