Introduce a tree map for all content

This commit introduces a new data structure to store pages and their resources.

This data structure is backed by radix trees.

This simplies tree operations, makes all pages a bundle,  and paves the way for #6310.

It also solves a set of annoying issues (see list below).

Not a motivation behind this, but this commit also makes Hugo in general a little bit faster and more memory effective (see benchmarks). Especially for partial rebuilds on content edits, but also when taxonomies is in use.

```
name                                   old time/op    new time/op    delta
SiteNew/Bundle_with_image/Edit-16        1.32ms ± 8%    1.00ms ± 9%  -24.42%  (p=0.029 n=4+4)
SiteNew/Bundle_with_JSON_file/Edit-16    1.28ms ± 0%    0.94ms ± 0%  -26.26%  (p=0.029 n=4+4)
SiteNew/Tags_and_categories/Edit-16      33.9ms ± 2%    21.8ms ± 1%  -35.67%  (p=0.029 n=4+4)
SiteNew/Canonify_URLs/Edit-16            40.6ms ± 1%    37.7ms ± 3%   -7.20%  (p=0.029 n=4+4)
SiteNew/Deep_content_tree/Edit-16        56.7ms ± 0%    51.7ms ± 1%   -8.82%  (p=0.029 n=4+4)
SiteNew/Many_HTML_templates/Edit-16      19.9ms ± 2%    18.3ms ± 3%   -7.64%  (p=0.029 n=4+4)
SiteNew/Page_collections/Edit-16         37.9ms ± 4%    34.0ms ± 2%  -10.28%  (p=0.029 n=4+4)
SiteNew/Bundle_with_image-16             10.7ms ± 0%    10.6ms ± 0%   -1.15%  (p=0.029 n=4+4)
SiteNew/Bundle_with_JSON_file-16         10.8ms ± 0%    10.7ms ± 0%   -1.05%  (p=0.029 n=4+4)
SiteNew/Tags_and_categories-16           43.2ms ± 1%    39.6ms ± 1%   -8.35%  (p=0.029 n=4+4)
SiteNew/Canonify_URLs-16                 47.6ms ± 1%    47.3ms ± 0%     ~     (p=0.057 n=4+4)
SiteNew/Deep_content_tree-16             73.0ms ± 1%    74.2ms ± 1%     ~     (p=0.114 n=4+4)
SiteNew/Many_HTML_templates-16           37.9ms ± 0%    38.1ms ± 1%     ~     (p=0.114 n=4+4)
SiteNew/Page_collections-16              53.6ms ± 1%    54.7ms ± 1%   +2.09%  (p=0.029 n=4+4)

name                                   old alloc/op   new alloc/op   delta
SiteNew/Bundle_with_image/Edit-16         486kB ± 0%     430kB ± 0%  -11.47%  (p=0.029 n=4+4)
SiteNew/Bundle_with_JSON_file/Edit-16     265kB ± 0%     209kB ± 0%  -21.06%  (p=0.029 n=4+4)
SiteNew/Tags_and_categories/Edit-16      13.6MB ± 0%     8.8MB ± 0%  -34.93%  (p=0.029 n=4+4)
SiteNew/Canonify_URLs/Edit-16            66.5MB ± 0%    63.9MB ± 0%   -3.95%  (p=0.029 n=4+4)
