feat: lint examples

[naseemkullah]

Which problem is this PR solving?

Fixes #603

Short description of the changes

Adds .eslintrc at root of examples folder, lints said examples (WIP) and adds a step in pipeline to validate that the examples are linted.

[codecov-io]

Codecov Report

Merging #649 into master will increase coverage by 1.75%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #649      +/-   ##
==========================================
+ Coverage   90.92%   92.67%   +1.75%     
==========================================
  Files         224      227       +3     
  Lines       10256    10337      +81     
  Branches      962      940      -22     
==========================================
+ Hits         9325     9580     +255     
+ Misses        931      757     -174

Impacted Files	Coverage Δ
...s/opentelemetry-web/test/StackScopeManager.test.ts	0% <0%> (ø)	⬆️
...ackages/opentelemetry-web/src/WebTracerRegistry.ts	100% <0%> (ø)	⬆️
...kages/opentelemetry-plugin-dns/test/utils/utils.ts	33.33% <0%> (-26.67%)	⬇️
...ages/opentelemetry-plugin-http/test/utils/utils.ts	33.33% <0%> (-26.67%)	⬇️
...es/opentelemetry-node/src/instrumentation/utils.ts	90.47% <0%> (-9.53%)	⬇️
packages/opentelemetry-plugin-mysql/src/utils.ts	90.9% <0%> (-4.55%)	⬇️
packages/opentelemetry-web/test/WebTracer.test.ts	0% <0%> (ø)	⬆️
packages/opentelemetry-web/src/utils.ts	94.73% <0%> (ø)	⬆️
...ry-scope-async-hooks/src/AsyncHooksScopeManager.ts	97.67% <0%> (ø)	⬆️
...try-propagator-jaeger/src/JaegerHttpTraceFormat.ts	95.65% <0%> (ø)	⬆️
... and 181 more

[dyladan]

Each example has to have its own .eslintrc? is there no way to share a single one in the whole examples folder?

[naseemkullah]

Each example has to have its own .eslintrc? is there no way to share a single one in the whole examples folder?

Sounds sensible, will look into that.
BTW airbnb tends to remove 'use strict;', do we care enough to override that rule? Should we try another eslint-config?

[dyladan]

Each example has to have its own .eslintrc? is there no way to share a single one in the whole examples folder?

Sounds sensible, will look into that.
BTW airbnb tends to remove 'use strict;', do we care enough to override that rule? Should we try another eslint-config?

I used the airbnb rules on a previous project and found them to be generally sensible, but one of the overrides we applied was to always use strict. The airbnb style guide assumes you are using the airbnb development toolchain which inserts use strict during the compile step :) https://github.com/airbnb/javascript/blob/master/packages/eslint-config-airbnb-base/rules/strict.js#L3

[dyladan]

@naseemkullah it looks like one of the rules is no-use-before-defined whose behavior I don't happen to like. JS has function hoisting which I find makes code a lot easier to understand. I like to have the "main" function at the top, with the utility functions it calls at the bottom, which reads much more naturally to me. With the airbnb rules you are required to scroll past all the utility functions before you get to the function that actually does the work.

[dyladan]

Can you add a yarn script lint:examples to the root package.json? Some people may not have eslint installed globally.

Also add the dev dependencies.

[naseemkullah]

Can you add a yarn script lint:examples to the root package.json? Some people may not have eslint installed globally.

Sure sounds good,
Why do some scripts separate words with : (e.g. codecov:browser) and others with - (e.g. docs-deploy) ? What's the convention here?

[dyladan]

Can you add a yarn script lint:examples to the root package.json? Some people may not have eslint installed globally.

Sure sounds good,
Why do some scripts separate words with : (e.g. codecov:browser) and others with - (e.g. docs-deploy) ? What's the convention here?

no convention afaik. just different people adding them

[naseemkullah]

@dyladan I've fixed conflicts and I've added many exceptions as there was too much non easily lintable code. Lets please get this in before more changes are made to examples to avoid fixing conflicts.

[naseemkullah]

bump

[OlivierAlbertini]

LGTM

[mayurkale22]

I think this is good to go, right? /cc @dyladan

[dyladan]

@mayurkale22 yes I think so. I didn't want to merge without your ✅