Implement proper error handling, add godoc comments, and implement expressions

ast.go

@@ -1,66 +1,105 @@
 package scpt
 
 import (
-	"reflect"
+	"fmt"
-	"strings"
+	"github.com/alecthomas/participle/lexer"
 )
 
+// AST stores the root of the Abstract Syntax Tree for scpt
 type AST struct {
+	Pos      lexer.Position
 	Commands []*Command `@@*`
 }
 
-func (ast *AST) Execute() {
+// Execute traverses the AST and executes any commands, it returns an error
+// containing the position at which the error was encountered and the error
+// itself
+func (ast *AST) Execute() error {
 	for _, cmd := range ast.Commands {
 		if cmd.Vars != nil {
 			for _, Var := range cmd.Vars {
-				val := ParseValue(Var.Value)
+				val, err := ParseValue(Var.Value)
-				if strings.Contains(reflect.TypeOf(val).String(), ".FuncCall") {
+				if err != nil {
+					return fmt.Errorf("%s: %s", Var.Value.Pos, err)
+				}
+				if IsFuncCall(val) {
 					Call := val.(*FuncCall)
-					Vars[Var.Key], _ = CallFunction(Call)
+					Vars[Var.Key], err = CallFunction(Call)
+					if err != nil {
+						return fmt.Errorf("%s: %s", Var.Value.Pos, err)
+					}
 				} else {
 					Vars[Var.Key] = val
 				}
 			}
 		} else if cmd.Calls != nil {
 			for _, Call := range cmd.Calls {
-				_, _ = CallFunction(Call)
+				_, err := CallFunction(Call)
+				if err != nil {
+					return fmt.Errorf("%s: %s", Call.Pos, err)
+				}
 			}
 		}
 	}
+	return nil
 }
 
+// Command stores any commands encountered while parsing a script
 type Command struct {
+	Pos   lexer.Position
 	Vars  []*Var      `( @@`
 	Calls []*FuncCall `| @@ )`
 }
 
+// FuncCall stores any function calls encountered while parsing a script
 type FuncCall struct {
-	Name string `@Ident`
+	Pos  lexer.Position
-	Args []*Arg  `@@*`
+	Name string `@Ident @("-" Ident)*`
+	Args []*Arg `@@*`
 }
 
+// Arg stores arguments for function calls
 type Arg struct {
-	Key string `"with" @Ident`
+	Pos   lexer.Position
-	Value *Value  `@@`
+	Key   string `("with" @Ident)?`
+	Value *Value `@@`
 }
 
+// Var stores any variables encountered while parsing a script
 type Var struct {
-	Key string `"set" @Ident "to"`
+	Pos   lexer.Position
-	Value  *Value  `@@`
+	Key   string `"set" @Ident "to"`
+	Value *Value `@@`
 }
 
+// Value stores any literal values encountered while parsing a script
 type Value struct {
-	String  *string  `  @String`
+	Pos     lexer.Position
-	Float   *float64 `| @Float`
+	String  *string     `  @String`
-	Integer *int64   `| @Int`
+	Float   *float64    `| @Float`
-	Bool    *Bool    `| @("true" | "false")`
+	Integer *int64      `| @Int`
-	SubCmd *FuncCall `| "(" @@ ")"`
+	Bool    *Bool       `| @("true" | "false")`
-	VarVal *string `| "$" @Ident`
+	SubCmd  *FuncCall   `| "(" @@ ")"`
+	VarVal  *string     `| "$" @Ident`
+	Expr    *Expression `| "{" @@ "}"`
 }
 
+// Bool stores boolean values encountered while parsing a script.
+// It is required for the Capture method
 type Bool bool
 
+// Capture parses a boolean literal encountered in the script into
+// a Go boolean value
 func (b *Bool) Capture(values []string) error {
 	*b = values[0] == "true"
 	return nil
 }
+
+// Expression stores any expressions encountered while parsing a
+// script for later evaluation
+type Expression struct {
+	Pos   lexer.Position
+	Left  *Value `@@`
+	Op    string `@( ">" | ">" "=" | "<" | "<" "=" | "!" "=" | "=" "=" | "+" | "-" | "*" | "/" | "^" | "%")`
+	Right *Value `@@`
+}

cmd/scpt/main.go

@@ -23,5 +23,8 @@ func main() {
 	if err != nil {
 		log.Fatalln("Error parsing file:", err)
 	}
-	ast.Execute()
+	err = ast.Execute()
+	if err != nil {
+		log.Fatalln("Error executing script:", err)
+	}
 }

