Pass .RenderShortcodes' Page to render hooks as .PageInner

The main use case for this is to resolve links and resources (e.g. images) relative to the included `Page`.

A typical `include` would similar to this:

```handlebars
{{ with site.GetPage (.Get 0) }}
  {{ .RenderShortcodes }}
{{ end }}
```

And when used in a Markdown file:

```markdown
{{% include "/posts/p1" %}}
```

Any render hook triggered while rendering `/posts/p1` will get `/posts/p1` when calling `.PageInner`.

Note that

* This is only relevant for shortcodes included with `{{%` that calls `.RenderShortcodes`.
* `.PageInner` is available in all render hooks that, before this commit, received `.Page`.
* `.PageInner` will fall back to the value of `.Page` if not relevant and will always have a value.

Fixes #12356

6 files changed, 142 insertions, 8 deletions

diff --git a/hugolib/content_map_page.go b/hugolib/content_map_page.go
index 336fe197c..aa32b5320 100644
--- a/hugolib/content_map_page.go
+++ b/hugolib/content_map_page.go
@@ -1603,7 +1603,7 @@ func (sa *sitePagesAssembler) assembleResources() error {
 			targetPaths := ps.targetPaths()
 			baseTarget := targetPaths.SubResourceBaseTarget
 			duplicateResourceFiles := true
-			if ps.s.ContentSpec.Converters.IsGoldmark(ps.m.pageConfig.Markup) {
+			if ps.m.pageConfig.IsGoldmark {
 				duplicateResourceFiles = ps.s.ContentSpec.Converters.GetMarkupConfig().Goldmark.DuplicateResourceFiles
 			}
 
diff --git a/hugolib/page__content.go b/hugolib/page__content.go
index 799fc89b6..f10c25d7b 100644
--- a/hugolib/page__content.go
+++ b/hugolib/page__content.go
@@ -522,6 +522,7 @@ func (c *cachedContent) contentRendered(ctx context.Context, cp *pageContentOutp
 			if err != nil {
 				return nil, err
 			}
+
 			if !ok {
 				return nil, errors.New("invalid state: astDoc is set but RenderContent returned false")
 			}
@@ -626,8 +627,10 @@ func (c *cachedContent) contentToC(ctx context.Context, cp *pageContentOutput) (
 			return nil, err
 		}
 
-		// Callback called from above (e.g. in .RenderString)
+		// Callback called from below (e.g. in .RenderString)
 		ctxCallback := func(cp2 *pageContentOutput, ct2 contentTableOfContents) {
+			cp.otherOutputs[cp2.po.p.pid] = cp2
+
 			// Merge content placeholders
 			for k, v := range ct2.contentPlaceholders {
 				ct.contentPlaceholders[k] = v
diff --git a/hugolib/page__meta.go b/hugolib/page__meta.go
index ebf57f3b3..d8203fe75 100644
--- a/hugolib/page__meta.go
+++ b/hugolib/page__meta.go
@@ -737,6 +737,8 @@ func (p *pageMeta) applyDefaultValues() error {
 		}
 	}
 
+	p.pageConfig.IsGoldmark = p.s.ContentSpec.Converters.IsGoldmark(p.pageConfig.Markup)
+
 	if p.pageConfig.Title == "" && p.f == nil {
 		switch p.Kind() {
 		case kinds.KindHome:
@@ -794,12 +796,26 @@ func (p *pageMeta) newContentConverter(ps *pageState, markup string) (converter.
 		path = p.Path()
 	}
 
+	doc := newPageForRenderHook(ps)
+
+	documentLookup := func(id uint64) any {
+		if id == ps.pid {
+			// This prevents infinite recursion in some cases.
+			return doc
+		}
+		if v, ok := ps.pageOutput.pco.otherOutputs[id]; ok {
+			return v.po.p
+		}
+		return nil
+	}
+
 	cpp, err := cp.New(
 		converter.DocumentContext{
-			Document:     newPageForRenderHook(ps),
-			DocumentID:   id,
-			DocumentName: path,
-			Filename:     filename,
+			Document:       doc,
+			DocumentLookup: documentLookup,
+			DocumentID:     id,
+			DocumentName:   path,
+			Filename:       filename,
 		},
 	)
 	if err != nil {
diff --git a/hugolib/page__per_output.go b/hugolib/page__per_output.go
index fac719ea9..4ff67c074 100644
--- a/hugolib/page__per_output.go
+++ b/hugolib/page__per_output.go
@@ -30,6 +30,7 @@ import (
 	"github.com/spf13/cast"
 
 	"github.com/gohugoio/hugo/markup/converter/hooks"
+	"github.com/gohugoio/hugo/markup/goldmark/hugocontext"
 	"github.com/gohugoio/hugo/markup/highlight/chromalexers"
 	"github.com/gohugoio/hugo/markup/tableofcontents"
 
@@ -68,8 +69,9 @@ var (
 
 func newPageContentOutput(po *pageOutput) (*pageContentOutput, error) {
 	cp := &pageContentOutput{
-		po:          po,
-		renderHooks: &renderHooks{},
+		po:           po,
+		renderHooks:  &renderHooks{},
+		otherOutputs: make(map[uint64]*pageContentOutput),
 	}
 	return cp, nil
 }
@@ -83,6 +85,10 @@ type renderHooks struct {
 type pageContentOutput struct {
 	po *pageOutput
 
+	// Other pages involved in rendering of this page,
+	// typically included with .RenderShortcodes.
+	otherOutputs map[uint64]*pageContentOutput
+
 	contentRenderedVersion int  // Incremented on reset.
 	contentRendered        bool // Set on content render.
 
