Support for native callbacks

builtins.go

@@ -589,13 +589,27 @@ func builtinExtVar(e *evaluator, namep potentialValue) (value, error) {
 	if err != nil {
 		return nil, err
 	}
-	index := ast.Identifier(name.getString())
+	index := name.getString()
 	if pv, ok := e.i.extVars[index]; ok {
 		return e.evaluate(pv)
 	}
 	return nil, e.Error("Undefined external variable: " + string(index))
 }
 
+func builtinNative(e *evaluator, namep potentialValue) (value, error) {
+	name, err := e.evaluateString(namep)
+	if err != nil {
+		return nil, err
+	}
+	index := name.getString()
+	if f, exists := e.i.nativeFuncs[index]; exists {
+		return &valueFunction{ec: f}, nil
+
+	}
+	return nil, e.Error(fmt.Sprintf("Unrecognized native function name: %v", index))
+
+}
+
 type unaryBuiltin func(*evaluator, potentialValue) (value, error)
 type binaryBuiltin func(*evaluator, potentialValue, potentialValue) (value, error)
 type ternaryBuiltin func(*evaluator, potentialValue, potentialValue, potentialValue) (value, error)
@@ -772,6 +786,7 @@ var funcBuiltins = buildBuiltinMap([]builtin{
 	&BinaryBuiltin{name: "pow", function: builtinPow, parameters: ast.Identifiers{"base", "exp"}},
 	&BinaryBuiltin{name: "modulo", function: builtinModulo, parameters: ast.Identifiers{"x", "y"}},
 	&UnaryBuiltin{name: "md5", function: builtinMd5, parameters: ast.Identifiers{"x"}},
+	&UnaryBuiltin{name: "native", function: builtinNative, parameters: ast.Identifiers{"x"}},
 
 	// internal
 	&UnaryBuiltin{name: "$objectFlatMerge", function: builtinUglyObjectFlatMerge, parameters: ast.Identifiers{"x"}},

desugarer.go

@@ -298,6 +298,12 @@ func desugar(astPtr *ast.Node, objLevel int) (err error) {
 				return
 			}
 		}
+		for i := range node.Arguments.Named {
+			err = desugar(&node.Arguments.Named[i].Arg, objLevel)
+			if err != nil {
+				return
+			}
+		}
 
 	case *ast.ApplyBrace:
 		err = desugar(&node.Left, objLevel)

interpreter.go

@@ -214,7 +214,10 @@ type interpreter struct {
 	stack callStack
 
 	// External variables
-	extVars map[ast.Identifier]potentialValue
+	extVars map[string]potentialValue
+
+	// Native functions
+	nativeFuncs map[string]*nativeFunction
 
 	// A part of std object common to all files
 	baseStd valueObject
@@ -730,6 +733,46 @@ func (i *interpreter) manifestAndSerializeJSON(trace *TraceElement, v value, mul
 	return buf.String(), nil
 }
 
+func jsonToValue(e *evaluator, v interface{}) (value, error) {
+	switch v := v.(type) {
+	case nil:
+		return &nullValue, nil
+
+	case []interface{}:
+		elems := make([]potentialValue, len(v))
+		for i, elem := range v {
+			val, err := jsonToValue(e, elem)
+			if err != nil {
+				return nil, err
+			}
+			elems[i] = &readyValue{val}
+		}
+		return makeValueArray(elems), nil
+
+	case bool:
+		return makeValueBoolean(v), nil
+	case float64:
+		return makeValueNumber(v), nil
+
+	case map[string]interface{}:
+		fieldMap := map[string]value{}
+		for name, f := range v {
+			val, err := jsonToValue(e, f)
+			if err != nil {
+				return nil, err
+			}
+			fieldMap[name] = val
+		}
+		return buildObject(ast.ObjectFieldInherit, fieldMap), nil
+
+	case string:
+		return makeValueString(v), nil
+
+	default:
+		return nil, e.Error(fmt.Sprintf("Not a json type: %#+v", v))
+	}
+}
+
 func (i *interpreter) EvalInCleanEnv(fromWhere *TraceElement, env *environment, ast ast.Node, trimmable bool) (value, error) {
 	err := i.newCall(fromWhere, *env, trimmable)
 	if err != nil {
@@ -776,8 +819,8 @@ func evaluateStd(i *interpreter) (value, error) {
 	return i.EvalInCleanEnv(evalTrace, &beforeStdEnv, node, false)
 }
 
