fix: making optional peer dependencies actually optional

@vue/server-renderer and @vue/compiler-dom were both required in the sense that
they will throw regardless of whether or not your are using functionality from
those libraries if they weren't installed. I don't believe this was intentional
so I have made them optional and they will now only throw if you try to use them
and the package isn't available.

package.json

@@ -65,10 +65,14 @@
  "vuex": "4.1.0"
  },
  "peerDependencies": {
+ "@vue/compiler-dom": "^3.0.1",
  "@vue/server-renderer": "^3.0.1",
  "vue": "^3.0.1"
  },
  "peerDependenciesMeta": {
+ "@vue/compiler-dom": {
+ "optional": true
+ },
  "@vue/server-renderer": {
  "optional": true
  }

src/renderToString.ts

@@ -1,8 +1,8 @@
-import { renderToString as baseRenderToString } from '@vue/server-renderer'
 import { DefineComponent } from 'vue'
 import { createInstance } from './createInstance'
 import { ComponentMountingOptions } from './mount'
 import { RenderMountingOptions } from './types'
+import { requireVueServerRenderer } from './utils/requireOptionalPeer'
 
 export function renderToString<
  T,
@@ -22,6 +22,8 @@ export function renderToString<
 ): Promise<string>
 
 export function renderToString(component: any, options?: any): Promise<string> {
+ const {renderToString: baseRenderToString} = requireVueServerRenderer()
+
  if (options?.attachTo) {
  console.warn('attachTo option is not available for renderToString')
  }

src/utils/compileSlots.ts

@@ -1,7 +1,9 @@
-import { compile } from '@vue/compiler-dom'
 import * as vue from 'vue'
+import { requireVueCompilerDom } from './requireOptionalPeer'
 
 export function processSlot(source = '', Vue = vue) {
+ const {compile} = requireVueCompilerDom();
+
  let template = source.trim()
  const hasWrappingTemplate = template && template.startsWith('<template')
 

src/utils/requireOptionalPeer.ts

@@ -0,0 +1,23 @@
+import { createRequire } from 'module'
+
+// @ts-ignore - cjs build will complain about import.meta not being allowed, but its not actually used as require will be defined there
+const require = globalThis.require ? globalThis.require : createRequire(import.meta.url);
+
+type StringLiteral<T> = T extends string ? string extends T ? never : T : never;
+export function requireOptional<T extends string>(packageName: StringLiteral<T>): unknown {
+ try {
+ return require(packageName);
+ } catch {
+ throw new Error(
+ `The optional peer-dependency ${packageName} is needed for this test and was not found. Please ensure that it has been installed as a dev-dependency and retry.`
+ );
+ }
+}
+
+export function requireVueCompilerDom() {
+ return requireOptional('@vue/compiler-dom') as typeof import('@vue/compiler-dom');
+}
+
+export function requireVueServerRenderer() {
+ return requireOptional('@vue/server-renderer') as typeof import('@vue/server-renderer');
+}