Adds Preact support to @rules_prerender/declarative_shadow_dom.

Refs #71.

This adds a new `/preact.mjs` entry point which is implemeted via an optional peer dep on `@rules_prerender/preact`.

I tried adding `exports` to specifically support jsut `/preact.mjs`, but unfortunately that requires `moduleResolution: "Node16"` in `tsconfig.json` which introduces a whole bunch of other problems I don't want to deal with at the moment.

examples/preact/component/BUILD.bazel

@@ -13,6 +13,7 @@ prerender_component(
         "//:node_modules/@rules_prerender/preact",
         "//:node_modules/preact",
     ],
+    deps = ["//:prerender_components/@rules_prerender/declarative_shadow_dom"],
 )
 
 ts_project(

examples/preact/component/component.tsx

@@ -1,3 +1,4 @@
+import { polyfillDeclarativeShadowDom } from '@rules_prerender/declarative_shadow_dom/preact.mjs';
 import { Template, includeScript, inlineStyle } from '@rules_prerender/preact';
 import { ComponentChildren, VNode } from 'preact';
 
@@ -19,6 +20,7 @@ export function Component({ text, children }: {
             <div id="replace">This text to be replaced by page JavaScript.</div>
             <slot></slot>
 
+            {polyfillDeclarativeShadowDom()}
             {includeScript('./script.mjs', import.meta)}
             {inlineStyle('./style.css', import.meta)}
         </Template>

packages/declarative_shadow_dom/BUILD.bazel

@@ -37,11 +37,18 @@ npm_publish(
 
 prerender_component(
     name = "declarative_shadow_dom",
-    srcs = ["declarative_shadow_dom.mts"],
+    srcs = [
+        "declarative_shadow_dom.mts",
+        "preact.mts",
+    ],
     tsconfig = "//:tsconfig",
     source_map = True,
     scripts = [":declarative_shadow_dom_polyfill"],
-    lib_deps = ["//:node_modules/rules_prerender"],
+    lib_deps = [
+        "//:node_modules/@rules_prerender/preact",
+        "//:node_modules/preact",
+        "//:node_modules/rules_prerender",
+    ],
     visibility = [
         "//:__pkg__",
         "//packages/rules_prerender:__pkg__",

packages/declarative_shadow_dom/package.json

@@ -4,6 +4,12 @@
     "type": "module",
     "main": "./declarative_shadow_dom.mjs",
     "peerDependencies": {
+        "@rules_prerender/preact": "^0.0.0-PLACEHOLDER",
         "rules_prerender": "^0.0.0-PLACEHOLDER"
+    },
+    "peerDependenciesMeta": {
+        "@rules_prerender/preact": {
+            "optional": true
+        }
     }
 }

packages/declarative_shadow_dom/preact.mts

@@ -0,0 +1,10 @@
+import { includeScript } from '@rules_prerender/preact';
+import type { VNode } from 'preact';
+
+/**
+ * Returns a prerender annotation used by the bundler to inject the declarative
+ * shadow DOM polyfill into the document.
+ */
+export function polyfillDeclarativeShadowDom(): VNode {
+    return includeScript('./declarative_shadow_dom_polyfill.mjs', import.meta);
+}