One change is that test/unit is now no longer part of the standard library, which Rails requires. The workaround is simple, "test-unit" must be added to the Gemfile.
A less easily fixed change is that the following syntax no longer works the same as it did in previous versions of Ruby:
def foo(bar = bar)
The recommended fix is the following: (I believe)
def foo(bar = bar())
Rails uses this syntax occasionally. It's simple to change, but the Rails team refuses to merge in the fixes because it's not a security issue.
A less easily fixed change is that the following syntax no longer works the same as it did in previous versions of Ruby:
The recommended fix is the following: (I believe) Rails uses this syntax occasionally. It's simple to change, but the Rails team refuses to merge in the fixes because it's not a security issue.