Remove Node.js requirement with Scala.js

[olafurpg]

Previously, it was not possible to use MUnit with browser-based
JavaScript environments because MUnit imported the Node.js fs module.
This commit refactors the code so that MUnit should gracefully recover
when the Node.js fs module is not available.

Fixes #247

[tgodzik]

Suggested change

	crossScalaVersions := allScalaVersions.filterNot(_.startsWith("0."))
	crossScalaVersions := allScalaVersions

just as a complete side note, I don't think we need this anymore

[gabro]

👍 I had a draft comment saying the same thing

[raquo]

Thanks, checked it out locally. It does not throw as before, but now MUnit does not print any information about the assertion failures except the name of the test in which they appeared.

Munit on a JVM project prints this kind of useful error on failure:

==> X com.raquo.mapk.v1.V1MapKSpec.xxx  0.016s munit.ComparisonFailException: <projectRoot>/src/test/scala/com/raquo/mapk/v1/V1MapKSpec.scala:32
31:  test("xxx") {
32:    assertEquals(true, false)
33:  }
values are not the same
=> Obtained
true
=> Diff (- obtained, + expected)
-true
+false

Whereas MUnit in this PR prints only the following on a similar test in a JS project:

==> X com.raquo.domtestutils.MUnitJsDomSpec.xxx 0.01s munit.ComparisonFailException:

Also, the console is now printing a warning (not an error) before the tests:

[info] Writing and bundling the test loader
[warn] ./domtestutils-test-fastopt.js 4434:33-48
[warn] Critical dependency: the request of a dependency is an expression
[warn]     at CommonJsRequireContextDependency.getWarnings (<projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/webpack/lib/dependencies/ContextDependency.js:40:18)
[warn]     at Compilation.reportDependencyErrorsAndWarnings (<projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/webpack/lib/Compilation.js:1360:24)
[warn]     at <projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/webpack/lib/Compilation.js:1168:10
[warn]     at AsyncSeriesHook.eval [as callAsync] (eval at create (<projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:13:1)
[warn]     at AsyncSeriesHook.lazyCompileHook (<projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/tapable/lib/Hook.js:154:20)
[warn]     at Compilation.finish (<projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/webpack/lib/Compilation.js:1163:28)
[warn]     at <projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/webpack/lib/Compiler.js:622:17
[warn]     at eval (eval at create (<projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:9:1)
[warn]     at <projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/webpack/lib/Compilation.js:1095:12
[warn]     at <projectRoot>/target/scala-2.13/scalajs-bundler/test/node_modules/webpack/lib/Compilation.js:1007:9
[warn]     at processTicksAndRejections (internal/process/task_queues.js:79:11)
[warn]  @ ./domtestutils-test-fastopt-loader.js

You mentioned in previous comments that you need the fs module to read the source files to display information about the failure. So... does this PR replace that logic with a stub if the fs module can't be loaded?

[gabro]

leftover?

[gabro]

👍 I had a draft comment saying the same thing

[olafurpg]

@raquo thank you for trying it out! What Scala.js linker settings are you using to reproduce that? It might require a small tweak to get the exception message

[raquo]

@olafurpg Here is all of the linker config and a few more relevant bits:

scalaVersion := "2.13.5" // Scala.js version is 1.5.0
(Test / scalaJSLinkerConfig ~= { _.withModuleKind(ModuleKind.CommonJSModule) })
(Test / requireJsDomEnv) := true
(installJsdom / version) := "16.4.0"
useYarn := true
(Test / parallelExecution) := false

No other scalaJSLinkerConfig settings (I also had source maps off, but commented that out, and still the same). I only added the line with CommonJSModule because MUnit docs told me to, but commenting it out does not change anything.

One weirdness on my side that I can think of is that my project where I'm trying to use this is a testing library, so it requires the MUnit dependency without appending % "test". Whereas my scalaJSLinkerConfig has a Test / prefix as you see above. So maybe something is not catching on? I tried removing that prefix or replacing it with Compile /, but that did not produce any effect.

For the record, the branch that I'm trying to build is here. The simple test that I made to fail is MUnitJsDomSpec. MUnit version is defined in Versions.sbt.

[armanbilge]

@olafurpg I can confirm this PR works over at http4s/http4s#4938.

Thanks for making this change, I'm badly in need of this. Is there anything I can do to get this merged and (snapshot) released ASAP? I'm happy to polish up this PR as @gabro and @tgodzik see fit.