Implement path to make mesop work in Windows

[kumaranvpl]

Description

MesopUI is not working in Windows with weird error. Flask was complaining that wakeup_component.js. After a short conversation with @davorinrusevljan, I have learnt about the patching we do for mesop. This patching is not working in Windows.

I have investigated further and discovered a bug in mesop.labs.web_component - https://github.com/google/mesop/blob/main/mesop/labs/web_component.py#L34-L35. Here a / is prepended to a path but this piece of code forgets the fact that the windows uses \ instead of /.

I have fixed it by introducing a patched function and using that patched function. Ideally this bug fix should be made at mesop repo itself but I don't want to wait till they make the fix as we have some potential Windows users.

Fixes #413

Type of change

• Documentation (typos, code examples, or any documentation updates)
• Bug fix (a non-breaking change that resolves an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a fix or feature that would disrupt existing functionality)
• This change requires a documentation update

Checklist

• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• I have included code examples to illustrate the modifications

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
fastagency/ui/mesop/timer.py	71.42%	5 Missing and 1 partial ⚠️

Files with missing lines	Coverage Δ
fastagency/ui/mesop/timer.py	60.00% <71.42%> (+18.33%)	⬆️

... and 3 files with indirect coverage changes

[davorrunje]

Let me check something first

[davorinrusevljan]

Looks good to me.

[davorinrusevljan]

Do we have to worry if 2 threads attempt to execute this at the same time? In that case the one that finishes first would possibly remove patch for the second one at too early stage.

But I am not sure if we could have 2 threads hitting this code at the same time.