Create a struct with all of Hugo's config options

Primary motivation is documentation, but it will also hopefully simplify the code.

Also,

* Lower case the default output format names; this is in line with the custom ones (map keys) and how
it's treated all the places. This avoids doing `stringds.EqualFold` everywhere.

Closes #10896
Closes #10620

3 files changed, 133 insertions, 159 deletions

diff --git a/modules/client.go b/modules/client.go
index 1fff787d1..59f6b25d3 100644
--- a/modules/client.go
+++ b/modules/client.go
@@ -433,9 +433,9 @@ func (c *Client) Clean(pattern string) error {
 		if g != nil && !g.Match(m.Path) {
 			continue
 		}
-		_, err = hugofs.MakeReadableAndRemoveAllModulePkgDir(c.fs, m.Dir)
+		dirCount, err := hugofs.MakeReadableAndRemoveAllModulePkgDir(c.fs, m.Dir)
 		if err == nil {
-			c.logger.Printf("hugo: cleaned module cache for %q", m.Path)
+			c.logger.Printf("hugo: removed %d dirs in module cache for %q", dirCount, m.Path)
 		}
 	}
 	return err
diff --git a/modules/collect.go b/modules/collect.go
index fcde1d379..c69e7e7ee 100644
--- a/modules/collect.go
+++ b/modules/collect.go
@@ -52,20 +52,6 @@ func IsNotExist(err error) bool {
 	return errors.Is(err, os.ErrNotExist)
 }
 
-// CreateProjectModule creates modules from the given config.
-// This is used in tests only.
-func CreateProjectModule(cfg config.Provider) (Module, error) {
-	workingDir := cfg.GetString("workingDir")
-	var modConfig Config
-
-	mod := createProjectModule(nil, workingDir, modConfig)
-	if err := ApplyProjectConfigDefaults(cfg, mod); err != nil {
-		return nil, err
-	}
-
-	return mod, nil
-}
-
 func (h *Client) Collect() (ModulesConfig, error) {
 	mc, coll := h.collect(true)
 	if coll.err != nil {
@@ -90,6 +76,9 @@ func (h *Client) Collect() (ModulesConfig, error) {
 }
 
 func (h *Client) collect(tidy bool) (ModulesConfig, *collector) {
+	if h == nil {
+		panic("nil client")
+	}
 	c := &collector{
 		Client: h,
 	}
@@ -133,6 +122,16 @@ type ModulesConfig struct {
 	GoWorkspaceFilename string
 }
 
+func (m ModulesConfig) HasConfigFile() bool {
+	for _, mod := range m.ActiveModules {
+		if len(mod.ConfigFilenames()) > 0 {
+			return true
+		}
+
+	}
+	return false
+}
+
 func (m *ModulesConfig) setActiveMods(logger loggers.Logger) error {
 	var activeMods Modules
 	for _, mod := range m.AllModules {
@@ -230,6 +229,7 @@ func (c *collector) getVendoredDir(path string) (vendoredModule, bool) {
 }
 
 func (c *collector) add(owner *moduleAdapter, moduleImport Import, disabled bool) (*moduleAdapter, error) {
+
 	var (
 		mod       *goModule
 		moduleDir string
@@ -299,7 +299,7 @@ func (c *collector) add(owner *moduleAdapter, moduleImport Import, disabled bool
 					return nil, nil
 				}
 				if found, _ := afero.Exists(c.fs, moduleDir); !found {
-					c.err = c.wrapModuleNotFound(fmt.Errorf(`module %q not found; either add it as a Hugo Module or store it in %q.`, modulePath, c.ccfg.ThemesDir))
+					c.err = c.wrapModuleNotFound(fmt.Errorf(`module %q not found in % q; either add it as a Hugo Module or store it in %q.`, modulePath, moduleDir, c.ccfg.ThemesDir))
 					return nil, nil
 				}
 			}
@@ -347,7 +347,7 @@ func (c *collector) addAndRecurse(owner *moduleAdapter, disabled bool) error {
 	moduleConfig := owner.Config()
 	if owner.projectMod {
 		if err := c.applyMounts(Import{}, owner); err != nil {
-			return err
+			return fmt.Errorf("failed to apply mounts for project module: %w", err)
 		}
 	}
 
