The redesign is focused around providing better static typings and
improved ease-of-use for the Go SDK. Most of the redesign revolves
around three pivots:
- Strongly-typed inputs, especially for nested types
- Struct-based resource and invoke APIs
- Ease-of-use of Apply
1. Strongly-typed inputs
Input is the type of a generic input value for a Pulumi resource.
This type is used in conjunction with Output to provide polymorphism
over strongly-typed input values.
The intended pattern for nested Pulumi value types is to define an
input interface and a plain, input, and output variant of the value
type that implement the input interface.
For example, given a nested Pulumi value type with the following shape:
```
type Nested struct {
Foo int
Bar string
}
```
We would define the following:
```
var nestedType = reflect.TypeOf((*Nested)(nil)).Elem()
type NestedInput interface {
pulumi.Input
ToNestedOutput() NestedOutput
ToNestedOutputWithContext(context.Context) NestedOutput
}
type Nested struct {
Foo int `pulumi:"foo"`
Bar string `pulumi:"bar"`
}
type NestedInputValue struct {
Foo pulumi.IntInput `pulumi:"foo"`
Bar pulumi.StringInput `pulumi:"bar"`
}
func (NestedInputValue) ElementType() reflect.Type {
return nestedType
}
func (v NestedInputValue) ToNestedOutput() NestedOutput {
return pulumi.ToOutput(v).(NestedOutput)
}
func (v NestedInputValue) ToNestedOutputWithContext(ctx context.Context) NestedOutput {
return pulumi.ToOutputWithContext(ctx, v).(NestedOutput)
}
type NestedOutput struct { *pulumi.OutputState }
func (NestedOutput) ElementType() reflect.Type {
return nestedType
}
func (o NestedOutput) ToNestedOutput() NestedOutput {
return o
}
func (o NestedOutput) ToNestedOutputWithContext(ctx context.Context) NestedOutput {
return o
}
func (o NestedOutput) Foo() pulumi.IntOutput {
return o.Apply(func (v Nested) int {
return v.Foo
}).(pulumi.IntOutput)
}
func (o NestedOutput) Bar() pulumi.StringOutput {
return o.Apply(func (v Nested) string {
return v.Bar
}).(pulumi.StringOutput)
}
```
The SDK provides input and output types for primitives, arrays, and
maps.
2. Struct-based APIs
Instead of providing expected output properties in the input map passed
to {Read,Register}Resource and returning the outputs as a map, the user
now passes a pointer to a struct that implements one of the Resource
interfaces and has appropriately typed and tagged fields that represent
its output properties.
For example, given a custom resource with an int-typed output "foo" and
a string-typed output "bar", we would define the following
CustomResource type:
```
type MyResource struct {
pulumi.CustomResourceState
Foo pulumi.IntOutput `pulumi:"foo"`
Bar pulumi.StringOutput `pulumi:"bar"`
}
```
And invoke RegisterResource like so:
```
var resource MyResource
err := ctx.RegisterResource(tok, name, props, &resource, opts...)
```
Invoke arguments and results are also provided via structs, but use
plain-old Go types for their fields:
```
type MyInvokeArgs struct {
Foo int `pulumi:"foo"`
}
type MyInvokeResult struct {
Bar string `pulumi:"bar"`
}
var result MyInvokeResult
err := ctx.Invoke(tok, MyInvokeArgs{Foo: 42}, &result, opts...)
```
3. Ease-of-use of Apply
All `Apply` methods now accept an interface{} as the callback type.
The provided callback value must have one of the following signatures:
func (v T) U
func (v T) (U, error)
func (ctx context.Context, v T) U
func (ctx context.Context, v T) (U, error)
T must be assignable from the ElementType of the Output. If U is a type
that has a registered Output type, the result of the Apply will be the
corresponding Output type. Otherwise, the result of the Apply will be
AnyOutput.
Fixes https://github.com/pulumi/pulumi/issues/2149.
Fixes https://github.com/pulumi/pulumi/issues/3488.
Fixes https://github.com/pulumi/pulumi/issues/3487.
Fixes https://github.com/pulumi/pulumi-aws/issues/248.
Fixes https://github.com/pulumi/pulumi/issues/3492.
Fixes https://github.com/pulumi/pulumi/issues/3491.
Fixes https://github.com/pulumi/pulumi/issues/3562.
We run the same suite of changes that we did on gometalinter. This
ended up catching a few new issues, some of which were addressed and
some of which were baselined.