Support for std.thisFile, fixes google#91.

Sadly it means that std in no longer the same object in each file.

imports.go

@@ -86,7 +86,7 @@ func codeToPV(e *evaluator, filename string, code string) potentialValue {
 		// The same thinking applies to external variables.
 		return makeErrorThunk(err)
 	}
-	return makeThunk(e.i.initialEnv, node)
+	return makeThunk(makeInitialEnv(filename, e.i.baseStd), node)
 }
 
 func (cache *ImportCache) ImportCode(codeDir, importedPath string, e *evaluator) (value, error) {

interpreter.go

@@ -203,7 +203,9 @@ type interpreter struct {
 
 	// The clean environment in which we execute imports, extVars as well
 	// as the main program. It contains std.
-	initialEnv environment
+	//initialEnv environment
+
+	baseStd valueObject
 
 	// Keeps imports
 	importCache *ImportCache
@@ -709,7 +711,7 @@ func (i *interpreter) EvalInCleanEnv(fromWhere *TraceElement, env *environment,
 	return val, err
 }
 
-func buildStdObject(i *interpreter) (value, error) {
+func buildStdObject(i *interpreter) (valueObject, error) {
 	objVal, err := evaluateStd(i)
 	if err != nil {
 		return nil, err
@@ -761,6 +763,14 @@ func prepareExtVars(i *interpreter, ext vmExtMap) map[ast.Identifier]potentialVa
 	return result
 }
 
+func buildObject(hide ast.ObjectFieldHide, fields map[string]value) valueObject {
+	fieldMap := valueSimpleObjectFieldMap{}
+	for name, v := range fields {
+		fieldMap[name] = valueSimpleObjectField{hide, &readyValue{v}}
+	}
+	return makeValueSimpleObject(bindingFrame{}, fieldMap, nil)
+}
+
 func buildInterpreter(ext vmExtMap, maxStack int, importer Importer) (*interpreter, error) {
 	i := interpreter{
 		stack:       makeCallStack(maxStack),
@@ -772,18 +782,25 @@ func buildInterpreter(ext vmExtMap, maxStack int, importer Importer) (*interpret
 		return nil, err
 	}
 
-	i.initialEnv = makeEnvironment(
-		bindingFrame{
-			"std": &readyValue{stdObj},
-		},
-		makeUnboundSelfBinding(),
-	)
+	i.baseStd = stdObj
 
 	i.extVars = prepareExtVars(&i, ext)
 
 	return &i, nil
 }
 
+func makeInitialEnv(filename string, baseStd valueObject) environment {
+	fileSpecific := buildObject(ast.ObjectFieldHidden, map[string]value{
+		"thisFile": makeValueString(filename),
+	})
+	return makeEnvironment(
+		bindingFrame{
+			"std": &readyValue{makeValueExtendedObject(baseStd, fileSpecific)},
+		},
+		makeUnboundSelfBinding(),
+	)
+}
+
 func evaluate(node ast.Node, ext vmExtMap, maxStack int, importer Importer) (string, error) {
 	i, err := buildInterpreter(ext, maxStack, importer)
 	if err != nil {
@@ -793,7 +810,8 @@ func evaluate(node ast.Node, ext vmExtMap, maxStack int, importer Importer) (str
 	evalTrace := &TraceElement{
 		loc: &evalLoc,
 	}
-	result, err := i.EvalInCleanEnv(evalTrace, &i.initialEnv, node)
+	env := makeInitialEnv(node.Loc().FileName, i.baseStd)
+	result, err := i.EvalInCleanEnv(evalTrace, &env, node)
 	if err != nil {
 		return "", err
 	}

testdata/std.thisFile.golden

@@ -0,0 +1 @@
+"testdata/std.thisFile"

testdata/std.thisFile.jsonnet

@@ -0,0 +1 @@
+std.thisFile

testdata/std.thisFile2.golden

@@ -0,0 +1 @@
+"testdata/std.thisFile.jsonnet"

testdata/std.thisFile2.jsonnet

@@ -0,0 +1 @@
+import "std.thisFile.jsonnet"