schemahcl: add helper/debug print function (#1834)

schemahcl/stdlib.go

@@ -5,6 +5,7 @@
 package schemahcl
 
 import (
+	"fmt"
 	"net/url"
 	"strconv"
 
@@ -14,6 +15,7 @@ import (
 	"github.com/zclconf/go-cty/cty/convert"
 	"github.com/zclconf/go-cty/cty/function"
 	"github.com/zclconf/go-cty/cty/function/stdlib"
+	"github.com/zclconf/go-cty/cty/json"
 )
 
 func stdTypes(ctx *hcl.EvalContext) *hcl.EvalContext {
@@ -128,6 +130,7 @@ func stdFuncs() map[string]function.Function {
 		"min":             stdlib.MinFunc,
 		"parseint":        stdlib.ParseIntFunc,
 		"pow":             stdlib.PowFunc,
+		"print":           printFunc,
 		"range":           stdlib.RangeFunc,
 		"regex":           stdlib.RegexFunc,
 		"regexall":        stdlib.RegexAllFunc,
@@ -306,3 +309,23 @@ var urlEscape = function.New(&function.Spec{
 		return cty.StringVal(u), nil
 	},
 })
+
+var printFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "print",
+			Type: cty.DynamicPseudoType,
+		},
+	},
+	Type: func(args []cty.Value) (cty.Type, error) {
+		return args[0].Type(), nil
+	},
+	Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
+		if b, err := json.Marshal(args[0], args[0].Type()); err != nil {
+			fmt.Println(args[0].GoString())
+		} else {
+			fmt.Println(string(b))
+		}
+		return args[0], nil
+	},
+})

schemahcl/stdlib_test.go

@@ -108,3 +108,38 @@ func TestURLEscapeFunc(t *testing.T) {
 		})
 	}
 }
+
+func Example_PrintFunc() {
+	for _, f := range []string{
+		`v  = print(1)`,
+		`v  = print(true)`,
+		`v  = print("hello, world")`,
+		`v  = print({"hello": "world"})`,
+		`v  = print(["hello", "world"])`,
+	} {
+		var d struct {
+			V cty.Value `spec:"v"`
+		}
+		if err := New().EvalBytes([]byte(f), &d, nil); err != nil {
+			fmt.Println("failed to evaluate:", err)
+			return
+		}
+		fmt.Printf("%#v\n\n", d.V)
+	}
+	// Output:
+	// 1
+	// cty.NumberIntVal(1)
+	//
+	// true
+	// cty.True
+	//
+	// "hello, world"
+	// cty.StringVal("hello, world")
+	//
+	// {"hello":"world"}
+	// cty.ObjectVal(map[string]cty.Value{"hello":cty.StringVal("world")})
+	//
+	// ["hello","world"]
+	// cty.ListVal([]cty.Value{cty.StringVal("hello"), cty.StringVal("world")})
+	//
+}