Repository: Azure/azure-service-bus-go (go)

Issue:
Unable to list more than 100 topics
Hi, I have trouble listing all the topics in my SB namespace. 

Azure Service Bus Go version: v0.10.12

When the namespace contains more than 100 topics, `func (*TopicManager) List` returns only first 100 of them. There is no way to increase the page size or get subsequent pages. I think the same problem occurs for queues and subscriptions.

Sample repro:

```go
package main

import (
	"context"
	"fmt"

	servicebus "github.com/Azure/azure-service-bus-go"
)

func main() {
	ns, _ := servicebus.NewNamespace(servicebus.NamespaceWithConnectionString("[CONN STRING HERE]"))
	topicManager := ns.NewTopicManager()

	topicsCreated := 0
	for i := 1; i <= 120; i++ {

		topicManager := ns.NewTopicManager()
		_, err := topicManager.Put(context.Background(), fmt.Sprintf("t%d", i))
		if err == nil {
			topicsCreated += 1
		}
	}

	fmt.Printf("Topics created: %d\n", topicsCreated)

	topics, _ := topicManager.List(context.Background())
	fmt.Printf("Topics listed: %d\n", len(topics))
}
```

Outputs:
```
Topics created: 120
Topics listed: 100
```


Pull request description:
Allow for passing in skip and top parameters to calls that list subscriptions, queues and topics
The current implementation that lists resources (using ATOM) doesn't allow passing in skip, which would allow you to list more than the default page size of 100 items.

This PR adds in skip (and top, which controls the size of the page) for listing queues, topics and subscriptions which allows you, over multiple calls and incrementing skip, to get the list of all entities.

Fixes #231 

Patch:
diff --git a/Makefile b/Makefile
index a5b3df5..354a280 100644
--- a/Makefile
+++ b/Makefile
@@ -40,8 +40,11 @@ test-race:    ARGS=-race         							## Run tests with race detector
 test-cover:   ARGS=-cover -coverprofile=cover.out -v     	## Run tests in verbose mode with coverage
 $(TEST_TARGETS): NAME=$(MAKECMDGOALS:test-%=%)
 $(TEST_TARGETS): test
-check test tests: cyclo lint vet terraform.tfstate; $(info $(M) running $(NAME:%=% )tests…) @ ## Run tests
-	$Q cd $(BASE) && $(GO) test -timeout $(TIMEOUT)s $(ARGS) $(TESTPKGS) 2>&1 | $(GOJUNITRPT) > report.xml
+check test tests: lint vet terraform.tfstate; $(info $(M) running $(NAME:%=% )tests…) @ ## Run tests
+	$Q cd $(BASE) && \
+	$(GO) test -timeout $(TIMEOUT)s $(ARGS) $(TESTPKGS) 2>&1 | tee gotestoutput.log && \
+	$(GOJUNITRPT) <  gotestoutput.log > report.xml && \
+	rm -f gotestoutput.log
 
 .PHONY: vet
 vet: $(GOLINT) ; $(info $(M) running vet…) @ ## Run vet
diff --git a/azuredeploy.tf b/azuredeploy.tf
index 7071eee..3e54d07 100644
--- a/azuredeploy.tf
+++ b/azuredeploy.tf
@@ -154,10 +154,14 @@ output "AZURE_TENANT_ID" {
 }
 
 output "AZURE_CLIENT_ID" {
-  value = compact(concat(azuread_application.test.*.application_id, list(data.azurerm_client_config.current.client_id)))[0]
+  value = compact(
+    concat(azuread_application.test.*.application_id, [data.azurerm_client_config.current.client_id])
+  )[0]
 }
 
 output "AZURE_CLIENT_SECRET" {
-  value     = compact(concat(azuread_service_principal_password.test.*.value, list(var.azure_client_secret)))[0]
+  value  = compact(
+    concat(azuread_service_principal_password.test.*.value, [var.azure_client_secret])
+  )[0]
   sensitive = true
 }
diff --git a/internal/manager_common.go b/internal/manager_common.go
new file mode 100644
index 0000000..8cb6a8e
--- /dev/null
+++ b/internal/manager_common.go
@@ -0,0 +1,26 @@
+package internal
+
+import (
+	"fmt"
+	"net/url"
+)
+
+// ConstructAtomPath adds the proper parameters for skip and top
+// This is common for the list operations for queues, topics and subscriptions.
+func ConstructAtomPath(basePath string, skip int, top int) string {
+	values := url.Values{}
+
+	if skip > 0 {
+		values.Add("$skip", fmt.Sprintf("%d", skip))
+	}
+
+	if top > 0 {
+		values.Add("$top", fmt.Sprintf("%d", top))
+	}
+
+	if len(values) == 0 {
+		return basePath
+	}
+
+	return fmt.Sprintf("%s?%s", basePath, values.Encode())
+}
diff --git a/queue_manager.go b/queue_manager.go
index 38aa332..61d5d99 100644
--- a/queue_manager.go
+++ b/queue_manager.go
@@ -13,6 +13,7 @@ import (
 	"github.com/devigned/tab"
 
