Avoid duplicate xsl:import statements

Fixed whitespace
Added HTTP test

Author: namedgraph

http-tests/admin/packages/install-package-stylesheet-no-duplicate.sh

@@ -0,0 +1,60 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+initialize_dataset "$END_USER_BASE_URL" "$TMP_END_USER_DATASET" "$END_USER_ENDPOINT_URL"
+initialize_dataset "$ADMIN_BASE_URL" "$TMP_ADMIN_DATASET" "$ADMIN_ENDPOINT_URL"
+purge_cache "$END_USER_VARNISH_SERVICE"
+purge_cache "$ADMIN_VARNISH_SERVICE"
+purge_cache "$FRONTEND_VARNISH_SERVICE"
+
+# Clean up any leftover package stylesheet files from previous test runs
+docker compose exec -T linkeddatahub rm -rf /usr/local/tomcat/webapps/ROOT/static/com/linkeddatahub/packages/skos 2>/dev/null || true
+docker compose exec -T linkeddatahub sed -i '/linkeddatahub\/packages\/skos\/layout.xsl/d' /usr/local/tomcat/webapps/ROOT/static/xsl/layout.xsl 2>/dev/null || true
+
+# Tomcat caches static files with default cacheTtl=5000ms (5 seconds)
+# See: https://tomcat.apache.org/tomcat-10.1-doc/config/resources.html#Attributes
+default_ttl=5
+
+# test package URI (SKOS package)
+package_uri="https://packages.linkeddatahub.com/skos/#this"
+
+# first install
+install-package.sh \
+  -b "$END_USER_BASE_URL" \
+  -f "$OWNER_CERT_FILE" \
+  -p "$OWNER_CERT_PWD" \
+  --package "$package_uri"
+
+# Wait for Tomcat's static resource cache to expire
+sleep $default_ttl
+
+# verify exactly one import after first install
+import_count=$(curl -k -s "${END_USER_BASE_URL}static/xsl/layout.xsl" \
+  | grep -c "com/linkeddatahub/packages/skos/layout.xsl" || true)
+if [ "$import_count" -ne 1 ]; then
+  exit 1
+fi
+
+# second install (same package)
+install-package.sh \
+  -b "$END_USER_BASE_URL" \
+  -f "$OWNER_CERT_FILE" \
+  -p "$OWNER_CERT_PWD" \
+  --package "$package_uri"
+
+# Wait for Tomcat's static resource cache to expire
+sleep $default_ttl
+
+# verify still exactly one import after second install (deduplication guard)
+import_count=$(curl -k -s "${END_USER_BASE_URL}static/xsl/layout.xsl" \
+  | grep -c "com/linkeddatahub/packages/skos/layout.xsl" || true)
+if [ "$import_count" -ne 1 ]; then
+  exit 1
+fi
+
+# cleanup
+uninstall-package.sh \
+  -b "$END_USER_BASE_URL" \
+  -f "$OWNER_CERT_FILE" \
+  -p "$OWNER_CERT_PWD" \
+  --package "$package_uri"

src/main/java/com/atomgraph/linkeddatahub/server/util/XSLTMasterUpdater.java

@@ -89,7 +89,7 @@ public void addPackageImport(Path masterFile, String packagePath) throws IOExcep
             Element stylesheet = doc.getDocumentElement();
             String href = "../" + packagePath + "/layout.xsl";
 
-            // Find the last xsl:import child element as insertion anchor
+            // Find the last xsl:import child element as insertion anchor, checking for duplicates
             Node lastImport = null;
             NodeList children = stylesheet.getChildNodes();
             for (int i = 0; i < children.getLength(); i++)
@@ -98,24 +98,32 @@ public void addPackageImport(Path masterFile, String packagePath) throws IOExcep
                 if (child.getNodeType() == Node.ELEMENT_NODE
                         && XSL_NS.equals(child.getNamespaceURI())
                         && "import".equals(child.getLocalName()))
+                {
+                    if (href.equals(((Element) child).getAttribute("href")))
+                    {
+                        if (log.isWarnEnabled()) log.warn("xsl:import href=\"{}\" already present in master stylesheet, skipping", href);
+                        return;
+                    }
                     lastImport = child;
+                }
             }
 
             Element newImport = doc.createElementNS(XSL_NS, "xsl:import");
             newImport.setAttribute("href", href);
 
             if (lastImport != null)
             {
-                // Insert after the last import (before its next sibling)
-                stylesheet.insertBefore(doc.createTextNode("\n    "), lastImport.getNextSibling());
-                stylesheet.insertBefore(newImport, lastImport.getNextSibling());
+                // Capture anchor before any insertion — getNextSibling() shifts after insertBefore
+                Node anchor = lastImport.getNextSibling();
+                stylesheet.insertBefore(newImport, anchor);
+                stylesheet.insertBefore(doc.createTextNode("\n    "), newImport);
             }
             else
             {
                 // No existing imports — prepend at start of stylesheet
                 Node firstChild = stylesheet.getFirstChild();
                 stylesheet.insertBefore(newImport, firstChild);
-                stylesheet.insertBefore(doc.createTextNode("\n    "), newImport.getNextSibling());
+                stylesheet.insertBefore(doc.createTextNode("\n    "), newImport);
             }
 
             serializeDocument(doc, masterFile);