Using lodash.merge for all merges (except webpack).

[Blackbaud-BobbyEarl]

Fixes blackbaud/skyux2#1148

[codecov-io]

Codecov Report

Merging #292 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #292   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          58     59    +1     
  Lines        1358   1365    +7     
  Branches      205    206    +1     
=====================================
+ Hits         1358   1365    +7

Flag	Coverage Δ
#builder	100% <100%> (ø)	⬆️
#runtime	100% <ø> (ø)	⬆️
#srcapp	100% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
cli/build.js	100% <100%> (ø)	⬆️
utils/runtime-test-utils.js	100% <100%> (ø)	⬆️
config/sky-pages/sky-pages.config.js	100% <100%> (ø)	⬆️
utils/merge.js	100% <100%> (ø)

---

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 92dfe68...b59b918. Read the comment docs.

[Blackbaud-BobbyEarl]

Also thanks to @blackbaud-brandonhare for tracking down the original bug in #288.

For future clarity, other alternatives and their pitfalls explained below:

1. https://www.npmjs.com/package/merge For reasons that aren't entirely clear, this merge library was unable to have the override merge delete a key. So if default was { test: { inner: true } } was merged override { test: false }, test was still set. This behavior was documented in the original bug.

2. https://www.npmjs.com/package/webpack-merge This almost worked, except for the plugin property in skyuxconfig.json. By design, those arrays are concatenated in order to work with Webpack.

3. https://www.npmjs.com/package/lodash.merge This was the best choice as we could pull in just the merge module, instead of all of lodash. It correctly handled recursively merging as well as deleting keys.

Update

4. Turns out, the default behavior for lodash.merge is merge arrays by taking the value at each index. So ['val1', 'val2'] merged with ['val3'] would produce ['val3', 'val2']. Not the behavior we want. Instead, we can use the lodash.mergeWith module and provider our own customizer. Again, @blackbaud-brandonhare has provided this work!

[Blackbaud-SteveBrush]

Related? blackbaud/skyux2#1181