[azcore] Add ETag type to Core

sdk/azcore/etag.go

@@ -0,0 +1,47 @@
+// +build go1.13
+
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package azcore
+
+import (
+	"strings"
+)
+
+// ETag is a property used for optimistic concurrency during updates
+// ETag is a validator based on https://tools.ietf.org/html/rfc7232#section-2.3.2
+// An ETag can be empty ("").
+type ETag string
+
+// ETagAny is an ETag that represents everything, the value is "*"
+const ETagAny ETag = "*"
+
+// Equals does a strong comparison of two ETags. Equals returns true when both
+// ETags are not weak and the values of the underlying strings are equal. If both ETags are "nil" they are considered equal
+func (e ETag) Equals(other ETag) bool {
+	return !e.IsWeak() && !other.IsWeak() && e == other
+}
+
+// WeakEquals does a weak compariosn of two ETags. Two ETags are equivalent if their opaque-tags match
+// character-by-character, regardless of either or both being tagged as "weak". If both ETags are "nil" they are considered equal
+func (e ETag) WeakEquals(other ETag) bool {
+	getStart := func(e1 ETag) int {
+		if e1.IsWeak() {
+			return 2
+		}
+		return 0
+	}
+	aStart := getStart(e)
+	bStart := getStart(other)
+
+	aVal := e[aStart:]
+	bVal := other[bStart:]
+
+	return aVal == bVal
+}
+
+// IsWeak specifies whether the ETag is strong or weak.
+func (e ETag) IsWeak() bool {
+	return len(e) >= 4 && strings.HasPrefix(string(e), "W/\"") && strings.HasSuffix(string(e), "\"")
+}

