fix: applying plugin on an empty css file

index.js

@@ -127,11 +127,13 @@ module.exports = (options) => {
           STATE.mapped = new Set()
           STATE.mapped_dark = new Set()
 
-          STATE.target_rule = new Rule({ selector: target_selector, source: node.first.source })
-          STATE.target_rule_dark = new Rule({ selector: target_selector_dark, source: node.first.source })
-          STATE.target_media_dark = new AtRule({ name: 'media', params: '(prefers-color-scheme: dark)', source: node.first.source })
+          if (node.first) {
+            STATE.target_rule = new Rule({ selector: target_selector, source: node.first.source })
+            STATE.target_rule_dark = new Rule({ selector: target_selector_dark, source: node.first.source })
+            STATE.target_media_dark = new AtRule({ name: 'media', params: '(prefers-color-scheme: dark)', source: node.first.source })
+          }
 
-          if (layer) {
+          if (layer && node.first) {
             STATE.target_layer = new AtRule({ name: 'layer', params: layer, source: node.first.source })
             node.root().prepend(STATE.target_layer)
             STATE.target_ss = STATE.target_layer

index.test.js

@@ -575,3 +575,18 @@ it('Supports parallel runners when reading from a file', async () => {
   expect(resultE.css).toEqual('a { color: green; }')
   expect(resultE.warnings()).toHaveLength(0)
 })
+
+// situation encountered when using postcs-jit-props for Open Props
+// together with having @nuxt/fonts module with no global font definition
+// it still creates an empty .nuxt/nuxt-fonts-global.css file
+// and postcs-jit-props started to fail trying to parse it
+// --
+// fixed by adding "node.first" null check into parsing method
+// (lines 130 and 136 in index.js)
+
+it('Parses an empty file and rule', async () => {
+  const pluginInstance = plugin({ files: ['./props.test.empty.css'] });
+  let result = await postcss([pluginInstance]).process('');
+  expect(result.css).toEqual("");
+  expect(result.warnings()).toHaveLength(0);
+})