Merge pull request #142 from Flipez/add-rescue

[object/error] Add ability to rescue errors and introduce `begin/rescue/end`

ast/ast_test.go

@@ -56,6 +56,10 @@ func TestString(t *testing.T) {
 			"break",
 			"break",
 		},
+		{
+			"begin\ntrue\nrescue e\nfalse\nend",
+			"begin\ntrue\nrescue e\nfalse\nend",
+		},
 	}
 
 	for _, tt := range tests {

ast/begin.go

@@ -0,0 +1,23 @@
+package ast
+
+import (
+	"bytes"
+
+	"github.com/flipez/rocket-lang/token"
+)
+
+type Begin struct {
+	Token token.Token
+	Block *Block
+}
+
+func (b *Begin) TokenLiteral() string { return b.Token.Literal }
+func (b *Begin) String() string {
+	var out bytes.Buffer
+
+	out.WriteString("begin\n")
+	out.WriteString(b.Block.String())
+	out.WriteString("\nend")
+
+	return out.String()
+}

ast/block.go

@@ -9,6 +9,7 @@ import (
 type Block struct {
 	Token      token.Token // the { token
 	Statements []Statement
+	Rescue     *Rescue
 }
 
 func (bs *Block) TokenLiteral() string { return bs.Token.Literal }
@@ -19,5 +20,13 @@ func (bs *Block) String() string {
 		out.WriteString(s.String())
 	}
 
+	if bs.Rescue != nil {
+		out.WriteString("\nrescue ")
+		out.WriteString(bs.Rescue.ErrorIdent.Literal + "\n")
+		for _, s := range bs.Rescue.Block.Statements {
+			out.WriteString(s.String())
+		}
+	}
+
 	return out.String()
 }

ast/rescue.go

@@ -0,0 +1,16 @@
+package ast
+
+import (
+	"github.com/flipez/rocket-lang/token"
+)
+
+type Rescue struct {
+	Token      token.Token // the { token
+	ErrorIdent token.Token
+	Block      *Block
+}
+
+func (r *Rescue) TokenLiteral() string { return r.Token.Literal }
+func (r *Rescue) String() string {
+	return r.Block.String()
+}

docs/docs/literals/error.md

@@ -1,10 +1,65 @@
 # Error
 
+An Error is created by RocketLang if unallowed or invalid code is run.
+An error does often replace the original return value of a function or identifier.
+The documentation of those functions does indicate ERROR as a potential return value.
 
+A program can rescue from errors within a block or alter it's behavior within other blocks like 'if' or 'def'.
 
 
+
+```js
+def test()
+  puts(nope)
+rescue e
+  puts("Got error: '" + e.msg() + "'")
+end
+
+test()
+
+=> "Got error in if: 'identifier not found: error'"
+
+if (true)
+  nope()
+rescue your_name
+  puts("Got error in if: '" + your_name.msg() + "'")
+end
+
+=> "Got error in if: 'identifier not found: nope'"
+
+begin
+  puts(nope)
+rescue e
+  puts("rescue")
+end
+
+=> "rescue"
+
+```
+
 ## Literal Specific Methods
 
+### msg()
+> Returns `STRING`
+
+Returns the error message
+
+:::caution
+Please note that performing `.msg()` on a ERROR object does result in a STRING object which then will no longer be treated as an error!
+:::
+
+
+```js
+» def ()
+puts(nope)
+rescue e
+puts((rescued error: + e.msg()))
+end
+🚀 » test()
+"rescued error:identifier not found: nope"
+```
+
+
 
 ## Generic Literal Methods
 

docs/generate.go

@@ -148,7 +148,43 @@ is_true = a != b;`,
 		DefaultMethods: default_methods}
 	create_doc("docs/templates/literal.md", "docs/docs/literals/boolean.md", tempData)
 
-	tempData = templateData{Title: "Error", LiteralMethods: error_methods, DefaultMethods: default_methods}
+	tempData = templateData{
+		Title: "Error",
+		Description: `An Error is created by RocketLang if unallowed or invalid code is run.
+An error does often replace the original return value of a function or identifier.
+The documentation of those functions does indicate ERROR as a potential return value.
+
+A program can rescue from errors within a block or alter it's behavior within other blocks like 'if' or 'def'.
+`,
+		Example: `def test()
+  puts(nope)
+rescue e
+  puts("Got error: '" + e.msg() + "'")
+end
+
+test()
+
+=> "Got error in if: 'identifier not found: error'"
+
+if (true)
+  nope()
+rescue your_name
+  puts("Got error in if: '" + your_name.msg() + "'")
+end
+
+=> "Got error in if: 'identifier not found: nope'"
+
+begin
+  puts(nope)
+rescue e
+  puts("rescue")
+end
+
+=> "rescue"
+`,
+		LiteralMethods: error_methods,
+		DefaultMethods: default_methods,
+	}
 	create_doc("docs/templates/literal.md", "docs/docs/literals/error.md", tempData)
 
 	tempData = templateData{

evaluator/block.go

@@ -13,7 +13,14 @@ func evalBlock(block *ast.Block, env *object.Environment) object.Object {
 
 		if result != nil {
 			rt := result.Type()
-			if rt == object.RETURN_VALUE_OBJ || rt == object.ERROR_OBJ || rt == object.BREAK_VALUE_OBJ || rt == object.NEXT_VALUE_OBJ {
+			if rt == object.ERROR_OBJ {
+				if block.Rescue != nil {
+					env.Set(block.Rescue.ErrorIdent.Literal, result)
+					result = evalBlock(block.Rescue.Block, env)
+				}
+				return result
+			}
+			if rt == object.RETURN_VALUE_OBJ || rt == object.BREAK_VALUE_OBJ || rt == object.NEXT_VALUE_OBJ {
 				return result
 			}
 		}

