Fix for the 'start' range of BlobDataItem when reading its stream

[octet-stream]

I was trying to upgrade fetch-blob to the latest version and got the following error when I run my tests:

Details

You can also reproduce this from node REPL:

1. Clone fetch-blob to your local machine
2. Install dependencies as usual
3. Open .editor REPL:
4. Put this code into console, then hit Ctrl+D to run it:

const {createWriteStream} = require("fs")

const blobFromPath = require("./from")

void blobFromPath("./LICENSE").stream().pipe(createWriteStream("/dev/null"))

Tried this on Node v15.13.0 and v16.0.0

Seems like the error appears because you didn't check if the start option present.
Here:

fetch-blob/from.js

Line 48 in cc929f3

end: this.start + this.size - 1

So when the start option is not set, the result of this operation would be NaN.

I think it also happens here:

fetch-blob/from.js

Line 37 in cc929f3

size: end - start

This PR should solve the problem.

I was also thinking to just set the start to 0 by default, but I'm not sure if I understand how Node.js will handle ReadStream in this case.

[codecov]

Codecov Report

Merging #85 (22ecc66) into master (cc929f3) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #85   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines          234       234           
  Branches        37        38    +1     
=========================================
  Hits           234       234           

Impacted Files	Coverage Δ
from.js	100.00% <100.00%> (ø)

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[jimmywarting]

Hmm, kind of expected that start would always be present on BlobDataItem... guess i have missed that or just skipped it entierly.
Would be nice to have it be 0 by default

[octet-stream]

Done

[octet-stream]

Just noticed it was present in v2.1.1

Details

Same function in v2.1.2

Details

[octet-stream]

Can't find it in from.js history. Maybe you forgot to push this change to github?

[jimmywarting]

Can't find it in from.js history. Maybe you forgot to push this change to github?

Could be