Fix implicit attach on subscribe

[sacOO7]

Fixed #1027

Summary by CodeRabbit

• New Features

  • Introduced a configurable option for channel subscriptions to control automatic attachment behavior.
  • Added a new field attachOnSubscribe in ChannelOptions to manage implicit attachment during subscriptions.

• Bug Fixes

  • Improved control flow in subscription methods to prevent unnecessary operations when implicit attachment is disabled.

• Tests

  • Added tests to validate subscription behavior without implicit channel attachment for both messages and presence events.

[coderabbitai]

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Commits

Files that changed from the base of the PR and between d8181e8 and 3ecab48.

Walkthrough

The changes introduce a new configuration option, attachOnSubscribe, to the Ably library, allowing users to control whether a channel automatically attaches upon subscription. This functionality is implemented in the ChannelBase, Presence, and ChannelOptions classes, along with corresponding tests to ensure proper behavior. The modifications enhance the subscription process by enabling conditional attachment, improving the configurability of channel interactions.

Changes

Files	Change Summary
lib/src/main/java/io/ably/lib/realtime/ChannelBase.java	Added method attachOnSubscribeEnabled() to control channel attachment on subscription based on options.
lib/src/main/java/io/ably/lib/realtime/Presence.java	Updated implicitAttachOnSubscribe to check attachOnSubscribeEnabled() before proceeding with subscription.
lib/src/main/java/io/ably/lib/types/ChannelOptions.java	Introduced public field attachOnSubscribe to specify automatic attachment behavior on subscription.
lib/src/test/java/io/ably/lib/test/realtime/RealtimeChannelTest.java	Added test method subscribe_without_implicit_attach to verify subscription behavior without automatic attachment.
lib/src/test/java/io/ably/lib/test/realtime/RealtimePresenceTest.java	Added test method presence_subscribe_without_implicit_attach to validate presence subscription without attachment.

Assessment against linked issues

Objective	Addressed	Explanation
Implement the attachOnSubscribe channel option (TB4)	✅

🐰 In the realm of code, a change takes flight,
With options for channels, oh what a delight!
Attach on subscribe, now users can choose,
A flexible path, no more to lose.
Tests are in place, to ensure it’s right,
Hopping along, our features shine bright! 🌟

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[coderabbitai]

Caution

Inline review comments failed to post

Actionable comments posted: 8

Outside diff range and nitpick comments (3)

lib/src/main/java/io/ably/lib/realtime/ChannelBase.java (1)

693-701: Ensure consistent terminology in comments

The JavaDoc comment refers to channelOptions, but the code uses options. For clarity and consistency, consider updating the comment to use options to match the code.

Apply this diff to update the comment:

     /**
-     * Checks for null channelOptions and checks if options.attachOnSubscribe is true
+     * Checks for null options and checks if options.attachOnSubscribe is true
-     * Defaults to @true@ when channelOptions is null.
+     * Defaults to @true@ when options is null.
      * Spec: TB4, RTL7g, RTL7gh, RTP6d, RTP6e
      */

lib/src/test/java/io/ably/lib/test/realtime/RealtimeChannelTest.java (2)

417-417: Specify generic type for List to enhance type safety

The receivedMsg list is currently declared with a raw type List<Object>. Since you're adding Boolean values, specifying the generic type as Boolean improves type safety and readability.

Apply this diff:

-List<Object> receivedMsg = new ArrayList<>();
+List<Boolean> receivedMsg = new ArrayList<>();

---

449-451: Update error message in catch block for clarity

The error message in the catch block refers to "init0," which may not accurately reflect the context of this test method. Consider updating the message to provide a clearer description of the exception.

Apply this diff:

-fail("init0: Unexpected exception instantiating library");
+fail("subscribe_without_implicit_attach: Unexpected exception");

Review details

Configuration used: CodeRabbit UI
Review profile: CHILL

Commits

Files that changed from the base of the PR and between e0e2317 and 0436cd9.

