fix: Sort preferences by descending weight.

src/storage/RepresentationConvertingStore.ts

@@ -84,16 +84,19 @@ export class RepresentationConvertingStore<T extends ResourceStore = ResourceSto
    * Helper function that converts a Representation using the given args and converter,
    * if the conversion is necessary and there is a converter.
    */
-  private async convertRepresentation(args: RepresentationConverterArgs, converter?: RepresentationConverter):
+  private async convertRepresentation(input: RepresentationConverterArgs, converter?: RepresentationConverter):
   Promise<Representation> {
-    if (!converter || !args.preferences.type || this.matchesPreferences(args.representation, args.preferences)) {
-      return args.representation;
+    if (!converter || !input.preferences.type || this.matchesPreferences(input.representation, input.preferences)) {
+      return input.representation;
     }
+    this.logger.debug(`Conversion needed for ${input.identifier
+      .path} from ${input.representation.metadata.contentType} to satisfy ${input.preferences.type
+      .map((pref): string => `${pref.value};q=${pref.weight}`).join(', ')}`);
 
-    const typeStr = args.preferences.type.map((pref): string => `${pref.value};q=${pref.weight}`).join(', ');
-    this.logger.info(`Convert ${args.identifier.path} from ${args.representation.metadata.contentType} to ${typeStr}`);
-
-    return converter.handleSafe(args);
+    const converted = await converter.handleSafe(input);
+    this.logger.info(`Converted representation for ${input.identifier
+      .path} from ${input.representation.metadata.contentType} to ${converted.metadata.contentType}`);
+    return converted;
   }
 
   /**

src/storage/conversion/ConversionUtil.ts

@@ -54,7 +54,10 @@ RepresentationPreference[] => {
     return { value: type, weight };
   });
 
-  return weightedSupported.filter((preference): boolean => preference.weight !== 0);
+  // Return all non-zero preferences in descending order of weight
+  return weightedSupported
+    .filter((pref): boolean => pref.weight !== 0)
+    .sort((prefA, prefB): number => prefB.weight - prefA.weight);
 };
 
 /**

test/unit/storage/RepresentationConvertingStore.test.ts

@@ -11,6 +11,8 @@ describe('A RepresentationConvertingStore', (): void => {
   let source: ResourceStore;
   let inConverter: RepresentationConverter;
   let outConverter: RepresentationConverter;
+  const convertedIn = { metadata: {}};
+  const convertedOut = { metadata: {}};
   const inType = 'text/turtle';
   const metadata = new RepresentationMetadata({ [CONTENT_TYPE]: 'text/turtle' });
   let representation: Representation;
@@ -22,8 +24,8 @@ describe('A RepresentationConvertingStore', (): void => {
       setRepresentation: jest.fn(),
     } as any;
 
-    inConverter = { handleSafe: jest.fn(async(): Promise<any> => 'inConvert') } as any;
-    outConverter = { handleSafe: jest.fn(async(): Promise<any> => 'outConvert') } as any;
+    inConverter = { handleSafe: jest.fn(async(): Promise<any> => convertedIn) } as any;
+    outConverter = { handleSafe: jest.fn(async(): Promise<any> => convertedOut) } as any;
 
     store = new RepresentationConvertingStore(source, { inType, inConverter, outConverter });
     representation = { binary: true, data: 'data', metadata } as any;
@@ -64,7 +66,7 @@ describe('A RepresentationConvertingStore', (): void => {
   it('calls the converter if another output is preferred.', async(): Promise<void> => {
     await expect(store.getRepresentation({ path: 'path' }, { type: [
       { value: 'text/plain', weight: 1 }, { value: 'text/turtle', weight: 0 },
-    ]})).resolves.toEqual('outConvert');
+    ]})).resolves.toEqual(convertedOut);
     expect(source.getRepresentation).toHaveBeenCalledTimes(1);
     expect(outConverter.handleSafe).toHaveBeenCalledTimes(1);
     expect(outConverter.handleSafe).toHaveBeenLastCalledWith({
@@ -95,11 +97,11 @@ describe('A RepresentationConvertingStore', (): void => {
 
     await expect(store.addResource(id, representation, 'conditions' as any)).resolves.toBeUndefined();
     expect(inConverter.handleSafe).toHaveBeenCalledTimes(1);
-    expect(source.addResource).toHaveBeenLastCalledWith(id, 'inConvert', 'conditions');
+    expect(source.addResource).toHaveBeenLastCalledWith(id, convertedIn, 'conditions');
 
     await expect(store.setRepresentation(id, representation, 'conditions' as any)).resolves.toBeUndefined();
     expect(inConverter.handleSafe).toHaveBeenCalledTimes(2);
-    expect(source.setRepresentation).toHaveBeenLastCalledWith(id, 'inConvert', 'conditions');
+    expect(source.setRepresentation).toHaveBeenLastCalledWith(id, convertedIn, 'conditions');
   });
 
   it('throws an error if no content-type is provided.', async(): Promise<void> => {

test/unit/storage/conversion/ConversionUtil.test.ts

@@ -62,6 +62,13 @@ describe('ConversionUtil', (): void => {
       expect(matchingMediaTypes(preferences, [ 'b/x', 'c/x' ])).toEqual([{ value: 'b/x', weight: 0.5 }]);
     });
 
+    it('sorts by descending weight.', async(): Promise<void> => {
+      const preferences: RepresentationPreferences = { type:
+          [{ value: 'a/x', weight: 1 }, { value: 'b/x', weight: 0.5 }, { value: 'c/x', weight: 0.8 }]};
+      expect(matchingMediaTypes(preferences, [ 'a/x', 'b/x', 'c/x' ]))
+        .toEqual([{ value: 'a/x', weight: 1 }, { value: 'c/x', weight: 0.8 }, { value: 'b/x', weight: 0.5 }]);
+    });
+
     it('errors if there are duplicate preferences.', async(): Promise<void> => {
       const preferences: RepresentationPreferences =
         { type: [{ value: 'b/x', weight: 1 }, { value: 'b/x', weight: 0 }]};