@@ -618,7 +618,7 @@ func (c *collector) mountCommonJSConfig(owner *moduleAdapter, mounts []Mount) ([
 	// Mount the common JS config files.
 	fis, err := afero.ReadDir(c.fs, owner.Dir())
 	if err != nil {
-		return mounts, err
+		return mounts, fmt.Errorf("failed to read dir %q: %q", owner.Dir(), err)
 	}
 
 	for _, fi := range fis {
diff --git a/modules/config.go b/modules/config.go
index 9d516e841..f8faf7969 100644
--- a/modules/config.go
+++ b/modules/config.go
@@ -20,10 +20,9 @@ import (
 	"strings"
 
 	"github.com/gohugoio/hugo/common/hugo"
+	"github.com/gohugoio/hugo/hugofs/files"
 
 	"github.com/gohugoio/hugo/config"
-	"github.com/gohugoio/hugo/hugofs/files"
-	"github.com/gohugoio/hugo/langs"
 	"github.com/mitchellh/mapstructure"
 )
 
@@ -58,12 +57,9 @@ var DefaultModuleConfig = Config{
 
 // ApplyProjectConfigDefaults applies default/missing module configuration for
 // the main project.
-func ApplyProjectConfigDefaults(cfg config.Provider, mod Module) error {
-	moda := mod.(*moduleAdapter)
+func ApplyProjectConfigDefaults(mod Module, cfgs ...config.AllProvider) error {
 
-	// Map legacy directory config into the new module.
-	languages := cfg.Get("languagesSortedDefaultFirst").(langs.Languages)
-	isMultiHost := languages.IsMultihost()
+	moda := mod.(*moduleAdapter)
 
 	// To bridge between old and new configuration format we need
 	// a way to make sure all of the core components are configured on
@@ -75,121 +71,92 @@ func ApplyProjectConfigDefaults(cfg config.Provider, mod Module) error {
 		}
 	}
 
-	type dirKeyComponent struct {
-		key          string
-		component    string
-		multilingual bool
-	}
-
-	dirKeys := []dirKeyComponent{
-		{"contentDir", files.ComponentFolderContent, true},
-		{"dataDir", files.ComponentFolderData, false},
-		{"layoutDir", files.ComponentFolderLayouts, false},
-		{"i18nDir", files.ComponentFolderI18n, false},
-		{"archetypeDir", files.ComponentFolderArchetypes, false},
-		{"assetDir", files.ComponentFolderAssets, false},
-		{"", files.ComponentFolderStatic, isMultiHost},
-	}
+	var mounts []Mount
 
-	createMountsFor := func(d dirKeyComponent, cfg config.Provider) []Mount {
-		var lang string
-		if language, ok := cfg.(*langs.Language); ok {
-			lang = language.Lang
+	for _, component := range []string{
+		files.ComponentFolderContent,
+		files.ComponentFolderData,
+		files.ComponentFolderLayouts,
+		files.ComponentFolderI18n,
+		files.ComponentFolderArchetypes,
+		files.ComponentFolderAssets,
+		files.ComponentFolderStatic,
+	} {
+		if componentsConfigured[component] {
+			continue
 		}
 
-		// Static mounts are a little special.
-		if d.component == files.ComponentFolderStatic {
-			var mounts []Mount
-			staticDirs := getStaticDirs(cfg)
-			if len(staticDirs) > 0 {
-				componentsConfigured[d.component] = true
+		first := cfgs[0]
+		dirsBase := first.DirsBase()
+		isMultiHost := first.IsMultihost()
+
+		for i, cfg := range cfgs {
+			dirs := cfg.Dirs()
+			var dir string
+			var dropLang bool
+			switch component {
+			case files.ComponentFolderContent:
+				dir = dirs.ContentDir
+				dropLang = dir == dirsBase.ContentDir
+			case files.ComponentFolderData:
+				dir = dirs.DataDir
+			case files.ComponentFolderLayouts:
+				dir = dirs.LayoutDir
+			case files.ComponentFolderI18n:
+				dir = dirs.I18nDir
+			case files.ComponentFolderArchetypes:
+				dir = dirs.ArcheTypeDir
+			case files.ComponentFolderAssets:
+				dir = dirs.AssetDir
+			case files.ComponentFolderStatic:
+				// For static dirs, we only care about the language in multihost setups.
+				dropLang = !isMultiHost
 			}
 
