fix(core): improved ssr (#2833)

Author: bennypowers

core/pfe-core/package.json

@@ -11,6 +11,11 @@
   "exports": {
     ".": "./core.js",
     "./*": "./*",
+    "./ssr-shims.js": {
+      "node": "./ssr-shims.js",
+      "import": "./core.js",
+      "default": "./core.js"
+    },
     "./controllers/*": "./controllers/*",
     "./decorators/*": "./decorators/*",
     "./functions/*": "./functions/*",

core/pfe-core/ssr-shims.ts

@@ -0,0 +1,56 @@
+class ObserverShim {
+  observe(): void {
+    void 0;
+  }
+
+  disconnect(): void {
+    void 0;
+  }
+}
+
+class MiniHTMLElement {
+  innerHTML = '';
+  constructor(public tagName: string) { }
+}
+
+class MiniHTMLTemplateElement extends MiniHTMLElement {
+  content = { cloneNode: (): string => this.innerHTML };
+}
+
+class MiniDocument {
+  createElement(tagName: string): MiniHTMLElement {
+    switch (tagName) {
+      case 'template':
+        return new MiniHTMLTemplateElement(tagName);
+      default:
+        return new MiniHTMLElement(tagName);
+    }
+  }
+}
+
+// @ts-expect-error: this runs in node
+globalThis.window ??= globalThis;
+// @ts-expect-error: this runs in node
+globalThis.document ??= new MiniDocument();
+// @ts-expect-error: this runs in node
+globalThis.navigator ??= { userAgent: '' };
+// @ts-expect-error: this runs in node
+globalThis.ErrorEvent ??= Event;
+// @ts-expect-error: this runs in node
+globalThis.IntersectionObserver ??= ObserverShim;
+// @ts-expect-error: this runs in node
+globalThis.MutationObserver ??= ObserverShim;
+// @ts-expect-error: this runs in node
+globalThis.getComputedStyle ??= function() {
+  return {
+    getPropertyPriority() {
+      return '';
+    },
+    getPropertyValue() {
+      return '';
+    },
+  };
+}
+
+;
+