Error aggregation

[akutuev]

Hello,

The purpose of this PR is to implement Enhancement #208

This allows aggregating errors from parsing, so if you have multiple missing variables it prints like: "env: required environment variable "NAME" is not set; env: required environment variable "FRUIT" is not set".

The idea is to refactor a method doParse() by moving out all parsing process to a separate method doParseField(). In that case doParseField() may return an error per field hence doParse() may accumulate errors

Do let me know if any changes are required

[codecov]

Codecov Report

Merging #233 (173496d) into main (4c93d81) will increase coverage by 0.87%.
The diff coverage is 96.66%.

❗ Current head 173496d differs from pull request most recent head 808b041. Consider uploading reports for the commit 808b041 to get more accurate results

@@            Coverage Diff             @@
##             main     #233      +/-   ##
==========================================
+ Coverage   98.84%   99.71%   +0.87%     
==========================================
  Files           2        2              
  Lines         345      347       +2     
==========================================
+ Hits          341      346       +5     
+ Misses          4        1       -3     

Impacted Files	Coverage Δ
env.go	99.70% <96.66%> (+0.88%)	⬆️

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

[caarlos0]

I think its a little weird that it prints the env: suffix so many times, maybe its worth revisiting where errors are returned and add the env prefix only once? wdyt?

[akutuev]

@caarlos0 I think this is a good idea, since we have a full control over all errors we can aggregate it nicely, let me try to improve this

[akutuev]

@caarlos0, updated PR as discussed.
Added aggregateError struct to be able to aggregate all errors and print "env" as a prefix only once

[caarlos0]

lg, thanks!