test(yaml): add parse() test for duplicate keys

[iuioiua]

Unblocks #5240

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.32%. Comparing base (cadf85c) to head (9c3e62a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5240      +/-   ##
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+ Coverage   95.30%   95.32%   +0.01%     
==========================================
  Files         460      460              
  Lines       38056    38056              
  Branches     5577     5580       +3     
==========================================
+ Hits        36269    36276       +7     
+ Misses       1745     1738       -7     
  Partials       42       42              

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[iuioiua]

Current documentation says that if ParseOptions.json is true, then duplicate keys cause parse() to throw, like JSON.parse(). But by default, ParseOptions.json is false, and duplicate keys still cause parse() to throw. In other words, ParseOptions.json currently does the exact opposite of what it should 😆

[kt3k]

JSON.parse() doesn't seem throwing with duplicated keys?

> JSON.parse('{"a":1,"a":2}')
{ a: 2 }

[iuioiua]

Ok - then my understanding of JSON.parse() was wrong 😆

[kt3k]

LGTM