[HOLD for payment 2023-09-21] [$500] [Distance] - There is NO animation of the transition when I have entered start and finish points

[lanitochka17]

If you haven’t already, check out our contributing guidelines for onboarding and email contributors@expensify.com to request to join our Slack channel!

---

Issue found when executing PR #26610

Action Performed:

1. Open app on small screen (height = +- 400px )
2. Go to FAB -> Request money -> Distance
3. Enter start and finish points
4. Click "Add stope"

Expected Result:

Should be an animation of the transition of the list elements to the end

Actual Result:

There is NO animation of the transition of the list elements to the end

Workaround:

Unknown

Platforms:

Which of our officially supported platforms is this issue occurring on?

• Android / native
• Android / Chrome
• iOS / native
• iOS / Safari
• Windows / Chrome
• MacOS / Desktop

Version Number: 1.3.63-0

Reproducible in staging?: Yes

Reproducible in production?: Yes

If this was caught during regression testing, add the test name, ID and link from TestRail:

Email or phone of affected tester (no customers):

Logs: https://stackoverflow.com/c/expensify/questions/4856

Notes/Photos/Videos: Any additional supporting documentation

Bug6188423_Recording__6138.3.mp4

Expensify/Expensify Issue URL:

Issue reported by: Applause - Internal Team

Slack conversation:

View all open jobs on GitHub

Upwork Automation - Do Not Edit

• Upwork Job URL: https://www.upwork.com/jobs/~0116cd2b0228d37197
• Upwork Job ID: 1699803735595442176
• Last Price Increase: 2023-09-07
• Automatic offers:
• jjcoffee | Reviewer | 26572301
• bernhardoj | Contributor | 26572302

[melvin-bot]

Triggered auto assignment to @puneetlath (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details.

[melvin-bot]

Bug0 Triage Checklist (Main S/O)

• This "bug" occurs on a supported platform (ensure Platforms in OP are ✅)
• This bug is not a duplicate report (check E/App issues and #expensify-bugs)
  • If it is, comment with a link to the original report, close the issue and add any novel details to the original issue instead
• This bug is reproducible using the reproduction steps in the OP. S/O
  • If the reproduction steps are clear and you're unable to reproduce the bug, check with the reporter and QA first, then close the issue.
  • If the reproduction steps aren't clear and you determine the correct steps, please update the OP.
• This issue is filled out as thoroughly and clearly as possible
  • Pay special attention to the title, results, platforms where the bug occurs, and if the bug happens on staging/production.
• I have reviewed and subscribed to the linked Slack conversation to ensure Slack/Github stay in sync

[jscardona12]

Proposal

Please re-state the problem that we are trying to solve in this issue.

Distance - There is NO animation of the transition when I have entered start and finish points.

What is the root cause of that problem?

The line

App/src/components/DistanceRequest.js

Line 174 in 8150ce0

scrollViewRef.current.scrollToEnd({animated: true});

scrollToEnd does not work.

What changes do you think we should make in order to solve the problem?

We should modify

App/src/components/DistanceRequest.js

Line 174 in 8150ce0

scrollViewRef.current.scrollToEnd({animated: true});

and set it as scrollViewRef.current.scrollTo({y:height, animated: true});

Solution Working

Screen.Recording.2023-09-04.at.4.40.43.PM.mov

What alternative solutions did you explore? (Optional)

[DylanDylann]

Proposal

Please re-state the problem that we are trying to solve in this issue.

There is NO animation of the transition when I have entered start and finish points

What is the root cause of that problem?

We are using usePrevious hook to save the previous waypoint. When this component is re-render 2 times, for example, waypoints are 2. The first re-rendering Waypoints is updated to 3 and previousWaypoints is updated to 2, the second re-rendering Waypoints is not updated but the previousWaypoints still updated to 3 (the value of Waypoints in the first time). It causes that numberOfWaypoints = numberOfPreviousWaypoints

App/src/components/DistanceRequest.js

Lines 173 to 175 in 6b1a667

	if (scrollContentHeight < height && numberOfWaypoints > numberOfPreviousWaypoints) {
	scrollViewRef.current.scrollToEnd({animated: true});
	}

scrollToEnd function is not called because numberOfWaypoints = numberOfPreviousWaypoints

What changes do you think we should make in order to solve the problem?

App/src/components/DistanceRequest.js

Lines 173 to 175 in 6b1a667

	if (scrollContentHeight < height && numberOfWaypoints > numberOfPreviousWaypoints) {
	scrollViewRef.current.scrollToEnd({animated: true});
	}

In here, we can remove the condition numberOfWaypoints > numberOfPreviousWaypoints
It still works well

Screen.Recording.2023-09-05.at.15.30.44.mov

What alternative solutions did you explore? (Optional)

We only update numberOfPreviousWaypoints if numberOfWaypoints changed

    const numberOfPreviousWaypoints = useMemo(() => _.size(previousWaypoints), [numberOfWaypoints]);

[bernhardoj]

Proposal

Please re-state the problem that we are trying to solve in this issue.

