cleanup: usages of resolver.Target.Endpoint

* feat(resolver): create Target.ToEndpoint()

** fix(resolver): strip leading "/" from URL.Opaque

** fix(resolver): document stripped "/" in ToEndpoint

* fix(internal): remove reliance on Target.Endpoint

** fix(dns_resolver_test): add escape for percent char

** feat(testutils): create helper function for dns_resolver_test

** fix(testutils/parse_url): return output of url.Parse

** fix(testutils/parse_url): simplify documentation

balancer/grpclb/grpclb.go

@@ -136,8 +136,8 @@ func (b *lbBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) bal
 
 	lb := &lbBalancer{
 		cc:              newLBCacheClientConn(cc),
-		dialTarget:      opt.Target.Endpoint,
-		target:          opt.Target.Endpoint,
+		dialTarget:      opt.Target.ToEndpoint(),
+		target:          opt.Target.ToEndpoint(),
 		opt:             opt,
 		fallbackTimeout: b.fallbackTimeout,
 		doneCh:          make(chan struct{}),

balancer/rls/balancer.go

@@ -448,7 +448,7 @@ func (b *rlsBalancer) sendNewPickerLocked() {
 	}
 	picker := &rlsPicker{
 		kbm:           b.lbCfg.kbMap,
-		origEndpoint:  b.bopts.Target.Endpoint,
+		origEndpoint:  b.bopts.Target.ToEndpoint(),
 		lb:            b,
 		defaultPolicy: b.defaultPolicy,
 		ctrlCh:        b.ctrlCh,

clientconn.go

@@ -256,7 +256,7 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 	if err != nil {
 		return nil, err
 	}
-	cc.authority, err = determineAuthority(cc.parsedTarget.Endpoint, cc.target, cc.dopts)
+	cc.authority, err = determineAuthority(cc.parsedTarget.ToEndpoint(), cc.target, cc.dopts)
 	if err != nil {
 		return nil, err
 	}

examples/features/load_balancing/client/main.go

@@ -111,7 +111,7 @@ type exampleResolver struct {
 }
 
 func (r *exampleResolver) start() {
-	addrStrs := r.addrsStore[r.target.Endpoint]
+	addrStrs := r.addrsStore[r.target.ToEndpoint()]
 	addrs := make([]resolver.Address, len(addrStrs))
 	for i, s := range addrStrs {
 		addrs[i] = resolver.Address{Addr: s}

examples/features/name_resolving/client/main.go

@@ -119,7 +119,7 @@ type exampleResolver struct {
 }
 
 func (r *exampleResolver) start() {
-	addrStrs := r.addrsStore[r.target.Endpoint]
+	addrStrs := r.addrsStore[r.target.ToEndpoint()]
 	addrs := make([]resolver.Address, len(addrStrs))
 	for i, s := range addrStrs {
 		addrs[i] = resolver.Address{Addr: s}

internal/resolver/dns/dns_resolver.go

@@ -116,7 +116,7 @@ type dnsBuilder struct{}
 
 // Build creates and starts a DNS resolver that watches the name resolution of the target.
 func (b *dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
-	host, port, err := parseTarget(target.Endpoint, defaultPort)
+	host, port, err := parseTarget(target.ToEndpoint(), defaultPort)
 	if err != nil {
 		return nil, err
 	}