 	"github.com/Azure/azure-service-bus-go/atom"
+	"github.com/Azure/azure-service-bus-go/internal"
 )
 
 type (
@@ -54,6 +55,34 @@ type (
 	}
 )
 
+type (
+	// ListQueuesOptions provides options for List() to control things like page size.
+	// NOTE: Use the ListQueuesWith* methods to specify this.
+	ListQueuesOptions struct {
+		top  int
+		skip int
+	}
+
+	// ListQueuesOption represents named options for listing topics
+	ListQueuesOption func(*ListQueuesOptions) error
+)
+
+// ListQueuesWithSkip will skip the specified number of entities
+func ListQueuesWithSkip(skip int) ListQueuesOption {
+	return func(options *ListQueuesOptions) error {
+		options.skip = skip
+		return nil
+	}
+}
+
+// ListQueuesWithTop will return at most `top` results
+func ListQueuesWithTop(top int) ListQueuesOption {
+	return func(options *ListQueuesOptions) error {
+		options.top = top
+		return nil
+	}
+}
+
 // TargetURI provides an absolute address to a target entity
 func (e Entity) TargetURI() string {
 	split := strings.Split(e.ID, "?")
@@ -300,11 +329,21 @@ func (qm *QueueManager) Put(ctx context.Context, name string, opts ...QueueManag
 }
 
 // List fetches all of the queues for a Service Bus Namespace
-func (qm *QueueManager) List(ctx context.Context) ([]*QueueEntity, error) {
+func (qm *QueueManager) List(ctx context.Context, options ...ListQueuesOption) ([]*QueueEntity, error) {
 	ctx, span := qm.startSpanFromContext(ctx, "sb.QueueManager.List")
 	defer span.End()
 
-	res, err := qm.entityManager.Get(ctx, `/$Resources/Queues`)
+	listQueuesOptions := ListQueuesOptions{}
+
+	for _, option := range options {
+		if err := option(&listQueuesOptions); err != nil {
+			return nil, err
+		}
+	}
+
+	basePath := internal.ConstructAtomPath(`/$Resources/Queues`, listQueuesOptions.skip, listQueuesOptions.top)
+
+	res, err := qm.entityManager.Get(ctx, basePath)
 	defer closeRes(ctx, res)
 
 	if err != nil {
diff --git a/subscription_manager.go b/subscription_manager.go
index 27fc9d3..8e91451 100644
--- a/subscription_manager.go
+++ b/subscription_manager.go
@@ -15,6 +15,7 @@ import (
 	"github.com/devigned/tab"
 
 	"github.com/Azure/azure-service-bus-go/atom"
+	"github.com/Azure/azure-service-bus-go/internal"
 )
 
 type (
@@ -156,6 +157,34 @@ type (
 	SubscriptionManagementOption func(*SubscriptionDescription) error
 )
 
+type (
+	// ListSubscriptionsOptions provides options for List() to control things like page size.
+	// NOTE: Use the ListSubscriptionsWith* methods to specify this.
+	ListSubscriptionsOptions struct {
+		top  int
+		skip int
+	}
+
+	//ListSubscriptionsOption represents named options for listing topics
+	ListSubscriptionsOption func(*ListSubscriptionsOptions) error
+)
+
+// ListSubscriptionsWithSkip will skip the specified number of entities
+func ListSubscriptionsWithSkip(skip int) ListSubscriptionsOption {
+	return func(options *ListSubscriptionsOptions) error {
+		options.skip = skip
+		return nil
+	}
+}
+
+// ListSubscriptionsWithTop will return at most `top` results
+func ListSubscriptionsWithTop(top int) ListSubscriptionsOption {
+	return func(options *ListSubscriptionsOptions) error {
+		options.top = top
+		return nil
+	}
+}
+
 // NewSubscriptionManager creates a new SubscriptionManager for a Service Bus Topic
 func (t *Topic) NewSubscriptionManager() *SubscriptionManager {
 	return &SubscriptionManager{
@@ -249,11 +278,21 @@ func (sm *SubscriptionManager) Put(ctx context.Context, name string, opts ...Sub
 }
 