SiteNew/Deep_content_tree/Edit-16        28.8MB ± 0%    25.8MB ± 0%  -10.55%  (p=0.029 n=4+4)
SiteNew/Many_HTML_templates/Edit-16      6.16MB ± 0%    5.56MB ± 0%   -9.86%  (p=0.029 n=4+4)
SiteNew/Page_collections/Edit-16         16.9MB ± 0%    16.0MB ± 0%   -5.19%  (p=0.029 n=4+4)
SiteNew/Bundle_with_image-16             2.28MB ± 0%    2.29MB ± 0%   +0.35%  (p=0.029 n=4+4)
SiteNew/Bundle_with_JSON_file-16         2.07MB ± 0%    2.07MB ± 0%     ~     (p=0.114 n=4+4)
SiteNew/Tags_and_categories-16           14.3MB ± 0%    13.2MB ± 0%   -7.30%  (p=0.029 n=4+4)
SiteNew/Canonify_URLs-16                 69.1MB ± 0%    69.0MB ± 0%     ~     (p=0.343 n=4+4)
SiteNew/Deep_content_tree-16             31.3MB ± 0%    31.8MB ± 0%   +1.49%  (p=0.029 n=4+4)
SiteNew/Many_HTML_templates-16           10.8MB ± 0%    10.9MB ± 0%   +1.11%  (p=0.029 n=4+4)
SiteNew/Page_collections-16              21.4MB ± 0%    21.6MB ± 0%   +1.15%  (p=0.029 n=4+4)

name                                   old allocs/op  new allocs/op  delta
SiteNew/Bundle_with_image/Edit-16         4.74k ± 0%     3.86k ± 0%  -18.57%  (p=0.029 n=4+4)
SiteNew/Bundle_with_JSON_file/Edit-16     4.73k ± 0%     3.85k ± 0%  -18.58%  (p=0.029 n=4+4)
SiteNew/Tags_and_categories/Edit-16        301k ± 0%      198k ± 0%  -34.14%  (p=0.029 n=4+4)
SiteNew/Canonify_URLs/Edit-16              389k ± 0%      373k ± 0%   -4.07%  (p=0.029 n=4+4)
SiteNew/Deep_content_tree/Edit-16          338k ± 0%      262k ± 0%  -22.63%  (p=0.029 n=4+4)
SiteNew/Many_HTML_templates/Edit-16        102k ± 0%       88k ± 0%  -13.81%  (p=0.029 n=4+4)
SiteNew/Page_collections/Edit-16           176k ± 0%      152k ± 0%  -13.32%  (p=0.029 n=4+4)
SiteNew/Bundle_with_image-16              26.8k ± 0%     26.8k ± 0%   +0.05%  (p=0.029 n=4+4)
SiteNew/Bundle_with_JSON_file-16          26.8k ± 0%     26.8k ± 0%   +0.05%  (p=0.029 n=4+4)
SiteNew/Tags_and_categories-16             273k ± 0%      245k ± 0%  -10.36%  (p=0.029 n=4+4)
SiteNew/Canonify_URLs-16                   396k ± 0%      398k ± 0%   +0.39%  (p=0.029 n=4+4)
SiteNew/Deep_content_tree-16               317k ± 0%      325k ± 0%   +2.53%  (p=0.029 n=4+4)
SiteNew/Many_HTML_templates-16             146k ± 0%      147k ± 0%   +0.98%  (p=0.029 n=4+4)
SiteNew/Page_collections-16                210k ± 0%      215k ± 0%   +2.44%  (p=0.029 n=4+4)
```