-func prepareExtVars(i *interpreter, ext vmExtMap, kind string) map[ast.Identifier]potentialValue {
-	result := make(map[ast.Identifier]potentialValue)
+func prepareExtVars(i *interpreter, ext vmExtMap, kind string) map[string]potentialValue {
+	result := make(map[string]potentialValue)
 	for name, content := range ext {
 		if content.isCode {
 			varLoc := ast.MakeLocationRangeMessage("During evaluation")
@@ -788,9 +831,9 @@ func prepareExtVars(i *interpreter, ext vmExtMap, kind string) map[ast.Identifie
 				i:     i,
 				trace: varTrace,
 			}
-			result[ast.Identifier(name)] = codeToPV(e, "<"+kind+":"+name+">", content.value)
+			result[name] = codeToPV(e, "<"+kind+":"+name+">", content.value)
 		} else {
-			result[ast.Identifier(name)] = &readyValue{makeValueString(content.value)}
+			result[name] = &readyValue{makeValueString(content.value)}
 		}
 	}
 	return result
@@ -804,10 +847,11 @@ func buildObject(hide ast.ObjectFieldHide, fields map[string]value) valueObject
 	return makeValueSimpleObject(bindingFrame{}, fieldMap, nil)
 }
 
-func buildInterpreter(ext vmExtMap, maxStack int, importer Importer) (*interpreter, error) {
+func buildInterpreter(ext vmExtMap, nativeFuncs map[string]*nativeFunction, maxStack int, importer Importer) (*interpreter, error) {
 	i := interpreter{
 		stack:       makeCallStack(maxStack),
 		importCache: MakeImportCache(importer),
+		nativeFuncs: nativeFuncs,
 	}
 
 	stdObj, err := buildStdObject(&i)
@@ -834,8 +878,9 @@ func makeInitialEnv(filename string, baseStd valueObject) environment {
 	)
 }
 
-func evaluate(node ast.Node, ext vmExtMap, tla vmExtMap, maxStack int, importer Importer) (string, error) {
-	i, err := buildInterpreter(ext, maxStack, importer)
+// TODO(sbarzowski) this function takes far too many arguments - build interpreter in vm instead
+func evaluate(node ast.Node, ext vmExtMap, tla vmExtMap, nativeFuncs map[string]*nativeFunction, maxStack int, importer Importer) (string, error) {
+	i, err := buildInterpreter(ext, nativeFuncs, maxStack, importer)
 	if err != nil {
 		return "", err
 	}
@@ -854,7 +899,7 @@ func evaluate(node ast.Node, ext vmExtMap, tla vmExtMap, maxStack int, importer
 			toplevelArgMap := prepareExtVars(i, tla, "top-level-arg")
 			args := callArguments{}
 			for argName, pv := range toplevelArgMap {
-				args.named = append(args.named, namedCallArgument{name: argName, pv: pv})
+				args.named = append(args.named, namedCallArgument{name: ast.Identifier(argName), pv: pv})
 			}
 			funcLoc := ast.MakeLocationRangeMessage("Top-level-function")
 			funcTrace := &TraceElement{

main_test.go

@@ -18,6 +18,7 @@ package jsonnet
 
 import (
 	"bytes"
+	"encoding/json"
 	"flag"
 	"io/ioutil"
 	"path/filepath"
@@ -25,6 +26,7 @@ import (
 	"testing"
 	"unicode/utf8"
 
+	"github.com/google/go-jsonnet/ast"
 	"github.com/sergi/go-diff/diffmatchpatch"
 )
 
@@ -100,6 +102,17 @@ func TestMain(t *testing.T) {
 				vm.ExtCode(name, value)
 			}
 
+			vm.NativeFunction(&nativeFunction{
+				name:   "jsonToString",
+				params: ast.Identifiers{"x"},
+				f: func(x []interface{}) (interface{}, error) {
+					bytes, err := json.Marshal(x[0])
+					if err != nil {
+						return nil, err
+					}
+					return string(bytes), nil
+				},
+			})
 			read := func(file string) []byte {
 				bytz, err := ioutil.ReadFile(file)
 				if err != nil {

testdata/native1.golden

@@ -0,0 +1 @@
+"\"test\""

testdata/native1.jsonnet

@@ -0,0 +1 @@
+std.native("jsonToString")("test")

testdata/native2.golden

@@ -0,0 +1 @@
+"{}"

testdata/native2.jsonnet

@@ -0,0 +1 @@
+std.native("jsonToString")({})

testdata/native3.golden

@@ -0,0 +1 @@
+"{\"x\":{\"y\":\"z\"},\"xx\":42}"

testdata/native3.jsonnet

@@ -0,0 +1 @@
+std.native("jsonToString")({"x": {"y": "z"}, "xx": 42})

