fix: Remove metadata content-type assumption from QuadUtil

src/storage/DataAccessorBasedStore.ts

@@ -246,7 +246,7 @@ export class DataAccessorBasedStore implements ResourceStore {
       if (representation.metadata.contentType === INTERNAL_QUADS) {
         quads = await arrayifyStream(representation.data);
       } else {
-        quads = await parseQuads(representation.data);
+        quads = await parseQuads(representation.data, representation.metadata.contentType);
       }
     } catch (error: unknown) {
       if (error instanceof Error) {

src/storage/accessors/FileDataAccessor.ts

@@ -94,7 +94,7 @@ export class FileDataAccessor implements DataAccessor {
     } catch (error: unknown) {
       // Delete the metadata if there was an error writing the file
       if (wroteMetadata) {
-        await fsPromises.unlink(await this.getMetadataPath(link.identifier));
+        await fsPromises.unlink((await this.getMetadataLink(link.identifier)).filePath);
       }
       throw error;
     }
@@ -125,7 +125,7 @@ export class FileDataAccessor implements DataAccessor {
     const stats = await this.getStats(link.filePath);
 
     try {
-      await fsPromises.unlink(await this.getMetadataPath(link.identifier));
+      await fsPromises.unlink((await this.getMetadataLink(link.identifier)).filePath);
     } catch (error: unknown) {
       // Ignore if it doesn't exist
       if (!isSystemError(error) || error.code !== 'ENOENT') {
@@ -161,11 +161,11 @@ export class FileDataAccessor implements DataAccessor {
   }
 
   /**
-   * Generates file path that corresponds to the metadata file of the given identifier.
-   * Starts from the identifier to make sure any potentially added extension has no impact on the path.
+   * Generates ResourceLink that corresponds to the metadata resource of the given identifier.
    */
-  private async getMetadataPath(identifier: ResourceIdentifier): Promise<string> {
-    return (await this.resourceMapper.mapUrlToFilePath({ path: `${identifier.path}.meta` })).filePath;
+  private async getMetadataLink(identifier: ResourceIdentifier): Promise<ResourceLink> {
+    const metaIdentifier = { path: `${identifier.path}.meta` };
+    return this.resourceMapper.mapUrlToFilePath(metaIdentifier);
   }
 
   /**
@@ -213,19 +213,20 @@ export class FileDataAccessor implements DataAccessor {
     metadata.removeAll(RDF.type);
     metadata.removeAll(CONTENT_TYPE);
     const quads = metadata.quads();
-    const metadataPath = await this.getMetadataPath(link.identifier);
+    const metadataLink = await this.getMetadataLink(link.identifier);
     let wroteMetadata: boolean;
 
     // Write metadata to file if there are quads remaining
     if (quads.length > 0) {
-      const serializedMetadata = serializeQuads(quads);
-      await this.writeDataFile(metadataPath, serializedMetadata);
+      // Determine required content-type based on mapper
+      const serializedMetadata = serializeQuads(quads, metadataLink.contentType);
+      await this.writeDataFile(metadataLink.filePath, serializedMetadata);
       wroteMetadata = true;
 
     // Delete (potentially) existing metadata file if no metadata needs to be stored
     } else {
       try {
-        await fsPromises.unlink(metadataPath);
+        await fsPromises.unlink(metadataLink.filePath);
       } catch (error: unknown) {
         // Metadata file doesn't exist so nothing needs to be removed
         if (!isSystemError(error) || error.code !== 'ENOENT') {
@@ -260,13 +261,13 @@ export class FileDataAccessor implements DataAccessor {
    */
   private async getRawMetadata(identifier: ResourceIdentifier): Promise<Quad[]> {
     try {
-      const metadataPath = await this.getMetadataPath(identifier);
+      const metadataLink = await this.getMetadataLink(identifier);
 
       // Check if the metadata file exists first
-      await fsPromises.lstat(metadataPath);
+      await fsPromises.lstat(metadataLink.filePath);
 