 // List fetches all of the Topics for a Service Bus Namespace
-func (sm *SubscriptionManager) List(ctx context.Context) ([]*SubscriptionEntity, error) {
+func (sm *SubscriptionManager) List(ctx context.Context, options ...ListSubscriptionsOption) ([]*SubscriptionEntity, error) {
 	ctx, span := sm.startSpanFromContext(ctx, "sb.SubscriptionManager.List")
 	defer span.End()
 
-	res, err := sm.entityManager.Get(ctx, "/"+sm.Topic.Name+"/subscriptions")
+	listSubscriptionsOptions := ListSubscriptionsOptions{}
+
+	for _, option := range options {
+		if err := option(&listSubscriptionsOptions); err != nil {
+			return nil, err
+		}
+	}
+
+	basePath := internal.ConstructAtomPath("/"+sm.Topic.Name+"/subscriptions", listSubscriptionsOptions.skip, listSubscriptionsOptions.top)
+
+	res, err := sm.entityManager.Get(ctx, basePath)
 	defer closeRes(ctx, res)
 
 	if err != nil {
diff --git a/topic_manager.go b/topic_manager.go
index 3f97325..da86f0f 100644
--- a/topic_manager.go
+++ b/topic_manager.go
@@ -12,6 +12,7 @@ import (
 	"github.com/devigned/tab"
 
 	"github.com/Azure/azure-service-bus-go/atom"
+	"github.com/Azure/azure-service-bus-go/internal"
 )
 
 type (
@@ -49,6 +50,34 @@ type (
 	TopicManagementOption func(*TopicDescription) error
 )
 
+type (
+	// ListTopicsOptions provides options for List() to control things like page size.
+	// NOTE: Use the ListTopicsWith* methods to specify this.
+	ListTopicsOptions struct {
+		top  int
+		skip int
+	}
+
+	// ListTopicsOption represents named options for listing topics
+	ListTopicsOption func(*ListTopicsOptions) error
+)
+
+// ListTopicsWithSkip will skip the specified number of entities
+func ListTopicsWithSkip(skip int) ListTopicsOption {
+	return func(options *ListTopicsOptions) error {
+		options.skip = skip
+		return nil
+	}
+}
+
+// ListTopicsWithTop will return at most `top` results
+func ListTopicsWithTop(top int) ListTopicsOption {
+	return func(options *ListTopicsOptions) error {
+		options.top = top
+		return nil
+	}
+}
+
 // NewTopicManager creates a new TopicManager for a Service Bus Namespace
 func (ns *Namespace) NewTopicManager() *TopicManager {
 	return &TopicManager{
@@ -122,11 +151,21 @@ func (tm *TopicManager) Put(ctx context.Context, name string, opts ...TopicManag
 }
 
 // List fetches all of the Topics for a Service Bus Namespace
-func (tm *TopicManager) List(ctx context.Context) ([]*TopicEntity, error) {
+func (tm *TopicManager) List(ctx context.Context, options ...ListTopicsOption) ([]*TopicEntity, error) {
 	ctx, span := tm.startSpanFromContext(ctx, "sb.TopicManager.List")
 	defer span.End()
 
-	res, err := tm.entityManager.Get(ctx, `/$Resources/Topics`)
+	listTopicsOptions := ListTopicsOptions{}
+
+	for _, option := range options {
+		if err := option(&listTopicsOptions); err != nil {
+			return nil, err
+		}
+	}
+
+	basePath := internal.ConstructAtomPath("/$Resources/Topics", listTopicsOptions.skip, listTopicsOptions.top)
+
+	res, err := tm.entityManager.Get(ctx, basePath)
 	defer closeRes(ctx, res)
 
