[Proof of Concept] provider: default tags implementation

.changelog/17941.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+provider: Add `default_tags` argument (in public preview, see note above)
+```

aws/config.go

@@ -191,9 +191,10 @@ type Config struct {
 	AllowedAccountIds   []string
 	ForbiddenAccountIds []string
 
-	Endpoints        map[string]string
-	IgnoreTagsConfig *keyvaluetags.IgnoreConfig
-	Insecure         bool
+	DefaultTagsConfig *keyvaluetags.DefaultConfig
+	Endpoints         map[string]string
+	IgnoreTagsConfig  *keyvaluetags.IgnoreConfig
+	Insecure          bool
 
 	SkipCredsValidation     bool
 	SkipGetEC2Platforms     bool
@@ -249,6 +250,7 @@ type AWSClient struct {
 	datapipelineconn                    *datapipeline.DataPipeline
 	datasyncconn                        *datasync.DataSync
 	daxconn                             *dax.DAX
+	DefaultTagsConfig                   *keyvaluetags.DefaultConfig
 	devicefarmconn                      *devicefarm.DeviceFarm
 	dlmconn                             *dlm.DLM
 	dmsconn                             *databasemigrationservice.DatabaseMigrationService
@@ -492,6 +494,7 @@ func (c *Config) Client() (interface{}, error) {
 		datapipelineconn:                    datapipeline.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["datapipeline"])})),
 		datasyncconn:                        datasync.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["datasync"])})),
 		daxconn:                             dax.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["dax"])})),
+		DefaultTagsConfig:                   c.DefaultTagsConfig,
 		devicefarmconn:                      devicefarm.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["devicefarm"])})),
 		dlmconn:                             dlm.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["dlm"])})),
 		dmsconn:                             databasemigrationservice.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["dms"])})),

aws/internal/keyvaluetags/key_value_tags.go

@@ -25,6 +25,11 @@ const (
 	ServerlessApplicationRepositoryTagKeyPrefix = `serverlessrepo:`
 )
 
+// DefaultConfig contains tags to default across all resources.
+type DefaultConfig struct {
+	Tags KeyValueTags
+}
+
 // IgnoreConfig contains various options for removing resource tags.
 type IgnoreConfig struct {
 	Keys        KeyValueTags
@@ -50,6 +55,32 @@ func (tags KeyValueTags) IgnoreAws() KeyValueTags {
 	return result
 }
 
+// Merge calls keyvaluetags.Merge() on the given DefaultConfig.Tags, if any,
+// with KeyValueTags provided as an argument, overriding the value
+// of any tag with a matching key.
+func (config *DefaultConfig) Merge(tags KeyValueTags) KeyValueTags {
+	if len(config.Tags) == 0 {
+		return tags
+	}
+
+	return config.Tags.Merge(tags)
+}
+
+// TagsEqual returns true if the given configuration's Tags
+// are equal to those passed in as an argument;
+// otherwise returns false
+func (config *DefaultConfig) TagsEqual(tags KeyValueTags) bool {
+	if len(config.Tags) == 0 {
+		return len(tags) == 0
+	}
+
+	if len(tags) == 0 {
+		return false
+	}
+
+	return config.Tags.ContainsAll(tags)
+}
+
 // IgnoreConfig returns any tags not removed by a given configuration.
 func (tags KeyValueTags) IgnoreConfig(config *IgnoreConfig) KeyValueTags {
 	if config == nil {
@@ -401,6 +432,27 @@ func (tags KeyValueTags) Hash() int {
 	return hash
 }
 
+// RemoveDefaultConfig returns tags not present in a DefaultConfig object
+// in addition to tags with key/value pairs that override those in a DefaultConfig;
+// however, if all tags present in the DefaultConfig object are equivalent to those
+// in the given KeyValueTags, then the KeyValueTags are returned, effectively
+// bypassing the need to remove differing tags.
+func (tags KeyValueTags) RemoveDefaultConfig(config *DefaultConfig) KeyValueTags {
+	if config == nil || len(config.Tags) == 0 {
+		return tags
+	}
+
+	result := make(KeyValueTags)
+
+	for k, v := range tags {
+		if defaultVal, ok := config.Tags[k]; !ok || !v.Equal(defaultVal) {
+			result[k] = v
+		}
+	}
+
+	return result
+}
+
 // String returns the default string representation of the KeyValueTags.
 func (tags KeyValueTags) String() string {
 	var builder strings.Builder
@@ -435,6 +487,30 @@ func (tags KeyValueTags) UrlEncode() string {
 	return values.Encode()
 }
 
+// MergeConfigTags creates KeyValueTags by merging KeyValueTags nested in
+// a configuration object with those represented as a map[string]interface{}.
+// Currently only supports the DefaultConfig type when passed to the interface{} argument.
+func MergeConfigTags(config interface{}, tags map[string]interface{}) KeyValueTags {
+	kvTags := New(tags)
+
+	if config == nil {
+		return kvTags
+	}
+
+	var result KeyValueTags
+
+	switch t := config.(type) {
+	case *DefaultConfig:
+		if t == nil || len(t.Tags) == 0 {
+			result = kvTags
+		} else {
+			result = t.Merge(kvTags)
+		}
+	}
+
+	return result
+}
+
 // New creates KeyValueTags from common Terraform Provider SDK types.
 // Supports map[string]string, map[string]*string, map[string]interface{}, and []interface{}.
 // When passed []interface{}, all elements are treated as keys and assigned nil values.