[DEV-3257] DelayedStagingBucket: Preempt infinite recursion on #processValues
* src/bucket/DelayedRecursionError.js: New class.
* src/bucket/DelayedStagingBucket.js: Update copyright and docblock.
(_processing): New field.
(getDataByName): Check against undefined before invoking
`#processValues'.
(processValues): Increment lock (_withProcessLock).
(_withProcessLock): Error on recursion >= 5.
DEV-3257
master
Mike Gerwitz
parent
9f944bb7ec
commit
9243eeb8bc
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@ -0,0 +1,26 @@
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/**
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* DelayedRecursionError
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*
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* Copyright (C) 2018 R-T Specialty, LLC.
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*
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* This file is part of the Liza Data Collection Framework
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*
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* liza is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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const { Class } = require( 'easejs' );
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module.exports = Class( 'DelayedRecursionError' )
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.extend( Error, {} );
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@ -19,16 +19,19 @@
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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var Class = require( 'easejs' ).Class,
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StagingBucket = require( './StagingBucket' );
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const { Class } = require( 'easejs' );
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const StagingBucket = require( './StagingBucket' );
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const DelayedRecursionError = require( './DelayedRecursionError' );
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/**
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* Holds changes until explicitly processed to avoid cascades
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*
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* Since each write could trigger any number of event listeners, writes
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* should be queued and done en-masse.
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*/
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* Holds changes until explicitly processed to avoid cascades
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*
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* Since each write could trigger any number of event listeners, writes
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* should be queued and done en-masse.
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*
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* TODO: Convert to Trait.
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*/
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module.exports = Class( 'DelayedStagingBucket' )
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.extend( StagingBucket,
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{
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@ -44,6 +47,12 @@ module.exports = Class( 'DelayedStagingBucket' )
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*/
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'private _timer': 0,
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/**
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* Whether #processValues is still on the stack
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* @type {boolean}
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*/
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'private _processing': 0,
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'public override setValues': function( data )
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{
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@ -73,8 +82,12 @@ module.exports = Class( 'DelayedStagingBucket' )
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// invoke when stack clears
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var _self = this;
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this._timer = setTimeout( function()
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this._timer = setTimeout( () =>
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{
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// just in case something prevented us from decrementing the
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// lock (e.g. an exception)
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this._processing = 0;
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_self.processValues();
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}, 0 );
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},
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@ -107,7 +120,7 @@ module.exports = Class( 'DelayedStagingBucket' )
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{
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// if enqueued data is requested, then we have no choice but to merge to
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// ensure that the data is up-to-date
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if ( this._queued[ name ] )
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if ( this._queued[ name ] !== undefined )
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{
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this.processValues();
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}
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@ -154,14 +167,60 @@ module.exports = Class( 'DelayedStagingBucket' )
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// since additional data may be queued as a consequence of the below
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// set, prepare for it by providing an empty queue
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var oldqueue = this._queued;
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this._queued = {};
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this._timer = 0;
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this._withProcessLock( () =>
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{
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var oldqueue = this._queued;
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this._queued = {};
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this._timer = 0;
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this.setValues['super'].call( this,
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oldqueue, true, true
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);
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this.setValues['super'].call( this,
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oldqueue, true, true
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);
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} );
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return this;
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},
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/**
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* Increment lock for duration of function F
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*
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* The lock is incremented before calling F and decremented after F
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* returns. The maximum lock count is hard-coded to 5, after which an
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* exception will be thrown. The intent of this value is to provide a
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* little bit of flexibility to hook implementations that allows for
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* some gentle recursion, but preempts hooks when it looks like things
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* may be going awry.
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*
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* @param {Function} f function to call
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*
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* @throws {DelayedRecursionError} when lock count exceeds maximum
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*
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* @return {undefined}
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*/
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'private _withProcessLock'( f )
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{
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// protect against runaway recursion from hooks
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if ( this._processing === 5 )
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{
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// throwing the exception will halt execution of the stack if
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// uncaught, meaning _processing will never be fully
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// decremented, so clear it out
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this._processing = 0;
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throw DelayedRecursionError(
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"Recursion on DelayedStagingBucket#processValues " +
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"(likely caused by a bucket hook)"
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);
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}
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// note that this isn't guarded with a try/catch, because we handle
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// resetting the lock in a couple other places---this is more
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// fool-proof, since catching an exception mail fail in certain
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// circumstances (e.g. when reaching a resource limit, like
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// stack/memory)
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this._processing++;
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f();
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this._processing--;
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}
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} );
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@ -0,0 +1,191 @@
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/**
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* Tests DelayedStagingBucket
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*
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* Copyright (C) 2018 R-T Specialty, LLC.
