Adds id to dcc.Loading DOM

[leeagustin]

Hi!👋 This is my first time contributing to an open-source project. I hope it's okay if I give the issue (#2878) a try.

I didn't add a test as I was unsure if it was needed for this (small) change; however, I'd be more than happy to add one if needed!

Contributor Checklist

• I have broken down my PR scope into the following TODO tasks
  • Adds id to dcc.Loading DOM
• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR

optionals

• I have added entry in the CHANGELOG.md
• If this PR needs a follow-up in dash docs, community thread, I have mentioned the relevant URLS as follows
  • this GitHub #PR number updates the dash docs
  • here is the show and tell thread in Plotly Dash community

[huong-li-nguyen]

Congrats on your first PR in an open-source project! 🎊

I forgot about raising the PR 😬 but happy that it lets you create your first PR! 👏

[T4rk1n]

I don't think we need to add new tests, but the existing ones could be modified to include an id here:

dash/components/dash-core-components/tests/integration/loading/test_loading_component.py

Line 23 in ba27733

dash_dcc.find_element(".loading .dash-spinner")

[T4rk1n]

The id should be on the outer div, the spinners https://github.com/plotly/dash/blob/4692acf61f3e282950a8d1014b152176addb2aec/components/dash-core-components/src/fragments/Loading/spinners/ don't have the id prop so it wouldn't render on the DOM.

[leeagustin]

Ah I see, good catch 😄

Changed in 9dcf243

[leeagustin]

I don't think we need to add new tests, but the existing ones could be modified to include an id here:

dash/components/dash-core-components/tests/integration/loading/test_loading_component.py

Line 23 in ba27733

dash_dcc.find_element(".loading .dash-spinner")

Sounds good!

Changed in ca5d66a

[T4rk1n]

Looks good, thank you 💃