 	if err != nil {


Test patch:
diff --git a/internal/manager_common_test.go b/internal/manager_common_test.go
new file mode 100644
index 0000000..dd2c004
--- /dev/null
+++ b/internal/manager_common_test.go
@@ -0,0 +1,20 @@
+package internal
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestConstructAtomPath(t *testing.T) {
+	basePath := ConstructAtomPath("/something", 1, 2)
+
+	// I'm assuming the ordering is non-deterministic since the underlying values are just a map
+	assert.Truef(t, basePath == "/something?%24skip=1&%24top=2" || basePath == "/something?%24top=2&%24skip=1", "%s wasn't one of our two variations", basePath)
+
+	basePath = ConstructAtomPath("/something", 0, -1)
+	assert.EqualValues(t, "/something", basePath, "Values <= 0 are ignored")
+
+	basePath = ConstructAtomPath("/something", -1, 0)
+	assert.EqualValues(t, "/something", basePath, "Values <= 0 are ignored")
+}
diff --git a/queue_test.go b/queue_test.go
index 896ce49..498d4a8 100644
--- a/queue_test.go
+++ b/queue_test.go
@@ -308,6 +308,22 @@ func testListQueues(ctx context.Context, t *testing.T, qm *QueueManager, names [
 	for _, name := range names {
 		assert.Contains(t, queueNames, name)
 	}
+
+	// there should be at least two entities but there could be others if the service isn't clean (which is fine)
+	firstSet, err := qm.List(ctx, ListQueuesWithSkip(0), ListQueuesWithTop(1))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 1, len(firstSet))
+
+	secondSet, err := qm.List(ctx, ListQueuesWithSkip(1), ListQueuesWithTop(1))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 1, len(secondSet))
+
+	// sanity check - we didn't just retrieve the same entity twice.
+	assert.NotEqualValues(t, firstSet[0].Name, secondSet[0].Name)
+
+	lastSet, err := qm.List(ctx, ListQueuesWithSkip(0), ListQueuesWithTop(2))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 2, len(lastSet))
 }
 
 func (suite *serviceBusSuite) randEntityName() string {
diff --git a/subscription_test.go b/subscription_test.go
index 38e64cc..cda9bb6 100644
--- a/subscription_test.go
+++ b/subscription_test.go
@@ -245,6 +245,50 @@ func (suite *serviceBusSuite) TestSubscriptionManagement() {
 	suite.testSubscriptionManager(tests)
 }
 
+func (suite *serviceBusSuite) TestSubscriptionManagementReads() {
+	tests := map[string]func(ctx context.Context, t *testing.T, sm *SubscriptionManager, topicName, name string){
+		"TestListSubscriptions": testListSubscriptions,
+	}
+
+	suite.testSubscriptionManager(tests)
+}
+
+func testListSubscriptions(ctx context.Context, t *testing.T, sm *SubscriptionManager, _, name string) {
+	names := []string{name + "-1", name + "-2"}
+
+	for _, name := range names {
+		buildSubscription(ctx, t, sm, name)
+	}
+
+	subs, err := sm.List(ctx)
+	assert.Nil(t, err)
+	assert.NotNil(t, subs)
+	subNames := make([]string, len(subs))
+	for idx, s := range subs {
+		subNames[idx] = s.Name
+	}
+
+	for _, name := range names {
+		assert.Contains(t, subNames, name)
+	}
+
+	// there should be at least two entities but there could be others if the service isn't clean (which is fine)
+	firstSet, err := sm.List(ctx, ListSubscriptionsWithSkip(0), ListSubscriptionsWithTop(1))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 1, len(firstSet))
+
+	secondSet, err := sm.List(ctx, ListSubscriptionsWithSkip(1), ListSubscriptionsWithTop(1))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 1, len(secondSet))
+
+	// sanity check - we didn't just retrieve the same entity twice.
+	assert.NotEqualValues(t, firstSet[0].Name, secondSet[0].Name)
+
+	lastSet, err := sm.List(ctx, ListSubscriptionsWithSkip(0), ListSubscriptionsWithTop(2))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 2, len(lastSet))
+}
+
 func testDefaultSubscription(ctx context.Context, t *testing.T, sm *SubscriptionManager, _, name string) {
 	s := buildSubscription(ctx, t, sm, name)
 	assert.False(t, *s.DeadLetteringOnMessageExpiration, "should not have dead lettering on expiration")
diff --git a/topic_test.go b/topic_test.go
index 3ec14d9..d489612 100644
--- a/topic_test.go
+++ b/topic_test.go
@@ -196,6 +196,22 @@ func testListTopics(ctx context.Context, t *testing.T, tm *TopicManager, names [
 	for _, name := range names {
 		assert.Contains(t, queueNames, name)
 	}
+
+	// there should be at least two entities but there could be others if the service isn't clean (which is fine)
+	firstSet, err := tm.List(ctx, ListTopicsWithSkip(0), ListTopicsWithTop(1))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 1, len(firstSet))
+
+	secondSet, err := tm.List(ctx, ListTopicsWithSkip(1), ListTopicsWithTop(1))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 1, len(secondSet))
+
+	// sanity check - we didn't just retrieve the same entity twice.
+	assert.NotEqualValues(t, firstSet[0].Name, secondSet[0].Name)
+
+	lastSet, err := tm.List(ctx, ListTopicsWithSkip(0), ListTopicsWithTop(2))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 2, len(lastSet))
 }
 
 func (suite *serviceBusSuite) TestTopicManagement() {