[babylon] Refactor mixin plugins handling & validation (#7999)

packages/babel-parser/src/plugin-utils.js

@@ -0,0 +1,50 @@
+// @flow
+
+import type Parser from "./parser";
+
+export type Plugin = string | [string, Object];
+
+export type PluginList = $ReadOnlyArray<Plugin>;
+
+export type MixinPlugin = (superClass: Class<Parser>) => Class<Parser>;
+
+export function hasPlugin(plugins: PluginList, name: string): boolean {
+  return plugins.some(plugin => {
+    if (Array.isArray(plugin)) {
+      return plugin[0] === name;
+    } else {
+      return plugin === name;
+    }
+  });
+}
+
+export function validatePlugins(plugins: PluginList) {
+  if (
+    hasPlugin(plugins, "decorators") &&
+    hasPlugin(plugins, "decorators-legacy")
+  ) {
+    throw new Error(
+      "Cannot use the decorators and decorators-legacy plugin together",
+    );
+  }
+
+  if (hasPlugin(plugins, "flow") && hasPlugin(plugins, "typescript")) {
+    throw new Error("Cannot combine flow and typescript plugins.");
+  }
+}
+
+// These plugins are defined using a mixin which extends the parser class.
+
+import estree from "./plugins/estree";
+import flow from "./plugins/flow";
+import jsx from "./plugins/jsx";
+import typescript from "./plugins/typescript";
+
+// NOTE: estree must load first; flow and typescript must load last.
+export const mixinPluginNames = ["estree", "jsx", "flow", "typescript"];
+export const mixinPlugins: { [name: string]: MixinPlugin } = {
+  estree,
+  jsx,
+  flow,
+  typescript,
+};