Add autoname implementation as an example (#255)

Add an example of how autonaming can be implemented with the
pulumi-go-provider.

examples/auto-naming/consumer/Pulumi.yaml

@@ -0,0 +1,18 @@
+name: consume-autoname
+runtime: yaml
+
+plugins:
+  providers:
+    - name: auto-naming
+      path: ..
+
+resources:
+  auto-named:
+    type: auto-naming:User
+  manually-named:
+    type: auto-naming:User
+    properties:
+      name: ${auto-named.name}
+
+outputs:
+  user: ${auto-named.name}

examples/auto-naming/main.go

@@ -0,0 +1,98 @@
+// package main shows how a [infer] based provider can implement auto-naming.
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	p "github.com/pulumi/pulumi-go-provider"
+	"github.com/pulumi/pulumi-go-provider/infer"
+	"github.com/pulumi/pulumi/sdk/v3/go/common/resource"
+	"github.com/pulumi/pulumi/sdk/v3/go/common/tokens"
+)
+
+func main() {
+	err := p.RunProvider("auto-naming", "0.1.0", provider())
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %s", err.Error())
+		os.Exit(1)
+	}
+}
+
+func provider() p.Provider {
+	return infer.Provider(infer.Options{
+		Resources: []infer.InferredResource{infer.Resource[*User, UserArgs, UserState]()},
+		ModuleMap: map[tokens.ModuleName]tokens.ModuleName{
+			"auto-naming": "index",
+		},
+	})
+}
+
+type (
+	User     struct{}
+	UserArgs struct {
+		Name *string `pulumi:"name,optional"`
+	}
+	UserState struct{ UserArgs }
+)
+
+func (*User) Create(ctx context.Context, name string, input UserArgs, preview bool) (string, UserState, error) {
+	return name, UserState{input}, nil
+}
+
+var _ infer.CustomCheck[UserArgs] = ((*User)(nil))
+
+func (*User) Check(
+	ctx context.Context, name string, oldInputs, newInputs resource.PropertyMap,
+) (UserArgs, []p.CheckFailure, error) {
+	// Apply default arguments
+	args, failures, err := infer.DefaultCheck[UserArgs](newInputs)
+	if err != nil {
+		return args, failures, err
+	}
+
+	// Apply autonaming
+	//
+	// If args.Name is unset, we set it to a value based off of the resource name.
+	args.Name, err = autoname(args.Name, name, "name", oldInputs)
+	return args, failures, err
+}
+
+// autoname makes the field it is called on auto-named.
+//
+// It should be called in [infer.CustomCheck.Check].
+//
+// field is a reference to a *string typed field.
+//
+// name is the name of the resource as passed in via check.
+//
+// fieldName is the name of the place referenced by field. This is what was written in the
+// `pulumi:"<fieldName>"` tag.
+//
+// oldInputs are the old inputs as passed in via [infer.CustomCheck.Check].
+func autoname(
+	field *string, name string, fieldName resource.PropertyKey,
+	oldInputs resource.PropertyMap,
+) (*string, error) {
+	if field != nil {
+		return field, nil
+	}
+
+	prev := oldInputs[fieldName]
+	if prev.IsSecret() {
+		prev = prev.SecretValue().Element
+	}
+
+	if prev.IsString() && prev.StringValue() != "" {
+		n := prev.StringValue()
+		field = &n
+	} else {
+		n, err := resource.NewUniqueHex(name+"-", 6, 20)
+		if err != nil {
+			return nil, err
+		}
+		field = &n
+	}
+	return field, nil
+}

