New preserve option

Close #6

Author: MoOx

.gitignore

@@ -1 +1,2 @@
 node_modules
+test/fixtures/*.actual.css

CHANGELOG.md

@@ -1,7 +1,9 @@
-# HEAD
+# 3.0.0 - 2014-11-24
 
 - New gnu like exceptions ([ref](https://github.com/postcss/postcss-calc/issues/4))
 - New `precision` option ([ref](https://github.com/postcss/postcss-calc/issues/5))
+- New `preserve` option ([ref](https://github.com/postcss/postcss-calc/issues/6))
+
 # 2.1.0 - 2014-10-15
 
 - Add source of the error (gnu like message) (fix [#3](https://github.com/postcss/postcss-calc/issues/3))

README.md

@@ -96,6 +96,17 @@ var out = postcss()
   .css
 ```
 
+#### `preserve` (default: `false`)
+
+Allow you to preserve calc() usage in output so browsers will handle decimal precision themselves.
+
+```js
+var out = postcss()
+  .use(calc({preserve: true}))
+  .process(css)
+  .css
+```
+
 ---
 
 ## Contributing

index.js

@@ -9,20 +9,27 @@ var helpers = require("postcss-message-helpers")
  */
 module.exports = function plugin(options) {
   options = options || {}
+  var precision = options.precision
+  var preserve = options.preserve
 
   return function(style) {
     style.eachDecl(function transformDecl(decl) {
-      if (!decl.value) {
+      if (!decl.value || decl.value.indexOf("calc(") === -1) {
         return
       }
 
-      decl.value = helpers.try(function transformCSSCalc() {
-        if (decl.value.indexOf("calc(") === -1) {
-          return decl.value
+      helpers.try(function transformCSSCalc() {
+        var value = reduceCSSCalc(decl.value, precision)
+
+        if (!preserve) {
+          decl.value = value
+          return
         }
 
-        return reduceCSSCalc(decl.value, options.precision)
-      })
+        var clone = decl.clone()
+        clone.value = value
+        decl.parent.insertBefore(decl, clone)
+      }, decl.source)
     })
   }
 }

test/fixtures/calc.actual.css

@@ -0,0 +1,3 @@
+calc {
+  value: calc(1/3);
+}

test/fixtures/precision.actual.css

@@ -0,0 +1,4 @@
+calc {
+  value: 0.33333;
+  value: calc(1/3);
+}

test/fixtures/preserve.css

@@ -31,5 +31,7 @@ test("calc", function(t) {
 
   compareFixtures(t, "precision", {precision: 3}, "should have a precision option that allow to control decimal precision of calcuations")
 
+  compareFixtures(t, "preserve", {preserve: true}, "should have a preserve option that allow to keep original calc() usage")
+
   t.end()
 })