feat: fix the logic short-circuit bug (#8)

* feat: fix the logic short-circuit bug

* fix: apply suggestions from code review

Co-authored-by: Zixuan Liu <[email protected]>

---------

Co-authored-by: Zixuan Liu <[email protected]>

Author: tx2002

Diff for: .eslintrc.json

@@ -23,7 +23,8 @@
 		"@typescript-eslint/no-unused-vars": ["warn", {"argsIgnorePattern": "^_"}],
 		"quotes": ["warn", "single"],
 		"max-len": ["warn", {"code": 100, "tabWidth": 4, "ignoreUrls": true, "ignorePattern": "^import|^export"}],
-		"newline-per-chained-call": [2, {"ignoreChainWithDepth": 3}]
+		"newline-per-chained-call": [2, {"ignoreChainWithDepth": 3}],
+		"no-case-declarations": "off"
 	},
 	"ignorePatterns": ["**/*.js"]
 }

Diff for: index.ts

@@ -150,12 +150,13 @@ function evaluate(_node: jsep.Expression, context: object) {
       return node.value;
 
     case 'LogicalExpression':
-      if (node.operator === '||') {
-        return evaluate(node.left, context) || evaluate(node.right, context);
-      } else if (node.operator === '&&') {
-        return evaluate(node.left, context) && evaluate(node.right, context);
+      const leftValue = evaluate(node.left, context);
+      if (node.operator === '||' && leftValue) {
+        return leftValue;
+      } else if (node.operator === '&&' && !leftValue) {
+        return leftValue;
       }
-      return binops[node.operator](evaluate(node.left, context), evaluate(node.right, context));
+      return binops[node.operator](leftValue, evaluate(node.right, context));
 
     case 'MemberExpression':
       return evaluateMember(node, context)[1];
@@ -222,15 +223,17 @@ async function evalAsync(_node: jsep.Expression, context: object) {
 
     case 'LogicalExpression': {
       if (node.operator === '||') {
-        return (
-          (await evalAsync(node.left, context)) ||
-          (await evalAsync(node.right, context))
-        );
+        const left = await evalAsync(node.left, context);
+        if (left) {
+          return left;
+        }
+        return await evalAsync(node.right, context);
       } else if (node.operator === '&&') {
-        return (
-          (await evalAsync(node.left, context)) &&
-          (await evalAsync(node.right, context))
-        );
+        const left = await evalAsync(node.left, context);
+        if (!left) {
+          return left;
+        }
+        return await evalAsync(node.right, context);
       }
 
       const [left, right] = await Promise.all([

Diff for: test.js

@@ -62,9 +62,9 @@ const fixtures = [
   {expr: '1 >= 2',          expected: false },
 
   // logical expression lazy evaluation
-  {expr: 'true || false',  expected: true  },
+  {expr: 'true || throw()',  expected: true  },
   {expr: 'false || true',    expected: true  },
-  {expr: 'false && true', expected: false  },
+  {expr: 'false && throw()', expected: false  },
   {expr: 'true && false',    expected: false  },
 
   // member expression