lang: funcs: Differentiate between empty and nil values

It would be good to differentiate between receiving an empty value or
not having received a value yet. This is similar to the previous commit.

lang/funcs/core/deploy/abspath_func.go

@@ -43,7 +43,7 @@ type AbsPathFunc struct {
 	data *interfaces.FuncData
 	last types.Value // last value received to use for diff
 
-	path   string  // the active path
+	path   *string // the active path
 	result *string // last calculated output
 
 	closeChan chan struct{}
@@ -110,10 +110,10 @@ func (obj *AbsPathFunc) Stream() error {
 
 			path := input.Struct()[pathArg].Str()
 			// TODO: add validation for absolute path?
-			if path == obj.path {
+			if obj.path != nil && *obj.path == path {
 				continue // nothing changed
 			}
-			obj.path = path
+			obj.path = &path
 
 			p := strings.TrimSuffix(obj.data.Base, "/")
 			if p == obj.data.Base { // didn't trim, so we fail
@@ -122,13 +122,13 @@ func (obj *AbsPathFunc) Stream() error {
 			}
 			result := p
 
-			if obj.path == "" {
+			if *obj.path == "" {
 				result += "/" // add the above trailing slash back
-			} else if !strings.HasPrefix(obj.path, "/") {
+			} else if !strings.HasPrefix(*obj.path, "/") {
-				return fmt.Errorf("path was not absolute, got: `%s`", obj.path)
+				return fmt.Errorf("path was not absolute, got: `%s`", *obj.path)
 				//result += "/" // be forgiving ?
 			}
-			result += obj.path
+			result += *obj.path
 
 			if obj.result != nil && *obj.result == result {
 				continue // result didn't change

lang/funcs/core/deploy/readfile_func.go

@@ -40,7 +40,7 @@ type ReadFileFunc struct {
 	data *interfaces.FuncData
 	last types.Value // last value received to use for diff
 
-	filename string  // the active filename
+	filename *string // the active filename
 	result   *string // last calculated output
 
 	closeChan chan struct{}
@@ -107,10 +107,11 @@ func (obj *ReadFileFunc) Stream() error {
 
 			filename := input.Struct()["filename"].Str()
 			// TODO: add validation for absolute path?
-			if filename == obj.filename {
+			// TODO: add check for empty string
+			if obj.filename != nil && *obj.filename == filename {
 				continue // nothing changed
 			}
-			obj.filename = filename
+			obj.filename = &filename
 
 			p := strings.TrimSuffix(obj.data.Base, "/")
 			if p == obj.data.Base { // didn't trim, so we fail
@@ -119,11 +120,11 @@ func (obj *ReadFileFunc) Stream() error {
 			}
 			path := p
 
-			if !strings.HasPrefix(obj.filename, "/") {
+			if !strings.HasPrefix(*obj.filename, "/") {
-				return fmt.Errorf("filename was not absolute, got: `%s`", obj.filename)
+				return fmt.Errorf("filename was not absolute, got: `%s`", *obj.filename)
 				//path += "/" // be forgiving ?
 			}
-			path += obj.filename
+			path += *obj.filename
 
 			fs, err := obj.init.World.Fs(obj.data.FsURI) // open the remote file system
 			if err != nil {

lang/funcs/core/deploy/readfileabs_func.go

@@ -40,7 +40,7 @@ type ReadFileAbsFunc struct {
 	data *interfaces.FuncData
 	last types.Value // last value received to use for diff
 
-	filename string  // the active filename
+	filename *string // the active filename
 	result   *string // last calculated output
 
 	closeChan chan struct{}
@@ -107,20 +107,21 @@ func (obj *ReadFileAbsFunc) Stream() error {
 
 			filename := input.Struct()["filename"].Str()
 			// TODO: add validation for absolute path?
-			if filename == obj.filename {
+			// TODO: add check for empty string
+			if obj.filename != nil && *obj.filename == filename {
 				continue // nothing changed
 			}
-			obj.filename = filename
+			obj.filename = &filename
 
 			fs, err := obj.init.World.Fs(obj.data.FsURI) // open the remote file system
 			if err != nil {
 				return errwrap.Wrapf(err, "can't load code from file system `%s`", obj.data.FsURI)
 			}
-			content, err := fs.ReadFile(obj.filename) // open the remote file system
+			content, err := fs.ReadFile(*obj.filename) // open the remote file system
 			// We could use it directly, but it feels like less correct.
-			//content, err := obj.data.Fs.ReadFile(obj.filename) // open the remote file system
+			//content, err := obj.data.Fs.ReadFile(*obj.filename) // open the remote file system
 			if err != nil {
-				return errwrap.Wrapf(err, "can't read file `%s`", obj.filename)
+				return errwrap.Wrapf(err, "can't read file `%s`", *obj.filename)
 			}
 
 			result := string(content) // convert to string

lang/funcs/core/os/readfile_func.go

@@ -41,7 +41,7 @@ type ReadFileFunc struct {
 	init *interfaces.Init
 	last types.Value // last value received to use for diff
 
-	filename   string // the active filename
+	filename   *string // the active filename
 	recWatcher *recwatch.RecWatcher
 	events     chan error // internal events
 	wg         *sync.WaitGroup
@@ -112,10 +112,11 @@ func (obj *ReadFileFunc) Stream() error {
 
 			filename := input.Struct()["filename"].Str()
 			// TODO: add validation for absolute path?
-			if filename == obj.filename {
+			// TODO: add check for empty string
+			if obj.filename != nil && *obj.filename == filename {
 				continue // nothing changed
 			}
-			obj.filename = filename
+			obj.filename = &filename
 
 			if obj.recWatcher != nil {
 				obj.recWatcher.Close() // close previous watcher
@@ -123,7 +124,7 @@ func (obj *ReadFileFunc) Stream() error {
 			}
 			// create new watcher
 			obj.recWatcher = &recwatch.RecWatcher{
-				Path:    obj.filename,
+				Path:    *obj.filename,
 				Recurse: false,
 				Flags: recwatch.Flags{
 					// TODO: add Logf
@@ -189,7 +190,7 @@ func (obj *ReadFileFunc) Stream() error {
 			}
 
 			// read file...
-			content, err := ioutil.ReadFile(obj.filename)
+			content, err := ioutil.ReadFile(*obj.filename)
 			if err != nil {
 				return errwrap.Wrapf(err, "error reading file")
 			}