evaluator/evaluator.go

@@ -16,6 +16,8 @@ func Eval(node ast.Node, env *object.Environment) object.Object {
 		return Eval(node.Expression, env)
 	case *ast.Block:
 		return evalBlock(node, env)
+	case *ast.Begin:
+		return evalBlock(node.Block, env)
 	case *ast.Foreach:
 		return evalForeach(node, env)
 	case *ast.While:
@@ -209,13 +211,13 @@ func evalBangOperatorExpression(right object.Object) object.Object {
 }
 
 func evalMinusPrefixOperatorExpression(right object.Object) object.Object {
-  switch val := right.(type) {
-  case *object.Integer:
-    return object.NewInteger(-val.Value)
-  case *object.Float:
-    return object.NewFloat(-val.Value)
-  }
-  return object.NewErrorFormat("unknown operator: -%s", right.Type())
+	switch val := right.(type) {
+	case *object.Integer:
+		return object.NewInteger(-val.Value)
+	case *object.Float:
+		return object.NewFloat(-val.Value)
+	}
+	return object.NewErrorFormat("unknown operator: -%s", right.Type())
 }
 
 func nativeBoolToBooleanObject(input bool) *object.Boolean {

evaluator/evaluator_test.go

@@ -218,6 +218,9 @@ func TestErrorHandling(t *testing.T) {
 		{"break(1.nope())", "undefined method `.nope()` for INTEGER"},
 		{"next(1.nope())", "undefined method `.nope()` for INTEGER"},
 		{"nil.nope()", "undefined method `.nope()` for NIL"},
+		{"begin puts(nope) end", "identifier not found: nope"},
+		{"begin puts(nope) rescue e e.nope() end", "undefined method `.nope()` for ERROR"},
+		{"a = begin puts(nope) rescue e e.msg() end; a.nope()", "undefined method `.nope()` for STRING"},
 	}
 
 	for _, tt := range tests {

object/error.go

@@ -19,3 +19,27 @@ func (e *Error) Inspect() string  { return "ERROR: " + e.Message }
 func (e *Error) InvokeMethod(method string, env Environment, args ...Object) Object {
 	return objectMethodLookup(e, method, env, args)
 }
+
+func init() {
+	objectMethods[ERROR_OBJ] = map[string]ObjectMethod{
+		"msg": ObjectMethod{
+			Layout: MethodLayout{
+				Description: "Returns the error message\n\n:::caution\nPlease note that performing `.msg()` on a ERROR object does result in a STRING object which then will no longer be treated as an error!\n:::",
+				Example: `» def test()
+puts(nope)
+rescue e
+puts((rescued error: + e.msg()))
+end
+🚀 » test()
+"rescued error:identifier not found: nope"`,
+				ReturnPattern: Args(
+					Arg(STRING_OBJ),
+				),
+			},
+			method: func(o Object, _ []Object, _ Environment) Object {
+				e := o.(*Error)
+				return NewString(e.Message)
+			},
+		},
+	}
+}

parser/begin.go

@@ -0,0 +1,11 @@
+package parser
+
+import (
+	"github.com/flipez/rocket-lang/ast"
+)
+
+func (p *Parser) parseBegin() ast.Expression {
+	expression := &ast.Begin{Token: p.curToken}
+	expression.Block = p.parseBlock()
+	return expression
+}

parser/block.go

@@ -11,7 +11,7 @@ func (p *Parser) parseBlock() *ast.Block {
 
 	p.nextToken()
 
-	for !p.curTokenIs(token.RBRACE) && !p.curTokenIs(token.EOF) && !p.curTokenIs(token.END) && !p.curTokenIs(token.ELSE) {
+	for !p.curTokenIs(token.RBRACE) && !p.curTokenIs(token.EOF) && !p.curTokenIs(token.END) && !p.curTokenIs(token.ELSE) && !p.curTokenIs(token.RESCUE) {
 		stmt := p.parseStatement()
 		if stmt != nil {
 			block.Statements = append(block.Statements, stmt)
@@ -20,5 +20,12 @@ func (p *Parser) parseBlock() *ast.Block {
 		p.nextToken()
 	}
 
+	if p.curTokenIs(token.RESCUE) {
+		block.Rescue = &ast.Rescue{Token: p.curToken}
+		p.expectPeek(token.IDENT)
+		block.Rescue.ErrorIdent = p.curToken
+		block.Rescue.Block = p.parseBlock()
+	}
+
 	return block
 }

parser/parser.go

@@ -89,6 +89,7 @@ func New(l *lexer.Lexer, imports map[string]struct{}) *Parser {
 	p.registerPrefix(token.LBRACE, p.parseHash)
 	p.registerPrefix(token.IMPORT, p.parseImport)
 	p.registerPrefix(token.NIL, p.parseNil)
+	p.registerPrefix(token.BEGIN, p.parseBegin)
 
 	p.infixParseFns = make(map[token.TokenType]infixParseFn)
 	p.registerInfix(token.ASSIGN, p.parseAssignExpression)

token/token.go

@@ -75,6 +75,9 @@ const (
 	IMPORT = "IMPORT"
 
 	NIL = "NIL"
+
+	BEGIN  = "BEGIN"
+	RESCUE = "RESCUE"
 )
 
 var keywords = map[string]TokenType{
@@ -95,6 +98,8 @@ var keywords = map[string]TokenType{
 	"nil":     NIL,
 	"and":     AND,
 	"or":      OR,
+	"begin":   BEGIN,
+	"rescue":  RESCUE,
 }
 
 func LookupIdent(ident string) TokenType {