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, 198 insertions, 0 deletions

diff --git a/hugolib/pages_process.go b/hugolib/pages_process.go
new file mode 100644
index 000000000..af029fee9
--- /dev/null
+++ b/hugolib/pages_process.go
@@ -0,0 +1,198 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hugolib
+
+import (
+	"context"
+	"fmt"
+	"path/filepath"
+
+	"github.com/gohugoio/hugo/config"
+	"github.com/gohugoio/hugo/source"
+
+	"github.com/gohugoio/hugo/hugofs/files"
+	"github.com/pkg/errors"
+	"golang.org/x/sync/errgroup"
+
+	"github.com/gohugoio/hugo/common/herrors"
+	"github.com/gohugoio/hugo/hugofs"
+)
+
+func newPagesProcessor(h *HugoSites, sp *source.SourceSpec) *pagesProcessor {
+	procs := make(map[string]pagesCollectorProcessorProvider)
+	for _, s := range h.Sites {
+		procs[s.Lang()] = &sitePagesProcessor{
+			m:           s.pageMap,
+			errorSender: s.h,
+			itemChan:    make(chan interface{}, config.GetNumWorkerMultiplier()*2),
+		}
+	}
+	return &pagesProcessor{
+		procs: procs,
+	}
+}
+
+type pagesCollectorProcessorProvider interface {
+	Process(item interface{}) error
+	Start(ctx context.Context) context.Context
+	Wait() error
+}
+
+type pagesProcessor struct {
+	// Per language/Site
+	procs map[string]pagesCollectorProcessorProvider
+}
+
+func (proc *pagesProcessor) Process(item interface{}) error {
+	switch v := item.(type) {
+	// Page bundles mapped to their language.
+	case pageBundles:
+		for _, vv := range v {
+			proc.getProcFromFi(vv.header).Process(vv)
+		}
+	case hugofs.FileMetaInfo:
+		proc.getProcFromFi(v).Process(v)
+	default:
+		panic(fmt.Sprintf("unrecognized item type in Process: %T", item))
+
+	}
+
+	return nil
+}
+
+func (proc *pagesProcessor) Start(ctx context.Context) context.Context {
+	for _, p := range proc.procs {
+		ctx = p.Start(ctx)
+	}
+	return ctx
+}
+
+func (proc *pagesProcessor) Wait() error {
+	var err error
+	for _, p := range proc.procs {
+		if e := p.Wait(); e != nil {
+			err = e
+		}
+	}
+	return err
+}
+
+func (proc *pagesProcessor) getProcFromFi(fi hugofs.FileMetaInfo) pagesCollectorProcessorProvider {
+	if p, found := proc.procs[fi.Meta().Lang()]; found {
+		return p
+	}
+	return defaultPageProcessor
+}
+
+type nopPageProcessor int
+
+func (nopPageProcessor) Process(item interface{}) error {
+	return nil
+}
+
+func (nopPageProcessor) Start(ctx context.Context) context.Context {
+	return context.Background()
+}
+
+func (nopPageProcessor) Wait() error {
+	return nil
+}
+
+var defaultPageProcessor = new(nopPageProcessor)
+
+type sitePagesProcessor struct {
+	m           *pageMap
+	errorSender herrors.ErrorSender
+
+	itemChan  chan interface{}
+	itemGroup *errgroup.Group
+}
+
+func (p *sitePagesProcessor) Process(item interface{}) error {
+	p.itemChan <- item
+	return nil
+}
+
+func (p *sitePagesProcessor) Start(ctx context.Context) context.Context {
+	p.itemGroup, ctx = errgroup.WithContext(ctx)
+	p.itemGroup.Go(func() error {
+		for item := range p.itemChan {
+			if err := p.doProcess(item); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+	return ctx
+}
+
+func (p *sitePagesProcessor) Wait() error {
+	close(p.itemChan)
+	return p.itemGroup.Wait()
+}
+
+func (p *sitePagesProcessor) copyFile(fim hugofs.FileMetaInfo) error {
+	meta := fim.Meta()
+	f, err := meta.Open()
+	if err != nil {
+		return errors.Wrap(err, "copyFile: failed to open")
+	}
+
+	s := p.m.s
+
+	target := filepath.Join(s.PathSpec.GetTargetLanguageBasePath(), meta.Path())
+
+	defer f.Close()
+
+	return s.publish(&s.PathSpec.ProcessingStats.Files, target, f)
+
+}
+
+func (p *sitePagesProcessor) doProcess(item interface{}) error {
+	m := p.m
+	switch v := item.(type) {
+	case *fileinfoBundle:
+		if err := m.AddFilesBundle(v.header, v.resources...); err != nil {
+			return err
+		}
+	case hugofs.FileMetaInfo:
+		if p.shouldSkip(v) {
+			return nil
+		}
+		meta := v.Meta()
+
+		classifier := meta.Classifier()
+		switch classifier {
+		case files.ContentClassContent:
+			if err := m.AddFilesBundle(v); err != nil {
+				return err
+			}
+		case files.ContentClassFile:
+			if err := p.copyFile(v); err != nil {
+				return err
+			}
+		default:
+			panic(fmt.Sprintf("invalid classifier: %q", classifier))
+		}
+	default:
+		panic(fmt.Sprintf("unrecognized item type in Process: %T", item))
+	}
+	return nil
+
+}
+
+func (p *sitePagesProcessor) shouldSkip(fim hugofs.FileMetaInfo) bool {
+	// TODO(ep) unify
+	return p.m.s.SourceSpec.DisabledLanguages[fim.Meta().Lang()]
+}