testdata/native4.golden

@@ -0,0 +1,15 @@
+RUNTIME ERROR: xxx
+-------------------------------------------------
+	testdata/native4:1:28-38	thunk from <$>
+
+std.native("jsonToString")(error "xxx")
+
+-------------------------------------------------
+	testdata/native4:1:1-40	$
+
+std.native("jsonToString")(error "xxx")
+
+-------------------------------------------------
+	During evaluation	
+
+

testdata/native4.jsonnet

@@ -0,0 +1 @@
+std.native("jsonToString")(error "xxx")

testdata/native5.golden

@@ -0,0 +1,10 @@
+RUNTIME ERROR: Couldn't manifest function in JSON output.
+-------------------------------------------------
+	testdata/native5:1:1-42	$
+
+std.native("jsonToString")(function() 42)
+
+-------------------------------------------------
+	During evaluation	
+
+

testdata/native5.jsonnet

@@ -0,0 +1 @@
+std.native("jsonToString")(function() 42)

testdata/native_nonexistent.golden

@@ -0,0 +1,8 @@
+RUNTIME ERROR: Unrecognized native function name: blah
+-------------------------------------------------
+	<builtin>	builtin function <native>
+
+-------------------------------------------------
+	During evaluation	
+
+

testdata/native_nonexistent.jsonnet

@@ -0,0 +1 @@
+std.native("blah")

thunks.go

@@ -287,6 +287,37 @@ func makeClosure(env environment, function *ast.Function) *closure {
 	}
 }
 
+type nativeFunction struct {
+	f      func([]interface{}) (interface{}, error)
+	params ast.Identifiers
+	name   string
+}
+
+func (native *nativeFunction) EvalCall(arguments callArguments, e *evaluator) (value, error) {
+	flatArgs := flattenArgs(arguments, native.Parameters())
+	nativeArgs := make([]interface{}, 0, len(flatArgs))
+	for _, arg := range flatArgs {
+		v, err := e.evaluate(arg)
+		if err != nil {
+			return nil, err
+		}
+		json, err := e.i.manifestJSON(e.trace, v)
+		if err != nil {
+			return nil, err
+		}
+		nativeArgs = append(nativeArgs, json)
+	}
+	resultJSON, err := native.f(nativeArgs)
+	if err != nil {
+		return nil, err
+	}
+	return jsonToValue(e, resultJSON)
+}
+
+func (native *nativeFunction) Parameters() Parameters {
+	return Parameters{required: native.params}
+}
+
 // partialPotentialValue
 // -------------------------------------
 

vm.go

@@ -31,12 +31,13 @@ import (
 // VM is the core interpreter and is the touchpoint used to parse and execute
 // Jsonnet.
 type VM struct {
-	MaxStack int
-	MaxTrace int // The number of lines of stack trace to display (0 for all of them).
-	ext      vmExtMap
-	tla      vmExtMap
-	importer Importer
-	ef       ErrorFormatter
+	MaxStack    int
+	MaxTrace    int // The number of lines of stack trace to display (0 for all of them).
+	ext         vmExtMap
+	tla         vmExtMap
+	nativeFuncs map[string]*nativeFunction
+	importer    Importer
+	ef          ErrorFormatter
 }
 
 // External variable or top level argument provided before execution
@@ -53,11 +54,12 @@ type vmExtMap map[string]vmExt
 // MakeVM creates a new VM with default parameters.
 func MakeVM() *VM {
 	return &VM{
-		MaxStack: 500,
-		ext:      make(vmExtMap),
-		tla:      make(vmExtMap),
-		ef:       ErrorFormatter{pretty: true, colorful: true, MaxStackTraceSize: 20},
-		importer: &FileImporter{},
+		MaxStack:    500,
+		ext:         make(vmExtMap),
+		tla:         make(vmExtMap),
+		nativeFuncs: make(map[string]*nativeFunction),
+		ef:          ErrorFormatter{pretty: true, colorful: true, MaxStackTraceSize: 20},
+		importer:    &FileImporter{},
 	}
 }
 
@@ -96,13 +98,18 @@ func (vm *VM) evaluateSnippet(filename string, snippet string) (output string, e
 	if err != nil {
 		return "", err
 	}
-	output, err = evaluate(node, vm.ext, vm.tla, vm.MaxStack, vm.importer)
+	output, err = evaluate(node, vm.ext, vm.tla, vm.nativeFuncs, vm.MaxStack, vm.importer)
 	if err != nil {
 		return "", err
 	}
 	return output, nil
 }
 
+// NativeFunction registers a native function
+func (vm *VM) NativeFunction(f *nativeFunction) {
+	vm.nativeFuncs[f.name] = f
+}
+
 // EvaluateSnippet evaluates a string containing Jsonnet code, return a JSON
 // string.
 //