Adding a new stop to the distance request didn't scroll the waypoint list to the bottom. This issue only happens if we fill in at least 2 valid waypoints.

What is the root cause of that problem?

Adding a new stop will increase the number of waypoints. We use ScrollView onContentSizeChange to decide whether we should scroll to the bottom or not.

App/src/components/DistanceRequest.js

Lines 172 to 177 in 1223e1e

	onContentSizeChange={(width, height) => {
	if (scrollContentHeight < height && numberOfWaypoints > numberOfPreviousWaypoints) {
	scrollViewRef.current.scrollToEnd({animated: true});
	}
	setScrollContentHeight(height);
	}}

The failing condition in our case is numberOfWaypoints > numberOfPreviousWaypoints. When we don't fill any of the waypoints, this condition works fine, but when we fill at least 2 valid waypoints, the condition starts to fail. Why?

numberOfPreviousWaypoints uses usePrevious to store the previous value.

App/src/components/DistanceRequest.js

Lines 85 to 88 in 1223e1e

	const waypoints = useMemo(() => lodashGet(transaction, 'comment.waypoints', {}), [transaction]);
	const previousWaypoints = usePrevious(waypoints);
	const numberOfWaypoints = _.size(waypoints);
	const numberOfPreviousWaypoints = _.size(previousWaypoints);

However, usePrevious stores the previous value of the previous render. When the component is rerendered once again, the previous value now is the same as the current value. So, if something triggers the re-render before onContentSizeChange is called, numberOfWaypoints becomes equal to numberOfPreviousWayPoints. But what is causing the re-render? Transaction.getRoute

App/src/components/DistanceRequest.js

Lines 155 to 161 in 1223e1e

	useEffect(() => {
	if (isOffline || !shouldFetchRoute) {
	return;
	}
	Transaction.getRoute(iou.transactionID, validatedWaypoints);
	}, [shouldFetchRoute, iou.transactionID, validatedWaypoints, isOffline]);

Transaction.getRoute will be called when shouldFetchRoute becomes true. One of the conditions of shouldFetchRoute is to have more than 1 valid waypoint.

App/src/components/DistanceRequest.js

Line 97 in 1223e1e

const shouldFetchRoute = (!doesRouteExist || haveWaypointsChanged) && !isLoadingRoute && _.size(validatedWaypoints) > 1;

So let's say we have 2 valid waypoints, then we add a new stop. Transaction.getRoute will happen first before ScrollView onContentSizeChange is triggered, which will re-render the component because we are merging optimistic data on doing the request.

That's why the issue only happens when we have at least 2 valid waypoints.

With 2 valid waypoints

Without valid waypoints

What changes do you think we should make in order to solve the problem?

I think checking the ScrollView content height changes is unnecessary. Adding a new stop will always increase the content height. I believe what we want is to always scroll to the bottom every time we add a new stop, so both my main and alternative solutions will not depends the content height value.

The simplest solution is to scroll to the bottom on every "Add stop" button click.

Transaction.addStop(iou.transactionID).then(/** scroll to bottom **/);

addStop will now return the onyx merge so we can wait for the promise until it completes before doing the scroll.

What alternative solutions did you explore? (Optional)

Scroll to the bottom immediately when the number of waypoints is changed.

useEffect(() => {
    if (numberOfWaypoints > numberOfPreviousWaypoints) {
        scrollViewRef.current.scrollToEnd({animated: true});
    }
}, [numberOfWaypoints, numberOfPreviousWaypoints]);

[melvin-bot]

Job added to Upwork: https://www.upwork.com/jobs/~0116cd2b0228d37197

[melvin-bot]

Current assignee @puneetlath is eligible for the External assigner, not assigning anyone new.

[melvin-bot]

Triggered auto assignment to Contributor-plus team member for initial proposal review - @jjcoffee (External)

[puneetlath]

@jjcoffee thoughts on the proposals so far?

[jjcoffee]

@jscardona12's proposal lacks enough detail to fully review - there's no "why" in either the RCA or the proposed solution. Maybe the solution works (as the video demonstrates), but we'd want to be sure we're actually fixing a problem, not just making something work without understanding what we're doing.

