From c0efa7ab22f8900f6fa1dadf0d306ec375569c8d Mon Sep 17 00:00:00 2001
From: Daniel Mensinger <daniel@mensinger-ka.de>
Date: Sun, 12 Sep 2021 16:53:54 +0200
Subject: [PATCH] interpreter: Add FeatureNew check

---
 mesonbuild/interpreter/primitives/string.py        | 12 ++++++++++++
 test cases/common/35 string operations/meson.build |  2 +-
 test cases/common/35 string operations/test.json   |  7 +++++++
 3 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 test cases/common/35 string operations/test.json

diff --git a/mesonbuild/interpreter/primitives/string.py b/mesonbuild/interpreter/primitives/string.py
index 82da6ce24..d9c441a9a 100644
--- a/mesonbuild/interpreter/primitives/string.py
+++ b/mesonbuild/interpreter/primitives/string.py
@@ -21,6 +21,11 @@ from ...interpreterbase import (
 
     InvalidArguments,
 )
+from ...mparser import (
+    MethodNode,
+    StringNode,
+    ArrayNode,
+)
 
 
 if T.TYPE_CHECKING:
@@ -105,6 +110,13 @@ class StringHolder(ObjectHolder[str]):
     @noKwargs
     @typed_pos_args('str.join', varargs=str)
     def join_method(self, args: T.Tuple[T.List[str]], kwargs: TYPE_kwargs) -> str:
+        # Implement some basic FeatureNew check on the AST level
+        assert isinstance(self.current_node, MethodNode)
+        n_args = self.current_node.args.arguments
+        if len(n_args) != 1 or not isinstance(n_args[0], ArrayNode) or not all(isinstance(x, StringNode) for x in n_args[0].args.arguments):
+            FeatureNew.single_use('str.join (varargs)', '0.60.0', self.subproject, 'List-flattening and variadic arguments')
+
+        # Actual implementation
         return self.held_object.join(args[0])
 
     @noKwargs
diff --git a/test cases/common/35 string operations/meson.build b/test cases/common/35 string operations/meson.build
index b86e13a1a..54eab88df 100644
--- a/test cases/common/35 string operations/meson.build	
+++ b/test cases/common/35 string operations/meson.build	
@@ -1,4 +1,4 @@
-project('string formatting', 'c')
+project('string formatting', 'c', meson_version: '>=0.59.0')
 
 templ = '@0@bar@1@'
 
diff --git a/test cases/common/35 string operations/test.json b/test cases/common/35 string operations/test.json
new file mode 100644
index 000000000..96f965947
--- /dev/null
+++ b/test cases/common/35 string operations/test.json	
@@ -0,0 +1,7 @@
+{
+  "stdout": [
+    {
+      "line": "WARNING: Project targeting '>=0.59.0' but tried to use feature introduced in '0.60.0': str.join (varargs). List-flattening and variadic arguments"
+    }
+  ]
+}