fix: Have AsyncHandlers only check what is necessary

src/ldp/http/BasicRequestParser.ts

@@ -28,20 +28,18 @@ export class BasicRequestParser extends RequestParser {
     Object.assign(this, args);
   }
 
-  public async canHandle(input: HttpRequest): Promise<void> {
-    if (!input.url) {
-      throw new Error('Missing URL.');
-    }
-    if (!input.method) {
-      throw new Error('Missing method.');
-    }
+  public async canHandle(): Promise<void> {
+    // Can handle all requests
   }
 
   public async handle(input: HttpRequest): Promise<Operation> {
+    if (!input.method) {
+      throw new Error('Missing method.');
+    }
     const target = await this.targetExtractor.handleSafe(input);
     const preferences = await this.preferenceParser.handleSafe(input);
     const body = await this.bodyParser.handleSafe(input);
 
-    return { method: input.method!, target, preferences, body };
+    return { method: input.method, target, preferences, body };
   }
 }

src/ldp/http/BasicResponseWriter.ts

@@ -10,10 +10,8 @@ import { ResponseWriter } from './ResponseWriter';
  */
 export class BasicResponseWriter extends ResponseWriter {
   public async canHandle(input: { response: HttpResponse; result: ResponseDescription | Error }): Promise<void> {
-    if (!(input.result instanceof Error)) {
-      if (input.result.body && !input.result.body.binary) {
-        throw new UnsupportedHttpError('Only binary results are supported.');
-      }
+    if (!(input.result instanceof Error) && input.result.body && !input.result.body.binary) {
+      throw new UnsupportedHttpError('Only binary results and errors are supported.');
     }
   }
 

src/ldp/http/BasicTargetExtractor.ts

@@ -10,16 +10,17 @@ import { TargetExtractor } from './TargetExtractor';
  * TODO: input requires more extensive cleaning/parsing based on headers (see #22).
  */
 export class BasicTargetExtractor extends TargetExtractor {
-  public async canHandle(input: HttpRequest): Promise<void> {
+  public async canHandle(): Promise<void> {
+    // Can handle all URLs
+  }
+
+  public async handle(input: HttpRequest): Promise<ResourceIdentifier> {
     if (!input.url) {
       throw new Error('Missing URL.');
     }
     if (!input.headers.host) {
       throw new Error('Missing host.');
     }
-  }
-
-  public async handle(input: HttpRequest): Promise<ResourceIdentifier> {
     const isHttps = input.connection && (input.connection as TLSSocket).encrypted;
     const url = format({
       protocol: `http${isHttps ? 's' : ''}`,

src/ldp/http/RawBodyParser.ts

@@ -27,7 +27,7 @@ export class RawBodyParser extends BodyParser {
     // While RFC7231 allows treating a body without content type as an octet stream,
     // such an omission likely signals a mistake, so force clients to make this explicit.
     if (!input.headers['content-type']) {
-      throw new Error('An HTTP request body was passed without Content-Type header');
+      throw new UnsupportedHttpError('An HTTP request body was passed without Content-Type header');
     }
 
     return {

src/ldp/http/SparqlUpdateBodyParser.ts

@@ -1,6 +1,7 @@
 import { PassThrough } from 'stream';
 import { translate } from 'sparqlalgebrajs';
 import type { HttpRequest } from '../../server/HttpRequest';
+import { APPLICATION_SPARQL_UPDATE } from '../../util/ContentTypes';
 import { UnsupportedHttpError } from '../../util/errors/UnsupportedHttpError';
 import { UnsupportedMediaTypeHttpError } from '../../util/errors/UnsupportedMediaTypeHttpError';
 import { CONTENT_TYPE } from '../../util/UriConstants';
@@ -16,9 +17,7 @@ import type { SparqlUpdatePatch } from './SparqlUpdatePatch';
  */
 export class SparqlUpdateBodyParser extends BodyParser {
   public async canHandle(input: HttpRequest): Promise<void> {
-    const contentType = input.headers['content-type'];
-
-    if (!contentType || contentType !== 'application/sparql-update') {
+    if (input.headers['content-type'] !== APPLICATION_SPARQL_UPDATE) {
       throw new UnsupportedMediaTypeHttpError('This parser only supports SPARQL UPDATE data.');
     }
   }
@@ -35,7 +34,7 @@ export class SparqlUpdateBodyParser extends BodyParser {
       const sparql = await readableToString(toAlgebraStream);
       const algebra = translate(sparql, { quads: true });
 
