Add config option to allow proper multiline comments

Author: AleksaC

rules/no_multiline_comments.go

@@ -1,6 +1,7 @@
 package rules
 
 import (
+	"bytes"
 	"strings"
 
 	hcl "github.com/hashicorp/hcl/v2"
@@ -13,6 +14,10 @@ type NoMultilineCommentsRule struct {
 	tflint.DefaultRule
 }
 
+type terraformNoMultilineCommentsRuleConfig struct {
+	SingleLineOnly bool `hclext:"single_line_only,optional"`
+}
+
 // NewNoMultilineCommentsRule returns a new rule
 func NewNoMultilineCommentsRule() *NoMultilineCommentsRule {
 	return &NoMultilineCommentsRule{}
@@ -49,6 +54,11 @@ func (r *NoMultilineCommentsRule) Check(runner tflint.Runner) error {
 		return nil
 	}
 
+	config := terraformNoMultilineCommentsRuleConfig{SingleLineOnly: false}
+	if err := runner.DecodeRuleConfig(r.Name(), &config); err != nil {
+		return err
+	}
+
 	files, err := runner.GetFiles()
 	if err != nil {
 		return err
@@ -67,9 +77,22 @@ func (r *NoMultilineCommentsRule) Check(runner tflint.Runner) error {
 		for _, token := range tokens {
 			if token.Type == hclsyntax.TokenComment {
 				if len(token.Bytes) >= 2 && token.Bytes[0] == '/' && token.Bytes[1] == '*' {
+					if config.SingleLineOnly {
+						if bytes.Contains(token.Bytes, []byte{'\n'}) {
+							continue
+						}
+						if err := runner.EmitIssue(
+							r,
+							"Using multiline comment syntax for single-line comments is not allowed. Use `#` instead.",
+							token.Range,
+						); err != nil {
+							return err
+						}
+						continue
+					}
 					if err := runner.EmitIssue(
 						r,
-						"Multiline comments are not allowed, use single-line comment",
+						"Multiline comments are not allowed. Replace the comment with single-line comment(s)",
 						token.Range,
 					); err != nil {
 						return err

rules/no_multiline_comments_test.go

@@ -11,6 +11,7 @@ func Test_NoMultilineComments(t *testing.T) {
 	tests := []struct {
 		Name     string
 		Content  string
+		Config   string
 		Expected helper.Issues
 	}{
 		{
@@ -23,7 +24,7 @@ This is a multiline comment
 			Expected: helper.Issues{
 				{
 					Rule:    NewNoMultilineCommentsRule(),
-					Message: "Multiline comments are not allowed, use single-line comment",
+					Message: "Multiline comments are not allowed. Replace the comment with single-line comment(s)",
 					Range: hcl.Range{
 						Filename: "resource.tf",
 						Start:    hcl.Pos{Line: 2, Column: 1},
@@ -32,6 +33,44 @@ This is a multiline comment
 				},
 			},
 		},
+		{
+			Name: "ProperMultilineAllowed",
+			Content: `
+/*
+This is a multiline comment
+*/
+`,
+			Config: `
+rule "no_multiline_comments" {
+  enabled = true
+
+  single_line_only = true
+}
+`,
+			Expected: helper.Issues{},
+		},
+		{
+			Name:    "SingleLineMultiline",
+			Content: `/* This isn't really a multiline comment */`,
+			Config: `
+rule "no_multiline_comments" {
+  enabled = true
+
+  single_line_only = true
+}
+`,
+			Expected: helper.Issues{
+				{
+					Rule:    NewNoMultilineCommentsRule(),
+					Message: "Using multiline comment syntax for single-line comments is not allowed. Use `#` instead.",
+					Range: hcl.Range{
+						Filename: "resource.tf",
+						Start:    hcl.Pos{Line: 1, Column: 1},
+						End:      hcl.Pos{Line: 1, Column: 44},
+					},
+				},
+			},
+		},
 		{
 			Name:     "SingleLine",
 			Content:  `//`,
@@ -48,7 +87,7 @@ This is a multiline comment
 
 	for _, test := range tests {
 		t.Run(test.Name, func(t *testing.T) {
-			runner := helper.TestRunner(t, map[string]string{"resource.tf": test.Content})
+			runner := helper.TestRunner(t, map[string]string{"resource.tf": test.Content, ".tflint.hcl": test.Config})
 
 			if err := rule.Check(runner); err != nil {
 				t.Fatalf("Unexpected error occurred: %s", err)