[edusperoni]

What is the current behavior?

The inspector serves one client at a time (#516). A second connection closes the first, and the single V8 session is reset or rebound for the newcomer. You cannot, for example, keep Chrome DevTools open while a CDP script or a second DevTools window attaches.

What is the new behavior?

Any number of clients can connect at once, as with Chrome and Node. Each gets its own V8 session and sees only replies to its own commands.

Sessions

• New InspectorSessions keeps one V8InspectorSession per connection on an isolate. Each session's channel writes only to its own connection. It is used for the main isolate and for every worker.
• Connect, disconnect and messages go through one per-isolate queue, so a client's session exists before its first message and outlives its last.
• A client's session is destroyed when it disconnects. Its destructor disables the client's agents, so a pause ends only if no other client still has the debugger enabled. This is the same rule V8 applies in Chrome.
• A session can't be destroyed while it is dispatching. The pause loop can sit under that client's own Runtime.evaluate. In that case it gets Debugger.disable right away, so the pause is released if nobody else wants it, and it is destroyed when that dispatch returns.
• This replaces fix(inspector): release the frontend's resources when DevTools disconnects #516's sync sentinel, session rebinding, frontend generations, deferred resets and lifecycle mutex.

Workers

• Each worker holds a session per client, created by the client's first message to that worker and dropped when the client disconnects. Output goes to the owning connection.
• Target.setAutoAttach and the set of announced workers are tracked per client. attachedToTarget and detachedFromTarget go only to the clients that asked.

Shared state

• Pauses are shared. Every client with the debugger enabled sees Debugger.paused, and any of them can resume.
• Debugger.pause schedules the pause in the requesting client's session. A request still pending when a pause starts is dropped, so it can't pause again after the resume.
• Tracing is process-global. One client owns it from Tracing.start until its Tracing.end or disconnect, and other clients get "Tracing is already started".
• Network.loadNetworkResource streams belong to the client that opened them. IO.read/IO.close from another client get "Invalid stream handle", and the streams are dropped when their client disconnects.
• The JS domains from @nativescript/core (DOM, CSS, Network) are global singletons that enable themselves:
  • Their events go to every client.
  • Command replies go only to the requesting client.
  • <Domain>.disable reaches the handler only once no other client has that domain enabled.
• Heap object tracking and sampling, and the pause-on-exceptions setting, are isolate-wide in V8. One client's HeapProfiler.disable (or its disconnect) stops tracking for everyone. This is a V8 limitation that Chrome shares, documented on the class.

Server

• InspectorServer no longer closes the previous client.
• Per connection, onClientConnected precedes its messages and onClientDisconnected follows them. A message read just before a write error closed the connection is dropped.
• A client more than 256 MB behind on writes is closed. Every client receives broadcast events, so a half-open socket would otherwise buffer forever.
• Connection reset and broken pipe are ordinary disconnects and are no longer logged as errors.

Also fixed: a pause triggered by a message the drain dispatched (e.g. evaluating debugger in the console) re-entered dispatch_sync on the queue the drain held and trapped in libdispatch. The drain now checks the pause-loop flag under that queue but dispatches outside it. The pause loop schedules a drain when it exits.

Known issues / follow-ups

• Debugger.pause on a worker never pauses it, while debugger; statements do. This also fails on main before this change, verified with the fix(inspector): release the frontend's resources when DevTools disconnects #516 build, so it is left for a separate fix.
• Disconnecting the last client doesn't disable core's JS domains. They enable themselves at startup, because they can miss the enable event, so they keep emitting into the void. Unchanged from before.
• Android parity comes later.

Testing

• Full suite (./run_tests.sh --keep-sim): 1835 specs, 0 failures.
• End-to-end on a simulator: a small CDP client drives TestRunner, which runs a keep-alive entry script.
  • Concurrent: two clients send the same message id and each gets its own reply. Both see console output. B keeps working after A leaves.
  • Shared pause: A pauses, both see Debugger.paused, B resumes, and both see Debugger.resumed.
  • Leave while paused: alone, the app resumes. With B debugging, it stays paused until B resumes.
  • Leave while paused inside A's own Runtime.evaluate (debugger;): alone, the app resumes. With B debugging, it stays paused, and A's evaluate reply never reaches B. In both cases a later client can pause and resume again. Before the drain fix, this path crashed in libdispatch.
  • Workers: both clients get attachedToTarget, and both evaluate in the worker with the same id, each getting its own reply. The worker pauses on debugger; and both see it. A leaves while paused, the worker stays paused for B, B resumes, and B's worker session keeps working.
  • Tracing: B is refused while A traces and can't end A's trace. After A leaves, B traces to completion.
  • fix(inspector): release the frontend's resources when DevTools disconnects #516's single-client scenarios (idle and paused disconnect, in-flight replies on the main isolate and a worker) still pass.
  • After all scenarios the app holds only its listening socket.

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