-      const metadata = new RepresentationMetadata({ [CONTENT_TYPE]: 'application/sparql-update' });
+      const metadata = new RepresentationMetadata({ [CONTENT_TYPE]: APPLICATION_SPARQL_UPDATE });
 
       // Prevent body from being requested again
       return {

src/ldp/operations/PostOperationHandler.ts

@@ -20,13 +20,13 @@ export class PostOperationHandler extends OperationHandler {
     if (input.method !== 'POST') {
       throw new UnsupportedHttpError('This handler only supports POST operations.');
     }
-    if (!input.body) {
-      throw new UnsupportedHttpError('POST operations require a body.');
-    }
   }
 
   public async handle(input: Operation): Promise<ResponseDescription> {
-    const identifier = await this.store.addResource(input.target, input.body!);
+    if (!input.body) {
+      throw new UnsupportedHttpError('POST operations require a body.');
+    }
+    const identifier = await this.store.addResource(input.target, input.body);
     return { identifier };
   }
 }

src/storage/conversion/ChainedConverter.ts

@@ -1,8 +1,6 @@
 import type { Representation } from '../../ldp/representation/Representation';
-import { RepresentationMetadata } from '../../ldp/representation/RepresentationMetadata';
-import type { RepresentationPreferences } from '../../ldp/representation/RepresentationPreferences';
-import { CONTENT_TYPE } from '../../util/UriConstants';
 import { matchingMediaType } from '../../util/Util';
+import { checkRequest } from './ConversionUtil';
 import type { RepresentationConverterArgs } from './RepresentationConverter';
 import { TypedRepresentationConverter } from './TypedRepresentationConverter';
 
@@ -44,18 +42,14 @@ export class ChainedConverter extends TypedRepresentationConverter {
 
   public async canHandle(input: RepresentationConverterArgs): Promise<void> {
     // We assume a chain can be constructed, otherwise there would be a configuration issue
-    // Check if the first converter can handle the input
-    const firstChain = await this.getMatchingType(this.converters[0], this.converters[1]);
-    const preferences: RepresentationPreferences = { type: [{ value: firstChain, weight: 1 }]};
-    await this.first.canHandle({ ...input, preferences });
+    // So we only check if the input can be parsed and the preferred type can be written
+    const inTypes = this.filterTypes(await this.first.getInputTypes());
+    const outTypes = this.filterTypes(await this.last.getOutputTypes());
+    checkRequest(input, inTypes, outTypes);
+  }
 
-    // Check if the last converter can produce the output
-    const idx = this.converters.length - 1;
-    const lastChain = await this.getMatchingType(this.converters[idx - 1], this.converters[idx]);
-    const oldMeta = input.representation.metadata;
-    const metadata = new RepresentationMetadata(oldMeta, { [CONTENT_TYPE]: lastChain });
-    const representation: Representation = { ...input.representation, metadata };
-    await this.last.canHandle({ ...input, representation });
+  private filterTypes(typeVals: { [contentType: string]: number }): string[] {
+    return Object.keys(typeVals).filter((name): boolean => typeVals[name] > 0);
   }
 
   public async handle(input: RepresentationConverterArgs): Promise<Representation> {

src/util/ContentTypes.ts

@@ -1,6 +1,7 @@
 // Well-known content types
 export const TEXT_TURTLE = 'text/turtle';
 export const APPLICATION_OCTET_STREAM = 'application/octet-stream';
+export const APPLICATION_SPARQL_UPDATE = 'application/sparql-update';
 
