Fixed panic and bugs in Exists()/GetValue()

[killabytenow]

I found several bugs in Exists() and GetValue(). The following test results in panics instead of finding the entries or returning expected results:

package main

import (
	"fmt"

	"github.com/gookit/config/v2"
	"github.com/gookit/config/v2/yaml"
)

type test struct {
	expected bool
	path     string
}

func run_test(t test) {
	var at_func string
	defer func() {
		if recover() != nil {
			fmt.Printf("[PANIC!] %s (at %s)\n", t.path, at_func)
		}
	}()

	result := "FAILED"
	at_func = "Exists"
	exists := config.Exists(t.path)
	at_func = "GetValue"
	v, ok := config.GetValue(t.path)
	if exists == t.expected && ok == t.expected {
		result = "  OK  "
	}
	fmt.Printf("[%s] %s: Exists() = %v ; GetValue() = (%v, %v)\n", result, t.path, exists, v, ok)

}

func main() {
	// config.ParseEnv: will parse env var in string value. eg: shell: ${SHELL}
	config.WithOptions(config.ParseEnv)

	// add driver for support yaml content
	config.AddDriver(yaml.Driver)

	yamlConfig := `
app:
  name: MyApp
  version: 1.0.0
lol:
  - test:
      bu: 1
      ba: ugly
      foo:
        - 1
        - 2
        - 3
  - another:
      - "pingu"
      - "pangu"
    gajo: nil
`

	err := config.LoadStrings(config.Yaml, yamlConfig)
	if err != nil {
		panic(err)
	}

	for _, t := range []test{
		{true, "lol"},
		{true, "lol.0"},
		{true, "lol.0.test.ba"},
		{true, "lol.0.test.foo"},
		{true, "lol.0.test.foo.0"},
		{true, "lol.0.test.foo.1"},
		{true, "lol.1.another.0"},
		{true, "lol.1.another.1"},
		{false, "lol.1.another.2"},
		{true, "lol.1.gajo"},
		{false, "lol.2"},
		{false, "lol.2.wat"},
	} {
		run_test(t)
	}
}

This small contribution/patch should fix this unexpected behavior.

[killabytenow]

This is the result when running with current version (v2.2.7):

$ go run test.go 
[  OK  ] lol: Exists() = true ; GetValue() = ([map[test:map[ba:ugly bu:1 foo:[1 2 3]]] map[another:[pingu pangu] gajo:nil]], true)
[  OK  ] lol.0: Exists() = true ; GetValue() = (map[test:map[ba:ugly bu:1 foo:[1 2 3]]], true)
[FAILED] lol.0.test.ba: Exists() = false ; GetValue() = (ugly, true)
[FAILED] lol.0.test.foo: Exists() = false ; GetValue() = ([1 2 3], true)
[FAILED] lol.0.test.foo.0: Exists() = false ; GetValue() = (1, true)
[FAILED] lol.0.test.foo.1: Exists() = false ; GetValue() = (2, true)
[FAILED] lol.1.another.0: Exists() = false ; GetValue() = (pingu, true)
[FAILED] lol.1.another.1: Exists() = false ; GetValue() = (pangu, true)
[PANIC!] lol.1.another.2 (at GetValue)
[FAILED] lol.1.gajo: Exists() = false ; GetValue() = (nil, true)
[PANIC!] lol.2 (at GetValue)
[PANIC!] lol.2.wat (at GetValue)

And this with this patch applied:

$ go run test.go 
[  OK  ] lol: Exists() = true ; GetValue() = ([map[test:map[ba:ugly bu:1 foo:[1 2 3]]] map[another:[pingu pangu] gajo:nil]], true)
[  OK  ] lol.0: Exists() = true ; GetValue() = (map[test:map[ba:ugly bu:1 foo:[1 2 3]]], true)
[  OK  ] lol.0.test.ba: Exists() = true ; GetValue() = (ugly, true)
[  OK  ] lol.0.test.foo: Exists() = true ; GetValue() = ([1 2 3], true)
[  OK  ] lol.0.test.foo.0: Exists() = true ; GetValue() = (1, true)
[  OK  ] lol.0.test.foo.1: Exists() = true ; GetValue() = (2, true)
[  OK  ] lol.1.another.0: Exists() = true ; GetValue() = (pingu, true)
[  OK  ] lol.1.another.1: Exists() = true ; GetValue() = (pangu, true)
[  OK  ] lol.1.another.2: Exists() = false ; GetValue() = (<nil>, false)
[  OK  ] lol.1.gajo: Exists() = true ; GetValue() = (nil, true)
[  OK  ] lol.2: Exists() = false ; GetValue() = (<nil>, false)
[  OK  ] lol.2.wat: Exists() = false ; GetValue() = (<nil>, false)