-			for _, dir := range staticDirs {
-				mounts = append(mounts, Mount{Lang: lang, Source: dir, Target: d.component})
+			var perLang bool
+			switch component {
+			case files.ComponentFolderContent, files.ComponentFolderStatic:
+				perLang = true
+			default:
+			}
+			if i > 0 && !perLang {
+				continue
 			}
 
-			return mounts
-
-		}
-
-		if cfg.IsSet(d.key) {
-			source := cfg.GetString(d.key)
-			componentsConfigured[d.component] = true
-
-			return []Mount{{
-				// No lang set for layouts etc.
-				Source: source,
-				Target: d.component,
-			}}
-		}
-
-		return nil
-	}
-
-	createMounts := func(d dirKeyComponent) []Mount {
-		var mounts []Mount
-		if d.multilingual {
-			if d.component == files.ComponentFolderContent {
-				seen := make(map[string]bool)
-				hasContentDir := false
-				for _, language := range languages {
-					if language.ContentDir != "" {
-						hasContentDir = true
-						break
-					}
-				}
+			var lang string
+			if perLang && !dropLang {
+				lang = cfg.Language().Lang
+			}
 
-				if hasContentDir {
-					for _, language := range languages {
-						contentDir := language.ContentDir
-						if contentDir == "" {
-							contentDir = files.ComponentFolderContent
-						}
-						if contentDir == "" || seen[contentDir] {
-							continue
-						}
-						seen[contentDir] = true
-						mounts = append(mounts, Mount{Lang: language.Lang, Source: contentDir, Target: d.component})
-					}
+			// Static mounts are a little special.
+			if component == files.ComponentFolderStatic {
+				staticDirs := cfg.StaticDirs()
+				for _, dir := range staticDirs {
+					mounts = append(mounts, Mount{Lang: lang, Source: dir, Target: component})
 				}
+				continue
+			}
 
-				componentsConfigured[d.component] = len(seen) > 0
-
-			} else {
-				for _, language := range languages {
-					mounts = append(mounts, createMountsFor(d, language)...)
-				}
+			if dir != "" {
+				mounts = append(mounts, Mount{Lang: lang, Source: dir, Target: component})
 			}
-		} else {
-			mounts = append(mounts, createMountsFor(d, cfg)...)
 		}
-
-		return mounts
 	}
 
-	var mounts []Mount
-	for _, dirKey := range dirKeys {
-		if componentsConfigured[dirKey.component] {
-			continue
-		}
-
-		mounts = append(mounts, createMounts(dirKey)...)
+	moda.mounts = append(moda.mounts, mounts...)
 
-	}
-
-	// Add default configuration
-	for _, dirKey := range dirKeys {
-		if componentsConfigured[dirKey.component] {
+	// Temporary: Remove duplicates.
+	seen := make(map[string]bool)
+	var newMounts []Mount
+	for _, m := range moda.mounts {
+		key := m.Source + m.Target + m.Lang
+		if seen[key] {
 			continue
 		}
-		mounts = append(mounts, Mount{Source: dirKey.component, Target: dirKey.component})
+		seen[key] = true
+		newMounts = append(newMounts, m)
 	}
-
-	// Prepend the mounts from configuration.
-	mounts = append(moda.mounts, mounts...)
-
-	moda.mounts = mounts
+	moda.mounts = newMounts
 
 	return nil
 }
@@ -275,7 +242,6 @@ func decodeConfig(cfg config.Provider, pathReplacements map[string]string) (Conf
 				Path: imp,
 			})
 		}
-
 	}
 
 	return c, nil
@@ -283,7 +249,10 @@ func decodeConfig(cfg config.Provider, pathReplacements map[string]string) (Conf
 
 // Config holds a module config.
 type Config struct {
-	Mounts  []Mount
+	// File system mounts.
+	Mounts []Mount
+
+	// Module imports.
 	Imports []Import
 
 	// Meta info about this module (license information etc.).
@@ -292,8 +261,7 @@ type Config struct {
 	// Will be validated against the running Hugo version.
 	HugoVersion HugoVersion
 
-	// A optional Glob pattern matching module paths to skip when vendoring, e.g.
-	// "github.com/**".
+	// Optional Glob pattern matching module paths to skip when vendoring, e.g. “github.com/**”
 	NoVendor string
 
