Merge pull request #19 from jeswr/feat/strip-unused-prefixes

feat: strip unused prefixes

__tests__/main-test.ts

@@ -4,9 +4,9 @@ import path from 'path';
 import { write } from '../lib';
 import 'jest-rdf';
 
-async function getQuads(file: string) {
+async function getQuads(file: string, _prefixes: Record<string, string> = {}) {
   const parser = new Parser({ rdfStar: true } as any);
-  const prefixes: Record<string, string> = {};
+  const prefixes = { ..._prefixes };
   const quads = parser.parse(fs.readFileSync(path.join(__dirname, '..', 'data', file)).toString(), undefined, (prefix, iri) => {
     prefixes[prefix] = iri.value;
   });
@@ -42,6 +42,30 @@ it('It should correctly write turtle files', async () => {
   }
 });
 
+it('Should should strip unnecessary prefixes', async () => {
+  for (const file of fs.readdirSync(path.join(__dirname, '..', 'data'))) {
+    try {
+      const { string, quads } = await getQuads(file, {
+        alt: 'http://example.alt.org/',
+        v1: 'http://example.v1.org/',
+      });
+
+      if (loose[file]) {
+        // If loose we only need the quads to match when we re-parse the string
+        expect((new Parser()).parse(string)).toBeRdfIsomorphic(quads);
+      } else {
+        // If not loose we expect an exact string match
+        expect(string.replace(/b\d+_/g, '')).toEqual(fs.readFileSync(path.join(__dirname, '..', 'data', file)).toString());
+      }
+    } catch (e: any) {
+      // Suppress errors on {| syntax since N3 cannot parse it for now
+      if (!`${e}`.includes('Unexpected "|"')) {
+        throw e;
+      }
+    }
+  }
+});
+
 it('Should throw error named graphs in quoted and asserted triples', () => {
   expect(write([DataFactory.quad(
     DataFactory.namedNode('s'),

data/bnodes4.ttl

@@ -1,3 +1,2 @@
-@prefix ex: <http://example.com/ns#> .
 
 _:s3 a _:s3 .

data/star-subject.ttl

@@ -1,8 +1,4 @@
 @prefix ex: <http://example.com/ns#> .
 @prefix owl: <http://www.w3.org/2002/07/owl#> .
-@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
-@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
-@prefix sh: <http://www.w3.org/ns/shacl#> .
-@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
 
 <<ex:ssn a owl:Thing>> a <<ex:ssn ex:knows owl:Thing>> .

lib/ttlwriter.ts

@@ -32,10 +32,37 @@ export class TTLWriter {
     writer: Writer,
     prefixes: { [prefix: string]: string } = {},
   ) {
+    const terms: Set<string> = new Set();
+
+    function addTerm(term: RDF.Term) {
+      if (term.termType === 'NamedNode') {
+        terms.add(term.value);
+      } else if (term.termType === 'Quad') {
+        addTerm(term.subject);
+        addTerm(term.predicate);
+        addTerm(term.object);
+        addTerm(term.graph);
+      }
+    }
+
+    for (const list of [
+      this.store.getSubjects(null, null, null),
+      this.store.getPredicates(null, null, null),
+      this.store.getObjects(null, null, null),
+    ]) {
+      for (const node of list) {
+        addTerm(node);
+      }
+    }
+
+    const termList = [...terms];
+
     for (const key of Object.keys(prefixes)) {
-      const iri = prefixes[key];
-      this.prefixRev[iri] = key;
-      this.prefixes[key] = iri;
+      if (termList.some((term) => term.startsWith(prefixes[key]))) {
+        const iri = prefixes[key];
+        this.prefixRev[iri] = key;
+        this.prefixes[key] = iri;
+      }
     }
     this.writer = writer;
   }