"pub upgrade" sometimes hangs for around 30s after it appears to have finished

[DanTup]

While investigating dart-lang/sdk#55621 I found that sometimes pub upgrade is just hanging at the end for around 30s:

All of the output shown here appeared almost immediately, then the process took over 20 seconds more to exit.

If I run with -v I see lots of output that seems like it may be retrying requests many times, but there is no information about why:

IO  : Attempt #5 for fetching versions for "stream_channel" from "https://pub.dev/api/packages/stream_channel"
IO  : HTTP GET https://pub.dev/api/packages/stack_trace
    | Accept: application/vnd.pub.v2+json
    | X-Pub-OS: windows
    | X-Pub-Command: upgrade
    | X-Pub-Session-ID: BA637EE2-3F42-4AE2-86C6-004FF2C77BAA
    | user-agent: Dart pub 3.3.0
IO  : Attempt #5 for fetching versions for "stack_trace" from "https://pub.dev/api/packages/stack_trace"
IO  : HTTP GET https://pub.dev/api/packages/boolean_selector
    | Accept: application/vnd.pub.v2+json
    | X-Pub-OS: windows
    | X-Pub-Command: upgrade
    | X-Pub-Session-ID: BA637EE2-3F42-4AE2-86C6-004FF2C77BAA
    | user-agent: Dart pub 3.3.0
IO  : Attempt #5 for fetching versions for "boolean_selector" from "https://pub.dev/api/packages/boolean_selector"
IO  : HTTP GET https://pub.dev/api/packages/test_api
    | Accept: application/vnd.pub.v2+json
    | X-Pub-OS: windows
    | X-Pub-Command: upgrade
    | X-Pub-Session-ID: BA637EE2-3F42-4AE2-86C6-004FF2C77BAA
    | user-agent: Dart pub 3.3.0
IO  : Attempt #5 for fetching versions for "test_api" from "https://pub.dev/api/packages/test_api"

It's not clear to me if this content is buffered and may have completed very quickly, or if it might be happening during the "hang" at the end (it seems to me like important requests for handling the upgrade, but the output suggests that completed very quickly?).

This was repro'd using current stable.. Is there anything I can do to get more information about what's going on during the hang?

[sigurdm]

I believe this is a duplicate of dart-lang/sdk#55289
Fixed in dart-lang/sdk@8acb0a4

Can you reproduce on main/latest dev?

[DanTup]

Ah! I cannot repro on the latest bleeding edge, so this looks like it.

I've had this hang before from not closing HttpClient too, it should've occurred to me 🙃