change the behaviour of excluding resources to allow specifying the t…

…ag value using a regular expression, fix #822

README.md

@@ -527,14 +527,21 @@ s3:
 
 #### Tag Filter
 
-You can also exclude resources by tags. The following config will exclude all s3 buckets that have a tag with key `foo`
-if the specified tag has a value, it must be set to `true` (case-insensitive),
-if the tag value is not set, cloud-nuke will only check for the tag name.
+You can also exclude resources by tags. The following configuration will exclude all S3 buckets that have a tag with the key `foo`.
+By default, we will check if the tag's value is set to `true` (case-insensitive).
 
 ```yaml
 s3:
   exclude:
-    tag: 'foo' # exclude if tag foo exists with empty value or 'true'
+    tag: 'foo' # exclude if tag foo exists with value of 'true'
+```
+
+You can also overwrite the expected value by specifying `tag_value` (you can use regular expressions).
+```yaml
+s3:
+  exclude:
+    tag: 'foo'
+    tag_value: 'dev-.*'
 ```
 #### Timeout
 You have the flexibility to set individual timeout options for specific resources. The execution will pause until the designated timeout is reached for each resource.

config/config.go

@@ -13,10 +13,11 @@ import (
 )
 
 const (
-	DefaultAwsResourceExclusionTagKey = "cloud-nuke-excluded"
-	CloudNukeAfterExclusionTagKey     = "cloud-nuke-after"
-	CloudNukeAfterTimeFormat          = time.RFC3339
-	CloudNukeAfterTimeFormatLegacy    = time.DateTime
+	DefaultAwsResourceExclusionTagKey   = "cloud-nuke-excluded"
+	DefaultAwsResourceExclusionTagValue = "true"
+	CloudNukeAfterExclusionTagKey       = "cloud-nuke-after"
+	CloudNukeAfterTimeFormat            = time.RFC3339
+	CloudNukeAfterTimeFormatLegacy      = time.DateTime
 )
 
 // Config - the config object we pass around
@@ -272,6 +273,7 @@ type FilterRule struct {
 	TimeAfter   *time.Time   `yaml:"time_after"`
 	TimeBefore  *time.Time   `yaml:"time_before"`
 	Tag         *string      `yaml:"tag"` // A tag to filter resources by. (e.g., If set under ExcludedRule, resources with this tag will be excluded).
+	TagValue    *Expression  `yaml:"tag_value"`
 }
 
 type Expression struct {
@@ -377,6 +379,14 @@ func (r ResourceType) getExclusionTag() string {
 	return DefaultAwsResourceExclusionTagKey
 }
 
+func (r ResourceType) getExclusionTagValue() *Expression {
+	if r.ExcludeRule.TagValue != nil {
+		return r.ExcludeRule.TagValue
+	}
+
+	return &Expression{RE: *regexp.MustCompile(DefaultAwsResourceExclusionTagValue)}
+}
+
 func ParseTimestamp(timestamp string) (*time.Time, error) {
 	parsed, err := time.Parse(CloudNukeAfterTimeFormat, timestamp)
 	if err != nil {
@@ -394,8 +404,9 @@ func ParseTimestamp(timestamp string) (*time.Time, error) {
 func (r ResourceType) ShouldIncludeBasedOnTag(tags map[string]string) bool {
 	// Handle exclude rule first
 	exclusionTag := r.getExclusionTag()
+	exclusionTagValue := r.getExclusionTagValue()
 	if value, ok := tags[exclusionTag]; ok {
-		if strings.ToLower(value) == "true" || value == "" {
+		if matches(strings.ToLower(value), []Expression{*exclusionTagValue}) {
 			return false
 		}
 	}

config/config_test.go

@@ -378,16 +378,41 @@ func TestShouldIncludeBasedOnTag(t *testing.T) {
 			given: arg{
 				ExcludeRule: FilterRule{
 					Tag: aws.String("my-custom-skip-tag"),
+					TagValue: &Expression{
+						RE: *regexp.MustCompile(""),
+					},
 				},
 				ProtectUntilExpire: false,
 			},
 			when:   map[string]string{"my-custom-skip-tag": ""},
 			expect: false,
 		},
 		{
-			name:   "should include resource with empty default exclude tag value",
-			given:  arg{},
-			when:   map[string]string{DefaultAwsResourceExclusionTagKey: ""},
+			name: "should include resource with custom exclude tag and empty value (using regular expression)",
+			given: arg{
+				ExcludeRule: FilterRule{
+					Tag: aws.String("my-custom-skip-tag"),
+					TagValue: &Expression{
+						RE: *regexp.MustCompile(".*"),
+					},
+				},
+				ProtectUntilExpire: false,
+			},
+			when:   map[string]string{"my-custom-skip-tag": ""},
+			expect: false,
+		},
+		{
+			name: "should include resource with custom exclude tag and prefix value (using regular expression)",
+			given: arg{
+				ExcludeRule: FilterRule{
+					Tag: aws.String("my-custom-skip-tag"),
+					TagValue: &Expression{
+						RE: *regexp.MustCompile("protected-.*"),
+					},
+				},
+				ProtectUntilExpire: false,
+			},
+			when:   map[string]string{"my-custom-skip-tag": "protected-database"},
 			expect: false,
 		},
 		{