feat: ga consent mode v2

web/src/lib/analytics-config.test.ts

@@ -0,0 +1,55 @@
+import { readdirSync, readFileSync } from "node:fs";
+import { join } from "node:path";
+import { fileURLToPath } from "node:url";
+import { describe, expect, it } from "vitest";
+
+// The analytics tag ships as a static file (`web/static/ga.js`) so it can be
+// gated by PUBLIC_GA_ENABLED at build time; these guards cover the promises of
+// docs/plan-seo.md section 0 - cookieless, no ads, and nothing about the image.
+const WEB_DIR = fileURLToPath(new URL("../../", import.meta.url));
+const GA_PATH = join(WEB_DIR, "static", "ga.js");
+
+function sourceFiles(dir: string): string[] {
+	return readdirSync(dir, { withFileTypes: true }).flatMap((entry) => {
+		const full = join(dir, entry.name);
+		if (entry.isDirectory()) return sourceFiles(full);
+		return entry.name.endsWith(".ts") || entry.name.endsWith(".svelte")
+			? [full]
+			: [];
+	});
+}
+
+describe("GA tag configuration", () => {
+	const ga = readFileSync(GA_PATH, "utf8");
+
+	it("denies analytics and ad storage before the config call", () => {
+		for (const key of [
+			"analytics_storage",
+			"ad_storage",
+			"ad_user_data",
+			"ad_personalization",
+		]) {
+			expect(ga, key).toMatch(new RegExp(`${key}:\\s*"denied"`));
+		}
+		expect(ga.indexOf('gtag("consent"')).toBeLessThan(
+			ga.indexOf('gtag("config"'),
+		);
+	});
+
+	it("keeps remarketing and Google signals off", () => {
+		expect(ga).toMatch(/allow_google_signals:\s*false/);
+		expect(ga).toMatch(/allow_ad_personalization_signals:\s*false/);
+	});
+
+	it("sends nothing but the page view", () => {
+		const callers = sourceFiles(join(WEB_DIR, "src"))
+			.filter((file) => !file.endsWith(".test.ts"))
+			.filter((file) =>
+				/gtag\s*\(|dataLayer\.push/.test(readFileSync(file, "utf8")),
+			);
+		expect(
+			callers.map((file) => file.replace(WEB_DIR, "")),
+			"gtag is configured in one place only",
+		).toEqual([]);
+	});
+});

web/static/ga.js

@@ -2,5 +2,26 @@ window.dataLayer = window.dataLayer || [];
 function gtag() {
 	window.dataLayer.push(arguments);
 }
+
+// Consent Mode v2, denied by default, before any config call: analytics then
+// run in cookieless mode (pings without cookies, no cross-site identity), which
+// is the configuration promised in `docs/plan-seo.md` section 0. No consent UI
+// is planned - nothing here is granted by default.
+gtag("consent", "default", {
+	analytics_storage: "denied",
+	ad_storage: "denied",
+	ad_user_data: "denied",
+	ad_personalization: "denied",
+	functionality_storage: "denied",
+	personalization_storage: "denied",
+	security_storage: "granted",
+});
+
 gtag("js", new Date());
-gtag("config", "G-MEQJ7JHRQQ");
+gtag("config", "G-MEQJ7JHRQQ", {
+	// No remarketing and no ad audiences: this site takes no ads (section 0).
+	allow_google_signals: false,
+	allow_ad_personalization_signals: false,
+	// GA4 drops the full IP either way; this removes the parameter outright.
+	ip_collection: false,
+});