Make Page an interface

The main motivation of this commit is to add a `page.Page` interface to replace the very file-oriented `hugolib.Page` struct.
This is all a preparation step for issue  #5074, "pages from other data sources".

But this also fixes a set of annoying limitations, especially related to custom output formats, and shortcodes.

Most notable changes:

* The inner content of shortcodes using the `{{%` as the outer-most delimiter will now be sent to the content renderer, e.g. Blackfriday.
  This means that any markdown will partake in the global ToC and footnote context etc.
* The Custom Output formats are now "fully virtualized". This removes many of the current limitations.
* The taxonomy list type now has a reference to the `Page` object.
  This improves the taxonomy template `.Title` situation and make common template constructs much simpler.

See #5074
Fixes #5763
Fixes #5758
Fixes #5090
Fixes #5204
Fixes #4695
Fixes #5607
Fixes #5707
Fixes #5719
Fixes #3113
Fixes #5706
Fixes #5767
Fixes #5723
Fixes #5769
Fixes #5770
Fixes #5771
Fixes #5759
Fixes #5776
Fixes #5777
Fixes #5778

1 files changed, 291 insertions, 0 deletions

diff --git a/hugolib/page__new.go b/hugolib/page__new.go
new file mode 100644
index 000000000..0f419b5da
--- /dev/null
+++ b/hugolib/page__new.go
@@ -0,0 +1,291 @@
+// 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 (
+	"html/template"
+	"strings"
+
+	"github.com/gohugoio/hugo/common/hugo"
+
+	"github.com/gohugoio/hugo/common/maps"
+	"github.com/gohugoio/hugo/source"
+
+	"github.com/gohugoio/hugo/parser/pageparser"
+	"github.com/pkg/errors"
+
+	"github.com/gohugoio/hugo/output"
+
+	"github.com/gohugoio/hugo/lazy"
+
+	"github.com/gohugoio/hugo/resources/page"
+	"github.com/gohugoio/hugo/resources/resource"
+)
+
+func newPageBase(metaProvider *pageMeta) (*pageState, error) {
+	if metaProvider.s == nil {
+		panic("must provide a Site")
+	}
+
+	s := metaProvider.s
+
+	ps := &pageState{
+		pageOutput: nopPageOutput,
+		pageCommon: &pageCommon{
+			FileProvider:            metaProvider,
+			AuthorProvider:          metaProvider,
+			Scratcher:               maps.NewScratcher(),
+			Positioner:              page.NopPage,
+			InSectionPositioner:     page.NopPage,
+			ResourceMetaProvider:    metaProvider,
+			ResourceParamsProvider:  metaProvider,
+			PageMetaProvider:        metaProvider,
+			RelatedKeywordsProvider: metaProvider,
+			OutputFormatsProvider:   page.NopPage,
+			ResourceTypesProvider:   pageTypesProvider,
+			RefProvider:             page.NopPage,
+			ShortcodeInfoProvider:   page.NopPage,
+			LanguageProvider:        s,
+
+			InternalDependencies: s,
+			init:                 lazy.New(),
+			m:                    metaProvider,
+			s:                    s},
+	}
+
+	siteAdapter := pageSiteAdapter{s: s, p: ps}
+
+	deprecatedWarningPage := struct {
+		source.FileWithoutOverlap
+		page.DeprecatedWarningPageMethods1
+	}{
+		FileWithoutOverlap:            metaProvider.File(),
+		DeprecatedWarningPageMethods1: &pageDeprecatedWarning{p: ps},
+	}
+
+	ps.DeprecatedWarningPageMethods = page.NewDeprecatedWarningPage(deprecatedWarningPage)
+	ps.pageMenus = &pageMenus{p: ps}
+	ps.PageMenusProvider = ps.pageMenus
+	ps.GetPageProvider = siteAdapter
+	ps.GitInfoProvider = ps
+	ps.TranslationsProvider = ps
+	ps.ResourceDataProvider = &pageData{pageState: ps}
+	ps.RawContentProvider = ps
+	ps.ChildCareProvider = ps
+	ps.TreeProvider = pageTree{p: ps}
+	ps.Eqer = ps
+	ps.TranslationKeyProvider = ps
+	ps.ShortcodeInfoProvider = ps
+	ps.PageRenderProvider = ps
+	ps.AlternativeOutputFormatsProvider = ps
+
+	return ps, nil
+
+}
+
+func newPageFromMeta(metaProvider *pageMeta) (*pageState, error) {
+	ps, err := newPageBase(metaProvider)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := metaProvider.applyDefaultValues(); err != nil {
+		return nil, err
+	}
+
+	ps.init.Add(func() (interface{}, error) {
+		pp, err := newPagePaths(metaProvider.s, ps, metaProvider)
+		if err != nil {
+			return nil, err
+		}
+
+		makeOut := func(f output.Format, render bool) *pageOutput {
+			return newPageOutput(nil, ps, pp, f, render)
+		}
+
+		if ps.m.standalone {
+			ps.pageOutput = makeOut(ps.m.outputFormats()[0], true)
+		} else {
