what are some development tools that your language of choice or its community provides that is not present in other programming languages?

for .e.g. the pprof support that Go provides is something i have always found very cool.

​

it doesn't have to be a tool that comes from the official language development team it could simply be a community project that is widely used.

i don't have any particular reason for asking this, just curious to know what are some of the good things being done in other ecosystems and if they can be brought to the languages that I use