 	// When enabled, we will pick the vendored module closest to the module
@@ -303,21 +271,31 @@ type Config struct {
 	// so once it is in use it cannot be redefined.
 	VendorClosest bool
 
+	// A comma separated (or a slice) list of module path to directory replacement mapping,
+	// e.g. github.com/bep/my-theme -> ../..,github.com/bep/shortcodes -> /some/path.
+	// This is mostly useful for temporary locally development of a module, and then it makes sense to set it as an
+	// OS environment variable, e.g: env HUGO_MODULE_REPLACEMENTS="github.com/bep/my-theme -> ../..".
+	// Any relative path is relate to themesDir, and absolute paths are allowed.
 	Replacements    []string
 	replacementsMap map[string]string
 
-	// Configures GOPROXY.
+	// Defines the proxy server to use to download remote modules. Default is direct, which means “git clone” and similar.
+	// Configures GOPROXY when running the Go command for module operations.
 	Proxy string
-	// Configures GONOPROXY.
+
+	// Comma separated glob list matching paths that should not use the proxy configured above.
+	// Configures GONOPROXY when running the Go command for module operations.
 	NoProxy string
-	// Configures GOPRIVATE.
+
+	// Comma separated glob list matching paths that should be treated as private.
+	// Configures GOPRIVATE when running the Go command for module operations.
 	Private string
 
 	// Defaults to "off".
 	// Set to a work file, e.g. hugo.work, to enable Go "Workspace" mode.
 	// Can be relative to the working directory or absolute.
-	// Requires Go 1.18+
-	// See https://tip.golang.org/doc/go1.18
+	// Requires Go 1.18+.
+	// Note that this can also be set via OS env, e.g. export HUGO_MODULE_WORKSPACE=/my/hugo.work.
 	Workspace string
 }
 
@@ -387,21 +365,33 @@ func (v HugoVersion) IsValid() bool {
 }
 
 type Import struct {
-	Path                string // Module path
-	pathProjectReplaced bool   // Set when Path is replaced in project config.
-	IgnoreConfig        bool   // Ignore any config in config.toml (will still follow imports).
-	IgnoreImports       bool   // Do not follow any configured imports.
-	NoMounts            bool   // Do not mount any folder in this import.
-	NoVendor            bool   // Never vendor this import (only allowed in main project).
-	Disable             bool   // Turn off this module.
-	Mounts              []Mount
+	// Module path
+	Path string
+	// Set when Path is replaced in project config.
+	pathProjectReplaced bool
+	// Ignore any config in config.toml (will still follow imports).
+	IgnoreConfig bool
+	// Do not follow any configured imports.
+	IgnoreImports bool
+	// Do not mount any folder in this import.
+	NoMounts bool
+	// Never vendor this import (only allowed in main project).
+	NoVendor bool
+	// Turn off this module.
+	Disable bool
+	// File mounts.
+	Mounts []Mount
 }
 
 type Mount struct {
-	Source string // relative path in source repo, e.g. "scss"
-	Target string // relative target path, e.g. "assets/bootstrap/scss"
+	// Relative path in source repo, e.g. "scss".
+	Source string
 
-	Lang string // any language code associated with this mount.
+	// Relative target path, e.g. "assets/bootstrap/scss".
+	Target string
+
+	// Any file in this mount will be associated with this language.
+	Lang string
 
 	// Include only files matching the given Glob patterns (string or slice).
 	IncludeFiles any
@@ -423,19 +413,3 @@ func (m Mount) ComponentAndName() (string, string) {
 	c, n, _ := strings.Cut(m.Target, fileSeparator)
 	return c, n
 }
-
-func getStaticDirs(cfg config.Provider) []string {
-	var staticDirs []string
-	for i := -1; i <= 10; i++ {
-		staticDirs = append(staticDirs, getStringOrStringSlice(cfg, "staticDir", i)...)
-	}
-	return staticDirs
-}
-
-func getStringOrStringSlice(cfg config.Provider, key string, id int) []string {
-	if id >= 0 {
-		key = fmt.Sprintf("%s%d", key, id)
-	}
-
-	return config.GetStringSlicePreserveString(cfg, key)
-}