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fix: push Arguments objects to dataLayer so gtag.js processes commands #64

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Merged
Aliferous3 merged 1 commit into from
Sep 29, 2026
Merged

fix: push Arguments objects to dataLayer so gtag.js processes commands #64

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7 changes: 5 additions & 2 deletions src/analytics/ga4.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -84,8 +84,11 @@ export function initGoogleAnalytics(): void {
if (!id || (!isGA4ProductionHost(host) && !isGA4DebugHost(host))) return;
try {
window.dataLayer = window.dataLayer || [];
window.gtag = function gtagShim(...args: unknown[]) {
window.dataLayer!.push(args);
// MUST push `arguments`, not a rest-args array — gtag.js's command
// interpreter only processes Arguments objects in dataLayer; plain
// arrays are ignored (container registers but no hits ever flush).
window.gtag = function gtagShim() {
window.dataLayer!.push(arguments);
};
window.gtag('js', new Date());
window.gtag('config', id, {
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8 changes: 8 additions & 0 deletions test/ga4-analytics.test.mjs
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Expand Up @@ -103,6 +103,14 @@ test('config disables automatic page_view and ads/identity features', () => {
assert.match(facade, /debug_mode: isGA4DebugHost/, 'localhost must run debug_mode');
});

test('dataLayer shim pushes arguments — plain arrays are ignored by gtag.js', () => {
// gtag.js's command interpreter only processes Arguments objects; a
// (...args) => push(args) shim silently drops every command.
const facade = codeOnly('src/analytics/ga4.ts');
assert.match(facade, /push\(arguments\)/);
assert.doesNotMatch(facade, /push\(args\)/);
});

test('gtag script loads async from googletagmanager.com only', () => {
const facade = src('src/analytics/ga4.ts');
assert.match(facade, /script\.async\s*=\s*true/);
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