Pay attention on errors in cancel functions

[bunglegrind]

Because of

parseq/parseq.js

Line 113 in 04aa2ee

} catch (ignore) {}

exceptions in cancel functions are catched and ignored.

Is this a problem? Well, it depends. If you write a test and put an assertion on the cancel function, and the assertion library you're using throws when failing (such as https://nodejs.org/docs/latest-v20.x/api/assert.html ), it definitely is 😛

Just pay attention 😉

[douglascrockford]

Cancel is a best effort mechanism. There is no guarantee that it will be successful. Given that, there should be no expectation that the reason for the cancel's failure should be delivered.

[bunglegrind]

Indeed...IMHO the problem is with the assertion library which should use a different mechanism to signal failures to the test runner, because "the exception channel" is already used by the program under test.

Since I spent one hour in order to understand what was happening, I thought to share my experience...

[douglascrockford]

Are you recommending a change to Parseq?

[bunglegrind]

Are you recommending a change to Parseq?

Well, probably just in the documentation. Explicitly saying that exceptions within cancel functions are catched and ignored by the parseq runtime should be enough.

[bunglegrind]

btw:

nodejs/node#52033