fix: incorrect reduction of subtraction from zero (postcss#88)

jasminexie · Sep 28, 2019 · 5338ae3 · 5338ae3
1 parent 29ff26e
commit 5338ae3
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Showing 2 changed files with 13 additions and 2 deletions.
diff --git a/src/__tests__/index.js b/src/__tests__/index.js
@@ -360,6 +360,13 @@ test(
   'calc(-1px + -1em)',
 );
 
+test(
+  'should reduce substracted division expression from zero',
+  testValue,
+  'calc( 0 - (100vw - 10px) / 2 )',
+  'calc((-100vw - -10px)/2)',
+);
+
 test(
   'should reduce nested expression',
   testValue,

diff --git a/src/lib/reducer.js b/src/lib/reducer.js
@@ -34,8 +34,12 @@ function flipValue(node) {
   if (isValueType(node.type)) {
     node.value = -node.value;
   } else if (node.type === 'MathExpression') {
-    node.left = flipValue(node.left);
-    node.right = flipValue(node.right);
+    if (node.operator === '*' || node.operator === '/') {
+      node.left = flipValue(node.left);
+    } else {
+      node.left = flipValue(node.left);
+      node.right = flipValue(node.right);
+    }
   }
 
   return node;