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refactor: Make piping consistent

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This commit is contained in:
Joachim Van Herwegen
2020-11-10 16:02:49 +01:00
parent 715ba126f9
commit 95ab0b4e76
7 changed files with 56 additions and 25 deletions
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6
src/util/MetadataController.ts
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@@ -7,7 +7,7 @@ import { RepresentationMetadata } from '../ldp/representation/RepresentationMeta
import { TEXT_TURTLE } from './ContentTypes';
import { LDP, RDF } from './UriConstants';
import { toNamedNode } from './UriUtil';
import { pipeStreamsAndErrors, pushQuad } from './Util';
import { pipeSafe, pushQuad } from './Util';
export class MetadataController {
/**
@@ -46,7 +46,7 @@ export class MetadataController {
* @returns The Readable object.
*/
public serializeQuads(quads: Quad[]): Readable {
return pipeStreamsAndErrors(streamifyArray(quads), new StreamWriter({ format: TEXT_TURTLE }));
return pipeSafe(streamifyArray(quads), new StreamWriter({ format: TEXT_TURTLE }));
}
/**
@@ -56,6 +56,6 @@ export class MetadataController {
* @returns A promise containing the array of quads.
*/
public async parseQuads(readable: Readable): Promise<Quad[]> {
return await arrayifyStream(pipeStreamsAndErrors(readable, new StreamParser({ format: TEXT_TURTLE })));
return await arrayifyStream(pipeSafe(readable, new StreamParser({ format: TEXT_TURTLE })));
}
}

16
src/util/Util.ts
View File

@@ -59,20 +59,26 @@ export const matchingMediaType = (mediaA: string, mediaB: string): boolean => {
};
/**
* Pipes one stream into another.
* Makes sure an error of the first stream gets passed to the second.
* Pipes one stream into another and emits errors of the first stream with the second.
* In case of an error in the first stream the second one will be destroyed with the given error.
* @param readable - Initial readable stream.
* @param destination - The destination for writing data.
* @param mapError - Optional function that takes the error and converts it to a new error.
*
* @returns The destination stream.
*/
export const pipeStreamsAndErrors = <T extends Writable>(readable: NodeJS.ReadableStream, destination: T,
export const pipeSafe = <T extends Writable>(readable: NodeJS.ReadableStream, destination: T,
mapError?: (error: Error) => Error): T => {
// Not using `stream.pipeline` since the result there only emits an error event if the last stream has the error
readable.pipe(destination);
readable.on('error', (error): boolean => {
readable.on('error', (error): void => {
logger.warn(`Piped stream errored with ${error.message}`);
return destination.emit('error', mapError ? mapError(error) : error);
// From https://nodejs.org/api/stream.html#stream_readable_pipe_destination_options :
// "One important caveat is that if the Readable stream emits an error during processing, the Writable destination
// is not closed automatically. If an error occurs, it will be necessary to manually close each stream
// in order to prevent memory leaks."
destination.destroy(mapError ? mapError(error) : error);
});
return destination;
};