perf(wsl-host): focus connects without first probing WSL when no bridge exists yet (#33110)

src/main/wsl/wsl-host-focus-reachability.ts

@@ -0,0 +1,15 @@
+import type { WslHostConnector } from './wsl-host-service'
+
+/**
+ * Whether a focused host answers. Without a bridge in this process nothing answers yet, and focus
+ * connects whatever the running list says, so the WSL round trip would only delay the connect.
+ * Polls never use this: they must read the running list so they never boot a stopped distro (E9).
+ */
+export function focusReachability(
+  connector: Pick<WslHostConnector, 'get' | 'reachability'>,
+  record: { distro: string; environmentId: string }
+): ReturnType<WslHostConnector['reachability']> {
+  return connector.get(record.distro)
+    ? connector.reachability(record.distro, record.environmentId)
+    : Promise.resolve('unreachable')
+}

src/main/wsl/wsl-host-service.test.ts

@@ -479,6 +479,39 @@ describe('WslHostService', () => {
     await vi.waitFor(() => expect(connector.connect).toHaveBeenCalledTimes(1))
   })
 
+  it('focus connects without probing WSL while this process has no bridge, but polls still read the running list', async () => {
+    const connector = makeConnector([UBUNTU])
+    const service = makeService(connector)
+    await service.add({ distro: 'Ubuntu' })
+    await connector.disconnect('Ubuntu')
+    connector.reachability.mockClear()
+    connector.connect.mockClear()
+
+    service.focusHost('wsl:ubuntu')
+    await vi.waitFor(() => expect(connector.connect).toHaveBeenCalledTimes(1))
+    expect(connector.reachability).not.toHaveBeenCalled()
+
+    // A poll never takes that shortcut: it reads the running list and refuses a stopped distro.
+    await connector.disconnect('Ubuntu')
+    connector.distro.state = 'stopped'
+    connector.connect.mockClear()
+    await expect(service.ensureForRuntimeCall('wsl:ubuntu')).rejects.toThrow('Ubuntu was stopped')
+    expect(connector.reachability).toHaveBeenCalledWith('Ubuntu', 'wsl:ubuntu')
+    expect(connector.connect).not.toHaveBeenCalled()
+  })
+
+  it('focus with a bridge still asks whether the host answers before connecting again', async () => {
+    const connector = makeConnector([UBUNTU])
+    const service = makeService(connector)
+    await service.add({ distro: 'Ubuntu' })
+    connector.reachability.mockClear()
+    connector.connect.mockClear()
+
+    service.focusHost('wsl:ubuntu')
+    await vi.waitFor(() => expect(connector.reachability).toHaveBeenCalledTimes(1))
+    expect(connector.connect).not.toHaveBeenCalled()
+  })
+
   it('parks a host the moment a poll finds its distro confirmed stopped, never booting it', async () => {
     const connector = makeConnector([UBUNTU])
     const service = makeService(connector)

src/main/wsl/wsl-host-service.ts

@@ -4,6 +4,7 @@
  * parked: polls and visible work keep it down until the user acts or the distro runs again.
  */
 import { errorMessage } from '../../shared/error-message'
+import { focusReachability } from './wsl-host-focus-reachability'
 import { removeWslHostEnvironment } from '../../shared/runtime-environment-wsl-host-store'
 import {
   readWslHostDeployments,
@@ -293,8 +294,7 @@ export class WslHostService {
       return
     }
     this.parked.delete(record.environmentId)
-    void this.connector
-      .reachability(record.distro, record.environmentId)
+    void focusReachability(this.connector, record)
       .then((reachability) =>
         reachability === 'available' ? undefined : this.connector?.connect(record.distro)
       )