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reflect: when creating anonymous fields, StructOf should attempt to compute the field name #26035

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jimmyfrasche opened this issue Jun 24, 2018 · 5 comments
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reflect: when creating anonymous fields, StructOf should attempt to compute the field name #26035

jimmyfrasche opened this issue Jun 24, 2018 · 5 comments
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FrozenDueToAge NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made.
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Go1.12

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@jimmyfrasche
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Creating an anonymous field with reflect.StructOf panics if not explicitly given a name.

A name must be provided when the embedded type is not defined or the name differs from the name of the defined type, to simulate embedding of an alias to a defined type. It is necessary to require an explicit name in these cases.

However, the common case, and hence user expectation, is that embedding a defined type creates a field with the same name as the defined type.

For any T representing a defined type, the following should be equivalent:

reflect.StructOf([]reflect.StructField{
  {
    Name: T.Name(), // Or T.Elem().Name()
    Type: T,
    Anonymous: true,
  },
})

and

reflect.StructOf([]reflect.StructField{
  {
    Type: T,
    Anonymous: true,
  },
})

Originally reported by @Merovius as part of #24781. I'm breaking it into a separate issue for easier tracking.
@gopherbot
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Change https://golang.org/cl/120698 mentions this issue: reflect: StructOf compute anonymous field name

@jimmyfrasche
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cc @rsc @ianlancetaylor per golang/s/owners

@ianlancetaylor ianlancetaylor added the NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made. label Jun 25, 2018
@ianlancetaylor ianlancetaylor added this to the Go1.12 milestone Jun 25, 2018
@ianlancetaylor
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Probably a dup of #24781.

@jimmyfrasche
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@ianlancetaylor I forked this off that issue because it has 2 or 3 other things going on that may or may not be bugs (which may be a dupe of #24721 though this is not a dupe of that). This can be handled and tracked separately.

@rsc
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rsc commented Sep 26, 2018

Given how difficult and subtle this all is, it seems better to require the caller to specify the name, as we always have. I'm already skeptical of StructOf, but more skeptical of more magic. Also we learned during alias that we may need to have the idea of anonymous fields with names different from types. The current behavior is more explicit, which is good.

@rsc rsc closed this as completed Sep 26, 2018
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