Replace third party deep-equal library with native implementation

[Fawke]

Type of change

• Utils Functions

Description of change

deep-equal module is replaced by a native implementation for deeply checking object equality.

This function is mainly used by the sizeMappingV2.js module, which is tested and working fine after the replacement. This implementation is simple, but should mostly work for our use cases.

Also, prebid- core.js is now almost 40kb lighter after removal of this module.

[snapwich]

Missed a few places where deep-equal should be removed (such as the whitelist): https://github.com/prebid/Prebid.js/search?q=deep-equal&unscoped_q=deep-equal

other than that, looks good

[idettman]

Other than what Rich mentioned, LGTM

[Fawke]

@snapwich @idettman Thanks for the review.

@snapwich, Good catch, I forgot to replace the reference from allowedModules.js. One place, where I can not remove it from is fake-responder.js file.

It runs in node environment and throws an error if I try to require the utils.js file because the utils file uses import statements which are not recognized by node. I tried few solutions, like:

• using the mjs extension on fake-responder.js file
• trying to include node environment as target in babelrc.js file
• adding type: "module" key in parent package.json file

None of these approaches work. So, in the end, I had to add back the deep-equal library, but this time as a devDependency which will only be used in fake-responder.js file. Util.js will still have the native implemenation and we still achieve reduction in overall size of prebid-core webpack chunk.

If you have any better solution to how I can import utils in a file running in node env, let me know, or we can merge this.

[idettman]

It runs in node environment and throws an error if I try to require the utils.js file because the utils file uses import statements which are not recognized by node. I tried few solutions, like:

• using the mjs extension on fake-responder.js file
• trying to include node environment as target in babelrc.js file
• adding type: "module" key in parent package.json file

Imports and exports support In Node.js 12 requires both:

1. Passing the --experimental-modules flag when running Node.js
2. using .mjs extension or set "type": "module" in your package.json.

I'm guessing you're missing the --experimental-modules flag step, but since we are using gulp, we may need to add a environment variable (NODE_OPTIONS="--experimental-modules") to set the flag.

[Fawke]

@idettman I tried the approach that you suggested, using the flag --experimental-modules

1. setting extension to .mjs doesn't work because then, we would need to change the extension of all the files which are es modules to .mjs, which would require us to change extension of utils.js file and all the files imported by it.

2. setting type, in package.json to module also creates some problem. In some places in the code, we are still using require instead of import. This will require us to remove all references to require which will be an elaborate change, deserving its own PR.

We can copy the implementation of deepEqual from utils to a separate function in fake-response.js file, or use the third party deep-equal library but only as a devDependency. Let me know your thoughts.

[snapwich]

I think moving deep-equal to a devDependency is perfectly acceptable