fix: substracted css-variable from zero (#111)

postcss · Aug 7, 2020 · 0282bdc · 0282bdc
1 parent 295b1df
commit 0282bdc
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Showing 3 changed files with 20 additions and 2 deletions.
diff --git a/src/__tests__/index.js b/src/__tests__/index.js
@@ -396,6 +396,13 @@ test(
   'calc(-100vw + -10px)',
 );
 
+test(
+  'should reduce substracted expression from zero (css-variable)',
+  testValue,
+  'calc( 0px - (var(--foo, 4px) / 2))',
+  'calc(0px - var(--foo, 4px)/2)',
+);
+
 test(
   'should reduce nested expression',
   testValue,

diff --git a/src/lib/reducer.js b/src/lib/reducer.js
@@ -62,7 +62,7 @@ function reduceAddSubExpression(node, precision) {
     isValueType(node.left.type) &&
     node.left.value === 0 &&
     node.operator === "-" &&
-    node.right.type !== "Function"
+    !isCSSFunction(node.right)
   ) {
     return flipValue(node.right);
   }
@@ -330,3 +330,14 @@ function reduce(node, precision) {
 }
 
 export default reduce;
+
+
+function isCSSFunction(node) {
+  if (node.type === "Function") {
+    return true;
+  }
+  if (node.type === "MathExpression") {
+    return isCSSFunction(node.left) || isCSSFunction(node.right);
+  }
+  return false;
+}
diff --git a/src/lib/transform.js b/src/lib/transform.js
@@ -1,5 +1,5 @@
 import selectorParser from 'postcss-selector-parser';
-import valueParser from 'postcss-value-parser'; 
+import valueParser from 'postcss-value-parser';
 
 // eslint-disable-next-line import/no-unresolved
 import { parser } from '../parser';