Files selected for processing (5)

• lib/src/main/java/io/ably/lib/realtime/ChannelBase.java (4 hunks)
• lib/src/main/java/io/ably/lib/realtime/Presence.java (1 hunks)
• lib/src/main/java/io/ably/lib/types/ChannelOptions.java (1 hunks)
• lib/src/test/java/io/ably/lib/test/realtime/RealtimeChannelTest.java (1 hunks)
• lib/src/test/java/io/ably/lib/test/realtime/RealtimePresenceTest.java (1 hunks)

Additional comments not posted (2)

lib/src/main/java/io/ably/lib/realtime/ChannelBase.java (2)

753-755: Duplication of conditional attach() logic

This code block duplicates the attach() logic found in other subscribe methods. Refer to the earlier refactoring suggestion to extract this logic into a common method and improve code maintainability.

---

789-791: Duplication of conditional attach() logic

This code block duplicates the attach() logic found in other subscribe methods. Refer to the earlier refactoring suggestion to extract this logic into a common method and improve code maintainability.

Comments failed to post (8)

lib/src/main/java/io/ably/lib/types/ChannelOptions.java (2)

48-48: Encapsulate 'attachOnSubscribe' field with getter and setter methods

Consider making the attachOnSubscribe field private and providing public getter and setter methods. This follows best practices for encapsulation and allows for additional control or validation when accessing or modifying the field.

Suggested changes:

-    public boolean attachOnSubscribe = true;
+    private boolean attachOnSubscribe = true;
+
+    public boolean isAttachOnSubscribe() {
+        return attachOnSubscribe;
+    }
+
+    public void setAttachOnSubscribe(boolean attachOnSubscribe) {
+        this.attachOnSubscribe = attachOnSubscribe;
+    }

Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

    private boolean attachOnSubscribe = true;

    public boolean isAttachOnSubscribe() {
        return attachOnSubscribe;
    }

    public void setAttachOnSubscribe(boolean attachOnSubscribe) {
        this.attachOnSubscribe = attachOnSubscribe;
    }

---

44-46: Use proper JavaDoc formatting for code references

In the JavaDoc comments, use {@code ...} for code snippets or values, and {@link ...} for method references. Replace @subscribe@ and @true@ with the appropriate JavaDoc syntax.

Suggested changes:

-     * Determines whether calling @subscribe@ on a channel or presence object should trigger an implicit attach.
-     * Defaults to @true@.
+     * Determines whether calling {@link io.ably.lib.realtime.Channel#subscribe} on a channel or presence object should trigger an implicit attach.
+     * Defaults to {@code true}.

Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

     * Determines whether calling {@link io.ably.lib.realtime.Channel#subscribe} on a channel or presence object should trigger an implicit attach.
     * Defaults to {@code true}.
     * Spec: TB4, RTL7g, RTL7gh, RTP6d, RTP6e

lib/src/main/java/io/ably/lib/realtime/Presence.java (1)

311-316: Ensure channel state is checked even when attachOnSubscribe is disabled

In the modified code, when channel.attachOnSubscribeEnabled() returns false, the method exits early without checking if the channel state is failed. This omission could allow operations to proceed on a failed channel, leading to unexpected behavior or unhandled exceptions. To maintain consistent error handling, the check for channel.state == ChannelState.failed should occur regardless of the attachOnSubscribe setting.

Apply this diff to include the channel state check before returning:

 if (!channel.attachOnSubscribeEnabled()) {
+    if (channel.state == ChannelState.failed) {
+        String errorString = String.format(Locale.ROOT, "Channel %s: subscribe in FAILED channel state", channel.name);
+        Log.v(TAG, errorString);
+        ErrorInfo errorInfo = new ErrorInfo(errorString, 90001);
+        throw AblyException.fromErrorInfo(errorInfo);
+    }
     if (completionListener != null) {
         completionListener.onSuccess();
     }
     return;
 }

Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

        if (!channel.attachOnSubscribeEnabled()) {
            if (channel.state == ChannelState.failed) {
                String errorString = String.format(Locale.ROOT, "Channel %s: subscribe in FAILED channel state", channel.name);
                Log.v(TAG, errorString);
                ErrorInfo errorInfo = new ErrorInfo(errorString, 90001);
                throw AblyException.fromErrorInfo(errorInfo);
            }
            if (completionListener != null) {
                completionListener.onSuccess();
            }
            return;
        }

lib/src/main/java/io/ably/lib/realtime/ChannelBase.java (1)

716-718: Consider refactoring to eliminate code duplication

The conditional attach() call based on attachOnSubscribeEnabled() is repeated in multiple subscribe methods. To improve maintainability and reduce duplication, consider extracting this logic into a private helper method.

