0.2.0 - Mid migration

web/node_modules/jss/src/utils/createRule.js

@@ -0,0 +1,26 @@
+// @flow
+import warning from 'tiny-warning'
+import type {Rule, RuleOptions, JssStyle} from '../types'
+import cloneStyle from './cloneStyle'
+
+/**
+ * Create a rule instance.
+ */
+export default function createRule(
+  name: string = 'unnamed',
+  decl: JssStyle,
+  options: RuleOptions
+): Rule | null {
+  const {jss} = options
+  const declCopy = cloneStyle(decl)
+
+  const rule = jss.plugins.onCreateRule(name, declCopy, options)
+  if (rule) return rule
+
+  // It is an at-rule and it has no instance.
+  if (name[0] === '@') {
+    warning(false, `[JSS] Unknown rule ${name}`)
+  }
+
+  return null
+}