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fix: register type with prefix #52

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merged 2 commits into from
Aug 12, 2023
Merged

fix: register type with prefix #52

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f8a0499
fix: register type with prefix
bcho Aug 4, 2023
fc1f717
doc: call out why we need pkgPath prefix
bcho Aug 12, 2023
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14 changes: 8 additions & 6 deletions mockgen/model/model.go
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Original file line number Diff line number Diff line change
Expand Up @@ -147,12 +147,14 @@ type Type interface {
}

func init() {
gob.Register(&ArrayType{})
gob.Register(&ChanType{})
gob.Register(&FuncType{})
gob.Register(&MapType{})
gob.Register(&NamedType{})
gob.Register(&PointerType{})
// Call gob.RegisterName with pkgPath as prefix to avoid conflicting with
// github.com/golang/mock/mockgen/model 's registration.
gob.RegisterName(pkgPath+".ArrayType", &ArrayType{})
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@r-hang r-hang Aug 10, 2023 •
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Should the registered named be prefixed with a "*"? From my understanding gob.Register is only misbehaving (i.e. not fully qualifying) for named pointer types.

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From gob's implementation, the registered type will be firstly reflected for the actual type (userType), then stored in two map, with <name, type> and <type, name> pairs: https://cs.opensource.google/go/go/+/refs/tags/go1.21.0:src/encoding/gob/type.go;l=836-844;drc=f80e270babcddd28e29a52c1cb834ffed427bd8a

In the encode part, encoder will use the same userType again to reflect the actual type, and look up the name: https://cs.opensource.google/go/go/+/refs/tags/go1.21.0:src/encoding/gob/encode.go;l=400-405;drc=6a51c000def084b820756f066397fd2505e75e25

In the decode part, a similar but reverse process will be used for looking up type by name: https://cs.opensource.google/go/go/+/refs/tags/go1.21.0:src/encoding/gob/decode.go;l=699-704;drc=f62c9701b4bc61da6a5f4db8ef81d816f112430e

The default gob.Register call infers the type name with this: https://cs.opensource.google/go/go/+/refs/tags/go1.21.0:src/encoding/gob/type.go;l=854-856;drc=f80e270babcddd28e29a52c1cb834ffed427bd8a (without calling user type etc) . For instance, giving a pointer to MapType from two different packages, the name here will be inferred as the same value (yes it will have a * prefix as it's a pointer type). As a result, we will see panic in later register when using like issue #51 .

The fix here is to add a qualified prefix to the value type, so we can avoid the panic on register. But to gob, it's just an unique identifier. Or, we can define it as something like {pkgPath}.*MapType. Let me know your thought!

gob.RegisterName(pkgPath+".ChanType", &ChanType{})
gob.RegisterName(pkgPath+".FuncType", &FuncType{})
gob.RegisterName(pkgPath+".MapType", &MapType{})
gob.RegisterName(pkgPath+".NamedType", &NamedType{})
gob.RegisterName(pkgPath+".PointerType", &PointerType{})
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Can we add a comment why we are using RegisterName ?

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Added a comment, @moisesvega / @sywhang PTAL


// Call gob.RegisterName to make sure it has the consistent name registered
// for both gob decoder and encoder.
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