chore(binding-coap): enable strict-boolean-expressions and null checks

[JKRhb]

This PR addresses one of the checkmarks in #1046.

[codecov]

Codecov Report

Patch coverage: 72.72% and no project coverage change.

Comparison is base (227be53) 75.31% compared to head (fd72a5d) 75.32%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1088   +/-   ##
=======================================
  Coverage   75.31%   75.32%           
=======================================
  Files          80       80           
  Lines       16060    16057    -3     
  Branches     1503     1503           
=======================================
- Hits        12096    12095    -1     
+ Misses       3925     3923    -2     
  Partials       39       39           

Files Changed	Coverage Δ
packages/binding-coap/src/coap-client.ts	82.28% <66.66%> (-0.07%)	⬇️
packages/binding-coap/src/coap-server.ts	78.55% <80.00%> (+0.18%)	⬆️

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[relu91]

I still didn't have proper time to review this, I want to be sure that is sufficient for check only for null and not for undefined. Given that in TS/JS world is way more common to leave values into the undefined state, I would like to be careful to only check for null

[JKRhb]

I still didn't have proper time to review this, I want to be sure that is sufficient for check only for null and not for undefined. Given that in TS/JS world is way more common to leave values into the undefined state, I would like to be careful to only check for null

foo != null is basically a shorthand for foo !== null && foo !== undefined – as mentioned elsewhere, this is apparently the only case where using the == operator is valid. So when checking for null this way, you get the check for undefined for free and vice versa. (Having both null and undefined has obviously not been a good language design decision 😅).

I haven't found a really good documentation link to point here, but some further explanations can be found here: https://basarat.gitbook.io/typescript/recap/null-undefined#checking-for-either

[relu91]

Silly me, I'm so used to the !== operator that I didn't even notice that you used the less strict version. Good to go.