-      const readMetadataStream = guardStream(createReadStream(metadataPath));
-      return await parseQuads(readMetadataStream);
+      const readMetadataStream = guardStream(createReadStream(metadataLink.filePath));
+      return await parseQuads(readMetadataStream, metadataLink.contentType);
     } catch (error: unknown) {
       // Metadata file doesn't exist so lets keep `rawMetaData` an empty array.
       if (!isSystemError(error) || error.code !== 'ENOENT') {

src/util/QuadUtil.ts

@@ -3,7 +3,6 @@ import arrayifyStream from 'arrayify-stream';
 import { DataFactory, StreamParser, StreamWriter } from 'n3';
 import type { Literal, NamedNode, Quad } from 'rdf-js';
 import streamifyArray from 'streamify-array';
-import { TEXT_TURTLE } from './ContentTypes';
 import type { Guarded } from './GuardedStream';
 import { pipeSafely } from './StreamUtil';
 
@@ -17,17 +16,19 @@ export const pushQuad =
 /**
  * Helper function for serializing an array of quads, with as result a Readable object.
  * @param quads - The array of quads.
+ * @param contentType - The content-type to serialize to.
  *
  * @returns The Readable object.
  */
-export const serializeQuads = (quads: Quad[]): Guarded<Readable> =>
-  pipeSafely(streamifyArray(quads), new StreamWriter({ format: TEXT_TURTLE }));
+export const serializeQuads = (quads: Quad[], contentType?: string): Guarded<Readable> =>
+  pipeSafely(streamifyArray(quads), new StreamWriter({ format: contentType }));
 
 /**
  * Helper function to convert a Readable into an array of quads.
  * @param readable - The readable object.
+ * @param contentType - The content-type of the stream.
  *
  * @returns A promise containing the array of quads.
  */
-export const parseQuads = async(readable: Guarded<Readable>): Promise<Quad[]> =>
-  arrayifyStream(pipeSafely(readable, new StreamParser({ format: TEXT_TURTLE })));
+export const parseQuads = async(readable: Guarded<Readable>, contentType?: string): Promise<Quad[]> =>
+  arrayifyStream(pipeSafely(readable, new StreamParser({ format: contentType })));

test/unit/util/QuadUtil.test.ts

@@ -1,7 +1,8 @@
 import 'jest-rdf';
 import { DataFactory } from 'n3';
 import type { Quad } from 'rdf-js';
-import { pushQuad } from '../../../src/util/QuadUtil';
+import { parseQuads, pushQuad, serializeQuads } from '../../../src/util/QuadUtil';
+import { guardedStreamFrom, readableToString } from '../../../src/util/StreamUtil';
 
 describe('QuadUtil', (): void => {
   describe('#pushQuad', (): void => {
@@ -13,4 +14,27 @@ describe('QuadUtil', (): void => {
       ]);
     });
   });
+
+  describe('#serializeQuads', (): void => {
+    it('converts quads to the requested format.', async(): Promise<void> => {
+      const quads = [ DataFactory.quad(
+        DataFactory.namedNode('pre:sub'),
+        DataFactory.namedNode('pre:pred'),
+        DataFactory.literal('obj'),
+      ) ];
+      const stream = serializeQuads(quads, 'application/n-triples');
+      await expect(readableToString(stream)).resolves.toMatch('<pre:sub> <pre:pred> "obj" .');
+    });
+  });
+
+  describe('#parseQuads', (): void => {
+    it('parses quads from the requested format.', async(): Promise<void> => {
+      const stream = guardedStreamFrom([ '<pre:sub> <pre:pred> "obj".' ]);
+      await expect(parseQuads(stream, 'application/n-triples')).resolves.toEqualRdfQuadArray([ DataFactory.quad(
+        DataFactory.namedNode('pre:sub'),
+        DataFactory.namedNode('pre:pred'),
+        DataFactory.literal('obj'),
+      ) ]);
+    });
+  });
 });