examples/auto-naming/main_test.go

@@ -0,0 +1,135 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/blang/semver"
+	p "github.com/pulumi/pulumi-go-provider"
+	"github.com/pulumi/pulumi-go-provider/integration"
+	"github.com/pulumi/pulumi/sdk/v3/go/common/resource"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAutoName(t *testing.T) {
+	t.Parallel()
+
+	s := integration.NewServer("autoname", semver.MustParse("0.1.0"), provider())
+
+	tests := []struct {
+		name     string
+		olds     resource.PropertyMap
+		news     resource.PropertyMap
+		validate func(*testing.T, resource.PropertyMap)
+	}{
+		{
+			name: "create new auto-named resource",
+			news: resource.PropertyMap{},
+			validate: func(t *testing.T, result resource.PropertyMap) {
+				name, ok := result["name"]
+				require.True(t, ok, "could not find name in %q", result)
+				assert.True(t, strings.HasPrefix(name.StringValue(), "name-"))
+				assert.Len(t, name.StringValue(), 11)
+				assert.Len(t, result, 1)
+			},
+		},
+		{
+			name: "create new manually named resource",
+			news: resource.PropertyMap{
+				"name": resource.NewProperty("custom-name"),
+			},
+			validate: func(t *testing.T, result resource.PropertyMap) {
+				name, ok := result["name"]
+				require.True(t, ok, "could not find name in %q", result)
+				assert.Equal(t, "custom-name", name.StringValue())
+			},
+		},
+		{
+			name: "update an auto-named resource (same name)",
+			news: resource.PropertyMap{},
+			olds: resource.PropertyMap{
+				"name": resource.NewProperty("name-123456"),
+			},
+			validate: func(t *testing.T, result resource.PropertyMap) {
+				name, ok := result["name"]
+				require.True(t, ok, "could not find name in %q", result)
+				assert.Equal(t, "name-123456", name.StringValue())
+			},
+		},
+		{
+			name: "update an auto-named resource (new name)",
+			news: resource.PropertyMap{
+				"name": resource.NewProperty("custom-name"),
+			},
+			olds: resource.PropertyMap{
+				"name": resource.NewProperty("name-123456"),
+			},
+			validate: func(t *testing.T, result resource.PropertyMap) {
+				name, ok := result["name"]
+				require.True(t, ok, "could not find name in %q", result)
+				assert.Equal(t, "custom-name", name.StringValue())
+			},
+		},
+		{
+			name: "update a manually named resource (same name)",
+			news: resource.PropertyMap{
+				"name": resource.NewProperty("custom-name"),
+			},
+			olds: resource.PropertyMap{
+				"name": resource.NewProperty("custom-name"),
+			},
+			validate: func(t *testing.T, result resource.PropertyMap) {
+				name, ok := result["name"]
+				require.True(t, ok, "could not find name in %q", result)
+				assert.Equal(t, "custom-name", name.StringValue())
+			},
+		},
+		{
+			name: "update a manually named resource (different name)",
+			news: resource.PropertyMap{
+				"name": resource.NewProperty("custom-name1"),
+			},
+			olds: resource.PropertyMap{
+				"name": resource.NewProperty("custom-name2"),
+			},
+			validate: func(t *testing.T, result resource.PropertyMap) {
+				name, ok := result["name"]
+				require.True(t, ok, "could not find name in %q", result)
+				assert.Equal(t, "custom-name1", name.StringValue())
+			},
+		},
+		{
+			name: "convert from a named to an auto-named resource",
+			news: resource.PropertyMap{},
+			olds: resource.PropertyMap{
+				"name": resource.NewProperty("custom-name"),
+			},
+			validate: func(t *testing.T, result resource.PropertyMap) {
+				t.Skipf("It's not possible to drop custom-named resources without a side channel")
+				name, ok := result["name"]
+				require.True(t, ok, "could not find name in %q", result)
+
+				assert.True(t, strings.HasPrefix(name.StringValue(), "name-"))
+				assert.Len(t, name.StringValue(), 11)
+				assert.Len(t, result, 1)
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			t.Helper()
+			resp, err := s.Check(p.CheckRequest{
+				Urn:  resource.NewURN("dev", "test", "", "autoname:index:User", "name"),
+				News: tt.news,
+				Olds: tt.olds,
+			})
+			require.NoError(t, err)
+			require.Empty(t, resp.Failures)
+			tt.validate(t, resp.Inputs)
+		})
+	}
+}