From f772998fa34927f469c70b83acdc72b62895d13e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Pedersen?=
 <bjorn.erik.pedersen@gmail.com>
Date: Mon, 10 Aug 2026 18:10:06 +0200
Subject: [PATCH] Fix resource transformation chaining after content access

When a transformed resource had been initialized (e.g. via .Data, .Content
or .RelPermalink) before chaining another transformation, the new chain
would run on the transformed output instead of the original source,
re-running all transformations on their own output.

Fixes #15189

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
---
 resources/transform.go            | 10 ++++++-
 tpl/css/build_integration_test.go | 43 +++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/resources/transform.go b/resources/transform.go
index 18c768b36..cee11f8ba 100644
--- a/resources/transform.go
+++ b/resources/transform.go
@@ -82,6 +82,7 @@ func newResourceAdapter(spec *Spec, lazyPublish bool, target transformableResour
 	return &resourceAdapter{
 		resourceTransformations: &resourceTransformations{},
 		metaProvider:            target,
+		sourceTarget:            target,
 		resourceAdapterInner: &resourceAdapterInner{
 			ctx:         context.Background(),
 			spec:        spec,
@@ -186,6 +187,12 @@ type resourceAdapter struct {
 	commonResource
 	*resourceTransformations
 	*resourceAdapterInner
+
+	// The original untransformed target. The inner target is replaced with the
+	// transformed resource once the transformation chain has run, so any new
+	// transformations appended to the chain must start from this.
+	sourceTarget transformableResource
+
 	metaProvider resource.ResourceMetaProvider
 }
 
@@ -230,6 +237,7 @@ func (r *resourceAdapter) GetDependencyManager() identity.Manager {
 
 func (r resourceAdapter) cloneTo(targetPath string) resource.Resource {
 	newtTarget := r.target.cloneTo(targetPath)
+	r.sourceTarget = newtTarget.(transformableResource)
 	newInner := &resourceAdapterInner{
 		ctx:    r.ctx,
 		spec:   r.spec,
@@ -379,7 +387,7 @@ func (r resourceAdapter) TransformWithContext(ctx context.Context, t ...Resource
 		spec:        r.spec,
 		Staler:      r.Staler,
 		publishOnce: &publishOnce{},
-		target:      r.target,
+		target:      r.sourceTarget,
 	}
 
 	return &r, nil
diff --git a/tpl/css/build_integration_test.go b/tpl/css/build_integration_test.go
index 6ddb23331..e72a1bb03 100644
--- a/tpl/css/build_integration_test.go
+++ b/tpl/css/build_integration_test.go
@@ -537,6 +537,49 @@ ARTIFACT: {{ .RelPermalink }}|{{ .Permalink }}|{{ .MediaType.Type }}
 	b.AssertFileExists("public/css/main.css.map", true)
 }
 
+func TestCSSBuildDataArtifactsAndThenFingerprint(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.org/mysite/"
+disableKinds = ['page','rss','section','sitemap','taxonomy','term']
+-- assets/css/main.css --
+@import "/fonts/fonts.css";
+body { color: #222; }
+-- assets/fonts/fonts.css --
+@font-face {
+  font-family: 'Comic Neue';
+  src: url(ComicNeue-Regular.woff2) format('woff2'), url(ComicNeue-Regular.ttf) format('truetype');
+}
+-- assets/fonts/ComicNeue-Regular.ttf --
+fakefontdata
+-- assets/fonts/ComicNeue-Regular.woff2 --
+fakefontdata2
+-- layouts/home.html --
+{{ with resources.Get "css/main.css" }}
+ORIG CSS SHA256: {{ .Content | crypto.Hash "sha256" }}|
+{{ with . | css.Build (dict "minify" true) }}
+{{ range .Data.Artifacts }}
+ARTIFACT: {{ .RelPermalink }}|{{ .Permalink }}|{{ .MediaType.Type }}
+{{ end }}
+BUILT CSS SHA256: {{ .Content | crypto.Hash "sha256" }}|
+{{ with . | fingerprint }}
+FINGERPRINTED: {{ .RelPermalink }}|
+{{ end }}
+{{ end }}
+{{ end }}
+`
+
+	b := hugolib.Test(t, files, hugolib.TestOptOsFs())
+	b.AssertFileContent("public/index.html",
+		"ARTIFACT: /mysite/css/ComicNeue-Regular-UA4ODE7N.ttf|",
+		"ORIG CSS SHA256: a2b878c05df0f346c3854caebd21f00bb0965b46628440b8ccb31ce675af6bfe|",
+		"BUILT CSS SHA256: 5f8757d5579386b8755e0df759c7eecfd069c385294dfe7bc3695862d7f218b1|",
+		"FINGERPRINTED: /mysite/css/main.5f8757d5579386b8755e0df759c7eecfd069c385294dfe7bc3695862d7f218b1.css|",
+	)
+}
+
 // Issue #14623
 func TestCSSBuildLoadersPartial(t *testing.T) {
 	t.Parallel()