Corrupted Padding Bits Brotli Decode Blazor Azure Static Web App

[SeanLeitzinger]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Getting the following error when deploying our Blazor WASM App to an Azure Static Web App resource.

I have followed all of the documentation and also tried using both the min version of decode and the non-min version. The app runs fine locally with Brotli and the decode script. The issue appears specific to the Azure Static Web App resource since I have had no issues deploying to other servers in the past. I was unable to find much info on the issue.

Here is what is served when navigating to the app:

The script code:
<script src="_framework/blazor.webassembly.js" autostart="false"></script> <script type="module"> import { BrotliDecode } from './decode.js'; Blazor.start({ loadBootResource: function (type, name, defaultUri, integrity) { if (type !== 'dotnetjs' && location.hostname !== 'localhost' && type !== 'configuration') { return (async function () { const response = await fetch(defaultUri + '.br', { cache: 'no-cache' }); if (!response.ok) { throw new Error(response.statusText); } const originalResponseBuffer = await response.arrayBuffer(); const originalResponseArray = new Int8Array(originalResponseBuffer); const decompressedResponseArray = BrotliDecode(originalResponseArray); const contentType = type === 'dotnetwasm' ? 'application/wasm' : 'application/octet-stream'; return new Response(decompressedResponseArray, { headers: { 'content-type': contentType } }); })(); } } }); </script>

Expected Behavior

The app should load without error when using Brotli in a Blazor WASM app and deploying to an Azure Static Web App.

Steps To Reproduce

No response

Exceptions (if any)

Uncaught (in promise) Error: Corrupted padding bits
at jumpToByteBoundary (decode.js:1759:23)
at decompress (decode.js:1352:13)
at decode (decode.js:2208:13)
at (index):38:59
at async at.initAsync (blazor.webassembly.js:1:36102)
at async Object.Vt [as start] (blazor.webassembly.js:1:61895)
jumpToByteBoundary @ decode.js:1759
decompress @ decode.js:1352
decode @ decode.js:2208
(anonymous) @ (index):38
await in (anonymous) (async)
(anonymous) @ (index):28

.NET Version

7.0.4

Anything else?

No response

[javiercn]

@SeanLeitzinger thanks for contacting us.

This seems to be an interaction with the library used to decode the brotli stream. I would suggest using an alternative library.

Is it correct to assume it works correctly when served locally without using a script to decode the payload manually?

Hi @SeanLeitzinger. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[SeanLeitzinger]

Hi Javier. We are using the same set up locally as when deployed. There is no difference except it works locally.

[javiercn]

@SeanLeitzinger thanks for the additional details.

Are there any errors on the network tab? Does the response look the same in both cases? (Content size, type, and other headers)

At the very least, I suggest you do the following:

• Open Dev tools.
• Break on all the exceptions.
• Navigate the stack to determine what brotli file is causing the issue you are observing.
• Save the file to disk from the Network Tab in the version that is not working
• Save the file to disk from the Network Tab in the version that is working.
• Use Get-FileHash to get a hash of both files and see if anyone is different.
• Do the same against your publish output to see if there are any differences.

Hi @SeanLeitzinger. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[javiercn]

Probably dupe of #45191

[SeanLeitzinger]

I saw that one before posting this. Don't think it's a dupe. I debugged this and it looks like it fails when trying to decode the blazor.boot.json.br. I pulled it down and that is JSON in plain text. When publishing locally that is a brotli file that doesn't load in plain text. It looks to me like this is getting published as a br file but not actually compressed with brotli. Maybe I need something in the devops pipeline? Seems weird that it is creating a brotli extension file but not actually compressing it.