[lmm]

> Why is this a bad thing?

Because it shows the language could be a lot better. A common, basic task shouldn't be so much easier outside the language (via reflection) than inside it.

> How is this different from, say, using Template Haskell?

It's the same thing. To the extent that people feel the need to use Template Haskell to do basic and common things, something is very wrong with Haskell.

> I have never found the existence of tests using mocks being a hindrance to refactoring in Java. Can you provide a more specific example?

I mean you can't refactor the test itself. Just basic things like: if you do expect(methodOne(matches("someComplexRegex"))) ; expect(methodTwo(matches("someComplexRegex"))), if you try to pull matches("someComplexRegex") out as a variable you'll break your test (you have to make it a function instead). You can't move an expect() above or below another method call without checking to see whether that was the method it was testing. Individually these things are trivial, but they add up to a chilling effect where people don't dare to improve mock-based tests a little as they work on them, so they end up as repetitive code with subtle variations, just like main code would if you never refactored it.

[mavelikara]

> Individually these things are trivial, but they add up to a chilling effect where people don't dare to improve mock-based tests a little as they work on them

In my experience, I have not come across such effects. People understand the purpose, strengths, weaknesses and limitations of the libraries they use and try not to "cut against the grain".

> people don't dare to improve mock-based tests a little as they work on them, so they end up as repetitive code with subtle variations, just like main code would if you never refactored it.

I understand this is a subjective preference, but I try not to refactor test code too much. I strive to make my test code not have branches ("if-less code" as some people call it). Sometimes this lead to slightly more verbose code, but in the long run I have found it useful for my test code to be rather boring.

----

I now understand the point you are making, and agree with it technically. I don't agree that those technical points lead to the social effect you call out, because I have not come across it.

Overall, Java makes two bad design choices - nullability by default, and mutability by default. But in the codebases I have worked with in the last few years I, and my colleagues, tend to not opt in to these defaults. This leads to pleasant, testable codebases to work with. We also enjoy acceptable performance, good tooling, easy-to-reason memory usage, great library ecosystem etc.

[lmm]

> Overall, Java makes two bad design choices - nullability by default, and mutability by default.

There are a few more, even today: using a weird secondary type system to track what kind of errors can occur (checked exceptions), classes being non-final by default, universal methods (every method in java.lang.Object except possibly getClass() ought to be moved to interfaces that user-defined types have the choice of not implementing), a bunch of syntactic ceremony around blocks (braces required everywhere, "return" being mandatory) which gets even worse once you want to move away from mutability by default, variance at use site only, no sum types, no HKT...

> This leads to pleasant, testable codebases to work with. We also enjoy acceptable performance, good tooling, easy-to-reason memory usage, great library ecosystem etc.

Sure. There are a lot of good things about the Java ecosystem, and if you see the language as a modest, incremental step over C++ then it is an improvement on that front at least. At the same time I do think ML-family languages - even ML itself - offer a lot of advantages especially if we're talking about them just as languages. In practice I work in Scala and gain most of the advantages of the Java ecosystem but with a language that has most of the advantages of Haskell as well.