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[CS2] Fix #4651: object spread destructuring bug #4652

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merged 8 commits into from
Sep 1, 2017
Merged

[CS2] Fix #4651: object spread destructuring bug #4652

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f9367ba
fix object spread destructuring bug: #4651
Aug 18, 2017
2664c2c
small fix
Aug 18, 2017
232041d
fixed issue with nested properties
Aug 21, 2017
2149c35
ensure Value; breaking test for {a={b...}} = c
helixbass Aug 21, 2017
1a6477a
resolve merge conflicts
helixbass Aug 21, 2017
2491d32
fix assign in nested properties
Aug 21, 2017
5a709ed
improve variable declaration
Aug 22, 2017
c212e6e
refactor
Aug 22, 2017
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26 changes: 20 additions & 6 deletions lib/coffeescript/nodes.js
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19 changes: 15 additions & 4 deletions src/nodes.coffee
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Original file line number Diff line number Diff line change
Expand Up @@ -2229,8 +2229,11 @@ exports.Assign = class Assign extends Base
nestedProperties = prop.value.variable.base.properties
[prop.value.value, nestedSourceDefault] = prop.value.value.cache o
if nestedProperties
nestedSource = new Value source.base, source.properties.concat [new Access getPropKey prop]
nestedSource = new Value new Op '?', nestedSource, nestedSourceDefault if nestedSourceDefault
if source.properties
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Is this another case that would work better if whatever source is was wrapped in a Value? @helixbass

Alternatively, should the case where there are no properties not wrap source in a Value? I can't really remember how this all works, but in the case that source has no properties, the next level of key won't be added (source.properties.concat [new Access getPropKey prop]). It must be working if the tests pass, but I don't really understand why...

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@connec I’m not sure I follow your comment. Is there something that needs to change here?

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I guess it's just not clear to me why we need to check if source.properties is set. I imagine this is roughly equivalent to source instanceof Value, and my 2 questions are:

  1. Would it be easier to ensure source is a Value (e.g. in the grammar/wherever source is created)?
  2. If source is not a value (e.g. not source.properties) then we do not execute the line where we concat the property key. Why does this work?

I'll try and find some time to poke around to answer my own questions, since it's probably just my own misunderstandings. Since the tests work etc. this can probably go in, and if I find any issues I can submit a new ticket/fix.

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@connec you're right there's some bugginess here, I'm poking around and ran into eg this:

{c:{a...}} = d: 1

compiles to this:

({
  c: {}
} = ref = {
  d: 1
});
a = objectWithoutKeys(ref, []);

This would seem to be a case of nestedSource not getting set correctly (the first arg to objectWithoutKeys() shouldn't be ref, I guess it should be ref.c?)

If I can figure it out I'll push a fix to this branch, otherwise I'll at least push breaking tests

nestedSource = new Value source.base, source.properties.concat [new Access getPropKey prop]
nestedSource = new Value new Op '?', nestedSource, nestedSourceDefault if nestedSourceDefault
else
nestedSource = source
restElements.push traverseRest(nestedProperties, nestedSource)...
else if prop instanceof Splat
prop.error "multiple rest elements are disallowed in object destructuring" if restIndex?
Expand All @@ -2247,8 +2250,16 @@ exports.Assign = class Assign extends Base

restElements

# Cache the value for reuse with rest elements
[@value, valueRef] = @value.cache o
# Cache the value for reuse with rest elements.
# `Obj` should be always cached.
# Examples:
# {a, r...} = {a:1, b:2, c:3}
# {a, r...} = {a:1, obj...}
shouldCache = (value) ->
return yes if value.base instanceof Obj
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Should we change Obj::shouldCache to always be true? I guess there may be unintended consequences of that, but I can't think of a situation where we'd rather duplicate an object literal rather than reusing it.

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I've already tried that, but then tests fail.
I also think object destructuring with spreads is the only place where this is necessary.
Besides, spreads might soon reach stage-4.

value.shouldCache()

[@value, valueRef] = @value.cache o, false, shouldCache

# Find all rest elements.
restElements = traverseRest @variable.base.properties, valueRef
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21 changes: 21 additions & 0 deletions test/assignment.coffee
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Original file line number Diff line number Diff line change
Expand Up @@ -296,6 +296,27 @@ test "destructuring assignment with multiple splats in different objects", ->
deepEqual a, val: 1
deepEqual b, val: 2

o = {
props: {
p: {
n: 1
m: 5
}
s: 6
}
}
{p: {m}, r...} = o.props
eq m, o.props.p.m
deepEqual r, s: 6

@props = o.props
{p: {m}, r...} = @props
eq m, @props.p.m
deepEqual r, s: 6

{p: {m}, r...} = {o.props..., p:{m:9}}
eq m, 9

# Should not trigger implicit call, e.g. rest ... => rest(...)
{
a: {
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