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master
Sven Slootweg 1 month ago
commit
0a25a80d33
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      index.js
  4. +24
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      package.json
  5. +1048
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      yarn.lock

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.eslintrc View File

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{
"extends": "@joepie91/eslint-config"
}

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.gitignore View File

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node_modules

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index.js View File

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"use strict";
const Promise = require("bluebird");
const consumable = require("@joepie91/consumable");
const pPause = require("p-pause");
const debug = require("debug")("promistream:last-will");
const isEndOfStream = require("@promistream/is-end-of-stream");
const isAborted = require("@promistream/is-aborted");
const { validateOptions } = require("@validatem/core");
const isFunction = require("@validatem/is-function");
const wrapValueAsOption = require("@validatem/wrap-value-as-option");
const requireEither = require("@validatem/require-either");
let NoValue = Symbol();
// MARKER: Test this in batchOn, then finalize the refactoring
// FIXME: Make NoValue its own reusable promistream package? For use as a marker in different types of streams which need to deal with multiple possibly-matching handlers, or eg. map-filter
// FIXME: Re-understand and refactor the logic, finish packaging it up
module.exports = function lastWill() {
let { onEndOfStream, onAborted, onAllEnds } = validateOptions(arguments, [
wrapValueAsOption("onEndOfStream"), {
onEndOfStream: [ isFunction ],
onAborted: [ isFunction ],
onAllEnds: [ isFunction ],
},
requireEither([ "onEndOfStream", "onAborted", "onAllEnds" ], { allowMultiple: true })
]);
let errorBuffer = consumable();
let hasExecutedLastWill = false;
// NOTE: We use a resettable pauser to ensure that when reading in parallel mode, all concurrent reads get held up while a stream end marker is being processed, but parallelization is otherwise permitted. Think of it as a conditional `sequentialize`.
// FIXME: Verify that this doesn't ever introduce race conditions
let pauser = pPause();
function throwBufferedError() {
// Run after all custom handlers have run out
throw errorBuffer.consume();
}
function processUntilValue(handlers) {
return Promise.reduce(handlers, (lastResult, handler, i) => {
if (lastResult === NoValue) {
debug(`Calling handler ${i}`);
return handler(errorBuffer.peek());
} else {
debug(`Skipping handler ${i}`);
return lastResult;
}
}, NoValue);
}
function handleMarker(marker, markerHandler) {
pauser.pause();
return Promise.try(() => {
let relevantHandlers = [ markerHandler, onAllEnds, throwBufferedError ]
.filter((handler) => handler != null);
debug(`${relevantHandlers.length - 1} handlers to try, excluding default handler`);
if (hasExecutedLastWill || relevantHandlers.length === 0) {
debug("Bailing");
throw marker;
} else {
errorBuffer.set(marker);
hasExecutedLastWill = true;
return processUntilValue(relevantHandlers);
}
}).finally(() => {
pauser.unpause();
});
}
return {
_promistreamVersion: 0,
description: `last-will handler`,
abort: function abort_lastWill(source, reason) {
// FIXME: propagate module
return source.abort(reason);
},
peek: function peek_lastWill(source) {
return Promise.try(() => {
return pauser.await();
}).then(() => {
if (errorBuffer.isSet()) {
/* We've reached the end of the source stream in some way; we'll have at least *some* response ready, whether it is an error or some value produced by a last-will handler */
return true;
} else {
return source.peek();
}
});
},
read: function produceValue_lastWill(source) {
return Promise.try(() => {
return pauser.await();
}).then(() => {
if (errorBuffer.isSet()) {
return throwBufferedError();
} else {
return Promise.try(() => {
return source.read();
}).catch(isEndOfStream, (err) => {
debug("Got EndOfStream marker");
return handleMarker(err, onEndOfStream);
}).catch(isAborted, (err) => {
debug("Got Aborted marker");
return handleMarker(err, onAborted);
});
}
});
}
};
};
module.exports.NoValue = NoValue;

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package.json View File

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{
"name": "@promistream/last-will",
"version": "0.1.0",
"main": "index.js",
"repository": "http://git.cryto.net/promistream/last-will.git",
"author": "Sven Slootweg <admin@cryto.net>",
"license": "WTFPL OR CC0-1.0",
"dependencies": {
"@joepie91/consumable": "^1.0.1",
"@promistream/is-aborted": "^0.1.0",
"@promistream/is-end-of-stream": "^0.1.0",
"@validatem/core": "^0.3.15",
"@validatem/is-function": "^0.1.0",
"@validatem/require-either": "^0.1.0",
"@validatem/wrap-value-as-option": "^0.1.0",
"bluebird": "^3.7.2",
"debug": "^4.3.1",
"p-pause": "^0.1.0"
},
"devDependencies": {
"@joepie91/eslint-config": "^1.1.0",
"eslint": "^7.23.0"
}
}

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yarn.lock
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