Allow to override builtins (#522)

* Allow to override builtins

* Add :: syntax to access builtin in case of override

builtin/builtin_test.go

@@ -284,37 +284,71 @@ func TestBuiltin_memory_limits(t *testing.T) {
 	}
 }
 
-func TestBuiltin_disallow_builtins_override(t *testing.T) {
-	t.Run("via env", func(t *testing.T) {
-		env := map[string]any{
-			"len": func() int { return 42 },
-			"repeat": func(a string) string {
-				return a
-			},
+func TestBuiltin_allow_builtins_override(t *testing.T) {
+	t.Run("via env var", func(t *testing.T) {
+		for _, name := range builtin.Names {
+			t.Run(name, func(t *testing.T) {
+				env := map[string]any{
+					name: "hello world",
+				}
+				program, err := expr.Compile(name, expr.Env(env))
+				require.NoError(t, err)
+
+				out, err := expr.Run(program, env)
+				require.NoError(t, err)
+				assert.Equal(t, "hello world", out)
+			})
+		}
+	})
+	t.Run("via env func", func(t *testing.T) {
+		for _, name := range builtin.Names {
+			t.Run(name, func(t *testing.T) {
+				env := map[string]any{
+					name: func() int { return 1 },
+				}
+				program, err := expr.Compile(fmt.Sprintf("%s()", name), expr.Env(env))
+				require.NoError(t, err)
+
+				out, err := expr.Run(program, env)
+				require.NoError(t, err)
+				assert.Equal(t, 1, out)
+			})
 		}
-		assert.Panics(t, func() {
-			_, _ = expr.Compile(`string(len("foo")) + repeat("0", 2)`, expr.Env(env))
-		})
 	})
 	t.Run("via expr.Function", func(t *testing.T) {
-		length := expr.Function("len",
-			func(params ...any) (any, error) {
-				return 42, nil
-			},
-			new(func() int),
-		)
-		repeat := expr.Function("repeat",
-			func(params ...any) (any, error) {
-				return params[0], nil
-			},
-			new(func(string) string),
-		)
-		assert.Panics(t, func() {
-			_, _ = expr.Compile(`string(len("foo")) + repeat("0", 2)`, length, repeat)
-		})
+		for _, name := range builtin.Names {
+			t.Run(name, func(t *testing.T) {
+				fn := expr.Function(name,
+					func(params ...any) (any, error) {
+						return 42, nil
+					},
+					new(func() int),
+				)
+				program, err := expr.Compile(fmt.Sprintf("%s()", name), fn)
+				require.NoError(t, err)
+
+				out, err := expr.Run(program, nil)
+				require.NoError(t, err)
+				assert.Equal(t, 42, out)
+			})
+		}
 	})
 }
 
+func TestBuiltin_override_and_still_accessible(t *testing.T) {
+	env := map[string]any{
+		"len": func() int { return 42 },
+		"all": []int{1, 2, 3},
+	}
+
+	program, err := expr.Compile(`::all(all, #>0) && len() == 42 && ::len(all) == 3`, expr.Env(env))
+	require.NoError(t, err)
+
+	out, err := expr.Run(program, env)
+	require.NoError(t, err)
+	assert.Equal(t, true, out)
+}
+
 func TestBuiltin_DisableBuiltin(t *testing.T) {
 	t.Run("via env", func(t *testing.T) {
 		for _, b := range builtin.Builtins {

checker/checker.go

@@ -156,24 +156,25 @@ func (v *checker) IdentifierNode(node *ast.IdentifierNode) (reflect.Type, info)
 	if node.Value == "$env" {
 		return mapType, info{}
 	}
-	if fn, ok := v.config.Builtins[node.Value]; ok {
-		return functionType, info{fn: fn}
-	}
-	if fn, ok := v.config.Functions[node.Value]; ok {
-		return functionType, info{fn: fn}
-	}
-	return v.env(node, node.Value, true)
+	return v.ident(node, node.Value, true, true)
 }
 
-// env method returns type of environment variable. env only lookups for
-// environment variables, no builtins, no custom functions.
-func (v *checker) env(node ast.Node, name string, strict bool) (reflect.Type, info) {
+// ident method returns type of environment variable, builtin or function.
+func (v *checker) ident(node ast.Node, name string, strict, builtins bool) (reflect.Type, info) {
 	if t, ok := v.config.Types[name]; ok {
 		if t.Ambiguous {
 			return v.error(node, "ambiguous identifier %v", name)
 		}
 		return t.Type, info{method: t.Method}
 	}
+	if builtins {
+		if fn, ok := v.config.Functions[name]; ok {
+			return functionType, info{fn: fn}
+		}
+		if fn, ok := v.config.Builtins[name]; ok {
+			return functionType, info{fn: fn}
+		}
+	}
 	if v.config.Strict && strict {
 		return v.error(node, "unknown name %v", name)
 	}
@@ -433,6 +434,7 @@ func (v *checker) MemberNode(node *ast.MemberNode) (reflect.Type, info) {
 	base, _ := v.visit(node.Node)
 	prop, _ := v.visit(node.Property)
 
