fix: N3 PATCH semicolon shorthand and 'a' keyword not parsed

melvincarvalho · melvincarvalho · commit 39b8bdaeec13 · 2026-03-16T06:39:12.000+01:00
The N3 parser split on semicolons (Turtle shorthand for same subject, different predicate) but dropped the subject for continuation statements. Statements with only predicate-object were silently discarded as they had fewer than 3 tokens. Also handle the 'a' keyword as rdf:type shorthand. Fixes JavaScriptSolidServer#212
diff --git a/src/patch/n3-patch.js b/src/patch/n3-patch.js
@@ -57,6 +57,7 @@ export function parseN3Patch(patchText, baseUri) {
 
 /**
  * Parse triples from N3 block content
+ * Handles Turtle semicolon shorthand (same subject, different predicate-object)
  */
 function parseTriples(content, prefixes, baseUri) {
   const triples = [];
@@ -68,11 +69,37 @@ function parseTriples(content, prefixes, baseUri) {
   // Split by '.' but be careful with strings containing '.'
   const statements = splitStatements(content);
 
+  let lastSubject = null;
   for (const stmt of statements) {
-    const triple = parseStatement(stmt.trim(), prefixes, baseUri);
-    if (triple) {
-      triples.push(triple);
+    const trimmed = stmt.trim();
+    if (!trimmed) continue;
+
+    const tokens = tokenize(trimmed);
+    if (tokens.length < 2) continue;
+
+    let subject, predicate, object;
+
+    if (tokens.length >= 3) {
+      // Full triple: subject predicate object
+      subject = resolveValue(tokens[0], prefixes, baseUri);
+      predicate = resolveValue(tokens[1], prefixes, baseUri);
+      object = resolveValue(tokens.slice(2).join(' '), prefixes, baseUri);
+      lastSubject = subject;
+    } else if (tokens.length === 2 && lastSubject) {
+      // Semicolon continuation: predicate object (reuse last subject)
+      subject = lastSubject;
+      predicate = resolveValue(tokens[0], prefixes, baseUri);
+      object = resolveValue(tokens[1], prefixes, baseUri);
+    } else {
+      continue;
+    }
+
+    // Handle 'a' as rdf:type
+    if (predicate === 'a') {
+      predicate = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type';
     }
+
+    triples.push({ subject, predicate, object });
   }
 
   return triples;
@@ -121,23 +148,6 @@ function splitStatements(content) {
   return statements;
 }
 
-/**
- * Parse a single N3 statement into a triple
- */
-function parseStatement(stmt, prefixes, baseUri) {
-  if (!stmt) return null;
-
-  // Tokenize - split by whitespace but respect quotes
-  const tokens = tokenize(stmt);
-  if (tokens.length < 3) return null;
-
-  const subject = resolveValue(tokens[0], prefixes, baseUri);
-  const predicate = resolveValue(tokens[1], prefixes, baseUri);
-  const object = resolveValue(tokens.slice(2).join(' '), prefixes, baseUri);
-
-  return { subject, predicate, object };
-}
-
 /**
  * Tokenize a statement respecting quoted strings
  */
@@ -430,6 +440,7 @@ function convertToJsonLd(object) {
  * Expand a potentially prefixed predicate to full URI
  */
 function expandPredicate(predicate) {
+  if (predicate === 'a') return 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type';
   const commonPrefixes = {
     'solid': SOLID_NS,
     'rdf': 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
diff --git a/test/patch.test.js b/test/patch.test.js
@@ -185,6 +185,52 @@ describe('PATCH Operations', () => {
       assert.ok(data['@graph'], 'Should have @graph');
       assert.strictEqual(data['@graph'].length, 2, 'Should have 2 nodes');
     });
+
+    it('should handle semicolon shorthand and rdf:type "a" keyword', async () => {
+      // Create initial resource with @graph
+      const initial = {
+        '@context': { 'solid': 'http://www.w3.org/ns/solid/terms#' },
+        '@graph': []
+      };
+
+      await request('/patchtest/public/patch-semicolon.json', {
+        method: 'PUT',
+        headers: { 'Content-Type': 'application/ld+json' },
+        body: JSON.stringify(initial),
+        auth: 'patchtest'
+      });
+
+      // Use semicolons and 'a' keyword (Turtle shorthand)
+      const patch = `
+        @prefix solid: <http://www.w3.org/ns/solid/terms#>.
+        @prefix wf: <http://www.w3.org/2005/01/wf/flow#>.
+        _:patch a solid:InsertDeletePatch;
+          solid:inserts {
+            <#reg1> a solid:TypeRegistration;
+              solid:forClass wf:Tracker;
+              solid:instance <https://example.com/todo/data.jsonld#this>.
+          }.
+      `;
+
+      const res = await request('/patchtest/public/patch-semicolon.json', {
+        method: 'PATCH',
+        headers: { 'Content-Type': 'text/n3' },
+        body: patch,
+        auth: 'patchtest'
+      });
+
+      assertStatus(res, 204);
+
+      // Verify all three triples were inserted
+      const verify = await request('/patchtest/public/patch-semicolon.json');
+      const data = await verify.json();
+      const node = data['@graph'].find(n => n['@id'] && n['@id'].includes('#reg1'));
+      assert.ok(node, 'Should have the reg1 node');
+      assert.ok(node['rdf:type'] || node['http://www.w3.org/1999/02/22-rdf-syntax-ns#type'],
+        'Should have rdf:type (from "a" keyword)');
+      assert.ok(node['solid:forClass'], 'Should have solid:forClass');
+      assert.ok(node['solid:instance'], 'Should have solid:instance');
+    });
   });
 
   describe('PATCH Error Handling', () => {