defaults.go

@@ -0,0 +1,54 @@
+package scpt
+
+import (
+	"errors"
+	"fmt"
+	"github.com/gen2brain/dlgs"
+	"os"
+	"os/exec"
+)
+
+func displayDialog(args map[string]interface{}) (interface{}, error) {
+	title, ok := args["title"]
+	if !ok {
+		return nil, errors.New("title not provided")
+	}
+	text, ok := args[""]
+	if !ok {
+		return nil, errors.New("text not provided")
+	}
+	switch args["type"] {
+	case "yesno":
+		return dlgs.Question(fmt.Sprint(title), fmt.Sprint(text), true)
+	case "info":
+		return dlgs.Info(fmt.Sprint(title), fmt.Sprint(text))
+	case "error":
+		return dlgs.Error(fmt.Sprint(title), fmt.Sprint(text))
+	case "entry":
+		defaultText, ok := args["default"]
+		if !ok {
+			defaultText = ""
+		}
+		input, _, err := dlgs.Entry(fmt.Sprint(title), fmt.Sprint(text), fmt.Sprint(defaultText))
+		return input, err
+	default:
+		return nil, fmt.Errorf("unknown dialog type: %v", args["type"])
+	}
+}
+
+func doShellScript(args map[string]interface{}) (interface{}, error) {
+	script, ok := args[""].(string)
+	if ok {
+		cmd := exec.Command("sh", "-c", script)
+		cmd.Stdout = os.Stdout
+		_ = cmd.Run()
+		return "", nil
+	} else {
+		return nil, errors.New("script not provided")
+	}
+}
+
+func print(args map[string]interface{}) (interface{}, error) {
+	fmt.Println(args)
+	return nil, nil
+}

go.mod

@@ -4,5 +4,8 @@ go 1.16
 
 require (
 	github.com/alecthomas/participle v0.7.1
+	github.com/antonmedv/expr v1.8.9
 	github.com/gen2brain/dlgs v0.0.0-20210222160047-2f436553172f
+	github.com/gopherjs/gopherjs v0.0.0-20210202160940-bed99a852dfe // indirect
+	github.com/rs/zerolog v1.20.0
 )

go.sum

@@ -1,18 +1,70 @@
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scpt.go

@@ -4,34 +4,42 @@ import (
 	"errors"
 	"fmt"
 	"github.com/alecthomas/participle"
-	"github.com/gen2brain/dlgs"
+	"github.com/antonmedv/expr"
 	"io"
-	"os"
+	"reflect"
-	"os/exec"
 	"strings"
 )
 
+// Vars stores any variables set during script runtime
 var Vars = map[string]interface{}{}
 
+// FuncMap is a map of strings mapped to suitable script functions
 type FuncMap map[string]func(map[string]interface{}) (interface{}, error)
 
+// Funcs stores the functions allowed for use in a script
 var Funcs = FuncMap{
-	"displaydialog": displayDialog,
+	"display-dialog":  displayDialog,
-	"doshellscript": doShellScript,
+	"do-shell-script": doShellScript,
+	"print":           print,
 }
 
+// AddFuncs adds all functions from the provided FuncMap into
+// the Funcs variable
 func AddFuncs(fnMap FuncMap) {
 	for name, fn := range fnMap {
 		Funcs[name] = fn
 	}
 }
 
+// AddVars adds all functions from the provided map into
+// the Vars variable
 func AddVars(varMap map[string]interface{}) {
 	for name, val := range varMap {
 		Vars[name] = val
 	}
 }
 
+// Parse uses participle to parse a script from r into a new AST
 func Parse(r io.Reader) (*AST, error) {
 	parser, err := participle.Build(&AST{})
 	if err != nil {
@@ -45,71 +53,102 @@ func Parse(r io.Reader) (*AST, error) {
 	return ast, nil
 }
 
