Support webpack 5

[haoqunjiang]

What's the problem this PR addresses?

Continues the work on #83

How did you fix it?

By fixing the isBuilt function.

---

Other thoughts:

1. Haven't checked webpack 4 compatibility. Shall I work on that or will this PR be released in a new major?
2. The 2 failing tests are caused by the usage of memory-fs in mochapack. It stops the devServer.writeToDisk option from writing actual files to the disk. In the past, it's handled by write-file-webpack-plugin, but the plugin is not compatible with webpack 5. Shall I add an additional option to the CLI just to fix the tests?

[larixer]

1. Haven't checked webpack 4 compatibility. Shall I work on that or will this PR be released in a new major?

I would be grateful if webpack 4 compatibility were retained in this PR, otherwise, it will be a maintenance nightmare to keep up to date both new major and old major to support users of webpack 4 and webpack 5 at the same time

2. The 2 failing tests are caused by the usage of memory-fs in mochapack. It stops the devServer.writeToDisk option from writing actual files to the disk. In the past, it's handled by write-file-webpack-plugin, but the plugin is not compatible with webpack 5. Shall I add an additional option to the CLI just to fix the tests?

I think env variable would be better, instead, no need to pollute CLI and its enough to have just short notice in the source code why it is needed.

Btw, why have you decided to continue work on Webpack 5 support here, what about instant-mocha, didn't it cover your needs?

[haoqunjiang]

Btw, why have you decided to continue work on Webpack 5 support here, what about instant-mocha, didn't it cover your needs?

It failed my tests with very obscure error messages. I have no idea how to fix or even reproduce the issue.

On the other hand, I've had a rough idea on how to fix the previous PR for a while, so I give it a try.

[haoqunjiang]

Done! All tests are passing.

In order to reduce the mental burden, though the implementations of the two versions are similar, I put them into different files:

1. getAffectedModuleIds.ts & getBuildStats.ts for webpack 5
2. webpack4GetAffectedModuleIds.ts & webpack4GetBuildStats.ts for webpack 4

I've also added two scripts in the TravisCI config to skip TypeScript/ESLint checking for unrelated files.

[codecov-commenter]

Codecov Report

Merging #98 (b30cc73) into master (6240eeb) will decrease coverage by 4.94%.
The diff coverage is 14.89%.

@@            Coverage Diff             @@
##           master      #98      +/-   ##
==========================================
- Coverage   65.87%   60.93%   -4.95%     
==========================================
  Files          42       44       +2     
  Lines        1225     1349     +124     
  Branches      137      158      +21     
==========================================
+ Hits          807      822      +15     
- Misses        400      509     +109     
  Partials       18       18              

Impacted Files	Coverage Δ
...rc/runner/runnerUtils/createWebpackConfig/index.ts	100.00% <ø> (ø)
src/webpack/compiler/registerInMemoryCompiler.ts	18.42% <0.00%> (-0.50%)	⬇️
src/webpack/compiler/registerReadyCallback.ts	22.22% <0.00%> (ø)
src/webpack/loader/entryLoader.ts	54.16% <0.00%> (ø)
src/webpack/util/createEntry.ts	33.33% <ø> (ø)
src/webpack/util/createStatsFormatter.ts	30.00% <ø> (ø)
src/webpack/util/getBuildStats.ts	18.18% <0.00%> (ø)
src/webpack/util/webpack4GetAffectedModuleIds.ts	12.24% <12.24%> (ø)
src/webpack/util/getAffectedModuleIds.ts	12.50% <15.38%> (+0.25%)	⬆️
src/webpack/util/webpack4GetBuildStats.ts	19.44% <19.44%> (ø)
... and 5 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6240eeb...b30cc73. Read the comment docs.

[larixer]

@sodatea Awesome, thank you so much! I'm going to review the PR shortly

[larixer]

@sodatea Merged your PR and published mochapack@2.1.0. Thanks again for your awesome work!