Simplify Bundling of UI assets

[mahadzaryab1]

Which problem is this PR solving?

• Closes Simplify bundling of UI assets #5913

Description of the changes

• Created one file assets.go that holds both the placeholder and actual assets.
• Added a helper GetStaticFiles to get the assets based on whether the actual filesystem has an index.html.gz. If it does, we return the assets. Otherwise, we return the placeholder index.html file.

How was this change tested?

Added unit tests and performed the following manual tests

Test 1

Makefile Target

.PHONY: run-all-in-one
run-all-in-one:
	go run ./cmd/all-in-one --log-level debug

Clearing out the actual directory and ran make run-all-in-one. Going to http://localhost:16686/ renders the placeholder HTML page.

Test 2

Makefile Target

.PHONY: run-all-in-one
run-all-in-one: build-ui
	go run ./cmd/all-in-one --log-level debug

Ran make run-all-in-one. Going to http://localhost:16686/ renders the Jaeger UI.

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• I have added unit tests for the new functionality
• I have run lint and test steps successfully
  • for jaeger: make lint test
  • for jaeger-ui: yarn lint and yarn test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.81%. Comparing base (5bd6980) to head (2b62656).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5917   +/-   ##
=======================================
  Coverage   96.81%   96.81%           
=======================================
  Files         342      343    +1     
  Lines       16525    16528    +3     
=======================================
+ Hits        15998    16001    +3     
  Misses        340      340           
  Partials      187      187           

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unittests	95.29% <100.00%> (+<0.01%)	⬆️

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[mahadzaryab1]

@yurishkuro anything we can do about the failing codecoverage step?

[yurishkuro]

you could have another test where you swap actualFS for a test fixture, e.g.

ui/testdata/
  actual/
    index.html.gz -- dummy file
  mock.go // embed fake actual here

[mahadzaryab1]

you could have another test where you swap actualFS for a test fixture, e.g.

ui/testdata/
  actual/
    index.html.gz -- dummy file
  mock.go // embed fake actual here

thanks for the suggestion! I added a second test in.

[yurishkuro]

Thanks!