Fixes #6312
Fixes #6087
Fixes #6738
Fixes #6412
Fixes #6743
Fixes #6875
Fixes #6034
Fixes #6902
Fixes #6173
Fixes #6590

1 files changed, 42 insertions, 120 deletions

diff --git a/hugolib/page.go b/hugolib/page.go
index bb5107747..4ffcb6264 100644
--- a/hugolib/page.go
+++ b/hugolib/page.go
@@ -25,13 +25,11 @@ import (
 
 	"github.com/mitchellh/mapstructure"
 
-	"github.com/gohugoio/hugo/tpl"
-
 	"github.com/gohugoio/hugo/identity"
 
 	"github.com/gohugoio/hugo/markup/converter"
 
-	"github.com/gohugoio/hugo/common/maps"
+	"github.com/gohugoio/hugo/tpl"
 
 	"github.com/gohugoio/hugo/hugofs/files"
 
@@ -153,7 +151,6 @@ func (p *pageState) getPagesAndSections() page.Pages {
 	return b.getPagesAndSections()
 }
 
-// TODO(bep) cm add a test
 func (p *pageState) RegularPages() page.Pages {
 	p.regularPagesInit.Do(func() {
 		var pages page.Pages
@@ -189,13 +186,12 @@ func (p *pageState) Pages() page.Pages {
 		case page.KindSection, page.KindHome:
 			pages = p.getPagesAndSections()
 		case page.KindTaxonomy:
-			termInfo := p.bucket
-			plural := maps.GetString(termInfo.meta, "plural")
-			term := maps.GetString(termInfo.meta, "termKey")
-			taxonomy := p.s.Taxonomies[plural].Get(term)
+			b := p.treeRef.n
+			viewInfo := b.viewInfo
+			taxonomy := p.s.Taxonomies()[viewInfo.name.plural].Get(viewInfo.termKey)
 			pages = taxonomy.Pages()
 		case page.KindTaxonomyTerm:
-			pages = p.getPagesAndSections()
+			pages = p.bucket.getTaxonomies()
 		default:
 			pages = p.s.Pages()
 		}
@@ -219,38 +215,35 @@ func (p *pageState) RawContent() string {
 	return string(p.source.parsed.Input()[start:])
 }
 
-func (p *pageState) Resources() resource.Resources {
-	p.resourcesInit.Do(func() {
-
-		sort := func() {
-			sort.SliceStable(p.resources, func(i, j int) bool {
-				ri, rj := p.resources[i], p.resources[j]
-				if ri.ResourceType() < rj.ResourceType() {
-					return true
-				}
-
-				p1, ok1 := ri.(page.Page)
-				p2, ok2 := rj.(page.Page)
+func (p *pageState) sortResources() {
+	sort.SliceStable(p.resources, func(i, j int) bool {
+		ri, rj := p.resources[i], p.resources[j]
+		if ri.ResourceType() < rj.ResourceType() {
+			return true
+		}
 
-				if ok1 != ok2 {
-					return ok2
-				}
+		p1, ok1 := ri.(page.Page)
+		p2, ok2 := rj.(page.Page)
 
-				if ok1 {
-					return page.DefaultPageSort(p1, p2)
-				}
+		if ok1 != ok2 {
+			return ok2
+		}
 
-				return ri.RelPermalink() < rj.RelPermalink()
-			})
+		if ok1 {
+			return page.DefaultPageSort(p1, p2)
 		}
 
-		sort()
+		return ri.RelPermalink() < rj.RelPermalink()
+	})
+}
 
+func (p *pageState) Resources() resource.Resources {
+	p.resourcesInit.Do(func() {
+		p.sortResources()
 		if len(p.m.resourcesMetadata) > 0 {
 			resources.AssignMetadata(p.m.resourcesMetadata, p.resources...)
-			sort()
+			p.sortResources()
 		}
-
 	})
 	return p.resources
 }
@@ -264,7 +257,7 @@ func (p *pageState) HasShortcode(name string) bool {
 }
 
 func (p *pageState) Site() page.Site {
-	return &p.s.Info
+	return p.s.Info
 }
 
 func (p *pageState) String() string {
@@ -324,7 +317,7 @@ func (ps *pageState) initCommonProviders(pp pagePaths) error {
 	ps.OutputFormatsProvider = pp
 	ps.targetPathDescriptor = pp.targetPathDescriptor
 	ps.RefProvider = newPageRef(ps)
-	ps.SitesProvider = &ps.s.Info
+	ps.SitesProvider = ps.s.Info
 
 	return nil
 }
@@ -384,8 +377,8 @@ func (p *pageState) getLayoutDescriptor() output.LayoutDescriptor {
 				section = sections[0]
 			}
 		case page.KindTaxonomyTerm, page.KindTaxonomy:
-			section = maps.GetString(p.bucket.meta, "singular")
-
+			b := p.getTreeRef().n
+			section = b.viewInfo.name.singular
 		default:
 		}
 
@@ -641,10 +634,6 @@ func (p *pageState) getContentConverter() converter.Converter {
 	return p.m.contentConverter
 }
 
-func (p *pageState) addResources(r ...resource.Resource) {
-	p.resources = append(p.resources, r...)
-}
-
 func (p *pageState) mapContent(bucket *pagesMapBucket, meta *pageMeta) error {
 
 	s := p.shortcodeState
@@ -665,6 +654,7 @@ func (p *pageState) mapContent(bucket *pagesMapBucket, meta *pageMeta) error {
 	// … it's safe to keep some "global" state
 	var currShortcode shortcode
 	var ordinal int
+	var frontMatterSet bool
 
