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feat(go): add UnsafeCast function (#3316)
The `UnsafeCast` function can be used to forcefully convert from one
type of jsii proxy value (including `interface{}`) to another jsii
interface (i.e: a class or interface instance).
If performs a "clean" cast when possible, and creates a new, aliased
proxy otherwise. It is the user's responsibility to ensure they are
passing the correct arguments into the function.
Fixes #2819
---
By submitting this pull request, I confirm that my contribution is made under the terms of the [Apache 2.0 license].
[Apache 2.0 license]: https://www.apache.org/licenses/LICENSE-2.0- Loading branch information
Romain Marcadier
committed
Jan 12, 2022
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -11,7 +11,7 @@ func New() abc.Cdk16625 { | |
| return c | ||
| } | ||
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| type cdk16625 struct{ | ||
| type cdk16625 struct { | ||
| abc.Cdk16625 | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,3 +1,4 @@ | ||
| //go:build tools | ||
| // +build tools | ||
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| // Package tools contains the necessary statements to ensure tool dependencies | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,59 @@ | ||
| package jsii | ||
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| import ( | ||
| "fmt" | ||
| "reflect" | ||
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| "github.com/aws/jsii-runtime-go/internal/kernel" | ||
| ) | ||
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| // UnsafeCast converts the given interface value to the desired target interface | ||
| // pointer. Panics if the from value is not a jsii proxy object, or if the to | ||
| // value is not a pointer to an interface type. | ||
| func UnsafeCast(from interface{}, into interface{}) { | ||
| rinto := reflect.ValueOf(into) | ||
| if rinto.Kind() != reflect.Ptr { | ||
| panic(fmt.Errorf("Second argument to UnsafeCast must be a pointer to an interface. Received %s", rinto.Type().String())) | ||
| } | ||
| rinto = rinto.Elem() | ||
| if rinto.Kind() != reflect.Interface { | ||
| panic(fmt.Errorf("Second argument to UnsafeCast must be a pointer to an interface. Received pointer to %s", rinto.Type().String())) | ||
| } | ||
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| rfrom := reflect.ValueOf(from) | ||
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| // If rfrom is essentially nil, set into to nil and return. | ||
| if !rfrom.IsValid() || rfrom.IsZero() { | ||
| null := reflect.Zero(rinto.Type()) | ||
| rinto.Set(null) | ||
| return | ||
| } | ||
| // Interfaces may present as a pointer to an implementing struct, and that's fine... | ||
| if rfrom.Kind() != reflect.Interface && rfrom.Kind() != reflect.Ptr { | ||
| panic(fmt.Errorf("First argument to UnsafeCast must be an interface value. Received %s", rfrom.Type().String())) | ||
| } | ||
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| // If rfrom can be directly converted to rinto, just do it. | ||
| if rfrom.CanConvert(rinto.Type()) { | ||
| rfrom = rfrom.Convert(rinto.Type()) | ||
| rinto.Set(rfrom) | ||
| return | ||
| } | ||
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| client := kernel.GetClient() | ||
| if objID, found := client.FindObjectRef(rfrom); found { | ||
| // Ensures the value is initialized properly. Panics if the target value is not a jsii interface type. | ||
| client.Types().InitJsiiProxy(rinto) | ||
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| // If the target type is a behavioral interface, add it to the ObjectRef.Interfaces list. | ||
| if fqn, found := client.Types().InterfaceFQN(rinto.Type()); found { | ||
| objID.Interfaces = append(objID.Interfaces, fqn) | ||
| } | ||
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| // Make the new value an alias to the old value. | ||
| client.RegisterInstance(rinto, objID) | ||
| return | ||
| } | ||
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| panic(fmt.Errorf("First argument to UnsafeCast must be a jsii proxy value. Received %s", rfrom.String())) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,101 @@ | ||
| package jsii | ||
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| import ( | ||
| "reflect" | ||
| "testing" | ||
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| "github.com/aws/jsii-runtime-go/internal/api" | ||
| "github.com/aws/jsii-runtime-go/internal/kernel" | ||
| ) | ||
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| type MockInterfaceABase interface { | ||
| MockMethodABase(_ float64) | ||
| } | ||
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| type mockABase struct { | ||
| _ int // padding | ||
| } | ||
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| func (m *mockABase) MockMethodABase(_ float64) {} | ||
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| type MockInterfaceA interface { | ||
