Repository: gohugoio/hugo (language: go)

Issue:
ERROR TOCSS: failed to transform file after v0.123.1
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### What version of Hugo are you using (`hugo version`)?

<pre>
$ hugo version
hugo v0.123.1-3f8434a62fc91a50f4e5bd43a4435d2d301844ff+extended linux/amd64 BuildDate=2024-02-21T08:17:45Z VendorInfo=gohugoio
</pre>

### Does this issue reproduce with the latest release?
Yes

---

After v0.123.0 (also 0.123.1) we are getting two build failures for our docs:

CI run: https://github.com/twbs/bootstrap/actions/runs/7987176517/job/21809124130?pr=39698

```
1. ERROR TOCSS: failed to transform "/scss/docs.scss" (text/x-scss): "/home/runner/work/bootstrap/bootstrap/site/assets/scss/_variables.scss:17:45": Undefined variable: "$pink-500".
2. ERROR [en] REF_NOT_FOUND: Ref "/docs/5.3/examples/": "/home/runner/work/bootstrap/bootstrap/site/content/docs/5.3/getting-started/rtl.md:68:52": page not found
```

For the second error, the shortcode is this one: https://github.com/twbs/bootstrap/blob/main/site/layouts/shortcodes/docsref.html

v0.122.0 works without errors. Is this due to the [breaking changes](#11455) in v0.123.0 or is it a regression?

Thanks for your hard work!


Discussion / hints:
>due to the [breaking changes](https://github.com/gohugoio/hugo/issues/12094#11455) in v0.123.0 or is it a regression?

A regression.
Should I create a separate issue for the second error?
My comment above is about the ToCSS (which is in the title) error. 

Fix patch:
diff --git a/hugolib/pagecollections.go b/hugolib/pagecollections.go
index 58c646334b4..3783dadab88 100644
--- a/hugolib/pagecollections.go
+++ b/hugolib/pagecollections.go
@@ -56,7 +56,7 @@ func (c *pageFinder) getPageRef(context page.Page, ref string) (page.Page, error
 }
 
 func (c *pageFinder) getPage(context page.Page, ref string) (page.Page, error) {
-	n, err := c.getContentNode(context, false, paths.ToSlashTrimTrailing(ref))
+	n, err := c.getContentNode(context, false, ref)
 	if err != nil {
 		return nil, err
 	}
@@ -121,6 +121,7 @@ func (c *pageFinder) getPageForRefs(ref ...string) (page.Page, error) {
 const defaultContentExt = ".md"
 
 func (c *pageFinder) getContentNode(context page.Page, isReflink bool, ref string) (contentNodeI, error) {
+	ref = paths.ToSlashTrimTrailing(ref)
 	inRef := ref
 	if ref == "" {
 		ref = "/"
diff --git a/resources/transform.go b/resources/transform.go
index 408decbb823..b9cbab8242d 100644
--- a/resources/transform.go
+++ b/resources/transform.go
@@ -446,7 +446,7 @@ func (r *resourceAdapter) transform(key string, publish, setContent bool) (*reso
 	tctx.To = b1
 
 	tctx.InPath = r.target.TargetPath()
-	tctx.SourcePath = tctx.InPath
+	tctx.SourcePath = strings.TrimPrefix(tctx.InPath, "/")
 
 	counter := 0
 	writeToFileCache := false


Test patch:
diff --git a/hugolib/config_test.go b/hugolib/config_test.go
index 14a23a03dff..0d517896fc7 100644
--- a/hugolib/config_test.go
+++ b/hugolib/config_test.go
@@ -854,6 +854,7 @@ Home.
 }
 
 func TestConfigParamSetOnLanguageLevel(t *testing.T) {
+	t.Skip("this has correctly started to fail now.")
 	t.Parallel()
 
 	files := `
diff --git a/hugolib/site_test.go b/hugolib/site_test.go
index 63088ee8829..1de1d688a69 100644
--- a/hugolib/site_test.go
+++ b/hugolib/site_test.go
@@ -992,6 +992,28 @@ func TestRefLinking(t *testing.T) {
 	// TODO: and then the failure cases.
 }
 
+func TestRelRefWithTrailingSlash(t *testing.T) {
+	files := `
+-- hugo.toml --
+-- content/docs/5.3/examples/_index.md --
+---
+title: "Examples"
+---
+-- content/_index.md --
+---
+title: "Home"
+---
+
+Examples: {{< relref "/docs/5.3/examples/" >}}
+-- layouts/home.html --
+Content: {{ .Content }}|
+`
+
+	b := Test(t, files)
+
+	b.AssertFileContent("public/index.html", "Examples: /docs/5.3/examples/")
+}
+
 func checkLinkCase(site *Site, link string, currentPage page.Page, relative bool, outputFormat string, expected string, t *testing.T, i int) {
 	t.Helper()
 	if out, err := site.refLink(link, currentPage, relative, outputFormat); err != nil || out != expected {