Improve Yaml Parsing & CRD Selection

[RichiCoder1]

Random idea I had while thinking about some issues was to subsititute some of the current regex'd logic with some more robust code based on yaml and yqlib.

This code supports both multi docs and uses yq for selecting CRD Nodes.

Psuedocode:

import (
    /* ...snip... */
	"github.com/mikefarah/yq/v4/pkg/yqlib"
	yaml "gopkg.in/yaml.v3"
)

/* ...snip... */

func splitYAML(greps []git.GrepResult, dir string) map[string][]*yaml.Node {
	allCRDs := map[string][]yaml.Node
	for _, res := range greps {
		b, err := ioutil.ReadFile(dir + "/" + res.FileName)
		if err != nil {
			log.Printf("failed to read yaml file: %s", res.FileName)
			continue
		}
        
        nodes, err := GetCrdNodes(b)
		if err != nil {
			log.Printf("failed to parse yaml file: %s", res.FileName)
			continue
		}
        allCRDS = append(allCRDS, nodes)
	}
	return allCRDs
}

func GetCrdNodes(rawFile []byte) ([]yaml.Node, error) {
	var candidates []*yaml.Node
	dec := yaml.NewDecoder(bytes.NewReader(rawFile))
	for {
		var node yaml.Node
		err := dec.Decode(&node)
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, err
		}
		candidates = append(candidates, &node)
	}

	evaluator := yqlib.NewAllAtOnceEvaluator()
	matches, err := evaluator.EvaluateNodes(`select(.kind == "CustomResourceDefinition")`, candidates...)
	if err != nil {
		fmt.Println(fmt.Errorf("Failed to parse nodes: %s", err))
	}

	nodes := make([]yaml.Node, 0)
	for match := matches.Front(); match != nil; match = match.Next() {
		candidate := match.Value.(*yqlib.CandidateNode)
		nodes = append(nodes, *candidate.Node)
	}

	return nodes, nil
}

Downside is YQ is not a light dependency

[RichiCoder1]

Related to #144, #126, #137, and potentially #134 if we wanted to allow tweaking yq expressions

[RichiCoder1]

Follow up: Could actually probably still get the benefit of multi-doc and selection without yqlib as we could just check for it ourselves on yaml.Node

[hasheddan]

As an update, I have observed panics on invalid YAMLs in yaml.v3 in situations where they are templated with {{ as described here.

[RichiCoder1]

Hmm. I'll add some panic handling to that method

[hasheddan]

@RichiCoder1 it isn't too big of a problem because the pod just gets restarted. Feel free to leave as is if you don't want to invest the time because we should have improved parsing soon :)