Apply this diff to refactor the repeated code:

+private void attachIfNeeded() throws AblyException {
+    if (attachOnSubscribeEnabled()) {
+        attach();
+    }
+}

 public synchronized void subscribe(MessageListener listener) throws AblyException {
     Log.v(TAG, "subscribe(); channel = " + this.name);
     listeners.add(listener);
-    if (attachOnSubscribeEnabled()) {
-        attach();
-    }
+    attachIfNeeded();
 }

And similarly update the other subscribe methods to use attachIfNeeded():

 public synchronized void subscribe(String name, MessageListener listener) throws AblyException {
     Log.v(TAG, "subscribe(); channel = " + this.name + "; event = " + name);
     subscribeImpl(name, listener);
-    if (attachOnSubscribeEnabled()) {
-        attach();
-    }
+    attachIfNeeded();
 }

 public synchronized void subscribe(String[] names, MessageListener listener) throws AblyException {
     Log.v(TAG, "subscribe(); channel = " + this.name + "; (multiple events)");
     for(String name : names)
         subscribeImpl(name, listener);
-    if (attachOnSubscribeEnabled()) {
-        attach();
-    }
+    attachIfNeeded();
 }

Committable suggestion was skipped due to low confidence.

lib/src/test/java/io/ably/lib/test/realtime/RealtimeChannelTest.java (2)

420-420: Swap parameters in assertEquals method

The assertEquals method expects the expected value as the first parameter and the actual value as the second. Currently, the parameters are reversed, which can lead to confusing error messages if the test fails.

Apply the following diff to correct the parameter order:

-assertEquals(channel.state, ChannelState.initialized);
+assertEquals(ChannelState.initialized, channel.state);

Repeat this change for all instances where assertEquals is used with reversed parameters.

Also applies to: 423-423, 426-426

---

419-419: Clarify the reasoning behind expecting two received messages

The test expects receivedMsg.size() == 2 after publishing a message, which might be unclear to someone reading the code. Adding a comment to explain why two messages are expected can improve the test's readability and maintainability.

For example, you could add a comment:

// Expecting two callbacks: one from the wildcard subscription and one from the specific event subscription

Also applies to: 422-422, 425-425

lib/src/test/java/io/ably/lib/test/realtime/RealtimePresenceTest.java (2)

1653-1654: Fix the order of arguments in assertEquals method calls

In JUnit's assertEquals(expected, actual) method, the first argument is the expected value, and the second is the actual value. Currently, the arguments are reversed in lines 1653, 1654, 1657, and 1658, which can lead to misleading assertion messages if a test fails.

Apply this diff to correct the assertEquals calls:

-        assertEquals(completionWaiter.successCount, 1);
+        assertEquals(1, completionWaiter.successCount);
-        assertEquals(channel.state, ChannelState.initialized);
+        assertEquals(ChannelState.initialized, channel.state);

-        assertEquals(completionWaiter.successCount, 2);
+        assertEquals(2, completionWaiter.successCount);
-        assertEquals(channel.state, ChannelState.initialized);
+        assertEquals(ChannelState.initialized, channel.state);

Also applies to: 1657-1658

---

1649-1652: Ensure thread-safe access to receivedPresenceMsg

The receivedPresenceMsg list is accessed from multiple threads since the PresenceListener callbacks may be invoked asynchronously. As ArrayList is not thread-safe, this can lead to concurrency issues. Consider using a thread-safe collection like Collections.synchronizedList(new ArrayList<>()) or a CopyOnWriteArrayList.

Apply this diff to make receivedPresenceMsg thread-safe:

 import java.util.ArrayList;
+import java.util.Collections;
 
 ...
 
-        List<Object> receivedPresenceMsg = new ArrayList<>();
+        List<Object> receivedPresenceMsg = Collections.synchronizedList(new ArrayList<>());

Also applies to: 1666-1675

[ttypic]

LGTM

[sacOO7]

LGTM

Thanks for the review