config/lang: string to int

config/lang/builtins.go

@@ -6,11 +6,14 @@ import (
 	"github.com/hashicorp/terraform/config/lang/ast"
 )
 
+// NOTE: All builtins are tested in engine_test.go
+
 func registerBuiltins(scope *Scope) {
 	if scope.FuncMap == nil {
 		scope.FuncMap = make(map[string]Function)
 	}
 	scope.FuncMap["__builtin_IntToString"] = builtinIntToString()
+	scope.FuncMap["__builtin_StringToInt"] = builtinStringToInt()
 }
 
 func builtinIntToString() Function {
@@ -22,3 +25,18 @@ func builtinIntToString() Function {
 		},
 	}
 }
+
+func builtinStringToInt() Function {
+	return Function{
+		ArgTypes:   []ast.Type{ast.TypeInt},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			v, err := strconv.ParseInt(args[0].(string), 0, 0)
+			if err != nil {
+				return nil, err
+			}
+
+			return int(v), nil
+		},
+	}
+}

config/lang/engine.go

@@ -33,6 +33,9 @@ func (e *Engine) Execute(root ast.Node) (interface{}, ast.Type, error) {
 		ast.TypeInt: {
 			ast.TypeString: "__builtin_IntToString",
 		},
+		ast.TypeString: {
+			ast.TypeInt: "__builtin_StringToInt",
+		},
 	}
 
 	// Build our own semantic checks that we always run

config/lang/engine_test.go

@@ -2,6 +2,7 @@ package lang
 
 import (
 	"reflect"
+	"strconv"
 	"testing"
 
 	"github.com/hashicorp/terraform/config/lang/ast"
@@ -94,6 +95,24 @@ func TestEngineExecute(t *testing.T) {
 			"foo 42",
 			ast.TypeString,
 		},
+
+		{
+			`foo ${foo("42")}`,
+			&Scope{
+				FuncMap: map[string]Function{
+					"foo": Function{
+						ArgTypes:   []ast.Type{ast.TypeInt},
+						ReturnType: ast.TypeString,
+						Callback: func(args []interface{}) (interface{}, error) {
+							return strconv.FormatInt(int64(args[0].(int)), 10), nil
+						},
+					},
+				},
+			},
+			false,
+			"foo 42",
+			ast.TypeString,
+		},
 	}
 
 	for _, tc := range cases {