From 80927bffe5ad1eb9da6521c7a060985f3500a187 Mon Sep 17 00:00:00 2001
From: Alexis Placet <alexis.placet.dev@pm.me>
Date: Wed, 26 Aug 2026 15:28:28 +0200
Subject: [PATCH] fix: to_js dict key 'size' collides with Map.prototype.size

The LiteralMap get trap read map[k] before map.get(k), so a stored key
named "size" returned Map.prototype.size (the entry count) instead of the
stored value. Check map.has(k) first, matching getOwnPropertyDescriptor.

Adds TestPyToJsDict regression tests (test_dict_size_key, int values,
roundtrip). Full browser suite: 88 pytest + 4 async passed.
---
 include/pyjs/pre_js/literal_map.js |  4 +++-
 tests/tests/test_conversion.py     | 22 ++++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/include/pyjs/pre_js/literal_map.js b/include/pyjs/pre_js/literal_map.js
index 4cf0085..7c2a7b9 100644
--- a/include/pyjs/pre_js/literal_map.js
+++ b/include/pyjs/pre_js/literal_map.js
@@ -16,11 +16,13 @@ const handler = {
   deleteProperty: (map, k) => (map.has(k) ? map.delete(k) : delete map[k]),
   get(map, k, proxy) {
     if (k === _) return map;
+    // Stored keys must win over Map.prototype members (e.g. a key named
+    // "size" would otherwise shadow the entry count getter `map.size`).
+    if (map.has(k)) return map.get(k);
     let v = map[k];
     if (typeof v === "function" && k !== "constructor") {
       v = v.bind(map);
     }
-    v ||= map.get(k);
     return v;
   },
   getOwnPropertyDescriptor(map, k) {
diff --git a/tests/tests/test_conversion.py b/tests/tests/test_conversion.py
index f5be36c..b7ed82d 100644
--- a/tests/tests/test_conversion.py
+++ b/tests/tests/test_conversion.py
@@ -16,3 +16,25 @@ def test_fundamentals(self, test_input):
     def test_none(self):
         t = pyjs.to_js(None)
         assert pyjs.pyjs_core._module._is_undefined(t) == True
+
+
+class TestPyToJsDict:
+    def test_dict_size_key(self):
+        # regression: a dict key named "size" used to collide with
+        # Map.prototype.size (the entry count getter) in the LiteralMap get trap.
+        d = pyjs.to_js({"size": 7})
+        assert pyjs.to_py(d["size"]) == 7
+
+    def test_dict_int_values(self):
+        d = pyjs.to_js({"size": 32, "usage": 136, "zero": 0, "one": 1})
+        assert pyjs.to_py(d["size"]) == 32
+        assert pyjs.to_py(d["usage"]) == 136
+        assert pyjs.to_py(d["zero"]) == 0
+        assert pyjs.to_py(d["one"]) == 1
+
+    def test_dict_roundtrip(self):
+        x = {"size": 32, "label": "hello", "flag": True}
+        d = pyjs.to_js(x)
+        assert pyjs.to_py(d["size"]) == 32
+        assert pyjs.to_py(d["label"]) == "hello"
+        assert pyjs.to_py(d["flag"]) is True