From d121e74c6f246005d2b115c10cf98a86d80f73f7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=93=9D=E7=AE=94?=
 <38349409+Sodium-Aluminate@users.noreply.github.com>
Date: Mon, 16 Jun 2025 18:17:54 +0800
Subject: [PATCH] Fix: lazy evaluation for logical expressions (#27) (#28)

* fix logical expression short-circuit evaluation (#27)

* test logical short-circuit cases (#27)
---
 src/operators.ts                     | 11 +++++++++--
 src/parser.ts                        |  4 ++--
 tests/lua-5.3/logical_operations.lua |  6 ++++++
 tests/test.js                        |  1 +
 4 files changed, 18 insertions(+), 4 deletions(-)
 create mode 100644 tests/lua-5.3/logical_operations.lua

diff --git a/src/operators.ts b/src/operators.ts
index 6556f00..5a91df4 100644
--- a/src/operators.ts
+++ b/src/operators.ts
@@ -37,8 +37,15 @@ const binaryBooleanArithmetic = (
 const bool = (value: LuaType): boolean => coerceToBoolean(value)
 
 // logical
-const and = (l: LuaType, r: LuaType): LuaType => coerceToBoolean(l) ? r : l
-const or = (l: LuaType, r: LuaType): LuaType => coerceToBoolean(l) ? l : r
+const and = (l: () => LuaType, r: () => LuaType): LuaType => {
+	const lv = l()
+	return coerceToBoolean(lv) ? r() : lv
+}
+
+const or = (l: () => LuaType, r: () => LuaType): LuaType => {
+	const lv = l()
+	return coerceToBoolean(lv) ? lv : r()
+}
 
 // unary
 const not = (value: LuaType): boolean => !bool(value)
diff --git a/src/parser.ts b/src/parser.ts
index c3d5caf..dca6690 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -303,10 +303,10 @@ const generate = (node: luaparse.Node): string | MemExpr => {
             const operator = node.operator
 
             if (operator === 'and') {
-                return `__lua.and(${left},${right})`
+                return `__lua.and(() => ${left}, () => ${right})`
             }
             if (operator === 'or') {
-                return `__lua.or(${left},${right})`
+                return `__lua.or(() => ${left}, () => ${right})`
             }
             throw new Error(`Unhandled logical operator: ${node.operator}`)
         }
diff --git a/tests/lua-5.3/logical_operations.lua b/tests/lua-5.3/logical_operations.lua
new file mode 100644
index 0000000..c9176c8
--- /dev/null
+++ b/tests/lua-5.3/logical_operations.lua
@@ -0,0 +1,6 @@
+local x = nil
+local x_ = (x and x.k or "fallback")
+assert(x_ == "fallback")
+local y = "ok"
+local y_ = (y or error("should not raise"))
+assert(y == y_)
\ No newline at end of file
diff --git a/tests/test.js b/tests/test.js
index 9406ea5..1d18745 100644
--- a/tests/test.js
+++ b/tests/test.js
@@ -24,6 +24,7 @@ let exitCode = 0
     })
     luaEnv.parseFile('goto.lua').exec()
     luaEnv.parseFile('bwcoercion.lua').exec()
+    luaEnv.parseFile('logical_operations.lua').exec()
 }
 
 {