Prevent duplicate entries in board_manager.additional_urls

[henrygab]

Fixes #1437.

Please check if the PR fulfills these requirements

• The PR has no duplicates (please search among the Pull Requests
  before creating one)
• The PR follows
  our contributing guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• UPGRADING.md has been updated with a migration guide (for breaking changes)

• What kind of change does this PR introduce?

This change ensures that duplicate values are not introduced into configuration, such as for board_manager.additional_urls

• What is the current behavior?

The following will result in two identical entries in the config:

arduino-cli config add board_manager.additional_urls http://drazzy.com/package_drazzy.com_index.json
arduino-cli config add board_manager.additional_urls http://drazzy.com/package_drazzy.com_index.json

• What is the new behavior?

Entries that accept multiple values are ensured to be unique. Care was taken to retain the order of entries. No error is generated due to duplicate entries (no error was previously generated ... this just prevents useless growth of this array).

• Does this PR introduce a breaking change, and is
  titled accordingly?

This is not a breaking change.

• Other information:

Fixes #1437

[codecov]

Codecov Report

Base: 36.71% // Head: 36.68% // Decreases project coverage by -0.03% ⚠️

Coverage data is based on head (dd85466) compared to base (e404a3b).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1902      +/-   ##
==========================================
- Coverage   36.71%   36.68%   -0.04%     
==========================================
  Files         231      231              
  Lines       19723    19740      +17     
==========================================
  Hits         7242     7242              
- Misses      11652    11669      +17     
  Partials      829      829              

Flag	Coverage Δ
unit	36.68% <0.00%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
cli/config/add.go	0.00% <0.00%> (ø)
cli/config/set.go	0.00% <0.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[henrygab]

The tests that exercise the code paths ran during CI. Not sure why codecov report isn't showing coverage. Some bug in codecov?

[per1234]

Hi @henrygab. Thanks so much for your pull request and also for your attention to code coverage!

Unfortunately the Python-based integration tests are not considered in the coverage data. This data only describes the coverage provided by the Go-based unit tests like the ones you see here:

https://github.com/arduino/arduino-cli/blob/master/arduino/builder/sketch_test.go

If you are interested in this subject, there is additional information in this proposal for how we might eventually also determine the coverage provided by the integration tests: #1829

[cmaglie]

Thank you @henrygab!

[cmaglie]

Unfortunately the Python-based integration tests are not considered in the coverage data. This data only describes the coverage provided by the Go-based unit tests like the ones you see here:

We are also migrating the python test into an equivalent version using golang test capabilities, you can find them inside the directory internal/integrationtests. The python test infrastructure will be eventually removed in the near future and the README updated accordingly.