resources: Fix the :counter placeholder

Closes #14921

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

hugolib/content_map_page.go

@@ -652,8 +652,9 @@ func (m *pageMap) getOrCreateResourcesForPage(ps *pageState) resource.Resources
 		sort.SliceStable(res, lessFunc)
 
 		if len(ps.m.pageConfig.ResourcesMeta) > 0 {
+			counters := make(map[string]int)
 			for i, r := range res {
-				res[i] = resources.CloneWithMetadataFromMapIfNeeded(ps.m.pageConfig.ResourcesMeta, r)
+				res[i] = resources.CloneWithMetadataFromMapIfNeeded(ps.m.pageConfig.ResourcesMeta, r, counters)
 			}
 			sort.SliceStable(res, lessFunc)
 		}

hugolib/page_resource_metadata_test.go

@@ -0,0 +1,58 @@
+// Copyright 2026 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 hugolib
+
+import (
+	"testing"
+)
+
+// Issue 14921
+func TestResourceMetaCounterPlaceholder(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['home','rss','section','sitemap','taxonomy','term']
+-- content/p1/index.md --
+---
+title: p1
+resources:
+  - src: "*specs.pdf"
+    title: "Specification #:counter"
+  - src: "**.pdf"
+    name: "pdf-file-:counter.pdf"
+---
+-- content/p1/checklist.pdf --
+-- content/p1/guide.pdf --
+-- content/p1/other_specs.pdf --
+-- content/p1/photo_specs.pdf --
+-- layouts/page.html --
+<ul>
+	{{- range seq 1 4 }}
+		{{- with $.Resources.Get (printf "pdf-file-%d.pdf" .) }}
+			<li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
+		{{- end }}
+	{{- end }}
+</ul>
+`
+
+	b := Test(t, files)
+
+	b.AssertFileContent("public/p1/index.html",
+		`<a href="/p1/checklist.pdf">checklist.pdf</a>`,
+		`<a href="/p1/guide.pdf">guide.pdf</a>`,
+		`<a href="/p1/other_specs.pdf">Specification #1</a>`,
+		`<a href="/p1/photo_specs.pdf">Specification #2</a>`,
+	)
+}

resources/resource_metadata.go

@@ -119,7 +119,8 @@ func cloneWithMetadataFromResourceConfigIfNeeded(rc *pagemeta.ResourceConfig, r
 }
 
 // CloneWithMetadataFromMapIfNeeded clones the given resource with the given metadata if the resource supports it.
-func CloneWithMetadataFromMapIfNeeded(m []map[string]any, r resource.Resource) resource.Resource {
+// The counters map is shared across all resources in a bundle so that the :counter placeholder increments correctly.
+func CloneWithMetadataFromMapIfNeeded(m []map[string]any, r resource.Resource, counters map[string]int) resource.Resource {
 	wmp, ok := r.(resource.WithResourceMetaProvider)
 	if !ok {
 		return r
@@ -131,7 +132,7 @@ func CloneWithMetadataFromMapIfNeeded(m []map[string]any, r resource.Resource) r
 		params: r.Params(),
 	}
 
-	assignMetadata(m, wrapped)
+	assignMetadata(m, wrapped, counters)
 	if !wrapped.changed {
 		return r
 	}
@@ -144,9 +145,7 @@ func CloneWithMetadataFromMapIfNeeded(m []map[string]any, r resource.Resource) r
 // This assignment is additive, but the most specific match needs to be first.
 // The `name` and `title` metadata field support shell-matched collection it got a match in.
 // See https://golang.org/pkg/path/#Match
-func assignMetadata(metadata []map[string]any, ma *metaResource) error {
-	counters := make(map[string]int)
-
+func assignMetadata(metadata []map[string]any, ma *metaResource, counters map[string]int) error {
 	var (
 		nameSet, titleSet                   bool
 		nameCounter, titleCounter           = 0, 0