-func ParseValue(val *Value) interface{} {
+// ParseValue parses a Value struct into a go value
+func ParseValue(val *Value) (interface{}, error) {
 	if val.String != nil {
-		return strings.Trim(*val.String, `"`)
+		return strings.Trim(*val.String, `"`), nil
 	} else if val.Bool != nil {
-		return *val.Bool
+		return *val.Bool, nil
 	} else if val.Float != nil {
-		return *val.Float
+		return *val.Float, nil
 	} else if val.Integer != nil {
-		return *val.Integer
+		return *val.Integer, nil
 	} else if val.SubCmd != nil {
-		return val.SubCmd
+		return val.SubCmd, nil
 	} else if val.VarVal != nil {
-		return Vars[*val.VarVal]
+		return Vars[*val.VarVal], nil
-	}
+	} else if val.Expr != nil {
-	return nil
+		left, _ := ParseValue(val.Expr.Left)
-}
+		if isStr(left) {
-
+			left = requoteStr(left.(string))
-func UnwrapArgs(args []*Arg) map[string]interface{} {
-	argMap := map[string]interface{}{}
-	for _, arg := range args {
-		argMap[arg.Key] = ParseValue(arg.Value)
-	}
-	return argMap
-}
-
-func CallFunction(call *FuncCall) (interface{}, error) {
-	argMap := UnwrapArgs(call.Args)
-	return Funcs[call.Name](argMap)
-}
-
-func displayDialog(args map[string]interface{}) (interface{}, error) {
-	title, ok := args["title"]
-	if !ok {
-		return nil, errors.New("title not provided")
-	}
-	text, ok := args["text"]
-	if !ok {
-		return nil, errors.New("text not provided")
-	}
-	switch args["type"] {
-	case "yesno":
-		return dlgs.Question(fmt.Sprint(title), fmt.Sprint(text), true)
-	case "info":
-		return dlgs.Info(fmt.Sprint(title), fmt.Sprint(text))
-	case "error":
-		return dlgs.Error(fmt.Sprint(title), fmt.Sprint(text))
-	case "entry":
-		defaultText, ok := args["default"]
-		if !ok {
-			defaultText = ""
 		}
-		input, _, err := dlgs.Entry(fmt.Sprint(title), fmt.Sprint(text), fmt.Sprint(defaultText))
+		right, _ := ParseValue(val.Expr.Right)
-		return input, err
+		if isStr(right) {
+			right = requoteStr(right.(string))
+		}
+		exp := fmt.Sprintf(
+			"%v %s %v",
+			left,
+			val.Expr.Op,
+			right,
+		)
+		fmt.Println(exp)
+		program, err := expr.Compile(strings.ReplaceAll(exp, "^", "**"))
+		if err != nil {
+			return nil, err
+		}
+		out, err := expr.Run(program, Vars)
+		if err != nil {
+			return nil, err
+		}
+		return out, nil
 	}
 	return nil, nil
 }
 
-func doShellScript(args map[string]interface{}) (interface{}, error) {
+// Add quotes to an unquoted string
-	script, ok := args["content"].(string)
+func requoteStr(s string) string {
-	if ok {
+	return `"` + s + `"`
-		cmd := exec.Command("sh", "-c", script)
+}
-		cmd.Stdout = os.Stdout
+
-		_ = cmd.Run()
+// Check if i is a string
-		return "", nil
+func isStr(i interface{}) bool {
-	} else {
+	if reflect.TypeOf(i).String() == "string" {
-		return nil, errors.New("script not provided")
+		return true
-	}
+	}
+	return false
+}
+
+// UnwrapArgs takes a slice of Arg structs and returns a map
+// storing the argument name and its value. If the argument has
+// no name, its key will be an empty string
+func UnwrapArgs(args []*Arg) (map[string]interface{}, error) {
+	argMap := map[string]interface{}{}
+	for _, arg := range args {
+		val, err := ParseValue(arg.Value)
+		if err != nil {
+			return nil, err
+		}
+		if IsFuncCall(val) {
+			argMap[arg.Key], err = CallFunction(val.(*FuncCall))
+			if err != nil {
+				return nil, err
+			}
+			continue
+		}
+		argMap[arg.Key] = val
+	}
+	return argMap, nil
+}
+
+// IsFuncCall checks if val is a FuncCall struct
+func IsFuncCall(val interface{}) bool {
+	if strings.Contains(reflect.TypeOf(val).String(), ".FuncCall") {
+		return true
+	}
+	return false
+}
+
+// CallFunction executes a given function call in the form of
+// a FuncCall struct
+func CallFunction(call *FuncCall) (interface{}, error) {
+	argMap, err := UnwrapArgs(call.Args)
+	if err != nil {
+		return nil, err
+	}
+	fn, ok := Funcs[call.Name]
+	if !ok {
+		return nil, errors.New("no such function: " + call.Name)
+	}
+	return fn(argMap)
 }

test.scpt

@@ -1,5 +1,6 @@
-set y to (displaydialog with text "Hello" with title 12 with type "yesno")
+set y to (display-dialog "Hello" with title 12 with type "yesno")
-displaydialog with text "Goodbye" with title 21 with type "error"
+display-dialog "Goodbye" with title 21 with type "error"
-doshellscript with content "notify-send Test Notification"
+do-shell-script "notify-send Test Notification"
-set g to (displaydialog with text "Test 2" with title 30 with type "entry" with default "text")
+print (display-dialog {"Test " + "2"} with title 30 with type "entry" with default "text")
-set x to $g
+set x to $y
+print { 3+4 }