Implement extra rule

defaultrule/argument-limit.go

@@ -0,0 +1,63 @@
+package defaultrule
+
+import (
+	"fmt"
+	"go/ast"
+	"strconv"
+
+	"github.com/mgechev/revive/file"
+	"github.com/mgechev/revive/rule"
+)
+
+// ArgumentsLimitRule lints given else constructs.
+type ArgumentsLimitRule struct{}
+
+// Apply applies the rule to given file.
+func (r *ArgumentsLimitRule) Apply(file *file.File, arguments rule.Arguments) []rule.Failure {
+	if len(arguments) != 1 {
+		panic(`invalid configuration for "argument-limit"`)
+	}
+	total, err := strconv.ParseInt(arguments[0], 10, 32)
+	if err != nil {
+		panic(`invalid configuration for "argument-limit"`)
+	}
+
+	var failures []rule.Failure
+
+	walker := lintArgsNum{
+		total: total,
+		onFailure: func(failure rule.Failure) {
+			failures = append(failures, failure)
+		},
+	}
+
+	ast.Walk(walker, file.GetAST())
+
+	return failures
+}
+
+// Name returns the rule name.
+func (r *ArgumentsLimitRule) Name() string {
+	return "argument-limit"
+}
+
+type lintArgsNum struct {
+	total     int64
+	onFailure func(rule.Failure)
+}
+
+func (w lintArgsNum) Visit(n ast.Node) ast.Visitor {
+	node, ok := n.(*ast.FuncDecl)
+	if ok {
+		num := int64(len(node.Type.Params.List))
+		if num > w.total {
+			w.onFailure(rule.Failure{
+				Failure: fmt.Sprintf("maximum number of arguments per function exceeded; max %d but got %d", w.total, num),
+				Type:    rule.FailureTypeWarning,
+				Node:    node.Type,
+			})
+			return nil
+		}
+	}
+	return w
+}

defaultrule/no-else-return-rule.go

@@ -8,11 +8,6 @@ import (
 	"github.com/mgechev/revive/rule"
 )
 
-const (
-	ruleName = "no-else-return"
-	failure  = "if block ends with a return statement, so drop this else and outdent its block"
-)
-
 // LintElseRule lints given else constructs.
 type LintElseRule struct{}
 
@@ -27,7 +22,7 @@ func (r *LintElseRule) Apply(file *file.File, arguments rule.Arguments) []rule.F
 
 // Name returns the rule name.
 func (r *LintElseRule) Name() string {
-	return ruleName
+	return "no-else-return"
 }
 
 type lintElse func(rule.Failure)
@@ -54,7 +49,7 @@ func (f lintElse) Visit(n ast.Node) ast.Visitor {
 		lastStmt := node.Body.List[len(node.Body.List)-1]
 		if _, ok := lastStmt.(*ast.ReturnStmt); ok {
 			f(rule.Failure{
-				Failure: failure,
+				Failure: "if block ends with a return statement, so drop this else and outdent its block",
 				Type:    rule.FailureTypeWarning,
 				Node:    node.Else,
 			})

linter/linter.go

@@ -27,7 +27,7 @@ func New(reader ReadFile) Linter {
 }
 
 // Lint lints a set of files with the specified rule.
-func (l *Linter) Lint(filenames []string, ruleSet []rule.Rule) ([]rule.Failure, error) {
+func (l *Linter) Lint(filenames []string, ruleSet []rule.Rule, rulesConfig rule.RulesConfig) ([]rule.Failure, error) {
 	var fileSet token.FileSet
 	var failures []rule.Failure
 	var ruleNames = []string{}
@@ -47,7 +47,8 @@ func (l *Linter) Lint(filenames []string, ruleSet []rule.Rule) ([]rule.Failure,
 		}
 
 		for _, currentRule := range ruleSet {
-			currentFailures := currentRule.Apply(file, []string{})
+			config := rulesConfig[currentRule.Name()]
+			currentFailures := currentRule.Apply(file, config)
 			for idx, failure := range currentFailures {
 				if failure.RuleName == "" {
 					failure.RuleName = currentRule.Name()

main.go

@@ -20,15 +20,23 @@ func main() {
       return 23;
     }
 	}
+	
+	func foobar(a int, b int, c int, d int) {
+		return a + b + c;
+	}
   `
 
 	linter := linter.New(func(file string) ([]byte, error) {
 		return []byte(src), nil
 	})
 	var result []rule.Rule
-	result = append(result, &defaultrule.LintElseRule{})
+	result = append(result, &defaultrule.LintElseRule{}, &defaultrule.ArgumentsLimitRule{})
 
-	failures, err := linter.Lint([]string{"foo.go", "bar.go", "baz.go"}, result)
+	var config = rule.RulesConfig{
+		"argument-limit": []string{"3"},
+	}
+
+	failures, err := linter.Lint([]string{"foo.go", "bar.go", "baz.go"}, result, config)
 	if err != nil {
 		panic(err)
 	}

rule/rule.go

@@ -53,6 +53,9 @@ type Config struct {
 	Arguments Arguments
 }
 
+// RulesConfig defiles the config for all rules.
+type RulesConfig = map[string]Arguments
+
 // Rule defines an abstract rule interaface
 type Rule interface {
 	Name() string