render does not reject when rendering fails

[ef4]

I would have expected this test to pass, but it fails with "expected not to get here" in addition to an out-of-band qunit failure for the actual Compiler Error: not-a-component is not a helper.

test('render can throw', async function(assert) {
  try {
    await render(hbs`{{not-a-component x="y"}}`);
  } catch (err) {
    assert.ok(/not-a-component is not a helper/.test(err.message), "expected to see failure");
  }
  throw new Error("expected not to get here");
});

[rwjblue]

This is ultimately due to how rendering is deferred in the render queue.

There are work arounds / solutions, I’ll try to list them so we can discuss the best path forward.

[ef4]

Yeah, I know the scheduling isn't synchronous, I was just a little surprised because we're already waiting here for everything to finish, so most of the plumbing for getting the state threaded back to us must already be present.

[cibernox]

I'm also trying to find a reliable way of testing errors/assertions during the render. What are the possible workarounds for this? (Or reliable fix for that matter)

[kellyselden]

This appears to be a bit stale, but I would love some workarounds as well.

[kellyselden]

With the help of @rwjblue's talk https://www.youtube.com/watch?v=PwQAj5UU9ng, I came up with a decent workaround.

  let onerror;

  hooks.beforeEach(function() {
    // `sinon.stub(Ember, 'onerror')` won't work because onerror
    // has a setter, it's not the real reference called
    onerror = Ember.onerror;
  });

  hooks.afterEach(function() {
    Ember.onerror = onerror;
  });

  test('it fails when passed a number', async function(assert) {
    let stub = sinon.stub();
    Ember.onerror = stub;

    await render(hbs`{{zip-filter 98101}}`);

    assert.ok(stub.withArgs(sinon.match({
      message: 'Assertion Failed: zip-filter helper expected a string. Got a number instead.'
    })).calledOnce);
  });

I guess this can be closed now?

[ef4]

I still think this is a bug. render should throw.

[ef4]

But thanks for sharing the workaround!

[rwjblue]

I still think this is a bug. render should throw.

Agreed. Though the actual details of how to implement this properly are non-trivial. I will try to gather better info and report here...

[Frozenfire92]

👍 Chiming in as someone who is being affected by this

Ember 3.3

Noting neither this workaround or the one @kellyselden mentioned above worked for me.

Noting I'm coming to this not when rendering fails, but when a click throws an error, but assuming its the same issue with the render queue

Test

test('Handles not having action passed in', async function(assert) {
    await render(hbs`{{async-button}}`);

    assert.throws(
      async () => {
        await click(find('.async-button'));
      },
      'Throws exception when action not passed in'
    );
  });

Relevant piece of component (within click handler)

else {
  throw new Error('missing passed in action to async-button');
}

How it looks in qunit browser window

[nlfurniss]

@Frozenfire92 out of curiosity, what happens if you do this instead:

  assert.throws(
    () => this.$('.async-button').click(),
    'Throws exception when action not passed in'
  );

I'm running into the same issue as you and only using jQuery works; neither click(myElem) nor find(myElem).click() works.

[nlfurniss]

This twiddle reproduces the issue.

TLDR

There is a component that will throw an error if two attrs arent passed in (x and y) and the component is clicked on.

There are three tests:

1. Ensure no errors if both attrs passed in and component is clicked ✅
2. Ensure an error is throw is only one attr is passed in and component is clicked (uses native JS and tests fails) ❌
3. Ensure an error is throw is only one attr is passed in and component is clicked (uses jquery and test passes) ✅

Here is where things go wrong:

// Qunit throws
try {
   block.call(currentTest.testEnvironment);  <====== This call doesnt trigger an error when it uses native JS. But FUN FACT: if you highlight this line at a breakpoint, it will log an error (???)
} catch (e) {
   actual = e;
}
...
if (actual) {     <==== `actual` needs to be set otherwise it wont catch the error and the test will fail.