@@ -165,6 +171,13 @@ func (pco *pageContentOutput) RenderShortcodes(ctx context.Context) (template.HT
 		cb(pco, ct)
 	}
 
+	if tpl.Context.IsInGoldmark.Get(ctx) {
+		// This content will be parsed and rendered by Goldmark.
+		// Wrap it in a special Hugo markup to assign the correct Page from
+		// the stack.
+		c = hugocontext.Wrap(c, pco.po.p.pid)
+	}
+
 	return helpers.BytesToHTML(c), nil
 }
 
diff --git a/hugolib/rendershortcodes_test.go b/hugolib/rendershortcodes_test.go
index 696ed8f41..67b1a85ef 100644
--- a/hugolib/rendershortcodes_test.go
+++ b/hugolib/rendershortcodes_test.go
@@ -200,3 +200,99 @@ Myshort Original.
 	b.Build()
 	b.AssertFileContent("public/p1/index.html", "Edited")
 }
+
+func TestRenderShortcodesNestedPageContextIssue12356(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ["taxonomy", "term", "rss", "sitemap", "robotsTXT", "404"]
+-- layouts/_default/_markup/render-image.html --
+{{- with .PageInner.Resources.Get .Destination -}}Image: {{ .RelPermalink }}|{{- end -}}
+-- layouts/_default/_markup/render-link.html --
+{{- with .PageInner.GetPage .Destination -}}Link: {{ .RelPermalink }}|{{- end -}}
+-- layouts/_default/_markup/render-heading.html --
+Heading: {{ .PageInner.Title }}: {{ .PlainText }}|
+-- layouts/_default/_markup/render-codeblock.html --
+CodeBlock: {{ .PageInner.Title }}: {{ .Type }}|
+-- layouts/_default/list.html --
+Content:{{ .Content }}|
+Fragments: {{ with .Fragments }}{{.Identifiers }}{{ end }}|
+-- layouts/_default/single.html --
+Content:{{ .Content }}|
+-- layouts/shortcodes/include.html --
+{{ with site.GetPage (.Get 0) }}
+  {{ .RenderShortcodes }}
+{{ end }}
+-- content/markdown/_index.md --
+---
+title: "Markdown"
+---
+# H1
+|{{% include "/posts/p1" %}}|
+![kitten](pixel3.png "Pixel 3")
+
+§§§go
+fmt.Println("Hello")
+§§§
+
+-- content/markdown2/_index.md --
+---
+title: "Markdown 2"
+---
+|{{< include "/posts/p1" >}}|
+-- content/html/_index.html --
+---
+title: "HTML"
+---
+|{{% include "/posts/p1" %}}|
+
+-- content/posts/p1/index.md --
+---
+title: "p1"
+---
+## H2-p1
+![kitten](pixel1.png "Pixel 1")
+![kitten](pixel2.png "Pixel 2")
+[p2](p2)
+
+§§§bash
+echo "Hello"
+§§§
+
+-- content/posts/p2/index.md --
+---
+title: "p2"
+---
+-- content/posts/p1/pixel1.png --
+iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNkYPhfDwAChwGA60e6kgAAAABJRU5ErkJggg==
+-- content/posts/p1/pixel2.png --
+iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNkYPhfDwAChwGA60e6kgAAAABJRU5ErkJggg==
+-- content/markdown/pixel3.png --
+iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNkYPhfDwAChwGA60e6kgAAAABJRU5ErkJggg==
+-- content/html/pixel4.png --
+iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNkYPhfDwAChwGA60e6kgAAAABJRU5ErkJggg==
+
+`
+
+	b := Test(t, files)
+
+	b.AssertFileContent("public/markdown/index.html",
+		// Images.
+		"Image: /posts/p1/pixel1.png|\nImage: /posts/p1/pixel2.png|\n|\nImage: /markdown/pixel3.png|</p>\n|",
+		// Links.
+		"Link: /posts/p2/|",
+		// Code blocks
+		"CodeBlock: p1: bash|", "CodeBlock: Markdown: go|",
+		// Headings.
+		"Heading: Markdown: H1|", "Heading: p1: H2-p1|",
+		// Fragments.
+		"Fragments: [h1 h2-p1]|",
+		// Check that the special context markup is not rendered.
+		"! hugo_ctx",
+	)
+
+	b.AssertFileContent("public/markdown2/index.html", "! hugo_ctx", "Content:<p>|\n  ![kitten](pixel1.png \"Pixel 1\")\n![kitten](pixel2.png \"Pixel 2\")\n|</p>\n|")
+
+	b.AssertFileContent("public/html/index.html", "! hugo_ctx")
+}
diff --git a/hugolib/shortcode.go b/hugolib/shortcode.go
index 7cc2cba27..af4454a89 100644
--- a/hugolib/shortcode.go
+++ b/hugolib/shortcode.go
@@ -321,10 +321,16 @@ func prepareShortcode(
 
 	// Allow the caller to delay the rendering of the shortcode if needed.
 	var fn shortcodeRenderFunc = func(ctx context.Context) ([]byte, bool, error) {
+		if p.m.pageConfig.IsGoldmark && sc.doMarkup {
+			// Signal downwards that the content rendered will be
+			// parsed and rendered by Goldmark.
+			ctx = tpl.Context.IsInGoldmark.Set(ctx, true)
+		}
 		r, err := doRenderShortcode(ctx, level, s, tplVariants, sc, parent, p, isRenderString)
 		if err != nil {
 			return nil, false, toParseErr(err)
 		}
+
 		b, hasVariants, err := r.renderShortcode(ctx)
 		if err != nil {
 			return nil, false, toParseErr(err)