State management and event handling interact badly leading to stale state

[mohe2015]

Problem
When multiple events are handled without rerendering the state accessed in event callbacks is stale.

Steps To Reproduce
Steps to reproduce the behavior:

1. Clone https://github.com/mohe2015/yew-bug
2. (cd frontend && trunk serve)
3. (cd tests && cargo run)
4. Open browser console in opened firefox (note: firefox will automatically close after 30 seconds)

Expected behavior
I expected the browser console to contain username: username, password: password but it contains username: username, password: (password missing). When clicking on the login button again the correct text is shown. This is only an issue in Firefox but not Chromium.
From the logs it seems like a rerender is required to update the value in the handle.

Screenshots

Environment:

• Yew version: 0.20 until master are all affected
• Rust version: nightly
• Build tool, if relevant: trunk
• OS, if relevant: Linux
• Browser and version, if relevant: Firefox

Questionnaire

• I'm interested in fixing this myself but don't know where to start
• I would like to fix and I have a solution
• I don't have time to fix this right now, but maybe later