Debug extension host without requiring a restart

[Haras (ArasHuseyin)]

Fixes #85422

Problem

Clicking Debug Extension Host In New Window (and Debug Extension Host and Renderer In New Window) always prompts for a restart, even when the extension host is already running. This defeats the main use case of the feature — attaching a debugger to a running extension host to investigate an issue that is happening right now.

Cause

Both actions go through the shared getExtensionHostPort helper, which called:

extensionService.getInspectPorts(ExtensionHostKind.LocalProcess, /* tryEnableInspector */ false)

With tryEnableInspector = false, the extension host manager never calls enableInspectPort(), so when the host was not started with --inspect-extensions there are no inspect ports and the code falls through to the restart prompt.

The profiling path (ExtensionHostProfileService.startProfiling) and the dev-tools path (DebugExtensionHostInDevToolsAction) already pass true, which enables the inspector on the running extension host via node's process._debugProcess(pid) (UtilityProcess.enableInspectPort) — no restart required. This matches the approach suggested by Andre Weinand (@weinand) and Johannes Rieken (@jrieken) in the issue, and explains Connor Peet (@connor4312)'s observation that profiling works without a restart while debugging does not.

Fix

Pass tryEnableInspector = true in the shared helper so the debug actions first try to enable the inspector on the running host, exactly like profiling. The restart prompt is kept as a fallback for the case where the inspector cannot be enabled on the fly (e.g. _debugProcess unavailable or the host is not running).

Notes

• No behavior change when the host was already started with --inspect-extensions: enableInspectPort() short-circuits when an inspect listener already exists.
• No new state and no new UI; the change is limited to the shared helper used by the two debug actions.

[Copilot]

Pull request overview

Enables debugging an already-running local extension host without restarting VS Code.

Changes:

• Attempts to enable the inspector dynamically.
• Retains the restart prompt as a fallback.

[Haras (ArasHuseyin)]

reduced the inline comment to a single line as suggested (3483d82). It now only notes the non-obvious intent (enabling the inspector on the running host to avoid a restart, matching the profiling path).