markup: Add blockquote render hooks

Closes #12590

9 files changed, 453 insertions, 2 deletions

diff --git a/hugolib/page__per_output.go b/hugolib/page__per_output.go
index 59ba722a8..59cb574df 100644
--- a/hugolib/page__per_output.go
+++ b/hugolib/page__per_output.go
@@ -440,8 +440,8 @@ func (pco *pageContentOutput) initRenderHooks() error {
 			var offset int
 
 			switch v := ctx.(type) {
-			case hooks.CodeblockContext:
-				offset = bytes.Index(source, []byte(v.Inner()))
+			case hooks.PositionerSourceTargetProvider:
+				offset = bytes.Index(source, v.PositionerSourceTarget())
 			}
 
 			pos := pco.po.p.posFromInput(source, offset)
@@ -481,6 +481,11 @@ func (pco *pageContentOutput) initRenderHooks() error {
 				if id != nil {
 					layoutDescriptor.KindVariants = id.(string)
 				}
+			case hooks.BlockquoteRendererType:
+				layoutDescriptor.Kind = "render-blockquote"
+				if id != nil {
+					layoutDescriptor.KindVariants = id.(string)
+				}
 			case hooks.CodeBlockRendererType:
 				layoutDescriptor.Kind = "render-codeblock"
 				if id != nil {
diff --git a/hugolib/site.go b/hugolib/site.go
index 0b089767a..bbf110d1d 100644
--- a/hugolib/site.go
+++ b/hugolib/site.go
@@ -919,6 +919,10 @@ func (hr hookRendererTemplate) RenderPassthrough(cctx context.Context, w io.Writ
 	return hr.templateHandler.ExecuteWithContext(cctx, hr.templ, w, ctx)
 }
 
+func (hr hookRendererTemplate) RenderBlockquote(cctx context.Context, w hugio.FlexiWriter, ctx hooks.BlockquoteContext) error {
+	return hr.templateHandler.ExecuteWithContext(cctx, hr.templ, w, ctx)
+}
+
 func (hr hookRendererTemplate) ResolvePosition(ctx any) text.Position {
 	return hr.resolvePosition(ctx)
 }
diff --git a/markup/converter/hooks/hooks.go b/markup/converter/hooks/hooks.go
index 1e335fa46..29e848d80 100644
--- a/markup/converter/hooks/hooks.go
+++ b/markup/converter/hooks/hooks.go
@@ -78,6 +78,33 @@ type CodeblockContext interface {
 	Ordinal() int
 }
 
+// BlockquoteContext is the context passed to a blockquote render hook.
+type BlockquoteContext interface {
+	AttributesProvider
+	text.Positioner
+	PageProvider
+
+	// Zero-based ordinal for all block quotes in the current document.
+	Ordinal() int
+
+	// The blockquote text.
+	// If type is "alert", this will be the alert text.
+	Text() hstring.RenderedString
+
+	/// Returns the blockquote type, one of "regular" and "alert".
+	// Type "alert" indicates that this is a GitHub type alert.
+	Type() string
+
+	// The GitHub alert type converted to lowercase, e.g. "note".
+	// Only set if Type is "alert".
+	AlertType() string
+}
+
+type PositionerSourceTargetProvider interface {
+	// For internal use.
+	PositionerSourceTarget() []byte
+}
+
 // PassThroughContext is the context passed to a passthrough render hook.
 type PassthroughContext interface {
 	AttributesProvider
@@ -87,6 +114,9 @@ type PassthroughContext interface {
 	// Currently one of "inline" or "block".
 	Type() string
 
+	// The inner content of the passthrough element, excluding the delimiters.
+	Inner() string
+
 	// Zero-based ordinal for all passthrough elements in the document.
 	Ordinal() int
 }
@@ -104,6 +134,10 @@ type CodeBlockRenderer interface {
 	RenderCodeblock(cctx context.Context, w hugio.FlexiWriter, ctx CodeblockContext) error
 }
 
+type BlockquoteRenderer interface {
+	RenderBlockquote(cctx context.Context, w hugio.FlexiWriter, ctx BlockquoteContext) error
+}
+
 type PassthroughRenderer interface {
 	RenderPassthrough(cctx context.Context, w io.Writer, ctx PassthroughContext) error
 }
@@ -161,6 +195,7 @@ const (
 	HeadingRendererType
 	CodeBlockRendererType
 	PassthroughRendererType
+	BlockquoteRendererType
 )
 
