Incremental compilation issues in large(ish) projects

[alexarchambault]

In the Scala CLI, but also in the coursier or Almond builds, we've been seeing consistently issues with incremental compilation. IIRC, these were things like whole module being re-compiled upon simple source changes that shouldn't require it.

These were frequent enough that we switched to mill-scala-cli to handle compilation in those projects (even it though it has some drawbacks). These issues are also quite hard or time-consuming to reproduce, and even more so to minimize. Which is quite frustrating, and is also why this wasn't reported earlier.

Sorry about the vague description here, I usually don't open issues if I don't have at least a repro, but I guess you asked for it ^^

[alexarchambault]

If you want to build Scala CLI without the mill-scala-cli plugin, you can add a line such as

  def enableScalaCli = false

right below this one.

[lefou]

Thanks for reporting. Although the description is vague, we recently fixed an issue with incremental compilation in 0.10.5, which could also be the cause for your observations.

• Issue: Incorrect zinc modified binary dependencies #1901
• Fix: fix zinc binary dependencies #1904
• Test case: Test case ensuring zinc is only re-compiling changed sources #1907

It would be very helpful, if you could check whether a recent version of Mill >= 0.10.5 fixes your issues as well.

[alexarchambault]

Closing this issue… As of VirtusLab/scala-cli#1335 (that uses Mill 0.10.7), it seems the incremental compilation issues went away. It seems to be the same on the coursier build, where I had enabled mill-scala-cli too.

[lefou]

Thanks for checking and reporting! This issue was already fixed in Mill 0.10.5 then.