From 641403f7de372497776dbed2fe5d01f87904b531 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Pedersen?=
 <bjorn.erik.pedersen@gmail.com>
Date: Mon, 17 Feb 2025 10:58:32 +0100
Subject: [PATCH] Fix Position for passthrough hooks

Fixes #13406
---
 markup/goldmark/internal/render/context.go  | 32 +++++++++++--
 tpl/transform/transform_integration_test.go | 50 +++++++++++++++++++++
 2 files changed, 78 insertions(+), 4 deletions(-)

diff --git a/markup/goldmark/internal/render/context.go b/markup/goldmark/internal/render/context.go
index 27029b670..fd8e788ed 100644
--- a/markup/goldmark/internal/render/context.go
+++ b/markup/goldmark/internal/render/context.go
@@ -19,6 +19,7 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/gohugoio/hugo-goldmark-extensions/passthrough"
 	bp "github.com/gohugoio/hugo/bufferpool"
 	east "github.com/yuin/goldmark-emoji/ast"
 
@@ -163,21 +164,44 @@ func (ctx *RenderContextDataHolder) DocumentContext() converter.DocumentContext
 // Note that this is not a copy of the source, but a slice of it,
 // so it assumes that the source is not mutated.
 func extractSourceSample(n ast.Node, src []byte) []byte {
+	if n.Type() == ast.TypeInline {
+		switch n := n.(type) {
+		case *passthrough.PassthroughInline:
+			return n.Segment.Value(src)
+		}
+
+		return nil
+	}
+
 	var sample []byte
 
-	// Extract a source sample to use for position information.
-	if nn := n.FirstChild(); nn != nil {
+	getStartStop := func(n ast.Node) (int, int) {
+		if n == nil {
+			return 0, 0
+		}
+
 		var start, stop int
-		for i := 0; i < nn.Lines().Len() && i < 2; i++ {
-			line := nn.Lines().At(i)
+		for i := 0; i < n.Lines().Len() && i < 2; i++ {
+			line := n.Lines().At(i)
 			if i == 0 {
 				start = line.Start
 			}
 			stop = line.Stop
 		}
+		return start, stop
+	}
+
+	start, stop := getStartStop(n)
+	if stop == 0 {
+		// Try first child.
+		start, stop = getStartStop(n.FirstChild())
+	}
+
+	if stop > 0 {
 		// We do not mutate the source, so this is safe.
 		sample = src[start:stop]
 	}
+
 	return sample
 }
 
diff --git a/tpl/transform/transform_integration_test.go b/tpl/transform/transform_integration_test.go
index 276b9b059..b9a98185c 100644
--- a/tpl/transform/transform_integration_test.go
+++ b/tpl/transform/transform_integration_test.go
@@ -263,6 +263,56 @@ $$%s$$
 	})
 }
 
+// Issue #13406.
+func TestToMathRenderHookPosition(t *testing.T) {
+	filesTemplate := `
+-- hugo.toml --
+disableKinds = ['rss','section','sitemap','taxonomy','term']
+[markup.goldmark.extensions.passthrough]
+enable = true
+[markup.goldmark.extensions.passthrough.delimiters]
+block  = [['\[', '\]'], ['$$', '$$']]
+inline = [['\(', '\)'], ['$', '$']]
+-- content/p1.md --
+---
+title: p1
+---
+
+Block:
+
+$$1+2$$
+
+Some inline $1+3$ math.
+
+-- layouts/index.html --
+Home.
+-- layouts/_default/single.html --
+Content: {{ .Content }}|
+-- layouts/_default/_markup/render-passthrough.html --
+{{ $opts := dict "throwOnError" true "displayMode" true }}
+{{- with try (transform.ToMath .Inner $opts ) }}
+  {{- with .Err }}
+    {{ errorf "KaTeX: %s: see %s." . $.Position }}
+  {{- else }}
+    {{- .Value }}
+  {{- end }}
+{{- end -}}
+
+`
+
+	// Block math.
+	files := strings.Replace(filesTemplate, "$$1+2$$", "$$\\foo1+2$$", 1)
+	b, err := hugolib.TestE(t, files)
+	b.Assert(err, qt.IsNotNil)
+	b.AssertLogContains("p1.md:6:1")
+
+	// Inline math.
+	files = strings.Replace(filesTemplate, "$1+3$", "$\\foo1+3$", 1)
+	b, err = hugolib.TestE(t, files)
+	b.Assert(err, qt.IsNotNil)
+	b.AssertLogContains("p1.md:8:13")
+}
+
 func TestToMathMacros(t *testing.T) {
 	files := `
 -- hugo.toml --