 type GetRendererFunc func(t RendererType, id any) any
diff --git a/markup/goldmark/blockquotes/blockquotes.go b/markup/goldmark/blockquotes/blockquotes.go
new file mode 100644
index 000000000..f4c908e0b
--- /dev/null
+++ b/markup/goldmark/blockquotes/blockquotes.go
@@ -0,0 +1,248 @@
+// Copyright 2024 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 blockquotes
+
+import (
+	"regexp"
+	"strings"
+	"sync"
+
+	"github.com/gohugoio/hugo/common/herrors"
+	htext "github.com/gohugoio/hugo/common/text"
+	"github.com/gohugoio/hugo/common/types/hstring"
+	"github.com/gohugoio/hugo/markup/converter/hooks"
+	"github.com/gohugoio/hugo/markup/goldmark/internal/render"
+	"github.com/gohugoio/hugo/markup/internal/attributes"
+	"github.com/yuin/goldmark"
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/util"
+)
+
+type (
+	blockquotesExtension struct{}
+	htmlRenderer         struct{}
+)
+
+func New() goldmark.Extender {
+	return &blockquotesExtension{}
+}
+
+func (e *blockquotesExtension) Extend(m goldmark.Markdown) {
+	m.Renderer().AddOptions(renderer.WithNodeRenderers(
+		util.Prioritized(newHTMLRenderer(), 100),
+	))
+}
+
+func newHTMLRenderer() renderer.NodeRenderer {
+	r := &htmlRenderer{}
+	return r
+}
+
+func (r *htmlRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	reg.Register(ast.KindBlockquote, r.renderBlockquote)
+}
+
+const (
+	typeRegular = "regular"
+	typeAlert   = "alert"
+)
+
+func (r *htmlRenderer) renderBlockquote(w util.BufWriter, src []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	ctx := w.(*render.Context)
+
+	n := node.(*ast.Blockquote)
+
+	if entering {
+		// Store the current pos so we can capture the rendered text.
+		ctx.PushPos(ctx.Buffer.Len())
+		return ast.WalkContinue, nil
+	}
+
+	pos := ctx.PopPos()
+	text := ctx.Buffer.Bytes()[pos:]
+	ctx.Buffer.Truncate(pos)
+
+	// Extract a source sample to use for position information.
+	nn := n.FirstChild()
+	var start, stop int
+	for i := 0; i < nn.Lines().Len() && i < 2; i++ {
+		line := nn.Lines().At(i)
+		if i == 0 {
+			start = line.Start
+		}
+		stop = line.Stop
+	}
+
+	// We do not mutate the source, so this is safe.
+	sourceRef := src[start:stop]
+
+	ordinal := ctx.GetAndIncrementOrdinal(ast.KindBlockquote)
+
+	texts := string(text)
+	typ := typeRegular
+	alertType := resolveGitHubAlert(texts)
+	if alertType != "" {
+		typ = typeAlert
+	}
+
+	renderer := ctx.RenderContext().GetRenderer(hooks.BlockquoteRendererType, typ)
+	if renderer == nil {
+		return r.renderBlockquoteDefault(w, n, texts)
+	}
+
+	if typ == typeAlert {
+		// Trim preamble: <p>[!NOTE]<br>\n but preserve leading paragraph.
+		// We could possibly complicate this by moving this to the parser, but
+		// keep it simple for now.
+		texts = "<p>" + texts[strings.Index(texts, "\n")+1:]
+	}
+
+	bqctx := &blockquoteContext{
+		page:             ctx.DocumentContext().Document,
+		pageInner:        r.getPageInner(ctx),
+		typ:              typ,
+		alertType:        alertType,
+		text:             hstring.RenderedString(texts),
+		sourceRef:        sourceRef,
+		ordinal:          ordinal,
+		AttributesHolder: attributes.New(n.Attributes(), attributes.AttributesOwnerGeneral),
+	}
+
+	bqctx.createPos = func() htext.Position {
+		if resolver, ok := renderer.(hooks.ElementPositionResolver); ok {
+			return resolver.ResolvePosition(bqctx)
+		}
+
+		return htext.Position{
+			Filename:     ctx.DocumentContext().Filename,
+			LineNumber:   1,
+			ColumnNumber: 1,
+		}
+	}
+
+	cr := renderer.(hooks.BlockquoteRenderer)
+
+	err := cr.RenderBlockquote(
+		ctx.RenderContext().Ctx,
+		w,
+		bqctx,
+	)
+	if err != nil {
+		return ast.WalkContinue, herrors.NewFileErrorFromPos(err, bqctx.createPos())
+	}
+
+	return ast.WalkContinue, nil
+}
+
+func (r *htmlRenderer) getPageInner(rctx *render.Context) any {
+	pid := rctx.PeekPid()
+	if pid > 0 {
+		if lookup := rctx.DocumentContext().DocumentLookup; lookup != nil {
+			if v := rctx.DocumentContext().DocumentLookup(pid); v != nil {
+				return v
+			}
+		}
+	}
+	return rctx.DocumentContext().Document
+}
+
+// Code borrowed from goldmark's html renderer.
+func (r *htmlRenderer) renderBlockquoteDefault(
+	w util.BufWriter, n ast.Node, text string,
+) (ast.WalkStatus, error) {
+	if n.Attributes() != nil {
+		_, _ = w.WriteString("<blockquote")
+		html.RenderAttributes(w, n, html.BlockquoteAttributeFilter)
+		_ = w.WriteByte('>')
+	} else {
+		_, _ = w.WriteString("<blockquote>\n")
+	}
+
+	_, _ = w.WriteString(text)
+
+	_, _ = w.WriteString("</blockquote>\n")
+	return ast.WalkContinue, nil
+}
+
+type blockquoteContext struct {
+	page      any
+	pageInner any
+	text      hstring.RenderedString
+	typ       string
+	sourceRef []byte
+	alertType string
+	ordinal   int
+
+	// This is only used in error situations and is expensive to create,
+	// so delay creation until needed.
+	pos       htext.Position
+	posInit   sync.Once
+	createPos func() htext.Position
