format modifies options objects given to it

[jaubourg]

const options = {
  "type": "jpeg",
  "quality": 50,
};

sharpInstance.format( options );

options.hasOwnProperty( "trellisQuantisation" ); // true

Bumped into this while doing some unit testing where I was using the object given to format elsewhere in a deepEqual.

It's usually considered good practice not to modify objects passed as arguments. I personally thought I was going mad before realizing sharp.format had this undocumented side effect.

Not sure if this is generalized to the whole code base.

[jaubourg]

I had some brain malfunction, it's jpeg(), webp(), png(), etc.

Was thinking about the old API :/

[lovell]

Good spot, thanks for reporting this. The options of jpeg with an alternative spelling were affected - commit a54fe9f should deal with the problem.

[jaubourg]

Thanks for this @lovell and merry Christmas 😊

[lovell]

v0.21.2 now available.