Refactoring of gRPC internals & tests and introducing the reflectMetadata

[olegbespalov]

What?

This PR contains several parts:

• First is refactoring of calling and connection params to make code more re-usable
• Second is the significant (but is mostly moving & cleaning) refactoring of the gRPC client's test
• last but not least is an introduction to the reflectMetadata

Why?

The refactoring was done to make the following changes tinier and pay some technical dept of removing copy-pasting.

The reflectMetadata was requested in #3241

Checklist

• I have performed a self-review of my code.
• I have added tests for my changes.
• I have run linter locally (make ci-like-lint) and all checks pass.
• I have run tests locally (make tests) and all tests pass.
• I have commented on my code, particularly in hard-to-understand areas.

Related PR(s)/Issue(s)

grafana/xk6-grpc#51

Closes: #3241

Changelog

epic-feature: a new gRPC connection's parameter reflectMetadata

In some workflows, the reflection call should also include some metadata. This PR adds a new connection parameter reflectMetadata that allows to specify the metadata to be sent with the reflection call.

[codecov-commenter]

Codecov Report

Patch coverage: 66.66% and no project coverage change.

Comparison is base (b8a6ecf) 73.17% compared to head (ce3833f) 73.17%.

❗ Current head ce3833f differs from pull request most recent head f100921. Consider uploading reports for the commit f100921 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3343   +/-   ##
=======================================
  Coverage   73.17%   73.17%           
=======================================
  Files         258      258           
  Lines       19886    19903   +17     
=======================================
+ Hits        14551    14564   +13     
- Misses       4414     4416    +2     
- Partials      921      923    +2     

Flag	Coverage Δ
ubuntu	73.11% <66.66%> (+<0.01%)	⬆️
windows	73.03% <66.66%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
js/modules/k6/grpc/client.go	83.38% <66.66%> (-0.98%)	⬇️

... and 2 files with indirect coverage changes

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[olegbespalov]

I rebased, since there was a minor conflict with master branch.

[codebien]

Out of curiosity, why are we moving them to a specific package? Do we have cycle dependencies or other issues? I'm not against it, but I've seen some ongoing discussions around gRPC and extensions and I have the feeling I lost something.

[olegbespalov]

I'd say it's just a better way of structuring the tests (best practice), basically test package becomes a user of the main package, which blocks access to the main package's internals, and as a result, we should write more robust tests, since even something internally in the package changed the tests continue to works since they rely on the public API

[codebien]

It sounds like it could be the time to drop it completly.

[olegbespalov]

The test is still relevant for the existing functionality. However, I like the idea of dropping the headers property, but how about opening a separate PR where we start erroring (right now, we just fallthrough to the metadata) and keep this for a cycle/too till we altogether remove it?

[codebien]

I'm fine with it 👍