Use Math.round() instead of Math.trunc() to fix floating-point precision issues #18816

therealsujitk · 2023-05-12T04:47:48Z

Details

I've changed Math.trunc() to use Math.round() to fix floating-point precision issues. This will work for numbers for more decimal places in case support for that is added in future (Unless the number of decimal places is incredibly large which will never be the case).

Fixed Issues

$ #18688
PROPOSAL: #18688 (comment)

Tests

Navigate to any chat that isn't Concierge.
Click on actions and request money.
Use numbers that can have precision issues (Ex: 80.60, 80.90, 80.99).
Click save and check if the amount that appears is the same.

Verify that no errors appear in the JS console

Offline tests

QA Steps

Navigate to any chat that isn't Concierge.
Click on actions and request money.
Use numbers that can have precision issues (Ex: 80.60, 80.90, 80.99).
Click save and check if the amount that appears is the same.

Verify that no errors appear in the JS console

PR Author Checklist

I linked the correct issue in the ### Fixed Issues section above
I wrote clear testing steps that cover the changes made in this PR
- I added steps for local testing in the Tests section
- I added steps for the expected offline behavior in the Offline steps section
- I added steps for Staging and/or Production testing in the QA steps section
- I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
- I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
- I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
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  - If any non-english text was added/modified, I verified the translation was requested/reviewed in #expensify-open-source and it was approved by an internal Expensify engineer. Link to Slack message:
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Screencast.from.10-05-23.09.34.41.AM.IST.webm

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screen-20230512-154832.mp4

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WhatsApp.Video.2023-05-12.at.15.58.11.mp4

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iOS

Android

screen-20230512-162625.mp4

melvin-bot · 2023-05-12T04:47:53Z

@dangrous @thesahindia One of you needs to copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

github-actions · 2023-05-12T04:48:05Z

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

therealsujitk · 2023-05-12T04:51:25Z

I have read the CLA Document and I hereby sign the CLA

thesahindia · 2023-05-12T10:13:14Z

@therealsujitk, please add the screen recording for all the platforms and also checkoff all the checkboxes.

therealsujitk · 2023-05-12T10:59:58Z

@thesahindia I've updated my post with screen recordings. Unfortunately I can't test on iOS native and desktop as I don't have access to a Macbook.

dangrous · 2023-05-12T14:59:04Z

@therealsujitk do you think you could add a couple test cases to the existing test, too, to cover the weird amounts?

App/tests/unit/CurrencyUtilsTest.js

Lines 88 to 99 in 9fa8c89

    
           describe('convertToSmallestUnit', () => { 
        
               test.each([ 
        
                   [CONST.CURRENCY.USD, 25, 2500], 
        
                   [CONST.CURRENCY.USD, 25.5, 2550], 
        
                   [CONST.CURRENCY.USD, 25.5, 2550], 
        
                   ['JPY', 25, 25], 
        
                   ['JPY', 2500, 2500], 
        
                   ['JPY', 25.5, 25], 
        
               ])('Correctly converts %s to amount in smallest units', (currency, amount, expectedResult) => { 
        
                   expect(CurrencyUtils.convertToSmallestUnit(currency, amount)).toBe(expectedResult); 
        
               }); 
        
           });

therealsujitk · 2023-05-12T15:04:05Z

@dangrous yeah sure! ~~Should I add a comment to the code too stating why we use Math.round() or should I leave it as is.~~

Edit: I'll take a look at why the test case failed as well.

therealsujitk · 2023-05-12T15:48:54Z

I went ahead and deleted a duplicate test case ([CONST.CURRENCY.USD, 25.5, 2550]).

dangrous · 2023-05-12T22:07:03Z

tests/unit/CurrencyUtilsTest.js

            [CONST.CURRENCY.USD, 25, 2500],
            [CONST.CURRENCY.USD, 25.5, 2550],
-            [CONST.CURRENCY.USD, 25.5, 2550],
+            [CONST.CURRENCY.USD, 80.6, 8060],
+            [CONST.CURRENCY.USD, 80.9, 8090],
+            [CONST.CURRENCY.USD, 80.99, 8099],
            ['JPY', 25, 25],
            ['JPY', 2500, 2500],
            ['JPY', 25.5, 25],


I think what this test was trying to do with that doubled test was to copy the same test cases in both USD and JPY, and something just got lost along the way. Here's my suggestion here:

[CONST.CURRENCY.USD, 25, 2500], [CONST.CURRENCY.USD, 25.5, 2550], [CONST.CURRENCY.USD, 2500, 250000], [CONST.CURRENCY.USD, 80.6, 8060], [CONST.CURRENCY.USD, 80.9, 8090], [CONST.CURRENCY.USD, 80.99, 8099], ['JPY', 25, 25], ['JPY', 2500, 2500], ['JPY', 25.5, 25], ['JPY', 80.6, 80], ['JPY', 80.9, 80], ['JPY', 80.99, 80],

My only question here is whether or not this would be expected behavior for the JPY cases. Would we really expect 80.99 to come in as 80? cc @roryabraham in case you happen to know. If you don't, I think we stick with it because that isn't changing any behavior from what exists now...

