From d2eb8fe6ecf8f884ad8dbf96962b04363c9efee4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matou=C5=A1=20Jan=20Fialka?= <mjf@mjf.cz>
Date: Fri, 20 Feb 2026 07:31:32 +0100
Subject: [PATCH] [SpaceLua] Use `luaFormatNumber` for number-to-string
 coercion in `..` and `table.concat`
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Replace raw `String(v)` calls with `luaFormatNumber` in the concatenation
operator and `table.concat`, so that floats are formatted according to Lua
semantics rather than JavaScript's. This fixes cases like `10.8*22..""`
producing `237.60000000000002` instead of `237.6`, and ensures
integer-valued floats carry the `.0` suffix as Lua requires.

Signed-off-by: Matouš Jan Fialka <mjf@mjf.cz>
---
 client/space_lua/arithmetic_test.lua   | 31 ++++++++++++++++++++++++++
 client/space_lua/eval.ts               |  5 +++--
 client/space_lua/stdlib/table.ts       |  5 +++--
 client/space_lua/stdlib/table_test.lua | 30 +++++++++++++++++++++++++
 4 files changed, 67 insertions(+), 4 deletions(-)

diff --git a/client/space_lua/arithmetic_test.lua b/client/space_lua/arithmetic_test.lua
index e576cbc8..daf69e0e 100644
--- a/client/space_lua/arithmetic_test.lua
+++ b/client/space_lua/arithmetic_test.lua
@@ -1741,3 +1741,34 @@ do
     assertEquals(math.type(sum_f), 'float', 'float sum stays float')
   end
 end
+
+-- 24. Concatenation number-to-string coercion
+
+-- 24.1. Integer formatting must not get decimal point
+assertEquals(1 .. "", "1", ".. int 1")
+assertEquals(0 .. "", "0", ".. int 0")
+assertEquals(-5 .. "", "-5", ".. int -5")
+
+-- 24.2. Integer-valued floats must show .0 suffix
+assertEquals(1.0 .. "", "1.0", ".. float 1.0")
+assertEquals(2.0 .. "", "2.0", ".. float 2.0")
+assertEquals(-3.0 .. "", "-3.0", ".. float -3.0")
+
+-- 24.3. 10.8*22 must produce Lua's "237.6" and not "237.60000000000002"
+local r = 10.8 * 22
+assertEquals(r .. "", "237.6", ".. 10.8*22 formats correctly")
+
+-- 24.4. Special float values
+assertEquals(1/0.0 .. "", "inf", ".. +inf")
+assertEquals(-1/0.0 .. "", "-inf", ".. -inf")
+assertEquals(0.0/0.0 .. "", "-nan", ".. nan")
+
+-- 24.5. Non-integer floats
+assertEquals(0.5 .. "", "0.5", ".. float 0.5")
+assertEquals(3.14 .. "", "3.14", ".. float 3.14")
+
+-- 24.6. LHS and RHS number coercion
+assertEquals("x=" .. 42, "x=42", ".. string..int")
+assertEquals("x=" .. 1.5, "x=1.5", ".. string..float")
+assertEquals(99 .. "!", "99!", ".. int..string")
+assertEquals(0.0 .. "!", "0.0!", ".. float..string")
diff --git a/client/space_lua/eval.ts b/client/space_lua/eval.ts
index 18e9928b..a709f30c 100644
--- a/client/space_lua/eval.ts
+++ b/client/space_lua/eval.ts
@@ -19,6 +19,7 @@ import {
   luaEnsureCloseStack,
   LuaEnv,
   luaEquals,
+  luaFormatNumber,
   LuaFunction,
   luaGet,
   luaIndexValue,
@@ -333,10 +334,10 @@ function luaOp(
             return v as string;
           }
           if (typeof v === "number") {
-            return String(v);
+            return luaFormatNumber(v);
           }
           if (isTaggedFloat(v)) {
-            return String(v.value);
+            return luaFormatNumber(v.value, "float");
           }
           const t = luaTypeName(v);
           throw new LuaRuntimeError(
diff --git a/client/space_lua/stdlib/table.ts b/client/space_lua/stdlib/table.ts
index c0aba789..c0d4e5e7 100644
--- a/client/space_lua/stdlib/table.ts
+++ b/client/space_lua/stdlib/table.ts
@@ -5,6 +5,7 @@ import {
   luaCall,
   type LuaEnv,
   luaEquals,
+  luaFormatNumber,
   luaGet,
   LuaMultiRes,
   LuaRuntimeError,
@@ -77,10 +78,10 @@ export const tableApi = new LuaTable({
           return v;
         }
         if (typeof v === "number") {
-          return String(v);
+          return luaFormatNumber(v);
         }
         if (isTaggedFloat(v)) {
-          return String(v.value);
+          return luaFormatNumber(v.value, "float");
         }
 
         const ty = typeof v === "object" && v instanceof LuaTable
diff --git a/client/space_lua/stdlib/table_test.lua b/client/space_lua/stdlib/table_test.lua
index b0e09e2b..4cef98af 100644
--- a/client/space_lua/stdlib/table_test.lua
+++ b/client/space_lua/stdlib/table_test.lua
@@ -255,3 +255,33 @@ do
     local c = a
     assertTrue(a == c)
 end
+
+-- table.concat
+do
+    assertEqual(table.concat(
+        { "Hello", "world" }, " "), "Hello world")
+    assertEqual(table.concat(
+        { "Hello", "world", "three" }, " ", 2, 3), "world three")
+
+    assertEqual(table.concat({ "a", "b", "c" }), "abc")
+    assertEqual(table.concat({ "a", "b", "c" }, "", 2, 1), "")
+
+    assertError(function() table.concat({ "a", {} }, "") end)
+
+    -- number coercion: integers must not get a decimal point
+    assertEqual(table.concat({ 1, 2, 3 }, ","), "1,2,3")
+
+    -- integer-valued floats must show .0 suffix (Lua semantics)
+    assertEqual(table.concat({ 1.0, 2.0 }, ","), "1.0,2.0")
+
+    -- motivating case: 10.8*22 must produce "237.6" not "237.60000000000002"
+    assertEqual(table.concat({ 10.8 * 22 }, ""), "237.6")
+
+    -- special float values
+    assertEqual(table.concat({ 1/0.0 }, ""), "inf")
+    assertEqual(table.concat({ -1/0.0 }, ""), "-inf")
+    assertEqual(table.concat({ 0.0/0.0 }, ""), "-nan")
+
+    -- mixed strings and numbers
+    assertEqual(table.concat({ "a", 1, "b", 2.5 }, "-"), "a-1-b-2.5")
+end