 // Internal (non-exposed) content types
 export const INTERNAL_QUADS = 'internal/quads';

test/unit/ldp/http/BasicRequestParser.test.ts

@@ -17,16 +17,12 @@ describe('A BasicRequestParser', (): void => {
     requestParser = new BasicRequestParser({ targetExtractor, bodyParser, preferenceParser });
   });
 
-  it('can handle input with both a URL and a method.', async(): Promise<void> => {
-    await expect(requestParser.canHandle({ url: 'url', method: 'GET' } as any)).resolves.toBeUndefined();
+  it('can handle any input.', async(): Promise<void> => {
+    await expect(requestParser.canHandle()).resolves.toBeUndefined();
   });
 
-  it('rejects input with no URL.', async(): Promise<void> => {
-    await expect(requestParser.canHandle({ method: 'GET' } as any)).rejects.toThrow('Missing URL.');
-  });
-
-  it('rejects input with no method.', async(): Promise<void> => {
-    await expect(requestParser.canHandle({ url: 'url' } as any)).rejects.toThrow('Missing method.');
+  it('errors if there is no input.', async(): Promise<void> => {
+    await expect(requestParser.handle({ url: 'url' } as any)).rejects.toThrow('Missing method.');
   });
 
   it('returns the output of all input parsers after calling handle.', async(): Promise<void> => {

test/unit/ldp/http/BasicTargetExtractor.test.ts

@@ -3,16 +3,16 @@ import { BasicTargetExtractor } from '../../../../src/ldp/http/BasicTargetExtrac
 describe('A BasicTargetExtractor', (): void => {
   const extractor = new BasicTargetExtractor();
 
-  it('can handle input with an URL and host.', async(): Promise<void> => {
-    await expect(extractor.canHandle({ url: 'url', headers: { host: 'test.com' }} as any)).resolves.toBeUndefined();
+  it('can handle any input.', async(): Promise<void> => {
+    await expect(extractor.canHandle()).resolves.toBeUndefined();
   });
 
-  it('rejects input without URL.', async(): Promise<void> => {
-    await expect(extractor.canHandle({ headers: { host: 'test.com' }} as any)).rejects.toThrow('Missing URL.');
+  it('errors if there is no URL.', async(): Promise<void> => {
+    await expect(extractor.handle({ headers: { host: 'test.com' }} as any)).rejects.toThrow('Missing URL.');
   });
 
-  it('rejects input without host.', async(): Promise<void> => {
-    await expect(extractor.canHandle({ url: 'url', headers: {}} as any)).rejects.toThrow('Missing host.');
+  it('errors if there is no host.', async(): Promise<void> => {
+    await expect(extractor.handle({ url: 'url', headers: {}} as any)).rejects.toThrow('Missing host.');
   });
 
   it('returns the input URL.', async(): Promise<void> => {

test/unit/ldp/operations/PostOperationHandler.test.ts

@@ -10,12 +10,15 @@ describe('A PostOperationHandler', (): void => {
   } as unknown as ResourceStore;
   const handler = new PostOperationHandler(store);
 
-  it('only supports POST operations with a body.', async(): Promise<void> => {
+  it('only supports POST operations.', async(): Promise<void> => {
     await expect(handler.canHandle({ method: 'POST', body: { }} as Operation))
       .resolves.toBeUndefined();
     await expect(handler.canHandle({ method: 'GET', body: { }} as Operation))
       .rejects.toThrow(UnsupportedHttpError);
-    await expect(handler.canHandle({ method: 'POST' } as Operation)).rejects.toThrow(UnsupportedHttpError);
+  });
+
+  it('errors if there is no body.', async(): Promise<void> => {
+    await expect(handler.handle({ method: 'POST' } as Operation)).rejects.toThrow(UnsupportedHttpError);
   });
 
   it('adds the given representation to the store and returns the new identifier.', async(): Promise<void> => {