fix: avoid overwriting the default values of options with undefined

[ryamaguchi0220]

The default values of options (append, releaseCount, skipUnstable...) appear to be not working as intended.

If releaseCount option is not specified, the options object initially has the property releaseCount: undefined, and then the default value releaseCount: 1 looks like to be assigned, but actually releaseCount: undefined is assigned again due to merging ...options (which has releaseCount: undefined) with the default values.

conventional-changelog/packages/conventional-changelog-core/lib/merge-config.js

Lines 66 to 95 in 11195f2

	options = {
	append: false,
	releaseCount: 1,
	skipUnstable: false,
	debug: function () {},
	transform: function (commit, cb) {
	if (typeof commit.gitTags === 'string') {
	const match = rtag.exec(commit.gitTags)
	rtag.lastIndex = 0
	if (match) {
	commit.version = match[1]
	}
	}
	if (commit.committerDate) {
	commit.committerDate = dateFormat(commit.committerDate, 'yyyy-mm-dd', true)
	}
	cb(null, commit)
	},
	lernaPackage: null,
	...options,
	pkg: {
	transform: function (pkg) {
	return pkg
	},
	...options?.pkg
	}
	}

This problem has been introduced by #959.

[ryamaguchi0220]

Here omits props whose value is undefined to avoid overwriting the default values with undefined.

[ryamaguchi0220]

@dangreen I would appreciate your review 🙏

[dangreen]

Thanks for the PR! Please fix CI errors and provide tests for your changes.

[coveralls]

coverage: 94.94% (+0.02%) from 94.924% when pulling ddf323b on ryamaguchi0220:fix/avoid-overwriting-default-values-of-options into 11195f2 on conventional-changelog:master.

[ryamaguchi0220]

@dangreen Thanks for your review!
I added the tests for merge-config 229622c

[ryamaguchi0220]

The test file names (merge-config.spec.js and index.spec.js) are based on other packages such as conventional-commits-parser, conventional-changelog-writer.

[ryamaguchi0220]

If props whose value is undefined are not omitted, this test will fail since the default values will be overwritten with undefined.

[dangreen]

let's optimize it to one loop

Suggested change

	function omitUndefinedValueProps (obj) {
	if (obj === null || typeof obj !== 'object') {
	return {}
	}
	const omittedObj = Object.entries(obj).filter(([, value]) => value !== undefined)
	return Object.fromEntries(omittedObj)
	}
	function omitUndefinedValueProps (obj) {
	if (!obj) {
	return {}
	}
	const omittedObj = {}
	for (const key in obj) {
	if (obj[key] !== undefined) {
	omittedObj[key] = obj[key]
	}
	}
	return omittedObj
	}

[ryamaguchi0220]

Optimized in ddf323b

[ryamaguchi0220]

@dangreen Thanks for the quick release!