+			ps.pageOutputs = make([]*pageOutput, len(ps.s.h.renderFormats))
+			created := make(map[string]*pageOutput)
+			outputFormatsForPage := ps.m.outputFormats()
+			for i, f := range ps.s.h.renderFormats {
+				po, found := created[f.Name]
+				if !found {
+					_, shouldRender := outputFormatsForPage.GetByName(f.Name)
+					po = makeOut(f, shouldRender)
+					created[f.Name] = po
+				}
+				ps.pageOutputs[i] = po
+			}
+		}
+
+		if err := ps.initCommonProviders(pp); err != nil {
+			return nil, err
+		}
+
+		return nil, nil
+
+	})
+
+	return ps, err
+
+}
+
+// Used by the legacy 404, sitemap and robots.txt rendering
+func newPageStandalone(m *pageMeta, f output.Format) (*pageState, error) {
+	m.configuredOutputFormats = output.Formats{f}
+	m.standalone = true
+	p, err := newPageFromMeta(m)
+
+	if err != nil {
+		return nil, err
+	}
+
+	if err := p.initPage(); err != nil {
+		return nil, err
+	}
+
+	return p, nil
+
+}
+
+func newPageWithContent(f *fileInfo, s *Site, content resource.OpenReadSeekCloser) (*pageState, error) {
+	sections := s.sectionsFromFile(f)
+	kind := s.kindFromFileInfoOrSections(f, sections)
+	if kind == page.KindTaxonomy {
+		s.PathSpec.MakePathsSanitized(sections)
+	}
+
+	metaProvider := &pageMeta{kind: kind, sections: sections, s: s, f: f}
+
+	ps, err := newPageBase(metaProvider)
+	if err != nil {
+		return nil, err
+	}
+
+	gi, err := s.h.gitInfoForPage(ps)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to load Git data")
+	}
+	ps.gitInfo = gi
+
+	r, err := content()
+	if err != nil {
+		return nil, err
+	}
+	defer r.Close()
+
+	parseResult, err := pageparser.Parse(
+		r,
+		pageparser.Config{EnableEmoji: s.siteCfg.enableEmoji},
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	ps.pageContent = pageContent{
+		source: rawPageContent{
+			parsed:         parseResult,
+			posMainContent: -1,
+			posSummaryEnd:  -1,
+			posBodyStart:   -1,
+		},
+	}
+
+	ps.shortcodeState = newShortcodeHandler(ps, ps.s, nil)
+
+	if err := ps.mapContent(metaProvider); err != nil {
+		return nil, ps.wrapError(err)
+	}
+
+	if err := metaProvider.applyDefaultValues(); err != nil {
+		return nil, err
+	}
+
+	ps.init.Add(func() (interface{}, error) {
+		reuseContent := ps.renderable && !ps.shortcodeState.hasShortcodes()
+
+		// Creates what's needed for each output format.
+		contentPerOutput := newPageContentOutput(ps)
+
+		pp, err := newPagePaths(s, ps, metaProvider)
+		if err != nil {
+			return nil, err
+		}
+
+		// Prepare output formats for all sites.
+		ps.pageOutputs = make([]*pageOutput, len(ps.s.h.renderFormats))
+		created := make(map[string]*pageOutput)
+		outputFormatsForPage := ps.m.outputFormats()
+
+		for i, f := range ps.s.h.renderFormats {
+			if po, found := created[f.Name]; found {
+				ps.pageOutputs[i] = po
+				continue
+			}
+
+			_, render := outputFormatsForPage.GetByName(f.Name)
+			var contentProvider *pageContentOutput
+			if reuseContent && i > 0 {
+				contentProvider = ps.pageOutputs[0].cp
+			} else {
+				var err error
+				contentProvider, err = contentPerOutput(f)
+				if err != nil {
+					return nil, err
+				}
+			}
+
+			po := newPageOutput(contentProvider, ps, pp, f, render)
+			ps.pageOutputs[i] = po
+			created[f.Name] = po
+		}
+
+		if err := ps.initCommonProviders(pp); err != nil {
+			return nil, err
+		}
+
+		return nil, nil
+	})
+
+	return ps, nil
+}
+
+type pageDeprecatedWarning struct {
+	p *pageState
+}
+
+func (p *pageDeprecatedWarning) IsDraft() bool          { return p.p.m.draft }
+func (p *pageDeprecatedWarning) Hugo() hugo.Info        { return p.p.s.Info.Hugo() }
+func (p *pageDeprecatedWarning) LanguagePrefix() string { return p.p.s.Info.LanguagePrefix }
+func (p *pageDeprecatedWarning) GetParam(key string) interface{} {
+	return p.p.m.params[strings.ToLower(key)]
+}
+func (p *pageDeprecatedWarning) RSSLink() template.URL {
+	f := p.p.OutputFormats().Get("RSS")
+	if f == nil {
+		return ""
+	}
+	return template.URL(f.Permalink())
+}
+func (p *pageDeprecatedWarning) URL() string {
+	if p.p.IsPage() && p.p.m.urlPaths.URL != "" {
+		// This is the url set in front matter
+		return p.p.m.urlPaths.URL
+	}
+	// Fall back to the relative permalink.
+	return p.p.RelPermalink()
+
+}