Wrap modulo operation in parens inside additive operation (#4413)

src/common/util.js

@@ -298,6 +298,10 @@ const equalityOperators = {
   "===": true,
   "!==": true
 };
+const additiveOperators = {
+  "+": true,
+  "-": true
+};
 const multiplicativeOperators = {
   "*": true,
   "/": true,
@@ -311,6 +315,11 @@ const bitshiftOperators = {
 
 function shouldFlatten(parentOp, nodeOp) {
   if (getPrecedence(nodeOp) !== getPrecedence(parentOp)) {
+    // x + y % z --> (x + y) % z
+    if (nodeOp === "%" && !additiveOperators[parentOp]) {
+      return true;
+    }
+
     return false;
   }
 

src/language-js/needs-parens.js

@@ -259,6 +259,10 @@ function needsParens(path, options) {
             return true;
           }
 
+          if (pp < np && no === "%") {
+            return !util.shouldFlatten(po, no);
+          }
+
           // Add parenthesis when working with binary operators
           // It's not stricly needed but helps with code understanding
           if (util.isBitwiseOperator(po)) {

tests/binary_math/__snapshots__/jsfmt.spec.js.snap

@@ -14,6 +14,11 @@ mantissa = ((b[2] & 0x7f) << 16) | (b[1] << 8) | b[0];
 2 / 3 * 10 / 2 + 2;
 const rotateX = ((RANGE / rect.height) * refY - RANGE / 2) * getXMultiplication(rect.width);
 const rotateY = ((RANGE / rect.width) * refX - RANGE / 2) * getYMultiplication(rect.width);
+
+a % 10 - 5;
+a * b % 10;
+a % 10 > 5;
+a % 10 == 0;
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 const result = (a + b) >>> 1;
 var sizeIndex = ((index - 1) >>> level) & MASK;
@@ -32,4 +37,9 @@ const rotateX =
 const rotateY =
   ((RANGE / rect.width) * refX - RANGE / 2) * getYMultiplication(rect.width);
 
+(a % 10) - 5;
+(a * b) % 10;
+a % 10 > 5;
+a % 10 == 0;
+
 `;

tests/binary_math/parens.js

@@ -11,3 +11,8 @@ mantissa = ((b[2] & 0x7f) << 16) | (b[1] << 8) | b[0];
 2 / 3 * 10 / 2 + 2;
 const rotateX = ((RANGE / rect.height) * refY - RANGE / 2) * getXMultiplication(rect.width);
 const rotateY = ((RANGE / rect.width) * refX - RANGE / 2) * getYMultiplication(rect.width);
+
+a % 10 - 5;
+a * b % 10;
+a % 10 > 5;
+a % 10 == 0;