Adding dictionary entry using string variable as key.

docs/markdown/snippets/add_dictionary_variable_key.md

@@ -0,0 +1,17 @@
+## Adding dictionary entry using string variable as key
+
+New dictionary entry can now be added using string variable as key, 
+in addition to using string literal as key.
+
+```meson
+dict = {}
+
+# A variable to be used as a key
+key = 'myKey'
+
+# Add new entry using the variable
+dict += {key : 'myValue'}
+
+# Test that the stored value is correct 
+assert(dict[key] == 'myValue', 'Incorrect value retrieved from dictionary')
+```

mesonbuild/interpreterbase.py

@@ -731,7 +731,16 @@ The result of this is undefined and will become a hard error in a future Meson r
         elif isinstance(old_variable, dict):
             if not isinstance(addition, dict):
                 raise InvalidArguments('The += operator requires a dict on the right hand side if the variable on the left is a dict')
-            new_value = {**old_variable, **addition}
+            new_addition = {}
+            for (key, value) in addition.items():
+                if isinstance(key, str):
+                    new_addition[key] = value
+                elif isinstance(key, mparser.IdNode):
+                    FeatureNew('Adding dictionary entry using string variable as key', '0.53.0').use(self.subproject)
+                    new_addition[self.get_variable(key.value)] = value
+                else:
+                    raise InvalidArguments('Dictionary key must be a string or string variable')
+            new_value = {**old_variable, **new_addition}
         # Add other data types here.
         else:
             raise InvalidArguments('The += operator currently only works with arrays, dicts, strings or ints ')
@@ -1021,8 +1030,6 @@ The result of this is undefined and will become a hard error in a future Meson r
         reduced_pos = [self.evaluate_statement(arg) for arg in args.arguments]
         reduced_kw = {}
         for key in args.kwargs.keys():
-            if not isinstance(key, str):
-                raise InvalidArguments('Keyword argument name is not a string.')
             a = args.kwargs[key]
             reduced_kw[key] = self.evaluate_statement(a)
         self.argument_depth -= 1

mesonbuild/mparser.py

@@ -676,14 +676,18 @@ class Parser:
         while not isinstance(s, EmptyNode):
             potential = self.current
             if self.accept('colon'):
-                if not isinstance(s, StringNode):
-                    raise ParseException('Key must be a string.',
-                                         self.getline(), s.lineno, s.colno)
+                if isinstance(s, StringNode):
                     if s.value in a.kwargs:
                         # + 1 to colno to point to the actual string, not the opening quote
-                    raise ParseException('Duplicate dictionary key: {}'.format(s.value),
-                                         self.getline(), s.lineno, s.colno + 1)
+                        raise ParseException('Duplicate dictionary key: {}'.format(s.value), self.getline(), s.lineno, s.colno + 1)
                     a.set_kwarg(s.value, self.statement())
+                elif isinstance(s, IdNode) and isinstance(s.value, str):
+                    for key in a.kwargs:
+                        if s.value == key.value:
+                            raise ParseException('Duplicate dictionary variable key: {}'.format(s.value), self.getline(), s.lineno, s.colno)
+                    a.set_kwarg(s, self.statement())
+                else:
+                    raise ParseException('Key must be a string or string variable', self.getline(), s.lineno, s.colno)
                 potential = self.current
                 if not self.accept('comma'):
                     return a

test cases/common/228 add dict variable key/meson.build

@@ -0,0 +1,12 @@
+project('add dictionary entry using string variable as key', meson_version: '>=0.52')
+
+dict = {}
+
+# A variable to be used as a key
+key = 'myKey'
+
+# Add new entry using the variable
+dict += {key : 'myValue'}
+
+# Test that the stored value is correct 
+assert(dict[key] == 'myValue', 'Incorrect value retrieved from dictionary')