From 6ff1cf35f78a24d52603d84eac9349b3d4670c6c Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 20 Feb 2024 09:37:50 +0200
Subject: Make json value type prepend non-overriding for consistency with map

---
 libbuild2/variable.hxx | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'libbuild2/variable.hxx')

diff --git a/libbuild2/variable.hxx b/libbuild2/variable.hxx
index b157806..d754edf 100644
--- a/libbuild2/variable.hxx
+++ b/libbuild2/variable.hxx
@@ -1237,6 +1237,12 @@ namespace build2
   // of what looks like harmless looseness in a few contexts (such as the
   // $json.member_*() functions).
   //
+  // Note that similar to map, JSON object append/+= is overriding while
+  // prepend/=+ is not. In a sense, whatever appears last (from left to right)
+  // is kept, which is consistent with what we expect to happen when
+  // specifying the same name repeatedly (provided it's not considered
+  // invalid) in a representation (e.g., {"a":1,"a":2}).
+  //
   template <>
   struct LIBBUILD2_SYMEXPORT value_traits<json_value>
   {
-- 
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