element-web: develop.element.io not updating after clicking update

Clicking “Check for update” in the “Help & About” dialog says an updated version is available even after the force-reload, and even though the version in the response matches what is showing in the about dialog (1.9.6-rc.2)

The request headers were:

GET /version?cachebuster=1638789283641 HTTP/2
Host: staging.element.io
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0
Accept: */*
Accept-Language: en-GB,en-US;q=0.7,en;q=0.3
Accept-Encoding: gzip, deflate, br
DNT: 1
Connection: keep-alive
TE: Trailers

and response was:

HTTP/2 200 OK
date: Mon, 06 Dec 2021 11:14:44 GMT
content-type: text/html
last-modified: Wed, 01 Dec 2021 11:53:16 GMT
x-xss-protection: 1; mode=block
x-content-type-options: nosniff
strict-transport-security: max-age=31536000; includeSubDomains; preload
x-frame-options: sameorigin
permissions-policy: interest-cohort=()
cf-cache-status: DYNAMIC
expect-ct: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
report-to: {"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v3?s=5Hp1edU7Q%2BKsMk62MNcLR6d1TVtIlN7kKzphMpC3RWVFKYDEmV%2BFFBmYuco0gUMk269dlbkraizp7hrMT4MFZvvn3UBEkBW7DOZlF0%2BZdtEYGPiIvRIC1Gks68%2B%2BCqM9bY294VytqeFTZtCvTmiMXw%3D%3D"}],"group":"cf-nel","max_age":604800}
nel: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
server: cloudflare
cf-ray: 6b95179eccb07777-LHR
content-encoding: br
X-Firefox-Spdy: h2

1.9.6-rc.2

Indeed, I can repro this on staging - I think this is a regression caused by https://github.com/vector-im/element-web/pull/19857

Creating a separate issue at https://github.com/vector-im/element-web/issues/20058 as I think its different to this one, it’s not due to cache-control headers but rather a bug

This also applies to staging.element.io - https://matrix.to/#/!YTvKGNlinIzlkMTVRl:matrix.org/$cHj7WJ38ET2sEaEZaplNHM_Wj68GEzvlxwubV0qMEqM?via=matrix.org&via=privacytools.io&via=mozilla.org

fwiw it looks like the cause in this case is that something at some point caused Element to update the current URL of the tab with a question mark, which just stuck around. Looks like I managed to fix things by removing the ? from the URL in the address bar. Not sure what the root cause is though.

aha! okay, great find - I think we’ll have to adjust the rule in Apache slightly then.

Right, it looks like in some cases the browser tries to request https://develop.element.io/#/... and other times https://develop.element.io/?#/... (notice the question mark). The cache-control header has the wrong value in the latter case but not the former.

Indeed, that’s returning a different header:

[10:10:15] babolivier@Noah:~$ curlie 'https://develop.element.io/?#/room/#matrix-internal:matrix.org' -H 'User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:93.0) Gecko/20100101 Firefox/93.0' -H 'Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8' -H 'Accept-Language: en-GB,en;q=0.8,fr-FR;q=0.5,en-US;q=0.3' --compressed -H 'DNT: 1' -H 'Upgrade-Insecure-Requests: 1' -H 'Sec-Fetch-Dest: document' -H 'Sec-Fetch-Mode: navigate' -H 'Sec-Fetch-Site: same-origin' -H 'Connection: keep-alive' -H 'Cookie: [REDACTED]' -H 'Pragma: no-cache' -H 'Cache-Control: no-cache' -H 'TE: trailers' > /dev/null
HTTP/2 200 
date: Mon, 06 Dec 2021 10:34:25 GMT
content-type: text/html
last-modified: Mon, 06 Dec 2021 10:28:52 GMT
vary: Accept-Encoding
x-xss-protection: 1; mode=block
x-content-type-options: nosniff
strict-transport-security: max-age=31536000; includeSubDomains; preload
x-frame-options: sameorigin
cache-control: max-age=691200
permissions-policy: interest-cohort=()
cf-cache-status: MISS
expect-ct: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
report-to: {"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v3?s=IQaRKvjvbiQyAS%2Bwe6sS%2FyhYPLHyk4eOrsPcEUQmI8zKAPYYO4cYVth1UzSzIJ7%2FyqCkB7HVqoIhaLWzeiCgSMYhOJezld65B02ZgGsrd5SaOFakEZ%2FMNWbiXr61V0P0%2BBNeqNhUuXvYCkwYdgMUFw%3D%3D"}],"group":"cf-nel","max_age":604800}
nel: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
server: cloudflare
cf-ray: 6b94dc9329be71c9-LHR
content-encoding: br

I’ve redacted the cookies in case they contain sensitive secrets, but removing them from the curl doesn’t change the cache-control header in the response.

I’ll try to tweak the line to see what makes that value change.