 Loop:
 	for {
@@ -679,7 +669,7 @@ Loop:
 			p.s.BuildFlags.HasLateTemplate.CAS(false, true)
 			rn.AddBytes(it)
 		case it.IsFrontMatter():
-			f := metadecoders.FormatFromFrontMatterType(it.Type)
+			f := pageparser.FormatFromFrontMatterType(it.Type)
 			m, err := metadecoders.Default.UnmarshalToMap(it.Val, f)
 			if err != nil {
 				if fe, ok := err.(herrors.FileError); ok {
@@ -692,6 +682,7 @@ Loop:
 			if err := meta.setMetadata(bucket, p, m); err != nil {
 				return err
 			}
+			frontMatterSet = true
 
 			next := iter.Peek()
 			if !next.IsDone() {
@@ -779,6 +770,14 @@ Loop:
 		}
 	}
 
+	if !frontMatterSet {
+		// Page content without front matter. Assign default front matter from
+		// cascades etc.
+		if err := meta.setMetadata(bucket, p, nil); err != nil {
+			return err
+		}
+	}
+
 	p.cmap = rn
 
 	return nil
@@ -856,12 +855,11 @@ func (p *pageState) shiftToOutputFormat(isRenderingSite bool, idx int) error {
 		return err
 	}
 
-	if idx >= len(p.pageOutputs) {
-		panic(fmt.Sprintf("invalid page state for %q: got output format index %d, have %d", p.pathOrTitle(), idx, len(p.pageOutputs)))
+	if len(p.pageOutputs) == 1 {
+		idx = 0
 	}
 
 	p.pageOutput = p.pageOutputs[idx]
-
 	if p.pageOutput == nil {
 		panic(fmt.Sprintf("pageOutput is nil for output idx %d", idx))
 	}
@@ -901,13 +899,6 @@ func (p *pageState) shiftToOutputFormat(isRenderingSite bool, idx int) error {
 		p.pageOutput.cp = cp
 	}
 
-	for _, r := range p.Resources().ByType(pageResourceType) {
-		rp := r.(*pageState)
-		if err := rp.shiftToOutputFormat(isRenderingSite, idx); err != nil {
-			return errors.Wrap(err, "failed to shift outputformat in Page resource")
-		}
-	}
-
 	return nil
 }
 
@@ -934,75 +925,6 @@ func (p *pageState) sourceRef() string {
 	return ""
 }
 
-func (p *pageState) sourceRefs() []string {
-	refs := []string{p.sourceRef()}
-
-	if !p.File().IsZero() {
-		meta := p.File().FileInfo().Meta()
-		path := meta.PathFile()
-
-		if path != "" {
-			ref := "/" + filepath.ToSlash(path)
-			if ref != refs[0] {
-				refs = append(refs, ref)
-			}
-
-		}
-	}
-	return refs
-}
-
-type pageStatePages []*pageState
-
-// Implement sorting.
-func (ps pageStatePages) Len() int { return len(ps) }
-
-func (ps pageStatePages) Less(i, j int) bool { return page.DefaultPageSort(ps[i], ps[j]) }
-
-func (ps pageStatePages) Swap(i, j int) { ps[i], ps[j] = ps[j], ps[i] }
-
-// findPagePos Given a page, it will find the position in Pages
-// will return -1 if not found
-func (ps pageStatePages) findPagePos(page *pageState) int {
-	for i, x := range ps {
-		if x.File().Filename() == page.File().Filename() {
-			return i
-		}
-	}
-	return -1
-}
-
-func (ps pageStatePages) findPagePosByFilename(filename string) int {
-	for i, x := range ps {
-		if x.File().Filename() == filename {
-			return i
-		}
-	}
-	return -1
-}
-
-func (ps pageStatePages) findPagePosByFilnamePrefix(prefix string) int {
-	if prefix == "" {
-		return -1
-	}
-
-	lenDiff := -1
-	currPos := -1
-	prefixLen := len(prefix)
-
-	// Find the closest match
-	for i, x := range ps {
-		if strings.HasPrefix(x.File().Filename(), prefix) {
-			diff := len(x.File().Filename()) - prefixLen
-			if lenDiff == -1 || diff < lenDiff {
-				lenDiff = diff
-				currPos = i
-			}
-		}
-	}
-	return currPos
-}
-
 func (s *Site) sectionsFromFile(fi source.File) []string {
 	dirname := fi.Dir()