lang: core, funcs: Port some functions to CallableFunc API

Some modern features of our function engine and language might require
this new API, so port what we can and figure out the rest later.

lang/core/deploy/abspath.go

@@ -60,8 +60,9 @@ type AbsPathFunc struct {
 	data *interfaces.FuncData
 	last types.Value // last value received to use for diff
 
-	path   *string // the active path
-	result *string // last calculated output
+	args   []types.Value
+	path   *string     // the active path
+	result types.Value // last calculated output
 }
 
 // String returns a simple name for this function. This is needed so this struct
@@ -128,43 +129,64 @@ func (obj *AbsPathFunc) Stream(ctx context.Context) error {
 			}
 			obj.last = input // store for next
 
-			path := input.Struct()[absPathArgNamePath].Str()
+			args, err := interfaces.StructToCallableArgs(input) // []types.Value, error)
+			if err != nil {
+				return err
+			}
+			obj.args = args
+
+			path := args[0].Str()
 			// TODO: add validation for absolute path?
 			if obj.path != nil && *obj.path == path {
 				continue // nothing changed
 			}
 			obj.path = &path
 
-			p := strings.TrimSuffix(obj.data.Base, "/")
-			if p == obj.data.Base { // didn't trim, so we fail
-				// programming error
-				return fmt.Errorf("no trailing slash on Base, got: `%s`", p)
+			result, err := obj.Call(ctx, obj.args)
+			if err != nil {
+				return err
 			}
-			result := p
 
-			if *obj.path == "" {
-				result += "/" // add the above trailing slash back
-			} else if !strings.HasPrefix(*obj.path, "/") {
-				return fmt.Errorf("path was not absolute, got: `%s`", *obj.path)
-				//result += "/" // be forgiving ?
-			}
-			result += *obj.path
-
-			if obj.result != nil && *obj.result == result {
+			// if the result is still the same, skip sending an update...
+			if obj.result != nil && result.Cmp(obj.result) == nil {
 				continue // result didn't change
 			}
-			obj.result = &result // store new result
+			obj.result = result // store new result
 
 		case <-ctx.Done():
 			return nil
 		}
 
 		select {
-		case obj.init.Output <- &types.StrValue{
-			V: *obj.result,
-		}:
+		case obj.init.Output <- obj.result: // send
+			// pass
 		case <-ctx.Done():
 			return nil
 		}
 	}
 }
+
+// Call this function with the input args and return the value if it is possible
+// to do so at this time.
+func (obj *AbsPathFunc) Call(ctx context.Context, args []types.Value) (types.Value, error) {
+	path := args[0].Str()
+
+	p := strings.TrimSuffix(obj.data.Base, "/")
+	if p == obj.data.Base { // didn't trim, so we fail
+		// programming error
+		return nil, fmt.Errorf("no trailing slash on Base, got: `%s`", p)
+	}
+	result := p
+
+	if path == "" {
+		result += "/" // add the above trailing slash back
+	} else if !strings.HasPrefix(path, "/") {
+		return nil, fmt.Errorf("path was not absolute, got: `%s`", path)
+		//result += "/" // be forgiving ?
+	}
+	result += path
+
+	return &types.StrValue{
+		V: result,
+	}, nil
+}