refactor: extract OAuth post-login resume into a composable

Both CloudLoginView and CloudSignupView had identical post-success
OAuth-resume blocks (capture request id, create session, navigate or
surface error). Extract into useOAuthPostLoginRedirect so the logic is
unit-testable in isolation without spinning up the full login views.

Also gives codecov diff coverage on the try/catch error path.

src/platform/cloud/oauth/useOAuthPostLoginRedirect.test.ts

@@ -0,0 +1,89 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { useOAuthPostLoginRedirect } from '@/platform/cloud/oauth/useOAuthPostLoginRedirect'
+
+const VALID_REQUEST_ID = '550e8400-e29b-41d4-a716-446655440000'
+
+const routerPush = vi.fn().mockResolvedValue(undefined)
+const createSessionOrThrow = vi.fn().mockResolvedValue(undefined)
+
+vi.mock('vue-router', () => ({
+  useRouter: () => ({ push: routerPush })
+}))
+
+vi.mock('@/platform/auth/session/useSessionCookie', () => ({
+  useSessionCookie: () => ({ createSessionOrThrow })
+}))
+
+describe('useOAuthPostLoginRedirect', () => {
+  beforeEach(() => {
+    sessionStorage.clear()
+    routerPush.mockClear()
+    createSessionOrThrow.mockReset().mockResolvedValue(undefined)
+  })
+
+  it('returns no-oauth when neither query nor sessionStorage holds a request id', async () => {
+    const { resumeOAuthIfNeeded } = useOAuthPostLoginRedirect()
+
+    const result = await resumeOAuthIfNeeded({})
+
+    expect(result).toEqual({ kind: 'no-oauth' })
+    expect(createSessionOrThrow).not.toHaveBeenCalled()
+    expect(routerPush).not.toHaveBeenCalled()
+  })
+
+  it('establishes session and navigates to consent when oauth_request_id is in the query', async () => {
+    const { resumeOAuthIfNeeded } = useOAuthPostLoginRedirect()
+
+    const result = await resumeOAuthIfNeeded({
+      oauth_request_id: VALID_REQUEST_ID
+    })
+
+    expect(createSessionOrThrow).toHaveBeenCalledOnce()
+    expect(routerPush).toHaveBeenCalledWith({
+      name: 'cloud-oauth-consent',
+      query: { oauth_request_id: VALID_REQUEST_ID }
+    })
+    expect(result).toEqual({ kind: 'resumed' })
+  })
+
+  it('resumes using a stashed sessionStorage id when the query is empty (multi-step flows)', async () => {
+    sessionStorage.setItem('Comfy.OAuthRequestId', VALID_REQUEST_ID)
+    const { resumeOAuthIfNeeded } = useOAuthPostLoginRedirect()
+
+    const result = await resumeOAuthIfNeeded({})
+
+    expect(result).toEqual({ kind: 'resumed' })
+    expect(routerPush).toHaveBeenCalledWith({
+      name: 'cloud-oauth-consent',
+      query: { oauth_request_id: VALID_REQUEST_ID }
+    })
+  })
+
+  it('returns an error with the thrown message when session creation fails', async () => {
+    createSessionOrThrow.mockRejectedValue(new Error('Unauthorized'))
+    const { resumeOAuthIfNeeded } = useOAuthPostLoginRedirect()
+
+    const result = await resumeOAuthIfNeeded({
+      oauth_request_id: VALID_REQUEST_ID
+    })
+
+    expect(result).toEqual({ kind: 'error', message: 'Unauthorized' })
+    expect(routerPush).not.toHaveBeenCalled()
+  })
+
+  it('falls back to a generic message when session creation rejects with a non-Error value', async () => {
+    createSessionOrThrow.mockRejectedValue('boom')
+    const { resumeOAuthIfNeeded } = useOAuthPostLoginRedirect()
+
+    const result = await resumeOAuthIfNeeded({
+      oauth_request_id: VALID_REQUEST_ID
+    })
+
+    expect(result.kind).toBe('error')
+    if (result.kind === 'error') {
+      expect(result.message).toMatch(/try again/i)
+    }
+    expect(routerPush).not.toHaveBeenCalled()
+  })
+})

src/platform/cloud/oauth/useOAuthPostLoginRedirect.ts

@@ -0,0 +1,50 @@
+import type { LocationQuery } from 'vue-router'
+import { useRouter } from 'vue-router'
+
+import { useSessionCookie } from '@/platform/auth/session/useSessionCookie'
+import {
+  captureOAuthRequestId,
+  getOAuthRequestId
+} from '@/platform/cloud/oauth/oauthState'
+
+export type OAuthResumeResult =
+  | { kind: 'no-oauth' }
+  | { kind: 'resumed' }
+  | { kind: 'error'; message: string }
+
+const FALLBACK_ERROR_MESSAGE = 'Failed to establish session. Please try again.'
+
+/**
+ * Post-login OAuth resume. If the current login flow originated from an OAuth
+ * authorize request, establishes the Cloud session cookie and navigates to the
+ * consent route. Used by both `CloudLoginView` and `CloudSignupView`.
+ */
+export function useOAuthPostLoginRedirect() {
+  const router = useRouter()
+  const sessionCookie = useSessionCookie()
+
+  async function resumeOAuthIfNeeded(
+    query: LocationQuery
+  ): Promise<OAuthResumeResult> {
+    captureOAuthRequestId(query)
+    const oauthRequestId = getOAuthRequestId()
+    if (!oauthRequestId) return { kind: 'no-oauth' }
+
+    try {
+      await sessionCookie.createSessionOrThrow()
+    } catch (error) {
+      return {
+        kind: 'error',
+        message: error instanceof Error ? error.message : FALLBACK_ERROR_MESSAGE
+      }
+    }
+
+    await router.push({
+      name: 'cloud-oauth-consent',
+      query: { oauth_request_id: oauthRequestId }
+    })
+    return { kind: 'resumed' }
+  }
+
+  return { resumeOAuthIfNeeded }
+}