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*
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* This file is part of the Liza Data Collection Framework
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*
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* Liza is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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'use strict';
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const { expect } = require( 'chai' );
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const {
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DelayedStagingBucket: Sut,
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DelayedRecursionError,
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} = require( '../../' ).bucket;
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describe( "DelayedStagingBucket", () =>
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{
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it( "sets values after stack clears", done =>
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{
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const name = 'foo';
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const value = [ 'value' ];
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// see end of this test
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let ready = false;
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const bucket = {
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on() {},
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setValues( given_data )
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{
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// set at the end of the test to ensure that this is
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// done asynchronously
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expect( ready ).to.be.true;
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expect( given_data ).to.deep.equal( { [name]: value } );
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done();
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},
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getData: () => ( {} ),
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};
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// queue set (should not yet call bucket#setValues)
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const sut = Sut( bucket ).setValues( { [name]: value } );
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// to write to the underlying bucket, we need to commit, but we
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// have to do so after the async code runs (we should convert
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// the SUT to a trait and avoid this madness)
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setTimeout( () => sut.commit(), 0 );
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// we're ready for the set to happen (once the stack clears)
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ready = true;
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} );
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describe( "#getDataByName", () =>
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{
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[
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{
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label: 'processes immediately retrieving modified key',
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name: 'foo',
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get_name: 'foo',
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immediate: true,
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},
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{
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label: 'does not processes immediately retrieving unmodified key',
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name: 'foo',
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get_name: 'bar',
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immediate: false,
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},
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].forEach( ( { label, name, get_name, immediate } ) =>
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{
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it( label, () =>
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{
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const value = [ 'getDataByName value' ];
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let called_set = false;
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const bucket = {
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on() {},
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setValues( given_data )
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{
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called_set = ( given_data[ name ] !== undefined );
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},
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getData: () => ( {} ),
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};
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// queue set (should not yet call bucket#setValues)
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const sut = Sut( bucket ).setValues( { [name]: value } );
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// force processing of data by requesting same value (note that
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// commit is necessary since the SUT extends StagingBucket)
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sut.getDataByName( get_name );
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sut.commit();
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expect( called_set ).to.equal( immediate );
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} );
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} );
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// Invoking processValues() writes to the underlying bucket which
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// may cause hooks to be invoked, which in turn may cause the
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// DelayedStagingBucket to be referenced, which would lead to
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// infinite recursion. This doesn't solve that problem, but it does
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// provide a useful error in case it happens, and preempts the
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// wasteful recursion which will exhaust the stack.
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[
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{
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n: 1,
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fail: false,
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},
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{
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n: 3,
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fail: false,
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},
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{
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n: 5,
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fail: true,
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},
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{
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n: 7,
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fail: true,
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},
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].forEach( ( { n, fail } ) =>
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{
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it( `throws error on deeply recursive processValues (n=${n})`, () =>
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{
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const name = 'recursive';
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const value = [ 'getDataByName value' ];
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let called_set = false;
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const bucket = {
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on() {},
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setValues( given_data ) {},
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getData: () => ( {} ),
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};
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// queue set (should not yet call bucket#setValues)
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const sut = Sut( bucket ).setValues( { [name]: value } );
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let calln = 0;
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// this hook will trigger the recursion (the set is required
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// to start another timer; see #processValues)
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sut.on( 'preStagingUpdate', () =>
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{
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// stop recursing at our goal
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if ( calln++ === n )
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{
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return;
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}
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sut.setValues( { [name]: value } )
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.getDataByName( name )
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} );
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// force processing of data by requesting same value
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if ( fail )
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{
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expect( () => sut.getDataByName( name ) )
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.to.throw( DelayedRecursionError );
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}
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else
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{
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expect( () => sut.getDataByName( name ) )
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.to.not.throw( Error );
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}
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} );
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} );
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} );
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} );
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