do not require plugins to use default exports

example/ts-gen-plugins/typechain/index.ts

@@ -15,7 +15,7 @@ interface TOptions {
   output?: string;
 }
 
-export default class Typechain extends TsGeneratorPlugin {
+export class Typechain extends TsGeneratorPlugin {
   name = "Typechain";
 
   private readonly runtimePathAbs: string;

src/plugins/loadPlugin.ts

@@ -1,10 +1,29 @@
 import { resolvePlugin } from "./resolvePlugin";
 import { TDeps } from "../deps";
 import { TContext, TsGeneratorPlugin } from "./types";
+import { Dictionary } from "../stl";
 
 export function loadPlugin(deps: TDeps, ctx: TContext): TsGeneratorPlugin {
   const pluginPath = resolvePlugin(deps, ctx.rawConfig.generator, ctx.cwd);
-  const PluginCtr = require(pluginPath).default as { new (ctx: TContext): TsGeneratorPlugin };
+  const PluginModule = require(pluginPath);
+
+  const moduleExportsCount = Object.keys(PluginModule).length;
+  if (moduleExportsCount !== 1) {
+    throw new Error(
+      `Loading plugin ${
+        ctx.rawConfig.generator
+      } failed. Plugin module has to export exactly one entity. Found ${moduleExportsCount} instead`,
+    );
+  }
+
+  const PluginCtr = getFirstKey<{ new (ctx: TContext): TsGeneratorPlugin }>(PluginModule);
 
   return new PluginCtr(ctx);
 }
+
+export function getFirstKey<T>(object: Dictionary<T>): T {
+  for (const k of Object.keys(object)) {
+    return object[k];
+  }
+  throw new Error("Any key missing!");
+}

test/integration/ts-gen-plugins/dummy-json/index.ts

@@ -3,7 +3,7 @@ import { join } from "path";
 
 const generateType = (name: string, type: string): string => `export const ${name}: ${type}`;
 
-export default class JsonPlugin extends TsGeneratorPlugin {
+export class JsonPlugin extends TsGeneratorPlugin {
   name = "JsonPlugin";
 
   transformFile({ path, contents }: TFileDesc): TFileDesc {