starlark/types: evaluate function implementation

Author: mcuadros

starlark/runtime/runtime.go

@@ -58,7 +58,9 @@ func NewRuntime(pm *terraform.PluginManager) *Runtime {
 			"backend":     types.BuiltinBackend(),
 			"hcl":         types.BuiltinHCL(),
 			"fn":          types.BuiltinFunctionComputed(),
+			"evaluate":    types.BuiltinEvaluate(),
 			"struct":      starlark.NewBuiltin("struct", starlarkstruct.Make),
+			"module":      starlark.NewBuiltin("module", starlarkstruct.MakeModule),
 		},
 	}
 }
@@ -68,6 +70,8 @@ func (r *Runtime) ExecFile(filename string) (starlark.StringDict, error) {
 	r.path, _ = osfilepath.Split(filename)
 
 	thread := &starlark.Thread{Name: "thread", Load: r.load}
+	thread.SetLocal("base_path", r.path)
+
 	return starlark.ExecFile(thread, filename, nil, r.predeclared)
 }
 

starlark/runtime/testdata/load.star

@@ -1,2 +1,9 @@
 # test relative loading
 load("includes/foo.star", "foo")
+
+# evaluate and correct base_path
+mod = evaluate("includes/foo.star")
+print(mod.foo)
+
+# module constructor
+module("foo")

starlark/types/evaluate.go

@@ -0,0 +1,44 @@
+package types
+
+import (
+	"fmt"
+	"path/filepath"
+
+	"go.starlark.net/starlark"
+	"go.starlark.net/starlarkstruct"
+)
+
+func BuiltinEvaluate() starlark.Value {
+	return starlark.NewBuiltin("evaluate", func(t *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
+		var raw starlark.String
+		switch len(args) {
+		case 1:
+			var ok bool
+			raw, 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")
+		}
+
+		dict := starlark.StringDict{}
+		for _, kwarg := range kwargs {
+			dict[kwarg.Index(0).(starlark.String).GoString()] = kwarg.Index(1)
+		}
+
+		filename := raw.GoString()
+		if base, ok := t.Local("base_path").(string); ok {
+			filename = filepath.Join(base, filename)
+		}
+
+		_, file := filepath.Split(filename)
+		name := file[:len(file)-len(filepath.Ext(file))]
+
+		global, err := starlark.ExecFile(t, filename, nil, dict)
+		return &starlarkstruct.Module{
+			Name:    name,
+			Members: global,
+		}, err
+	})
+}

starlark/types/evaluate_test.go

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

starlark/types/provider_test.go

@@ -57,6 +57,8 @@ func doTest(t *testing.T, filename string) {
 
 	log.SetOutput(ioutil.Discard)
 	thread := &starlark.Thread{Load: load}
+	thread.SetLocal("base_path", "testdata")
+
 	test.SetReporter(thread, t)
 
 	pm := &terraform.PluginManager{".providers"}
@@ -67,6 +69,7 @@ func doTest(t *testing.T, filename string) {
 		"backend":     BuiltinBackend(),
 		"hcl":         BuiltinHCL(),
 		"fn":          BuiltinFunctionComputed(),
+		"evaluate":    BuiltinEvaluate(),
 	}
 
 	_, err := starlark.ExecFile(thread, filename, nil, predeclared)

starlark/types/testdata/evaluate.star

@@ -0,0 +1,6 @@
+load("assert.star", "assert")
+
+bar = "bar"
+module = evaluate("evaluate/test.star", bar=bar)
+assert.eq(str(module), '<module "test">')
+assert.eq(module.foo, bar)

starlark/types/testdata/evaluate/test.star

@@ -0,0 +1 @@
+foo = bar