fix: avoid reading files when the size is empty

[jimmywarting]

The purpose of this PR is:

... to fix a range error when it tries to read a empty file:
"RangeError [ERR_OUT_OF_RANGE]: The value of "end" is out of range. It must be >= 0 && <= 9007199254740991. Received -1"

This is what had to change:

... Avoid pushing empty chunks into the bucket and avoid reading them all together.

This is what like reviewers to know:

... this affected the blob backed up by the filesystem

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• I prefixed the PR-title with docs: , fix(area): , feat(area): or breaking(area):
• I Added unit test(s)

[jimmywarting]

also made sure it checks the stat.size if it has changed for good measures... some application can change the content without modifying the date

[LinusU]

I personally try to treat null and undefined the same in the code, to avoid unexpected behaviour. This also lets us transition to the ?? operator when we drop support for Node.js 12.x, without changing the behaviour of the code.

Suggested change

	this.originalSize = options.originalSize === undefined
	this.originalSize = options.originalSize == null

(x == null is the same as x === undefined || x === null)

[jimmywarting]

i know that, i also try to avoid null from time to times. and i can't wait until we can start using ??=

but i wanted to avoid using == instead of === and breaking any compatibility with nullish stuff
also since there is no occurrences of null in the code, then i tought it would be fine to just check for undefined

could also just do this.originalSize = options.originalSize || options.size

[LinusU]

options.originalSize || options.size will use options.size if options.originalSize is 0 though, that's probably not what we want

[jimmywarting]

i thought about it too, but after commit 568b309 then that might not be needed after all, cuz 0-sized blob and typedarrays will not be in the source anymore

[LinusU]

Neat 👍