Ensure transactions are always

[stefanpenner]

• need to see if this actually fixes the problem
• tests
• review

fixes #484

[stefanpenner]

Although I think ^ should be added, this wont address all cases (or even that many cases) as.

begin -> commit are actually the public API for interacting with then VM, so code from the calling library between they two may still fail. Which means that could also needs the try/finally.

Question is, should we enforce the commit, or implement a "abort" transaction.

let needsAbort = true;
try {
  env.begin();
  env.commit();
  needsAbort = false; // everything went ok, no abort required.
} finally { 
  if (needsAbort) {
    env.abort();
  }
}

---

Alternatively, one could remove the assertion and merely assume begin -> begin means, release the last transaction and create a new one. (no nesting).

[stefanpenner]

Rather then enforcing the caller to be aware of this. I change the PR to take a different approach.

• commit always resets the active transaction to null
• calling begin with an active transaction warns, then commits that transaction, and then starts the next transaction.

[stefanpenner]

There are different ways we can skin this cat, would love others opinions.

[stefanpenner]

throw in debug

[krisselden]

This looks good

[krisselden]

I like the fix, I'm not crazy about the test, why not throw on a component hook once like didInsertElement and test that you can rerender again?