service/s3: Adds Support for S3 AccessPoints (#476)

Author: skmcgrail

CHANGELOG_PENDING.md

@@ -19,6 +19,9 @@ SDK Features
 ---
 * `aws`: `PartitionID` has been added to `aws.Endpoint` structure, and is used by the endpoint resolver to indicate which AWS partition an endpoint was resolved for ([#473](https://github.com/aws/aws-sdk-go-v2/pull/473))
 * `aws/endpoints`: Updated resolvers to populate `PartitionID` for a resolved `aws.Endpoint` ([#473](https://github.com/aws/aws-sdk-go-v2/pull/473))
+* `service/s3`: Add support for Access Point resources
+  * Adds support for using Access Point resource with Amazon S3 API operation calls. The Access Point resource are identified by an Amazon Resource Name (ARN).
+  * To make operation calls to an S3 Access Point instead of a S3 Bucket, provide the Access Point ARN string as the value of the Bucket parameter. You can create an Access Point for your bucket with the Amazon S3 Control API. The Access Point ARN can be obtained from the S3 Control API. You should avoid building the ARN directly.
 
 SDK Enhancements
 ---

aws/arn/arn.go

@@ -75,6 +75,12 @@ func Parse(arn string) (ARN, error) {
 	}, nil
 }
 
+// IsARN returns whether the given string is an arn
+// by looking for whether the string starts with arn:
+func IsARN(arn string) bool {
+	return strings.HasPrefix(arn, arnPrefix) && strings.Count(arn, ":") >= arnSections-1
+}
+
 // String returns the canonical representation of the ARN
 func (arn ARN) String() string {
 	return arnPrefix +

aws/arn/arn_test.go

@@ -86,3 +86,44 @@ func TestParseARN(t *testing.T) {
 		})
 	}
 }
+
+func TestIsARN(t *testing.T) {
+
+	cases := map[string]struct {
+		In     string
+		Expect bool
+		// Params
+	}{
+		"valid ARN slash resource": {
+			In:     "arn:aws:service:us-west-2:123456789012:restype/resvalue",
+			Expect: true,
+		},
+		"valid ARN colon resource": {
+			In:     "arn:aws:service:us-west-2:123456789012:restype:resvalue",
+			Expect: true,
+		},
+		"valid ARN resource": {
+			In:     "arn:aws:service:us-west-2:123456789012:*",
+			Expect: true,
+		},
+		"empty sections": {
+			In:     "arn:::::",
+			Expect: true,
+		},
+		"invalid ARN": {
+			In: "some random string",
+		},
+		"invalid ARN missing resource": {
+			In: "arn:aws:service:us-west-2:123456789012",
+		},
+	}
+
+	for name, c := range cases {
+		t.Run(name, func(t *testing.T) {
+			actual := IsARN(c.In)
+			if e, a := c.Expect, actual; e != a {
+				t.Errorf("expect %s valid %v, got %v", c.In, e, a)
+			}
+		})
+	}
+}