src/platform/cloud/onboarding/CloudLoginView.vue

@@ -116,11 +116,7 @@ import { useRoute, useRouter } from 'vue-router'
 
 import Button from '@/components/ui/button/Button.vue'
 import { useAuthActions } from '@/composables/auth/useAuthActions'
-import { useSessionCookie } from '@/platform/auth/session/useSessionCookie'
-import {
-  captureOAuthRequestId,
-  getOAuthRequestId
-} from '@/platform/cloud/oauth/oauthState'
+import { useOAuthPostLoginRedirect } from '@/platform/cloud/oauth/useOAuthPostLoginRedirect'
 import CloudSignInForm from '@/platform/cloud/onboarding/components/CloudSignInForm.vue'
 import { useFreeTierOnboarding } from '@/platform/cloud/onboarding/composables/useFreeTierOnboarding'
 import { getSafePreviousFullPath } from '@/platform/cloud/onboarding/utils/previousFullPath'
@@ -132,7 +128,7 @@ const { t } = useI18n()
 const router = useRouter()
 const route = useRoute()
 const authActions = useAuthActions()
-const sessionCookie = useSessionCookie()
+const { resumeOAuthIfNeeded } = useOAuthPostLoginRedirect()
 const isSecureContext = globalThis.isSecureContext
 const authError = ref('')
 const toastStore = useToastStore()
@@ -159,24 +155,12 @@ const onSuccess = async () => {
     life: 2000
   })
 
-  captureOAuthRequestId(route.query)
-  const oauthRequestId = getOAuthRequestId()
-  if (oauthRequestId) {
-    try {
-      await sessionCookie.createSessionOrThrow()
-    } catch (error) {
-      authError.value =
-        error instanceof Error
-          ? error.message
-          : 'Failed to establish session. Please try again.'
-      return
-    }
-    await router.push({
-      name: 'cloud-oauth-consent',
-      query: { oauth_request_id: oauthRequestId }
-    })
+  const oauthResume = await resumeOAuthIfNeeded(route.query)
+  if (oauthResume.kind === 'error') {
+    authError.value = oauthResume.message
     return
   }
+  if (oauthResume.kind === 'resumed') return
 
   const previousFullPath = getSafePreviousFullPath(route.query)
   if (previousFullPath) {

src/platform/cloud/onboarding/CloudSignupView.vue

@@ -141,11 +141,7 @@ import { useRoute, useRouter } from 'vue-router'
 import SignUpForm from '@/components/dialog/content/signin/SignUpForm.vue'
 import Button from '@/components/ui/button/Button.vue'
 import { useAuthActions } from '@/composables/auth/useAuthActions'
-import { useSessionCookie } from '@/platform/auth/session/useSessionCookie'
-import {
-  captureOAuthRequestId,
-  getOAuthRequestId
-} from '@/platform/cloud/oauth/oauthState'
+import { useOAuthPostLoginRedirect } from '@/platform/cloud/oauth/useOAuthPostLoginRedirect'
 import { useFreeTierOnboarding } from '@/platform/cloud/onboarding/composables/useFreeTierOnboarding'
 import { getSafePreviousFullPath } from '@/platform/cloud/onboarding/utils/previousFullPath'
 import { isCloud } from '@/platform/distribution/types'
@@ -159,7 +155,7 @@ const { t } = useI18n()
 const router = useRouter()
 const route = useRoute()
 const authActions = useAuthActions()
-const sessionCookie = useSessionCookie()
+const { resumeOAuthIfNeeded } = useOAuthPostLoginRedirect()
 const isSecureContext = globalThis.isSecureContext
 const authError = ref('')
 const userIsInChina = ref(false)
@@ -185,24 +181,12 @@ const onSuccess = async () => {
     life: 2000
   })
 
-  captureOAuthRequestId(route.query)
-  const oauthRequestId = getOAuthRequestId()
-  if (oauthRequestId) {
-    try {
-      await sessionCookie.createSessionOrThrow()
-    } catch (error) {
-      authError.value =
-        error instanceof Error
-          ? error.message
-          : 'Failed to establish session. Please try again.'
-      return
-    }
-    await router.push({
-      name: 'cloud-oauth-consent',
-      query: { oauth_request_id: oauthRequestId }
-    })
+  const oauthResume = await resumeOAuthIfNeeded(route.query)
+  if (oauthResume.kind === 'error') {
+    authError.value = oauthResume.message
     return
   }
+  if (oauthResume.kind === 'resumed') return
 
   const previousFullPath = getSafePreviousFullPath(route.query)
   if (previousFullPath) {