internal/resolver/dns/dns_resolver_test.go

@@ -23,7 +23,6 @@ import (
 	"errors"
 	"fmt"
 	"net"
-	"net/url"
 	"os"
 	"reflect"
 	"strings"
@@ -735,7 +734,7 @@ func testDNSResolver(t *testing.T) {
 	for _, a := range tests {
 		b := NewBuilder()
 		cc := &testClientConn{target: a.target}
-		r, err := b.Build(resolver.Target{Endpoint: a.target}, cc, resolver.BuildOptions{})
+		r, err := b.Build(resolver.Target{Endpoint: a.target, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", a.target))}, cc, resolver.BuildOptions{})
 		if err != nil {
 			t.Fatalf("%v\n", err)
 		}
@@ -807,7 +806,7 @@ func TestDNSResolverExponentialBackoff(t *testing.T) {
 			cc := &testClientConn{target: test.target}
 			// Cause ClientConn to return an error.
 			cc.updateStateErr = balancer.ErrBadResolverState
-			r, err := b.Build(resolver.Target{Endpoint: test.target}, cc, resolver.BuildOptions{})
+			r, err := b.Build(resolver.Target{Endpoint: test.target, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", test.target))}, cc, resolver.BuildOptions{})
 			if err != nil {
 				t.Fatalf("Error building resolver for target %v: %v", test.target, err)
 			}
@@ -962,7 +961,7 @@ func testDNSResolverWithSRV(t *testing.T) {
 	for _, a := range tests {
 		b := NewBuilder()
 		cc := &testClientConn{target: a.target}
-		r, err := b.Build(resolver.Target{Endpoint: a.target}, cc, resolver.BuildOptions{})
+		r, err := b.Build(resolver.Target{Endpoint: a.target, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", a.target))}, cc, resolver.BuildOptions{})
 		if err != nil {
 			t.Fatalf("%v\n", err)
 		}
@@ -1046,7 +1045,7 @@ func testDNSResolveNow(t *testing.T) {
 	for _, a := range tests {
 		b := NewBuilder()
 		cc := &testClientConn{target: a.target}
-		r, err := b.Build(resolver.Target{Endpoint: a.target}, cc, resolver.BuildOptions{})
+		r, err := b.Build(resolver.Target{Endpoint: a.target, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", a.target))}, cc, resolver.BuildOptions{})
 		if err != nil {
 			t.Fatalf("%v\n", err)
 		}
@@ -1124,7 +1123,7 @@ func testIPResolver(t *testing.T) {
 	for _, v := range tests {
 		b := NewBuilder()
 		cc := &testClientConn{target: v.target}
-		r, err := b.Build(resolver.Target{Endpoint: v.target}, cc, resolver.BuildOptions{})
+		r, err := b.Build(resolver.Target{Endpoint: v.target, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", v.target))}, cc, resolver.BuildOptions{})
 		if err != nil {
 			t.Fatalf("%v\n", err)
 		}
@@ -1175,7 +1174,7 @@ func TestResolveFunc(t *testing.T) {
 		{"[2001:db8:a0b:12f0::1]:21", nil},
 		{":80", nil},
 		{"127.0.0...1:12345", nil},
-		{"[fe80::1%lo0]:80", nil},
+		{"[fe80::1%25lo0]:80", nil},
 		{"golang.org:http", nil},
 		{"[2001:db8::1]:http", nil},
 		{"[2001:db8::1]:", errEndsWithColon},
@@ -1187,7 +1186,7 @@ func TestResolveFunc(t *testing.T) {
 	b := NewBuilder()
 	for _, v := range tests {
 		cc := &testClientConn{target: v.addr, errChan: make(chan error, 1)}
-		r, err := b.Build(resolver.Target{Endpoint: v.addr}, cc, resolver.BuildOptions{})
+		r, err := b.Build(resolver.Target{Endpoint: v.addr, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", v.addr))}, cc, resolver.BuildOptions{})
 		if err == nil {
 			r.Close()
 		}
@@ -1226,7 +1225,7 @@ func TestDisableServiceConfig(t *testing.T) {
 	for _, a := range tests {
 		b := NewBuilder()
 		cc := &testClientConn{target: a.target}
-		r, err := b.Build(resolver.Target{Endpoint: a.target}, cc, resolver.BuildOptions{DisableServiceConfig: a.disableServiceConfig})
+		r, err := b.Build(resolver.Target{Endpoint: a.target, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", a.target))}, cc, resolver.BuildOptions{DisableServiceConfig: a.disableServiceConfig})
 		if err != nil {
 			t.Fatalf("%v\n", err)
 		}
@@ -1264,7 +1263,7 @@ func TestTXTError(t *testing.T) {
 		envconfig.TXTErrIgnore = ignore
 		b := NewBuilder()
 		cc := &testClientConn{target: "ipv4.single.fake"} // has A records but not TXT records.
-		r, err := b.Build(resolver.Target{Endpoint: "ipv4.single.fake"}, cc, resolver.BuildOptions{})
+		r, err := b.Build(resolver.Target{Endpoint: "ipv4.single.fake", URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", "ipv4.single.fake"))}, cc, resolver.BuildOptions{})
 		if err != nil {
 			t.Fatalf("%v\n", err)
 		}
@@ -1300,7 +1299,7 @@ func TestDNSResolverRetry(t *testing.T) {
 	b := NewBuilder()
 	target := "ipv4.single.fake"
 	cc := &testClientConn{target: target}
-	r, err := b.Build(resolver.Target{Endpoint: target}, cc, resolver.BuildOptions{})
+	r, err := b.Build(resolver.Target{Endpoint: target, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", target))}, cc, resolver.BuildOptions{})
 	if err != nil {
 		t.Fatalf("%v\n", err)
 	}
@@ -1443,7 +1442,7 @@ func TestCustomAuthority(t *testing.T) {
 		target := resolver.Target{
 			Endpoint:  "foo.bar.com",
 			Authority: a.authority,
-			URL:       url.URL{Host: a.authority},
+			URL:       *testutils.MustParseURL(fmt.Sprintf("scheme://%s/foo.bar.com", a.authority)),
 		}
 		r, err := b.Build(target, cc, resolver.BuildOptions{})
 
