Add Filter Parameter (#327)

This allows for conditionally processing imports based on their URLs.

Closes #279, #254, #299, #259

README.md

@@ -35,6 +35,8 @@ If this behavior is not what you want, look at `skipDuplicates` option
 please look at
 [postcss-easy-import](https://github.com/trysound/postcss-easy-import)
 (which use this plugin under the hood).
+- Imports which are not modified (by `options.filter` or because they are remote
+  imports) are moved to the top of the output.
 - **This plugin attempts to follow the CSS `@import` spec**; `@import`
   statements must precede all other statements (besides `@charset`).
 
@@ -110,6 +112,14 @@ Checkout the [tests](test) for more examples.
 
 ### Options
 
+### `filter`
+Type: `Function`  
+Default: `() => true`
+
+Only transform imports for which the test function returns `true`. Imports for
+which the test function returns `false` will be left as is. The function gets
+the path to import as an argument and should return a boolean.
+
 #### `root`
 
 Type: `String`  

index.js

@@ -109,6 +109,7 @@ function applyMedia(bundle) {
 function applyStyles(bundle, styles) {
   styles.nodes = []
 
+  // Strip additional statements.
   bundle.forEach(stmt => {
     if (stmt.type === "import") {
       stmt.node.parent = undefined
@@ -140,6 +141,11 @@ function parseStyles(result, styles, options, state, media) {
             return
           }
 
+          if (options.filter && !options.filter(stmt.uri)) {
+            // rejected by filter
+            return
+          }
+
           return resolveImportId(result, stmt, options, state)
         })
       }, Promise.resolve())

test/filter.js

@@ -0,0 +1,17 @@
+// external tooling
+import test from "ava"
+
+// internal tooling
+import checkFixture from "./helpers/check-fixture"
+
+test("should filter all imported stylesheets", checkFixture, "filter-all", {
+  filter: () => false,
+})
+
+test("should filter some stylesheets", checkFixture, "filter-some", {
+  filter: url => url !== "foobar.css",
+})
+
+test("shouldn't accept ignored stylesheets", checkFixture, "filter-ignore", {
+  filter: () => true,
+})

test/fixtures/filter-all.css

@@ -0,0 +1,12 @@
+@import "foo.css";
+@import "foo.css" screen;
+@import 'bar.css';
+@import 'bar.css' screen;
+@import url(baz.css);
+@import url(baz.css) screen;
+@import url("foobar.css");
+@import url("foobar.css") screen and (min-width: 25em);
+@import url('foobarbaz.css');
+@import url('foobarbaz.css') print, screen and (min-width: 25em);
+
+content{}

test/fixtures/filter-all.expected.css

@@ -0,0 +1,11 @@
+@import "foo.css";
+@import "foo.css" screen;
+@import 'bar.css';
+@import 'bar.css' screen;
+@import url(baz.css);
+@import url(baz.css) screen;
+@import url("foobar.css");
+@import url("foobar.css") screen and (min-width: 25em);
+@import url('foobarbaz.css');
+@import url('foobarbaz.css') print, screen and (min-width: 25em);
+content{}

test/fixtures/filter-ignore.css

@@ -0,0 +1,15 @@
+@import "ignore.css" (min-width: 25em);
+@import "http://css";
+@import "https://css";
+@import 'http://css';
+@import 'https://css';
+@import url(http://css);
+@import url(https://css);
+@import url("http://css");
+@import url("https://css");
+@import url('http://css');
+@import url('https://css');
+@import url("//css");
+@import url('//css');
+@import url(//css);
+content{}

test/fixtures/filter-ignore.expected.css

@@ -0,0 +1,19 @@
+@import "http://css" (min-width: 25em);
+@import "http://css-screen" (min-width: 25em) and screen;
+@import "http://css";
+@import "https://css";
+@import 'http://css';
+@import 'https://css';
+@import url(http://css);
+@import url(https://css);
+@import url("http://css");
+@import url("https://css");
+@import url('http://css');
+@import url('https://css');
+@import url("//css");
+@import url('//css');
+@import url(//css);
+@media (min-width: 25em){
+ignore{}
+}
+content{}

test/fixtures/filter-some.css

@@ -0,0 +1,12 @@
+@import "foo.css";
+@import "foo.css" screen;
+@import 'bar.css';
+@import 'bar.css' screen;
+@import url(baz.css);
+@import url(baz.css) screen;
+@import url("foobar.css");
+@import url("foobar.css") screen and (min-width: 25em);
+@import url('foobarbaz.css');
+@import url('foobarbaz.css') print, screen and (min-width: 25em);
+
+content{}

test/fixtures/filter-some.expected.css

@@ -0,0 +1,20 @@
+
+@import url("foobar.css");
+@import url("foobar.css") screen and (min-width: 25em);
+foo{}
+@media screen{
+foo{}
+}
+bar{}
+@media screen{
+bar{}
+}
+baz{}
+@media screen{
+baz{}
+}
+foobarbaz{}
+@media print, screen and (min-width: 25em){
+foobarbaz{}
+}
+content{}