Add new rule

fixtures/max-public-structs.go

@@ -0,0 +1,11 @@
+// Package pkg ...
+package pkg // MATCH /you have exceeded the maximum number of public struct declarations/
+
+type Foo struct {
+}
+
+type Bar struct {
+}
+
+type Baz struct {
+}

rule/max-public-structs.go

@@ -0,0 +1,69 @@
+package rule
+
+import (
+	"fmt"
+	"go/ast"
+
+	"strings"
+
+	"github.com/mgechev/revive/lint"
+)
+
+// MaxPublicStructsRule lints given else constructs.
+type MaxPublicStructsRule struct{}
+
+// Apply applies the rule to given file.
+func (r *MaxPublicStructsRule) Apply(file *lint.File, arguments lint.Arguments) []lint.Failure {
+	var failures []lint.Failure
+
+	fileAst := file.AST
+	walker := &lintMaxPublicStructs{
+		fileAst: fileAst,
+		onFailure: func(failure lint.Failure) {
+			failures = append(failures, failure)
+		},
+	}
+
+	ast.Walk(walker, fileAst)
+
+	max, ok := arguments[0].(int64) // Alt. non panicking version
+	if !ok {
+		panic(`invalid value passed as argument number to the "max-public-structs" rule`)
+	}
+
+	fmt.Println("Name:", max, walker.current)
+	if walker.current > max {
+		walker.onFailure(lint.Failure{
+			Failure:    "you have exceeded the maximum number of public struct declarations",
+			Confidence: 1,
+			Node:       fileAst,
+			Category:   "style",
+		})
+	}
+
+	return failures
+}
+
+// Name returns the rule name.
+func (r *MaxPublicStructsRule) Name() string {
+	return "max-public-structs"
+}
+
+type lintMaxPublicStructs struct {
+	current   int64
+	fileAst   *ast.File
+	onFailure func(lint.Failure)
+}
+
+func (w *lintMaxPublicStructs) Visit(n ast.Node) ast.Visitor {
+	switch v := n.(type) {
+	case *ast.TypeSpec:
+		name := v.Name.Name
+		first := string(name[0])
+		if strings.ToUpper(first) == first {
+			w.current++
+		}
+		break
+	}
+	return w
+}

testutil/lint_test.go

@@ -56,7 +56,7 @@ var rules = []lint.Rule{
 	&rule.ContextArgumentsRule{},
 }
 
-func TestVarDeclaration(t *testing.T) {
+func TestCyclomatic(t *testing.T) {
 	testRule(t, "cyclomatic", &rule.CyclomaticRule{}, &lint.RuleConfig{
 		Arguments: []interface{}{int64(1)},
 	})
@@ -65,6 +65,12 @@ func TestVarDeclaration(t *testing.T) {
 	})
 }
 
+func TestMaxPublicStructs(t *testing.T) {
+	testRule(t, "max-public-structs", &rule.MaxPublicStructsRule{}, &lint.RuleConfig{
+		Arguments: []interface{}{int64(1)},
+	})
+}
+
 func testRule(t *testing.T, filename string, rule lint.Rule, config ...*lint.RuleConfig) {
 	baseDir := "../fixtures/"
 	filename = filename + ".go"
@@ -94,8 +100,9 @@ func TestAll(t *testing.T) {
 	baseDir := "../fixtures/"
 
 	ignoreFiles := map[string]bool{
-		"cyclomatic.go":   true,
-		"cyclomatic-2.go": true,
+		"cyclomatic.go":         true,
+		"cyclomatic-2.go":       true,
+		"max-public-structs.go": true,
 	}
 
 	rx, err := regexp.Compile(*lintMatch)