feat: change avoid-returning-widgets

[incendial]

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix
[ ] New rule
[X] Changes an existing rule
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What changes did you make? (Give an overview)

As mentioned here dart-archive/linter#2582 (comment) we should not lint every class method with Widget return type, because there are cases where it's totally valid to have a Widget-returning method and it's used in builders. So this request supports this approach for methods, but still lint getters and global functions as before.

[incendial]

@roman-petrov could you please a look too? I'd very happy to get your feedback about this one.

[codecov]

Codecov Report

Merging #369 (4c391e4) into master (1ee3797) will increase coverage by 0.27%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #369      +/-   ##
==========================================
+ Coverage   79.16%   79.44%   +0.27%     
==========================================
  Files         155      156       +1     
  Lines        3562     3610      +48     
==========================================
+ Hits         2820     2868      +48     
  Misses        742      742              

Impacted Files	Coverage Δ
...oid_returning_widgets/avoid_returning_widgets.dart	100.00% <100.00%> (ø)
...ist/avoid_returning_widgets/visit_declaration.dart	100.00% <100.00%> (ø)
...es/rules_list/avoid_returning_widgets/visitor.dart	100.00% <100.00%> (ø)

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[dkrutskikh]

@incendial please add test cases for uncovered cases
https://codecov.io/gh/dart-code-checker/dart-code-metrics/src/improve-avoid-returning-widgets/lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_returning_widgets/visitor.dart

https://codecov.io/gh/dart-code-checker/dart-code-metrics/src/improve-avoid-returning-widgets/lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_returning_widgets/visit_declaration.dart

[roman-petrov]

@incendial sorry for late response, you mentioned me above but I missed @mention notification in my mail. I will try to improve my email filters to solve this, I am still quite interesting in contributing to this project.

This specific update logically looks quite good to me, returning widgets from getters for me looks even worse than returning from functions.

[incendial]

@incendial sorry for late response, you mentioned me above but I missed @mention notification in my mail.

No problem.

This specific update logically looks quite good to me, returning widgets from getters for me looks even worse than returning from functions.

Thanks for taking a look!