| MockInterfaceABase | ||
| MockMethodA(_ string) | ||
| } | ||
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| func NewMockInterfaceA() MockInterfaceA { | ||
| return &mockA{mockABase{}} | ||
| } | ||
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| type mockA struct { | ||
| mockABase | ||
| } | ||
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| func (m *mockA) MockMethodA(_ string) {} | ||
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| type MockInterfaceB interface { | ||
| MockMethodB(_ int) | ||
| } | ||
|
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| func NewMockInterfaceB() MockInterfaceB { | ||
| return &mockB{} | ||
| } | ||
|
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| type mockB struct { | ||
| _ int // Padding | ||
| } | ||
|
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| func (m *mockB) MockMethodB(_ int) {} | ||
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| func TestNilSource(t *testing.T) { | ||
| // Make "into" not nil to ensure the cast function overwrites it. | ||
| into := NewMockInterfaceB() | ||
| UnsafeCast(nil, &into) | ||
|
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| if into != nil { | ||
| t.Fail() | ||
| } | ||
| } | ||
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| func TestSourceAndTargetAreTheSame(t *testing.T) { | ||
| into := NewMockInterfaceB() | ||
| original := into | ||
| UnsafeCast(into, &into) | ||
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| if into != original { | ||
| t.Fail() | ||
| } | ||
| } | ||
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| func TestTargetIsSubclassOfSource(t *testing.T) { | ||
| from := NewMockInterfaceA() | ||
| var into MockInterfaceABase | ||
| UnsafeCast(from, &into) | ||
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| if into != from { | ||
| t.Fail() | ||
| } | ||
| } | ||
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| func TestRegistersAlias(t *testing.T) { | ||
| client := kernel.GetClient() | ||
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| objid := api.ObjectRef{InstanceID: "Object@1337#42"} | ||
| from := NewMockInterfaceA() | ||
| client.RegisterInstance(reflect.ValueOf(from), objid) | ||
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| var into MockInterfaceB | ||
| client.Types().RegisterInterface(api.FQN("mock.InterfaceB"), reflect.TypeOf(&into).Elem(), []api.Override{}, func() interface{} { return NewMockInterfaceB() }) | ||
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| UnsafeCast(from, &into) | ||
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| if into == nil { | ||
| t.Fail() | ||
| } | ||
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| if refid, found := client.FindObjectRef(reflect.ValueOf(into)); !found { | ||
| t.Fail() | ||
| } else if refid.InstanceID != objid.InstanceID { | ||
| t.Fail() | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,10 +1,16 @@ | ||
| module github.com/aws/jsii-runtime-go | ||
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| go 1.16 | ||
| go 1.17 | ||
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| require ( | ||
| github.com/Masterminds/semver/v3 v3.1.1 | ||
| github.com/stretchr/testify v1.7.0 | ||
| ) | ||
|
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| require ( | ||
| github.com/davecgh/go-spew v1.1.1 // indirect | ||
| github.com/pmezard/go-difflib v1.0.0 // indirect | ||
| gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect | ||
| ) | ||
|
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||
| retract v1.27.0 |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,14 +1,15 @@ | ||
| github.com/Masterminds/semver/v3 v3.1.1 h1:hLg3sBzpNErnxhQtUy/mmLR2I9foDujNK030IGemrRc= | ||
| github.com/Masterminds/semver/v3 v3.1.1/go.mod h1:VPu/7SZ7ePZ3QOrcuXROw5FAcLl4a0cBrbBpGY/8hQs= | ||
| github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8= | ||
| github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38= | ||
| github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c= | ||
| github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38= | ||
| github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM= | ||
| github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4= | ||
| github.com/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4= | ||
| github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME= | ||
| github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY= | ||
| github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg= | ||
| gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM= | ||
| gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0= | ||
| gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo= | ||
| gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM= | ||
| gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo= | ||
| gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM= |
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