+
+	*attributes.AttributesHolder
+}
+
+func (c *blockquoteContext) Type() string {
+	return c.typ
+}
+
+func (c *blockquoteContext) AlertType() string {
+	return c.alertType
+}
+
+func (c *blockquoteContext) Page() any {
+	return c.page
+}
+
+func (c *blockquoteContext) PageInner() any {
+	return c.pageInner
+}
+
+func (c *blockquoteContext) Text() hstring.RenderedString {
+	return c.text
+}
+
+func (c *blockquoteContext) Ordinal() int {
+	return c.ordinal
+}
+
+func (c *blockquoteContext) Position() htext.Position {
+	c.posInit.Do(func() {
+		c.pos = c.createPos()
+	})
+	return c.pos
+}
+
+func (c *blockquoteContext) PositionerSourceTarget() []byte {
+	return c.sourceRef
+}
+
+var _ hooks.PositionerSourceTargetProvider = (*blockquoteContext)(nil)
+
+// https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#alerts
+// Five types:
+// [!NOTE], [!TIP], [!WARNING], [!IMPORTANT], [!CAUTION]
+var gitHubAlertRe = regexp.MustCompile(`^<p>\[!(NOTE|TIP|WARNING|IMPORTANT|CAUTION)\]`)
+
+// resolveGitHubAlert returns one of note, tip, warning, important or caution.
+// An empty string if no match.
+func resolveGitHubAlert(s string) string {
+	m := gitHubAlertRe.FindStringSubmatch(s)
+	if len(m) == 2 {
+		return strings.ToLower(m[1])
+	}
+	return ""
+}
diff --git a/markup/goldmark/blockquotes/blockquotes_integration_test.go b/markup/goldmark/blockquotes/blockquotes_integration_test.go
new file mode 100644
index 000000000..45c7caa0f
--- /dev/null
+++ b/markup/goldmark/blockquotes/blockquotes_integration_test.go
@@ -0,0 +1,83 @@
+// Copyright 2024 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 blockquotes_test
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/gohugoio/hugo/hugolib"
+)
+
+func TestBlockquoteHook(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+[markup]
+  [markup.goldmark]
+    [markup.goldmark.parser]
+      [markup.goldmark.parser.attribute]
+        block = true
+        title = true
+-- layouts/_default/_markup/render-blockquote.html --
+Blockquote: |{{ .Text | safeHTML }}|{{ .Type }}|
+-- layouts/_default/_markup/render-blockquote-alert.html --
+{{ $text := .Text | safeHTML }}
+Blockquote Alert: |{{ $text }}|{{ .Type }}|
+Blockquote Alert Attributes: |{{ $text }}|{{ .Attributes }}|
+Blockquote Alert Page: |{{ $text }}|{{ .Page.Title }}|{{ .PageInner.Title }}|
+{{ if .Attributes.showpos }}
+Blockquote Alert Position: |{{ $text }}|{{ .Position | safeHTML }}|
+{{ end }}
+-- layouts/_default/single.html --
+Content: {{ .Content }}
+-- content/p1.md --
+---
+title: "p1"
+---
+
+> [!NOTE]  
+> This is a note with some whitespace after the alert type.
+
+
+> [!TIP]
+> This is a tip.
+
+>   [!CAUTION]
+> This is a caution with some whitespace before the alert type.
+
+> A regular blockquote.
+
+> [!TIP]
+> This is a tip with attributes.
+{class="foo bar" id="baz"}
+
+> [!NOTE]  
+> Note triggering showing the position.
+{showpos="true"}
+
+`
+
+	b := hugolib.Test(t, files)
+	b.AssertFileContent("public/p1/index.html",
+		"Blockquote Alert: |<p>This is a note with some whitespace after the alert type.</p>\n|alert|",
+		"Blockquote Alert: |<p>This is a tip.</p>",
+		"Blockquote Alert: |<p>This is a caution with some whitespace before the alert type.</p>\n|alert|",
+		"Blockquote: |<p>A regular blockquote.</p>\n|regular|",
+		"Blockquote Alert Attributes: |<p>This is a tip with attributes.</p>\n|map[class:foo bar id:baz]|",
+		filepath.FromSlash("/content/p1.md:20:3"),
+		"Blockquote Alert Page: |<p>This is a tip with attributes.</p>\n|p1|p1|",
+	)
+}
diff --git a/markup/goldmark/blockquotes/blockquotes_test.go b/markup/goldmark/blockquotes/blockquotes_test.go
new file mode 100644
index 000000000..5b2680a0d
--- /dev/null
+++ b/markup/goldmark/blockquotes/blockquotes_test.go
@@ -0,0 +1,60 @@
+// Copyright 2024 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 blockquotes
+
+import (
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+)
+
+func TestResolveGitHubAlert(t *testing.T) {
+	t.Parallel()
+
+	c := qt.New(t)
+
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{
+			input:    "[!NOTE]",
+			expected: "note",
+		},
+		{
+			input:    "[!WARNING]",
+			expected: "warning",
+		},
+		{
+			input:    "[!TIP]",
+			expected: "tip",
+		},
+		{
+			input:    "[!IMPORTANT]",
+			expected: "important",
+		},
+		{
+			input:    "[!CAUTION]",
+			expected: "caution",
+		},
+		{
+			input:    "[!FOO]",
+			expected: "",
+		},
+	}
+
+	for _, test := range tests {
+		c.Assert(resolveGitHubAlert("<p>"+test.input), qt.Equals, test.expected)
+	}
+}
diff --git a/markup/goldmark/codeblocks/render.go b/markup/goldmark/codeblocks/render.go
index 51f3b20f8..fad3ac458 100644
--- a/markup/goldmark/codeblocks/render.go
+++ b/markup/goldmark/codeblocks/render.go
@@ -147,6 +147,8 @@ func (r *htmlRenderer) getPageInner(rctx *render.Context) any {
 	return rctx.DocumentContext().Document
 }
 
