feat(project): update definitions when the bundle gets reloaded

[homer0]

What does this PR do?

This is a follow up for #74.

Variables from .env files and browser target configurations were being loaded and sent to the webpack.DefinePlugin, but the problem was that if a variable would change, even after triggering a bundle reload, its value wouldn't be updated on the target code nor its configuration.

Short version: Definitions are now refreshed every time the bundle gets reloaded.

And now, for the long a breaking version:

The first thing I did was to convert the params.definitions the engine moves around from an object into a function that would return the object.

Then, webpack.DefinePlugin allows for computed definitions as functions... but each key needs to be function, you can't have a single one that would return everything; so I created a webpack plugin that wraps webpack.DefinePlugin and supports a single function.

Finally, I replaced webpack.DefinePlugin on the browsers' configurations with the new plugin.

Now, this is very important: because using computed definitions without specifying a file that depends on the definition marks ALL files as "non-cachable", which makes the build slower, the build engine only reloads the definitions when the target entry file changes. Yes, it's not the best solution, but the alternative would be slower builds.

How should it be tested manually?

In order to test this, you need to install homer0/projext#next and make sure you delete the copy of projext npm/yarn will install inside this package's node_modules.

Create a browser target, and .env file with a declared variable and configuration for the target that uses the variable.

Then run your target and check if the configuration has the right value. Update the variable on the .env file and "save the target entry file" (cmd/ctrl+s would trigger the rebuild), the configuration should have the new value.

And, of course...

yarn test
# or
npm test

[coveralls]

Pull Request Test Coverage Report for Build 279

• 43 of 43 (100.0%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 276:	0.0%
Covered Lines:	646
Relevant Lines:	646

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💛 - Coveralls