Add throws clause to beginMethod about javapoet

[cgruber]

This code has a few uses in dagger and elsewhere, not just in square.
But it evolved out of the needs of Dagger generating adapters which
never needed to throw checked exceptions. If you need the feature,
please feel free to create a pull-request, or one of us will get to it
at some point.

[swankjesse]

Getting a nice API for this might be challenging. The problem is the throws list doesn't fit in well with the current beginMethod() API which already uses its varargs for parameters.

Do you hate this?

  javaWriter.throwing("java.io.IOException").beginMethod(...);
  javaWriter.closeMethod();

[cgruber]

I don't hate it, though I think it might be better to move off of the
varargs a bit - deprecated it and go this way.

# no throws
javaWriter.beginMethod(asList(params…));

# throws
javaWriter.beginMethod(asList(params…), asList(MyException.class, 
ThatException.class));

I generally like fluent APIs such as you're proposing, but the existing
APIs aren't really fluent, so it's a very odd example in the midst of
non-fluent approaches. This gives a near-varargs style, with two sets
of pseudo-varargs. asList() is a fairly limited amount of boilerplate
to make things clear, and taking a collection is no biggie considering
this code isn't tuned to run on android, it's tuned to run on the JVM.

[JakeWharton]

You typed markdown and GitHub ignored you because it was an email :(

I really like that approach you outlined, though.

[cgruber]

Argh. I hate that. It won't even let me correct it from the web. Grumble

# no throws 
javaWriter.beginMethod(asList(params…)); 

# throws 
javaWriter.beginMethod(asList(params…), asList(MyException.class, ThatException.class));

[swankjesse]

Lists instead of varargs? I think that's fine as long as we also keep the varargs versions. And we could require the list overload if you want to use throws.

[cgruber]

That's what I was thinking.