The aggregate change percentage is `NaN` if no files were mangled

[ericcornelissen]

Package(s)

webmangler-cli (v0.1.8)

Description

The stats module of the CLI package returns the value NaN for the overall/aggregate changePercentage if 0 files were mangled (i.e. inFiles.lenght === 0).

The impact on existing reporters is minimal (no impact on the DefaultReporter and limited impact on the JsonReporter, see below).

Actual Behaviour

Mangling 0 files with the CLI results in stats.aggregate.changePercentage === NaN.

Expected Behaviour

Mangling 0 files with the CLI results in stats.aggregate.changePercentage === 0.

---

The unit test suite for compute.ts should ideally be updated accordingly to test the values of changePercentage, sizeBefore, and sizeAfter:

webmangler/packages/cli/src/stats/__tests__/unit/compute.test.ts

Lines 183 to 187 in 57f6e70

	if (aggregate.changed) {
	expect(aggregate.changePercentage).not.to.equal(0);
	expect(aggregate.sizeBefore).to.equal(expectedAggregate.sizeBefore);
	expect(aggregate.sizeAfter).to.equal(expectedAggregate.sizeAfter);
	}

Working Example

1. In packages/cli, create a file called .webmanglerrc.js with the contents:

   const { JsonReporter } = require("webmangler-cli/reporters");
   
   module.exports = {
     reporters: [
       new JsonReporter({ prettyPrint: true }),
     ],
   };

2. In the project root, run:

   git checkout 57f6e70aed5ebacd23991a5e8f76f939064f5f44
   npm ci
   npm run cli --workspace=packages/cli -- ../../testdata/foobar --stats

3. Observe in the output the line "changePercentage": null.

Workaround

No response

Notes

Originally posted in #333 (comment)