feat(server): check that serverMode implementation is correct

[knagaitsev]

• This is a bugfix
• This is a feature
• This is a code refactor
• This is a test update
• This is a docs update
• This is a metadata update

For Bugs and Features; did you add new tests?

Yes

Motivation / Use-Case

This feature gives useful error messages when the user provides an incorrect serverMode implementation.

Breaking Changes

None

Additional Info

[codecov]

Codecov Report

Merging #2051 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2051      +/-   ##
==========================================
+ Coverage   92.77%   92.82%   +0.04%     
==========================================
  Files          29       29              
  Lines        1149     1156       +7     
  Branches      327      329       +2     
==========================================
+ Hits         1066     1073       +7     
  Misses         79       79              
  Partials        4        4

Impacted Files	Coverage Δ
lib/utils/getSocketServerImplementation.js	90.9% <100%> (+1.43%)	⬆️
lib/utils/runOpen.js	100% <0%> (ø)	⬆️

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[alexander-akait]

I think it is extra checking and should be solved using schema-util instead adding checks in source code, we should search way how we can integrate this in schema util

[knagaitsev]

I think it is extra checking and should be solved using schema-util instead adding checks in source code, we should search way how we can integrate this in schema util

Switched to use of schema-util. I don't think it has the ability out of the box to check the parameter count of a function, but also that is not a check we really need.

[alexander-akait]

Good job, one note

[alexander-akait]

I think we can have one schema (put this inside original schema) for better maintenance

[knagaitsev]

@evilebottnawi The problem is that I couldn't find a way to test the prototype of a function with schema-utils when it matched "instanceof": "Function". I think it only looks at "properties" if the thing in question matches "type": "object", hence why I pass ServerImplementation.prototype into the schema

[knagaitsev]

Unless you just mean make options.json into something like:

{
"defaultSchema": { ... },
"socketServerImplementationPrototypeSchema": { ... }
}

But that could be a breaking change if something else is using this schema.

[alexander-akait]

hm we can rewrite schema-utils and allow to define own validator (where we can implement any logic), i will take care about this, let's keep this PR open, it is not high priority because we can improve documentation