Regarding JPY, somewhere in the comments this issue was linked: #15878

Ha, that is a LONG chain. I THINK, if I'm understanding it correctly, that we actually DO want to round up 80.99 to 81 because that's what we'd display:

When we display the value, we're using the standard Intl.NumberFormat function so it's displaying 25.75 JPY correctly as 26 JPY

I think most of the floor/trunc logic is only when we're splitting things, so we wouldn't want to also do it here.

But I'll cc @aldo-expensify since he worked on that issue and maybe he can confirm one way or the other - do we want to round up/down decimals in currencies without decimals, or should we always truncate/floor them?

I'm not sure I understand everything going on here... but I would ask first why are we testing conversions of decimal JPY. Is it possible for a user to input JPY with decimal positions? if it is not, maybe then these test are testing things that can't happen.

ahh, this is not necessarily related to currencies like JPY, but this instead:

Number.parseFloat('80.60') * 100 8059.999999999999

.. yeah the trunc result is definitely wrong:

Math.trunc(80.6 * 100); 8059

I had that question too actually, just checked and yes, you can enter decimal for JPN currently.

Unrelated to this issue but it would be better to prevent users from doing that IMO.

I think the code changes make sense.

Regarding JPY, I wouldn't care much about that for now. I'm guessing that some code in the backend could produce JPY decimals... but 🤷

thesahindia · 2023-05-15T10:42:43Z

Reviewer Checklist

I have verified the author checklist is complete (all boxes are checked off).
I verified the correct issue is linked in the ### Fixed Issues section above
I verified testing steps are clear and they cover the changes made in this PR
- I verified the steps for local testing are in the Tests section
- I verified the steps for Staging and/or Production testing are in the QA steps section
- I verified the steps cover any possible failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
- I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
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- I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
- I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
- I verified all numbers, amounts, dates and phone numbers shown in the product are using the localization methods
- I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is approved by marketing by adding the Waiting for Copy label for a copy review on the original GH to get the correct copy.
- I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
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- The file is named correctly
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- The only data being stored in the state is data necessary for rendering and nothing else
- For Class Components, any internal methods passed to components event handlers are bound to this properly so there are no scoping issues (i.e. for onClick={this.submit} the method this.submit should be bound to this in the constructor)
- Any internal methods bound to this are necessary to be bound (i.e. avoid this.submit = this.submit.bind(this); if this.submit is never passed to a component event handler like onClick)
- All JSX used for rendering exists in the render method
- The component has the minimum amount of code necessary for its purpose, and it is broken down into smaller components in order to separate concerns and functions
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If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
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thesahindia · 2023-05-15T10:44:39Z

@therealsujitk, you will need to checkoff all the items in the "PR author checklist"

thesahindia · 2023-05-15T10:45:29Z

@thesahindia I've updated my post with screen recordings. Unfortunately I can't test on iOS native and desktop as I don't have access to a Macbook.

I think it's fine for one PR. However, I want to inform you that it's necessary to provide screenshots for all platforms, which requires access to a Mac. Other option is to use cloud services (more info).

Please refrain from applying to any new job until this matter is resolved.

therealsujitk · 2023-05-15T11:10:54Z

@therealsujitk, you will need to checkoff all the items in the "PR author checklist"

Done 👍

thesahindia

Works well!

@dangrous, let's rerun the checks.

dangrous

LGTM!

OSBotify · 2023-05-17T01:09:21Z

🚀 Deployed to staging by https://github.com/dangrous in version: 1.3.15-0 🚀

platform	result
🤖 android 🤖	success ✅
🖥 desktop 🖥	success ✅
🍎 iOS 🍎	success ✅
🕸 web 🕸	success ✅

OSBotify · 2023-05-18T06:52:32Z

🚀 Deployed to production by https://github.com/yuwenmemon in version: 1.3.15-12 🚀

platform	result
🤖 android 🤖	success ✅
🖥 desktop 🖥	success ✅
🍎 iOS 🍎	success ✅
🕸 web 🕸	success ✅

Use round() instead of trunc() to fix precision issues

58cbcaf

therealsujitk requested a review from a team as a code owner May 12, 2023 04:47

melvin-bot bot requested review from dangrous and thesahindia and removed request for a team May 12, 2023 04:47

therealsujitk added 2 commits May 12, 2023 21:05

Add logic to to take care of zero-decimal currencies

b849daa

Add unit test cases to check for precision loss

08f6a64

dangrous reviewed May 12, 2023

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therealsujitk added 2 commits May 13, 2023 03:52

Add unit test cases to check for precision loss

89ceb30

Use round() instead of trunc() for all currencies

62761e5

therealsujitk requested a review from dangrous May 15, 2023 03:56

thesahindia approved these changes May 15, 2023

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dangrous approved these changes May 15, 2023

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dangrous merged commit f4d6059 into Expensify:main May 15, 2023

OSBotify mentioned this pull request May 16, 2023

Deploy Checklist: New Expensify 2023-05-16 #19088

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melvin-bot bot mentioned this pull request May 18, 2023

[HOLD for payment 2023-05-25] [$1000] When request money for $80.60 the last digit changes #18688

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Use Math.round() instead of Math.trunc() to fix floating-point precision issues #18816

Use Math.round() instead of Math.trunc() to fix floating-point precision issues #18816

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Use Math.round() instead of Math.trunc() to fix floating-point precision issues #18816

Use Math.round() instead of Math.trunc() to fix floating-point precision issues #18816

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