starlack/types: basic backend support

Author: mcuadros

_examples/backend.star

@@ -0,0 +1,3 @@
+b = backend("gcs")
+b.bucket = "tf-state-prod"
+b.prefix = "terraform/state"

cmd/run.go

@@ -5,8 +5,8 @@ import (
 	"io/ioutil"
 	"os"
 
-	"github.com/mcuadros/ascode/starlark/types"
 	"github.com/hashicorp/hcl2/hclwrite"
+	"github.com/mcuadros/ascode/starlark/types"
 	"go.starlark.net/starlark"
 )
 
@@ -54,12 +54,13 @@ func (c *RunCmd) dumpToHCL(ctx starlark.StringDict) error {
 
 	f := hclwrite.NewEmptyFile()
 	for _, v := range ctx {
-		p, ok := v.(*types.Provider)
-		if !ok {
-			continue
+		// TODO(mcuadros): replace this logic with a global object terraform
+		switch o := v.(type) {
+		case *types.Provider:
+			o.ToHCL(f.Body())
+		case *types.Backend:
+			o.ToHCL(f.Body())
 		}
-
-		p.ToHCL(f.Body())
 	}
 
 	return ioutil.WriteFile(c.ToHCL, f.Bytes(), 0644)

go.sum

@@ -88,6 +88,7 @@ github.com/apparentlymart/go-cidr v1.0.0/go.mod h1:EBcsNrHc3zQeuaeCeCtQruQm+n9/Y
 github.com/apparentlymart/go-cidr v1.0.1 h1:NmIwLZ/KdsjIUlhf+/Np40atNXm/+lZ5txfTJ/SpF+U=
 github.com/apparentlymart/go-cidr v1.0.1/go.mod h1:EBcsNrHc3zQeuaeCeCtQruQm+n9/YjEn/vI25Lg7Gwc=
 github.com/apparentlymart/go-dump v0.0.0-20180507223929-23540a00eaa3/go.mod h1:oL81AME2rN47vu18xqj1S1jPIPuN7afo62yKTNn3XMM=
+github.com/apparentlymart/go-dump v0.0.0-20190214190832-042adf3cf4a0 h1:MzVXffFUye+ZcSR6opIgz9Co7WcDx6ZcY+RjfFHoA0I=
 github.com/apparentlymart/go-dump v0.0.0-20190214190832-042adf3cf4a0/go.mod h1:oL81AME2rN47vu18xqj1S1jPIPuN7afo62yKTNn3XMM=
 github.com/apparentlymart/go-textseg v1.0.0 h1:rRmlIsPEEhUTIKQb7T++Nz/A5Q6C9IuX2wFoYVvnCs0=
 github.com/apparentlymart/go-textseg v1.0.0/go.mod h1:z96Txxhf3xSFMPmb5X/1W05FF/Nj9VFpLOpjS5yuumk=

starlark/runtime/runtime.go

@@ -49,6 +49,7 @@ func NewRuntime(pm *terraform.PluginManager) *Runtime {
 		predeclared: starlark.StringDict{
 			"provider":    types.BuiltinProvider(pm),
 			"provisioner": types.BuiltinProvisioner(pm),
+			"backend":     types.BuiltinBackend(),
 			"hcl":         types.BuiltinHCL(),
 		},
 	}

starlark/types/backend.go

@@ -0,0 +1,50 @@
+package types
+
+import (
+	"fmt"
+
+	backend "github.com/hashicorp/terraform/backend/init"
+	"go.starlark.net/starlark"
+)
+
+func init() {
+	backend.Init(nil)
+}
+
+func BuiltinBackend() starlark.Value {
+	return starlark.NewBuiltin("backend", func(_ *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
+		var name starlark.String
+		switch len(args) {
+		case 1:
+			var ok bool
+			name, ok = args.Index(0).(starlark.String)
+			if !ok {
+				return nil, fmt.Errorf("expected string, got %s", args.Index(0).Type())
+			}
+		default:
+			return nil, fmt.Errorf("unexpected positional arguments count")
+		}
+
+		p, err := MakeBackend(name.GoString())
+		if err != nil {
+			return nil, err
+		}
+
+		return p, p.loadKeywordArgs(kwargs)
+	})
+}
+
+type Backend struct {
+	*Resource
+}
+
+func MakeBackend(name string) (*Backend, error) {
+	fn := backend.Backend(name)
+	if fn == nil {
+		return nil, fmt.Errorf("unable to find backend %q", name)
+	}
+
+	return &Backend{
+		Resource: MakeResource(name, "", BackendKind, fn().ConfigSchema(), nil),
+	}, nil
+}

starlark/types/backend_test.go

@@ -0,0 +1,9 @@
+package types
+
+import (
+	"testing"
+)
+
+func TestBackend(t *testing.T) {
+	doTest(t, "testdata/backend.star")
+}

starlark/types/hcl.go

@@ -35,6 +35,7 @@ func BuiltinHCL() starlark.Value {
 
 func (s *Provider) ToHCL(b *hclwrite.Body) {
 	block := b.AppendNewBlock("provider", []string{s.name})
+
 	block.Body().SetAttributeValue("alias", cty.StringVal(s.Name()))
 	block.Body().SetAttributeValue("version", cty.StringVal(string(s.meta.Version)))
 	s.Resource.doToHCLAttributes(block.Body())
@@ -48,6 +49,13 @@ func (s *Provisioner) ToHCL(b *hclwrite.Body) {
 	s.Resource.doToHCLAttributes(block.Body())
 }
 
+func (s *Backend) ToHCL(b *hclwrite.Body) {
+	parent := b.AppendNewBlock("terraform", nil)
+
+	block := parent.Body().AppendNewBlock("backend", []string{s.name})
+	s.Resource.doToHCLAttributes(block.Body())
+}
+
 func (t *MapSchema) ToHCL(b *hclwrite.Body) {
 	names := make(sort.StringSlice, len(t.collections))
 	var i int
@@ -75,7 +83,8 @@ func (r *Resource) ToHCL(b *hclwrite.Body) {
 
 	var block *hclwrite.Block
 	if r.kind != NestedKind {
-		block = b.AppendNewBlock(string(r.kind), []string{r.typ, r.Name()})
+		labels := []string{r.typ, r.Name()}
+		block = b.AppendNewBlock(string(r.kind), labels)
 	} else {
 		block = b.AppendNewBlock(r.typ, nil)
 	}

starlark/types/provider_test.go

@@ -60,6 +60,7 @@ func doTest(t *testing.T, filename string) {
 	predeclared := starlark.StringDict{
 		"provider":    BuiltinProvider(pm),
 		"provisioner": BuiltinProvisioner(pm),
+		"backend":     BuiltinBackend(),
 		"hcl":         BuiltinHCL(),
 	}
 

starlark/types/resource.go

@@ -28,6 +28,7 @@ const (
 	ResourceKind   Kind = "resource"
 	DataSourceKind Kind = "data"
 	NestedKind     Kind = "nested"
+	BackendKind    Kind = "backend"
 )
 
 // Resource represents a resource as a starlark.Value, it can be of four kinds,

starlark/types/testdata/backend.star

@@ -0,0 +1,13 @@
+load("assert.star", "assert")
+
+b = backend("gcs")
+b.bucket = "tf-state-prod"
+b.prefix = "terraform/state"
+
+assert.eq(hcl(b), "" +
+'terraform {\n' + \
+'  backend "gcs" {\n' + \
+'    bucket = "tf-state-prod"\n' + \
+'    prefix = "terraform/state"\n' + \
+'  }\n' + \
+'}\n')