+	// $env variable
 	if an, ok := node.Node.(*ast.IdentifierNode); ok && an.Value == "$env" {
 		if name, ok := node.Property.(*ast.StringNode); ok {
 			strict := v.config.Strict
@@ -443,7 +445,7 @@ func (v *checker) MemberNode(node *ast.MemberNode) (reflect.Type, info) {
 				// should throw error if field is not found & v.config.Strict.
 				strict = false
 			}
-			return v.env(node, name.Value, strict)
+			return v.ident(node, name.Value, strict, false /* no builtins and no functions */)
 		}
 		return anyType, info{}
 	}

conf/config.go

@@ -98,20 +98,14 @@ func (c *Config) Check() {
 			}
 		}
 	}
-	for fnName, t := range c.Types {
-		if kind(t.Type) == reflect.Func {
-			for _, b := range c.Builtins {
-				if b.Name == fnName {
-					panic(fmt.Errorf(`cannot override builtin %s(): use expr.DisableBuiltin("%s") to override`, b.Name, b.Name))
-				}
-			}
-		}
+}
+
+func (c *Config) IsOverridden(name string) bool {
+	if _, ok := c.Functions[name]; ok {
+		return true
 	}
-	for _, f := range c.Functions {
-		for _, b := range c.Builtins {
-			if b.Name == f.Name {
-				panic(fmt.Errorf(`cannot override builtin %s(); use expr.DisableBuiltin("%s") to override`, f.Name, f.Name))
-			}
-		}
+	if _, ok := c.Types[name]; ok {
+		return true
 	}
+	return false
 }

parser/lexer/lexer_test.go

@@ -225,6 +225,14 @@ func TestLex(t *testing.T) {
 				{Kind: EOF},
 			},
 		},
+		{
+			`: ::`,
+			[]Token{
+				{Kind: Operator, Value: ":"},
+				{Kind: Operator, Value: "::"},
+				{Kind: EOF},
+			},
+		},
 	}
 
 	for _, test := range tests {

parser/lexer/state.go

@@ -37,11 +37,14 @@ func root(l *lexer) stateFn {
 	case r == '|':
 		l.accept("|")
 		l.emit(Operator)
+	case r == ':':
+		l.accept(":")
+		l.emit(Operator)
 	case strings.ContainsRune("([{", r):
 		l.emit(Bracket)
 	case strings.ContainsRune(")]}", r):
 		l.emit(Bracket)
-	case strings.ContainsRune(",:;%+-^", r): // single rune operator
+	case strings.ContainsRune(",;%+-^", r): // single rune operator
 		l.emit(Operator)
 	case strings.ContainsRune("&!=*<>", r): // possible double rune operator
 		l.accept("&=*")

parser/parser.go

@@ -275,6 +275,13 @@ func (p *parser) parsePrimary() Node {
 		}
 	}
 
+	if token.Is(Operator, "::") {
+		p.next()
+		token = p.current
+		p.expect(Identifier)
+		return p.parsePostfixExpression(p.parseCall(token, false))
+	}
+
 	return p.parseSecondary()
 }
 
@@ -300,7 +307,7 @@ func (p *parser) parseSecondary() Node {
 			node.SetLocation(token.Location)
 			return node
 		default:
-			node = p.parseCall(token)
+			node = p.parseCall(token, true)
 		}
 
 	case Number:
@@ -379,15 +386,17 @@ func (p *parser) toFloatNode(number float64) Node {
 	return &FloatNode{Value: number}
 }
 
-func (p *parser) parseCall(token Token) Node {
+func (p *parser) parseCall(token Token, checkOverrides bool) Node {
 	var node Node
 	if p.current.Is(Bracket, "(") {
 		var arguments []Node
 
-		if b, ok := predicates[token.Value]; ok {
-			p.expect(Bracket, "(")
+		isOverridden := p.config.IsOverridden(token.Value)
+		isOverridden = isOverridden && checkOverrides
 
-			// TODO: Refactor parser to use builtin.Builtins instead of predicates map.
+		// TODO: Refactor parser to use builtin.Builtins instead of predicates map.
+		if b, ok := predicates[token.Value]; ok && !isOverridden {
+			p.expect(Bracket, "(")
 
 			if b.arity == 1 {
 				arguments = make([]Node, 1)
@@ -417,7 +426,7 @@ func (p *parser) parseCall(token Token) Node {
 				Arguments: arguments,
 			}
 			node.SetLocation(token.Location)
-		} else if _, ok := builtin.Index[token.Value]; ok && !p.config.Disabled[token.Value] {
+		} else if _, ok := builtin.Index[token.Value]; ok && !p.config.Disabled[token.Value] && !isOverridden {
 			node = &BuiltinNode{
 				Name:      token.Value,
 				Arguments: p.parseArguments(),

parser/parser_test.go

@@ -498,6 +498,29 @@ world`},
 				},
 			},
 		},
+		{
+			`::split("a,b,c", ",")`,
+			&BuiltinNode{
+				Name: "split",
+				Arguments: []Node{
+					&StringNode{Value: "a,b,c"},
+					&StringNode{Value: ","},
+				},
+			},
+		},
+		{
+			`::split("a,b,c", ",")[0]`,
+			&MemberNode{
+				Node: &BuiltinNode{
+					Name: "split",
+					Arguments: []Node{
+						&StringNode{Value: "a,b,c"},
+						&StringNode{Value: ","},
+					},
+				},
+				Property: &IntegerNode{Value: 0},
+			},
+		},
 	}
 	for _, test := range tests {
 		t.Run(test.input, func(t *testing.T) {