sdk/azcore/etag_test.go

@@ -0,0 +1,134 @@
+// +build go1.13
+
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package azcore
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func createETag(s string) ETag {
+	return ETag(s)
+}
+
+func TestETagEquals(t *testing.T) {
+	e1 := createETag("tag")
+	require.Equal(t, string(e1), "tag")
+
+	e2 := createETag("\"tag\"")
+	require.Equal(t, string(e2), "\"tag\"")
+
+	e3 := createETag("W/\"weakETag\"")
+	require.Equal(t, string(e3), "W/\"weakETag\"")
+	require.Truef(t, e3.IsWeak(), "ETag is expected to be weak")
+
+	strongETag := createETag("\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\"")
+	require.Equal(t, string(strongETag), "\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\"")
+
+	require.Falsef(t, ETagAny.IsWeak(), "ETagAny should not be weak")
+}
+
+func TestETagWeak(t *testing.T) {
+	et1 := createETag("tag")
+	require.Falsef(t, et1.IsWeak(), "expected etag to be strong")
+
+	et2 := createETag("\"tag\"")
+	require.Falsef(t, et2.IsWeak(), "expected etag to be strong")
+
+	et3 := createETag("W/\"weakETag\"")
+	require.Truef(t, et3.IsWeak(), "expected etag to be weak")
+
+	et4 := createETag("W/\"\"")
+	require.Truef(t, et4.IsWeak(), "expected etag to be weak")
+
+	et5 := ETagAny
+	require.Falsef(t, et5.IsWeak(), "expected etag to be strong")
+}
+
+func TestETagEquality(t *testing.T) {
+	weakTag := createETag("W/\"\"")
+	weakTag1 := createETag("W/\"1\"")
+	weakTag2 := createETag("W/\"Two\"")
+	strongTag1 := createETag("\"1\"")
+	strongTag2 := createETag("\"Two\"")
+	strongTagValidChars := createETag("\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\"")
+	weakTagValidChars := createETag("W/\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\"")
+
+	require.Falsef(t, weakTag.Equals(weakTag), "Expected etags to not be equal")
+	require.Falsef(t, weakTag1.Equals( weakTag1), "Expected etags to not be equal")
+	require.Falsef(t, weakTag2.Equals(weakTag2), "Expected etags to not be equal")
+	require.Falsef(t, weakTagValidChars.Equals(weakTagValidChars), "Expected etags to not be equal")
+
+	require.Truef(t, strongTag1.Equals(strongTag1), "Expected etags to be equal")
+	require.Truef(t, strongTag2.Equals(strongTag2), "Expected etags to be equal")
+	require.Truef(t, strongTagValidChars.Equals(strongTagValidChars), "Expected etags to be equal")
+
+	require.Falsef(t, weakTag1.Equals(weakTag), "Expected etags to not be equal")
+	require.Falsef(t, strongTagValidChars.Equals(weakTagValidChars), "Expected etags to not be equal")
+	require.Falsef(t, weakTag2.Equals(weakTag1), "Expected etags to not be equal")
+	require.Falsef(t, strongTag1.Equals(weakTag1), "Expected etags to not be equal")
+	require.Falsef(t, strongTag2.Equals(weakTag2), "Expected etags to not be equal")
+}
+
+func TestEtagAny(t *testing.T) {
+	anyETag := ETagAny
+	star := createETag("*")
+	weakStar := createETag("W\"*\"")
+	quotedStar := createETag("\"*\"")
+
+	require.Truef(t, anyETag.Equals(anyETag), "Expected etags to be equal")
+	require.Truef(t, ETagAny.Equals(anyETag), "Expected etags to be equal")
+
+	require.Truef(t, star.Equals(star), "Expected etags to be equal")
+	require.Truef(t, ETagAny.Equals(star), "Expected etags to be equal")
+	require.Truef(t, anyETag.Equals(star), "Expected etags to be equal")
+
+	require.Falsef(t, star.Equals(weakStar), "Expected etags to be equal")
+	require.Falsef(t, ETagAny.Equals(weakStar), "Expected etags to be equal")
+	require.Falsef(t, weakStar.Equals(quotedStar), "Expected etags to be equal")
+
+	require.Falsef(t, quotedStar.Equals(star), "Expected etags to be equal")
+
+	require.Truef(t, star.Equals(ETagAny), "Expected etags to be equal")
+}
+
+func TestETagWeakComparison(t *testing.T) {
+	// W/""
+	weakTag := createETag("W/\"\"")
+	// W/"1"
+	weakTag1 := createETag("W/\"1\"")
+	// W/"Two"
+	weakTagTwo := createETag("W/\"Two\"")
+	// W/"two"
+	weakTagtwo := createETag("W/\"two\"")
+	// "1"
+	strongTag1 := createETag("\"1\"")
+	// "Two"
+	strongTagTwo := createETag("\"Two\"")
+	// "two"
+	strongTagtwo := createETag("\"two\"")
+
+	require.Truef(t, weakTag.WeakEquals(weakTag), "expected etags to be equal")
+	require.Truef(t, weakTag1.WeakEquals(weakTag1), "expected etags to be equal")
+	require.Truef(t, weakTagTwo.WeakEquals(weakTagTwo), "expected etags to be equal")
+	require.Truef(t, weakTagtwo.WeakEquals(weakTagtwo), "expected etags to be equal")
+	require.Truef(t, strongTag1.WeakEquals(strongTag1), "expected etags to be equal")
+	require.Truef(t, strongTagTwo.WeakEquals(strongTagTwo), "expected etags to be equal")
+	require.Truef(t, strongTagtwo.WeakEquals(strongTagtwo), "expected etags to be equal")
+
+	require.Falsef(t, weakTag1.WeakEquals(weakTag), "Expected etags to not be equal")
+	require.Falsef(t, weakTagTwo.WeakEquals(weakTag1), "Expected etags to not be equal")
+
+	require.Truef(t, strongTag1.WeakEquals(weakTag1), "expected etags to be equal")
+	require.Truef(t, strongTagTwo.WeakEquals(weakTagTwo), "expected etags to be equal")
+
+	require.Falsef(t, weakTag1.WeakEquals(strongTagTwo), "Expected etags to not be equal")
+	require.Falsef(t, weakTagtwo.WeakEquals(strongTagTwo), "Expected etags to not be equal")
+
+	require.Falsef(t, strongTagtwo.WeakEquals(strongTagTwo), "Expected etags to not be equal")
+	require.Falsef(t, weakTagtwo.WeakEquals(weakTagTwo), "Expected etags to not be equal")
+}

sdk/azcore/go.mod

@@ -2,6 +2,7 @@ module github.com/Azure/azure-sdk-for-go/sdk/azcore
 
 require (
 	github.com/Azure/azure-sdk-for-go/sdk/internal v0.5.2
+	github.com/stretchr/testify v1.7.0 // indirect
 	golang.org/x/net v0.0.0-20210610132358-84b48f89b13b
 )
 

sdk/azcore/go.sum

@@ -1,11 +1,14 @@
 github.com/Azure/azure-sdk-for-go/sdk/internal v0.5.2 h1:E2xwjsWU81O/XuSaxAGa8Jmqz4Vm4NmrpMSO9/XevDg=
 github.com/Azure/azure-sdk-for-go/sdk/internal v0.5.2/go.mod h1:Hl9Vte0DDolj9zqzmfnmY9/zfZbiT5KnvXqVwAvnR8Q=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dnaeon/go-vcr v1.2.0/go.mod h1:R4UdLID7HZT3taECzJs4YgbbH6PIGXB6W/sc5OLb6RQ=
 github.com/modocache/gover v0.0.0-20171022184752-b58185e213c5/go.mod h1:caMODM3PzxT8aQXRPkAt8xlV/e7d7w8GM5g0fa5F0D8=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 golang.org/x/net v0.0.0-20210610132358-84b48f89b13b h1:k+E048sYJHyVnsr1GDrRZWQ32D2C7lWs9JRc0bel53A=
 golang.org/x/net v0.0.0-20210610132358-84b48f89b13b/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
@@ -19,4 +22,5 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
 gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=