What I expect from a programming language today
Nowadays, programming languages have a lot of good tools available. In my opinion, some of these tools are essential.
I won't be able to evaluate this for every programming language. That's why I will only mention languages that I am most experienced in (Go, PHP, Python).
Must-Have
Coding standard with formatting tool
Consistency matters to me:
I prefer one unified coding standard, even with some formatting quirks, over multiple standards that lead to fragmented code styles.
To ensure this, the programming language should provide a formatting tool.
Go provides a formatting tool that VS Code, for example, uses to format files each time changes are saved.
Although PHP has an official coding standard (PHP Standards Recommendations), there are many other PHP coding standards, as well as multiple formatting tools. If you use the Laravel framework, you can use Pint to format your project according to the Laravel coding standard.
In Python, it is called a Python Enhancement Proposal (PEP 8 - "Style Guide for Python Code"). However, there are multiple tools for formatting. One well-known example is black.
Testing
A programming language should provide a testing framework that requires very little configuration effort to ensure the application works as expected. Above all, if you can display the code coverage with these tools, this is very helpful in finding areas of the code that have not yet been tested.
In Go, there is a testing package for test cases, benchmarks, and fuzzing, as well as a go test command for executing test cases.
The PHPUnit package is well known in PHP. In the Laravel ecosystem, PEST, which builds on PHPUnit, is often used.
Python provides an assert statement and a unittest module out of the box.
Nice-to-have
Automated refactoring
As far as I know, Go, PHP and Python do not provide this feature.
But for PHP there is the tool rector for "instant upgrades and automated refactoring".
You can use it to upgrade PHP versions, Laravel upgrades, and a lot more depending on the applied upgrade rules.
I wish that such tools would be available for every programming language so that most of the migration work can be automated.