Misc config loading fixes

The main motivation behind this is simplicity and correctnes, but the new small config library is also faster:

```
BenchmarkDefaultConfigProvider/Viper-16         	  252418	      4546 ns/op	    2720 B/op	      30 allocs/op
BenchmarkDefaultConfigProvider/Custom-16        	  450756	      2651 ns/op	    1008 B/op	       6 allocs/op
```

Fixes #8633
Fixes #8618
Fixes #8630
Updates #8591
Closes #6680
Closes #5192

1 files changed, 13 insertions, 13 deletions

diff --git a/hugolib/testhelpers_test.go b/hugolib/testhelpers_test.go
index 09988f972..451022e5c 100644
--- a/hugolib/testhelpers_test.go
+++ b/hugolib/testhelpers_test.go
@@ -30,6 +30,7 @@ import (
 
 	"github.com/fsnotify/fsnotify"
 	"github.com/gohugoio/hugo/common/herrors"
+	"github.com/gohugoio/hugo/common/maps"
 	"github.com/gohugoio/hugo/config"
 	"github.com/gohugoio/hugo/deps"
 	"github.com/gohugoio/hugo/resources/page"
@@ -39,7 +40,6 @@ import (
 
 	"github.com/gohugoio/hugo/helpers"
 	"github.com/gohugoio/hugo/tpl"
-	"github.com/spf13/viper"
 
 	"github.com/gohugoio/hugo/resources/resource"
 
@@ -83,7 +83,7 @@ type sitesBuilder struct {
 	// Default toml
 	configFormat  string
 	configFileSet bool
-	viperSet      bool
+	configSet      bool
 
 	// Default is empty.
 	// TODO(bep) revisit this and consider always setting it to something.
@@ -111,7 +111,7 @@ type filenameContent struct {
 }
 
 func newTestSitesBuilder(t testing.TB) *sitesBuilder {
-	v := viper.New()
+	v := config.New()
 	fs := hugofs.NewMem(v)
 
 	litterOptions := litter.Options{
@@ -140,7 +140,7 @@ func newTestSitesBuilderFromDepsCfg(t testing.TB, d deps.DepsCfg) *sitesBuilder
 
 	b.WithWorkingDir(workingDir)
 
-	return b.WithViper(d.Cfg.(*viper.Viper))
+	return b.WithViper(d.Cfg.(config.Provider))
 }
 
 func (s *sitesBuilder) Running() *sitesBuilder {
@@ -186,26 +186,26 @@ func (s *sitesBuilder) WithConfigTemplate(data interface{}, format, configTempla
 	return s.WithConfigFile(format, b.String())
 }
 
-func (s *sitesBuilder) WithViper(v *viper.Viper) *sitesBuilder {
+func (s *sitesBuilder) WithViper(v config.Provider) *sitesBuilder {
 	s.T.Helper()
 	if s.configFileSet {
 		s.T.Fatal("WithViper: use Viper or config.toml, not both")
 	}
 	defer func() {
-		s.viperSet = true
+		s.configSet = true
 	}()
 
 	// Write to a config file to make sure the tests follow the same code path.
 	var buff bytes.Buffer
-	m := v.AllSettings()
+	m := v.Get("").(maps.Params)
 	s.Assert(parser.InterfaceToConfig(m, metadecoders.TOML, &buff), qt.IsNil)
 	return s.WithConfigFile("toml", buff.String())
 }
 
 func (s *sitesBuilder) WithConfigFile(format, conf string) *sitesBuilder {
 	s.T.Helper()
-	if s.viperSet {
-		s.T.Fatal("WithConfigFile: use Viper or config.toml, not both")
+	if s.configSet {
+		s.T.Fatal("WithConfigFile: use config.Config or config.toml, not both")
 	}
 	s.configFileSet = true
 	filename := s.absFilename("config." + format)
@@ -845,14 +845,14 @@ func (th testHelper) replaceDefaultContentLanguageValue(value string) string {
 	return value
 }
 
-func loadTestConfig(fs afero.Fs, withConfig ...func(cfg config.Provider) error) (*viper.Viper, error) {
+func loadTestConfig(fs afero.Fs, withConfig ...func(cfg config.Provider) error) (config.Provider, error) {
 	v, _, err := LoadConfig(ConfigSourceDescriptor{Fs: fs}, withConfig...)
 	return v, err
 }
 
-func newTestCfgBasic() (*viper.Viper, *hugofs.Fs) {
+func newTestCfgBasic() (config.Provider, *hugofs.Fs) {
 	mm := afero.NewMemMapFs()
-	v := viper.New()
+	v := config.New()
 	v.Set("defaultContentLanguageInSubdir", true)
 
 	fs := hugofs.NewFrom(hugofs.NewBaseFileDecorator(mm), v)
@@ -860,7 +860,7 @@ func newTestCfgBasic() (*viper.Viper, *hugofs.Fs) {
 	return v, fs
 }
 
-func newTestCfg(withConfig ...func(cfg config.Provider) error) (*viper.Viper, *hugofs.Fs) {
+func newTestCfg(withConfig ...func(cfg config.Provider) error) (config.Provider, *hugofs.Fs) {
 	mm := afero.NewMemMapFs()
 
 	v, err := loadTestConfig(mm, func(cfg config.Provider) error {