@@ -1501,7 +1500,7 @@ func TestRateLimitedResolve(t *testing.T) {
 	b := NewBuilder()
 	cc := &testClientConn{target: target}
 
-	r, err := b.Build(resolver.Target{Endpoint: target}, cc, resolver.BuildOptions{})
+	r, err := b.Build(resolver.Target{Endpoint: target, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", target))}, cc, resolver.BuildOptions{})
 	if err != nil {
 		t.Fatalf("resolver.Build() returned error: %v\n", err)
 	}
@@ -1610,7 +1609,7 @@ func TestReportError(t *testing.T) {
 	cc := &testClientConn{target: target, errChan: make(chan error)}
 	totalTimesCalledError := 0
 	b := NewBuilder()
-	r, err := b.Build(resolver.Target{Endpoint: target}, cc, resolver.BuildOptions{})
+	r, err := b.Build(resolver.Target{Endpoint: target, URL: *testutils.MustParseURL(fmt.Sprintf("scheme:///%s", target))}, cc, resolver.BuildOptions{})
 	if err != nil {
 		t.Fatalf("Error building resolver for target %v: %v", target, err)
 	}

internal/resolver/passthrough/passthrough.go

@@ -31,7 +31,7 @@ const scheme = "passthrough"
 type passthroughBuilder struct{}
 
 func (*passthroughBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
-	if target.Endpoint == "" && opts.Dialer == nil {
+	if target.ToEndpoint() == "" && opts.Dialer == nil {
 		return nil, errors.New("passthrough: received empty target in Build()")
 	}
 	r := &passthroughResolver{
@@ -52,7 +52,7 @@ type passthroughResolver struct {
 }
 
 func (r *passthroughResolver) start() {
-	r.cc.UpdateState(resolver.State{Addresses: []resolver.Address{{Addr: r.target.Endpoint}}})
+	r.cc.UpdateState(resolver.State{Addresses: []resolver.Address{{Addr: r.target.ToEndpoint()}}})
 }
 
 func (*passthroughResolver) ResolveNow(o resolver.ResolveNowOptions) {}

internal/testutils/parse_url.go

@@ -0,0 +1,34 @@
+/*
+ *
+ * Copyright 2022 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package testutils
+
+import (
+	"fmt"
+	"net/url"
+)
+
+// MustParseURL attempts to parse the provided target using url.Parse()
+// and panics if the url parsing fails.
+func MustParseURL(target string) *url.URL {
+	u, err := url.Parse(target)
+	if err != nil {
+		panic(fmt.Sprintf("Error parsing target(%s): %v", target, err))
+	}
+	return u
+}

resolver/resolver.go

@@ -24,6 +24,7 @@ import (
 	"context"
 	"net"
 	"net/url"
+	"strings"
 
 	"google.golang.org/grpc/attributes"
 	"google.golang.org/grpc/credentials"
@@ -247,8 +248,7 @@ type Target struct {
 	Scheme string
 	// Deprecated: use URL.Host instead.
 	Authority string
-	// Deprecated: use URL.Path or URL.Opaque instead. The latter is set when
-	// the former is empty.
+	// Deprecated: use ToEndpoint() instead.
 	Endpoint string
 	// URL contains the parsed dial target with an optional default scheme added
 	// to it if the original dial target contained no scheme or contained an
@@ -257,6 +257,17 @@ type Target struct {
 	URL url.URL
 }
 
+// ToEndpoint retrieves endpoint without leading "/" from either `URL.Path`
+// or `URL.Opaque`. The latter is set when the former is empty.
+func (t Target) ToEndpoint() string {
+	endpoint := t.URL.Path
+	if endpoint == "" {
+		endpoint = t.URL.Opaque
+	}
+	// Leading "/" is stripped to support existing resolver implementations.
+	return strings.TrimPrefix(endpoint, "/")
+}
+
 // Builder creates a resolver that will be used to watch name resolution updates.
 type Builder interface {
 	// Build creates a new resolver for the given target.