Make yaml.Unmarshal strict

[ronensc]

Using yaml.UnmarshalStrict() will prevent us from making typos in our yamls without being noticed.

[codecov-commenter]

Codecov Report

Merging #271 (59612db) into main (6c1dae1) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #271   +/-   ##
=======================================
  Coverage   66.83%   66.83%           
=======================================
  Files          73       73           
  Lines        4149     4149           
=======================================
  Hits         2773     2773           
  Misses       1197     1197           
  Partials      179      179           

Flag	Coverage Δ
unittests	66.83% <100.00%> (ø)

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Impacted Files	Coverage Δ
pkg/confgen/config.go	33.33% <100.00%> (ø)

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[KalmanMeth]

@ronensc What is your general rule when you want to use UnmarshalStrict as opposed to Unmarshal?

[ronensc]

Assume we have a type like this:

type Person struct {
	Name string `yaml:"name"`
	Age  int    `yaml:"age"`
}

and data that we want to parse:

person:
  name: John
  Age: 42

Notice that the age field is misspelled (it should be age with lowercase a).

Using unstrict yaml.Unmarshal() won't raise an error on this. It will simply ignore the unrecognized field Age and set the default value for the missing field age.

I think in our use-case, where we parse config files, we want to make sure that all fields are recognized and emit an error otherwise.

[KalmanMeth]

So aren't there numerous places in the code where we Marshal the config data where we should also use UnmarshalStrict ?

[ronensc]

I replaced all the yaml.Unmarshal() invocations that I found (I found only 3).
Please let me know if I missed something.

[KalmanMeth]

There are also lots of json.Unmarshal() calls.

[ronensc]

Unfortunately, the json library doesn't have a strict version of Unmarshal() like the yaml has.
But, we can get the strict behavior with json.NewDecoder and DisallowUnknownFields() as suggested here:
https://groups.google.com/g/golang-nuts/c/MJuJDte5YHg/m/JMs0S-4uAQAJ

[KalmanMeth]

Can't some of those be changed to to yaml.UnmarshalStrict?

[jotak]

lgtm
Indeed I remember having seen hostname and hostName in some places and was confused about that

[ronensc]

Note: This PR deals only with confgen. That is, flowlogs-pipeline would start normally even if its config has unknown fields. I created an issue for it and will solve it in a later PR. #274