@DylanDylann's proposal has the correct RCA (numberOfPreviousWaypoints isn't always what we'd expect), but misses a little bit on what actually causes the re-render. The solution seems decent, but has the downside that we'll scroll to the bottom on any onContentSizeChange, e.g. if you remove a waypoint you'll also be scrolled to the bottom which isn't necessarily expected behaviour (and probably why the numberOfWaypoints condition was added).

@bernhardoj's proposal - love the level of detail and clarity here! The RCA is correct too, but also explains why the behaviour happens only once you add the start and finish points. I agree with him that we always want to scroll to the bottom when a new waypoint is added, regardless of ScrollView content height (so we can just ignore it). I think I prefer the alternative solution as the delay when waiting for the Onyx promise to resolve feels a bit too long and is unnecessary. The alternative solution also feels cleaner than slapping a scroll right onto the addStop call.

To summarise, happy to go with @bernhardoj's alternative solution!

🎀👀🎀 C+ reviewed

[melvin-bot]

Current assignees @puneetlath and @arosiclair are eligible for the choreEngineerContributorManagement assigner, not assigning anyone new.

[arosiclair]

@bernhardoj's alternate solution LGTM too 👍

[melvin-bot]

📣 @jjcoffee 🎉 An offer has been automatically sent to your Upwork account for the Reviewer role 🎉 Thanks for contributing to the Expensify app!

Offer link
Upwork job

[melvin-bot]

📣 @bernhardoj 🎉 An offer has been automatically sent to your Upwork account for the Contributor role 🎉 Thanks for contributing to the Expensify app!

Offer link
Upwork job
Please accept the offer and leave a comment on the Github issue letting us know when we can expect a PR to be ready for review 🧑‍💻
Keep in mind: Code of Conduct | Contributing 📖

[bernhardoj]

PR is ready

cc: @jjcoffee

[melvin-bot]

🎯 ⚡️ Woah @jjcoffee / @bernhardoj, great job pushing this forwards! ⚡️

The pull request got merged within 3 working days of assignment, so this job is eligible for a 50% #urgency bonus 🎉

• when @bernhardoj got assigned: 2023-09-08 21:33:43 Z
• when the PR got merged: 2023-09-12 15:02:05 UTC

On to the next one 🚀

[melvin-bot]

Reviewing label has been removed, please complete the "BugZero Checklist".

[melvin-bot]

The solution for this issue has been 🚀 deployed to production 🚀 in version 1.3.69-2 and is now subject to a 7-day regression period 📆. Here is the list of pull requests that resolve this issue:

• Fix scroll to bottom when number of waypoints increases don't work properly #27076

If no regressions arise, payment will be issued on 2023-09-21. 🎊

After the hold period is over and BZ checklist items are completed, please complete any of the applicable payments for this issue, and check them off once done.

• External issue reporter
• Contributor that fixed the issue
• Contributor+ that helped on the issue and/or PR

For reference, here are some details about the assignees on this issue:

• @jjcoffee requires payment offer (Reviewer)
• @bernhardoj requires payment offer (Contributor)

As a reminder, here are the bonuses/penalties that should be applied for any External issue:

• Merged PR within 3 business days of assignment - 50% bonus
• Merged PR more than 9 business days after assignment - 50% penalty

[melvin-bot]

BugZero Checklist: The PR fixing this issue has been merged! The following checklist (instructions) will need to be completed before the issue can be closed:

• [@jjcoffee] The PR that introduced the bug has been identified. Link to the PR:
• [@jjcoffee] The offending PR has been commented on, pointing out the bug it caused and why, so the author and reviewers can learn from the mistake. Link to comment:
• [@jjcoffee] A discussion in #expensify-bugs has been started about whether any other steps should be taken (e.g. updating the PR review checklist) in order to catch this type of bug sooner. Link to discussion:
• [@jjcoffee] Determine if we should create a regression test for this bug.
• [@jjcoffee] If we decide to create a regression test for the bug, please propose the regression test steps to ensure the same bug will not reach production again.
• [@puneetlath] Link the GH issue for creating/updating the regression test once above steps have been agreed upon:

[jjcoffee]

• The PR that introduced the bug has been identified. Link to the PR: Ensure multiple waypoints are visible on smaller screens #26610
• The offending PR has been commented on, pointing out the bug it caused and why, so the author and reviewers can learn from the mistake. Link to comment: Ensure multiple waypoints are visible on smaller screens #26610 (comment)
• A discussion in #expensify-bugs has been started about whether any other steps should be taken (e.g. updating the PR review checklist) in order to catch this type of bug sooner. Link to discussion: N/A - just needed more thorough testing
• Determine if we should create a regression test for this bug. No - not impactful enough, more of a "nice to have"
• If we decide to create a regression test for the bug, please propose the regression test steps to ensure the same bug will not reach production again. N/A

[puneetlath]

All paid. Thanks everyone!