Print sub-nodes of `@import` in Less (#2646)

Fixes part of #2584.

src/printer-postcss.js

@@ -129,7 +129,16 @@ function genericPrint(path, options, print) {
         " ",
         n.directives ? concat([n.directives, " "]) : "",
         adjustStrings(n.importPath, options),
-        ";"
+        n.nodes.length > 0
+          ? concat([
+              " {",
+              indent(
+                concat([softline, printNodeSequence(path, options, print)])
+              ),
+              softline,
+              "}"
+            ])
+          : ";"
       ]);
     }
     // postcss-media-query-parser

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

@@ -7,6 +7,23 @@ exports[`directives.css 1`] = `
 
 `;
 
+exports[`nodes.css 1`] = `
+@import "test.less" {}
+
+@import "test.less" {
+  a: b;
+  c: d;
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+@import "test.less";
+
+@import "test.less" {
+  a: b;
+  c: d;
+}
+
+`;
+
 exports[`url.css 1`] = `
 @import url('foo');
 $dir: 'fonts';

tests/css_import/nodes.css

@@ -0,0 +1,6 @@
+@import "test.less" {}
+
+@import "test.less" {
+  a: b;
+  c: d;
+}