Support modern Flexmark

[DanySK]

Scalatest recently switched from pegdown to flexmark.
Besides a lack of documentation, as discussed in #1736, scalatest currently works with a small range of flexmark versions.

I propose to:

1. add support for the more recent versions of Flexmark;
2. possibly, declare Flexmark as a runtime dependency, so that users do not need to guess what's needed in order to make scalatest reporting system work;
3. fail more clearly: the current error message is An exception or error caused a run to abort. This may have been caused by a problematic custom reporter.: it's truthful, but not particularly useful for resolution.

It is likely that the former two points make the third way less important, however my feeling is that the third is a low hanging fruit, while there might be need for more work to address the former.

[ldeck]

Ideally, this should be a plugin dependency so it doesn’t interfere with project dependencies. It should definitely be documented.

[caoilte]

Just ran into this issue trying to integrate with https://github.com/pact-foundation/pact-jvm on jdk8 (maybe modules makes it less of an issue on jdk9+, not sure) and which has a dependency on flexmark 0.62.2.

@DanySK where did you get to investigating an upgrade?

[DanySK]

@caoilte I did not even start trying to upgrade scalatest, frankly. I just investigated where the issue was from. Worst case, I'll switch to kotest, Scala is becoming more and more marginal on most of my projects.

[cheeseng]

Hi, fyi I submitted a PR to update flexmark version to 0.62.2:

#2050

[caoilte]

@cheeseng Hey nice! I was experimenting with pretty much the same changes using a locally built snapshot over the weekend. Weirdly, I found that even though the tests passed I couldn't use the snapshot (got runtime class not found) unless I added an extra dependency. Specifically,

"com.vladsch.flexmark" % "flexmark-profile-pegdown" % "0.62.2"

Would be interesting to know if you were also able to test locally?

[cheeseng]

@caoilte I didn't try local snapshot, the tests should be using HtmlReporter to generate the html report under target/html. Afaik, to use local snapshot (even the real release build) we need to explicitly add the flexmark dependency like the following:

"com.vladsch.flexmark" % "flexmark-all" % "0.62.2"

The reason I think is the flexmark dependency is marked as "optional", here:

https://github.com/scalatest/scalatest/blob/3.2.x-new/project/scalatest.scala#L178

Your import does seems to be more specific than flexmark-all though, I wonder if scalatest should use flexmark-profile-pegdown instead.

[caoilte]

@cheeseng Just checked and you're right. It also works with flexmark-all and that makes sense because every project I know running scalatest 3.1+ has to manually add that dependency (ie #1736).

It would certainly be interesting to explore whether profile-pegdown is a better choice overall.