feat(analytics-browser): add page-url-previous-page plugin #1110

cyhk · 2025-05-28T05:44:33Z

Summary

This adds a page-url-previous-page plugin to the analytics browser, enriching events with a set of page url and previous page related properties.

The PRD is here.

Note that the plugin is default off right now, but there are plans to make this default on in the future.

Checklist

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Does your PR have a breaking change?: Yes

cyhk · 2025-06-13T05:03:30Z

Bug: Invalid URL Handling Causes Function Failure

The getPrevPageType function lacks error handling for invalid URLs. The new URL(previousPage) constructor throws an error if previousPage (sourced from document.referrer or sessionStorage) is malformed or invalid, causing the function and potentially the plugin to crash.

packages/analytics-browser/src/plugins/page-url-previous-page.ts#L27-L40
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this is fine since currentURL is never stored without first being run through getDecodeURI first and previousURL is always taken from currentURL

packages/analytics-browser/src/plugins/page-url-previous-page.ts

daniel-graham-amplitude · 2025-06-13T23:00:29Z

Thanks @cyhk ! Generally looks, had some comments.

General question though: was there a formal process for deciding the namings of the config and events?

For the config (autocapture. pageUrlPreviousPage) and for the event properties ([Amplitude] Previous Page URL, etc...).

I'm asking just because API changes (in this case the config definition) and event properties can't be reverted once they've been released.

cursor

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Mercy811

Thanks @cyhk for making this PR. I have two major concerns.

Is it necessary to add more event properties to all events? Potential COGS. Or at least we should have a filter to decide which events to add.
The definition of previous page url is the same as the event property referrer of page view. I read the proposal but didn't find the case where referrer cannot help.

packages/analytics-browser/src/plugins/page-url-previous-page.ts

Mercy811 · 2025-06-16T16:06:15Z

packages/analytics-browser/src/plugins/page-url-previous-page.ts

+      let previousPage = '';
+      if (sessionStorage && isStorageEnabled) {
+        const URLInfo = await sessionStorage.get(URL_INFO_STORAGE_KEY);
+        previousPage = URLInfo?.[PREVIOUS_PAGE_STORAGE_KEY] || document.referrer || '';


May result in different previous page location and referrer event properties and thus cause confusion.

Mercy811 · 2025-06-16T16:11:31Z

packages/analytics-browser/src/plugins/page-url-previous-page.ts

+        event.event_properties = {
+          ...(event.event_properties || {}),
+          '[Amplitude] Page Domain':
+            /* istanbul ignore next */ (typeof location !== 'undefined' && location.hostname) || '',
+          '[Amplitude] Page Location': locationHREF,
+          '[Amplitude] Page Path':
+            /* istanbul ignore next */ (typeof location !== 'undefined' && getDecodeURI(location.pathname)) || '',
+          '[Amplitude] Page Title':
+            /* istanbul ignore next */ (typeof document !== 'undefined' && document.title) || '',
+          '[Amplitude] Page URL': locationHREF.split('?')[0],
+          '[Amplitude] Previous Page Location': previousPage,
+          '[Amplitude] Previous Page Type': getPrevPageType(previousPage),
+        };
+      }


Any COGS concern @izaaz if we add extra event properties to all events?

Any plan to add a filter to apply to specific events? I'm thinking about config.autocapture.pageUrlPreviousPage.trackOn, a function returning boolean.

packages/analytics-browser/src/plugins/page-url-previous-page.ts

… wrapper

…nrichment

cyhk changed the title ~~AMP-130401 create previous page page url plugin~~ feat(analytics-browser): add page-url-previous-page plugin May 28, 2025

cyhk requested a review from Dogfalo June 2, 2025 17:37

cyhk force-pushed the AMP-130401-create-previous-page-page-url-plugin branch 4 times, most recently from c2223a5 to d8e6eba Compare June 12, 2025 21:19

cyhk marked this pull request as ready for review June 12, 2025 21:19

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cyhk force-pushed the AMP-130401-create-previous-page-page-url-plugin branch from d5d2b40 to c3dbbce Compare June 13, 2025 04:21

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cyhk requested review from Mercy811 and daniel-graham-amplitude June 13, 2025 21:21

daniel-graham-amplitude reviewed Jun 13, 2025

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cursor bot reviewed Jun 14, 2025

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Mercy811 reviewed Jun 16, 2025

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cyhk added 6 commits June 30, 2025 08:54

feat(analytics-browser): add page-url-previous-page plugin

c07bfb7

fix(autocapture-browser): fix bug and remove console.log

984d593

fix(autocapture-browser): fix plugin name

b0425da

fix(autocapture-browser): address unconvered cases and add more tests

d635778

fix(autocapture-browser): add listener for replaceState

77750b8

fix(autocapture-browser): improve tests

ca4f164

cyhk and others added 4 commits June 30, 2025 08:54

fix(autocapture-browser): remove console log

6a621dc

fix(autocapture-browser): fix bug, improve naming, use BrowserStorage…

1ecbb4f

… wrapper

fix: added precision tracked example event

b9fbbae

chore: copy page url enrichment into separate package

af0aa65

Dogfalo force-pushed the AMP-130401-create-previous-page-page-url-plugin branch from 6bf3702 to af0aa65 Compare June 30, 2025 16:54

fix(autocapture-browser): migrate tests and name change to page url e…

ca95788

…nrichment

feat(analytics-browser): add page-url-previous-page plugin #1110

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feat(analytics-browser): add page-url-previous-page plugin #1110

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cyhk commented May 28, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

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cyhk commented Jun 13, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Bug: Invalid URL Handling Causes Function Failure

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daniel-graham-amplitude commented Jun 13, 2025

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cyhk commented May 28, 2025 •

edited

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cyhk commented Jun 13, 2025 •

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