8000 When merging modified primitive type objects, added properties get dropped · Issue #2008 · lodash/lodash · GitHub
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When merging modified primitive type objects, added properties get dropped #2008

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codingmatty opened this issue Feb 16, 2016 · 4 comments
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When merging modified primitive type objects, added properties get dropped #2008

codingmatty opened this issue Feb 16, 2016 · 4 comments
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enhancement

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@codingmatty
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Bug when using v4.4.0
We use a pattern where we add properties to a string object. When we try to merge that string property into another object, all the properties originally added are dropped.
I'm not sure if this is specifically an issue with merge, or if other functions are affected.

> var testStr = new String('testStr');
> testStr.prop1 = 'testStr.prop1'
> testStr
{ [String: 'testStr'] prop1: 'testStr.prop1' }

// It seems to work 1 level deep.
> _.merge({}, { testStr: testStr })
{ testStr: { [String: 'testStr'] prop1: 'testStr.prop1' } }

// but any deeper and it doesn't work as expected.
> _.merge({}, { testStr: { testStr: testStr } })
{ testStr: { testStr: [String: 'testStr'] } }
@jdalton
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jdalton commented Feb 16, 2016

This is a lodash wide behavior. When cloning or comparing boolean, number, & string objects any added properties are ignored. The use of those is so rare that I could see putting them down the plain object path.

@codingmatty
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This behavior seemed to change from 4.3 to 4.4, why might that have changed between minor versions?

@jdalton
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jdalton commented Feb 16, 2016

Our clone/equality behavior did not change between 4.3 and 4.4. We did fix an issue where we weren't cloning a value properly which may be what you're seeing. Lodash has never supported expando properties on the object form of primitives.

I'll add support for it though. It'll slow those paths down but they aren't used nearly as often as arrays and plain objects so it's cool.

jdalton added a commit that referenced this issue Feb 17, 2016
@jdalton
Ensure clone methods clone expando properties of boolean, number, & s…
3a42318 
…tring objects. [closes #2008]
jdalton added a commit that referenced this issue Feb 17, 2016
@jdalton
Ensure clone methods clone expando properties of boolean, number, & s…
7b93dc9 
…tring objects. [closes #2008]
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lock bot commented Jan 19, 2019

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.

@lock lock bot locked as resolved and limited conversation to collaborators Jan 19, 2019
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