+var _ hooks.PositionerSourceTargetProvider = (*codeBlockContext)(nil)
+
 type codeBlockContext struct {
 	page      any
 	pageInner any
@@ -190,6 +192,11 @@ func (c *codeBlockContext) Position() htext.Position {
 	return c.pos
 }
 
+// For internal use.
+func (c *codeBlockContext) PositionerSourceTarget() []byte {
+	return []byte(c.code)
+}
+
 func getLang(node *ast.FencedCodeBlock, src []byte) string {
 	langWithAttributes := string(node.Language(src))
 	lang, _, _ := strings.Cut(langWithAttributes, "{")
diff --git a/markup/goldmark/convert.go b/markup/goldmark/convert.go
index efb3100aa..357be7328 100644
--- a/markup/goldmark/convert.go
+++ b/markup/goldmark/convert.go
@@ -18,6 +18,7 @@ import (
 	"bytes"
 
 	"github.com/gohugoio/hugo-goldmark-extensions/extras"
+	"github.com/gohugoio/hugo/markup/goldmark/blockquotes"
 	"github.com/gohugoio/hugo/markup/goldmark/codeblocks"
 	"github.com/gohugoio/hugo/markup/goldmark/goldmark_config"
 	"github.com/gohugoio/hugo/markup/goldmark/hugocontext"
@@ -107,6 +108,7 @@ func newMarkdown(pcfg converter.ProviderConfig) goldmark.Markdown {
 			hugocontext.New(),
 			newLinks(cfg),
 			newTocExtension(tocRendererOptions),
+			blockquotes.New(),
 		}
 		parserOptions []parser.Option
 	)
diff --git a/markup/goldmark/passthrough/passthrough.go b/markup/goldmark/passthrough/passthrough.go
index 20e42211e..aafb1544b 100644
--- a/markup/goldmark/passthrough/passthrough.go
+++ b/markup/goldmark/passthrough/passthrough.go
@@ -217,3 +217,10 @@ func (p *passthroughContext) Position() htext.Position {
 	})
 	return p.pos
 }
+
+// For internal use.
+func (p *passthroughContext) PositionerSourceTarget() []byte {
+	return []byte(p.inner)
+}
+
+var _ hooks.PositionerSourceTargetProvider = (*passthroughContext)(nil)