fix: template query param stripped during login views (#6677)

Fixes issue where query params from
https://github.com/Comfy-Org/ComfyUI_frontend/pull/6593 are stripped
during the login/signup views/flow by storing initial params in session
storage via router plugin.



https://github.com/user-attachments/assets/51642e8c-af5c-43ef-ab7d-133bc7e511aa




┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6677-fix-template-query-param-stripped-during-login-views-2aa6d73d365081a1bdc7d22b35f72a77)
by [Unito](https://www.unito.io)

tests-ui/tests/platform/navigation/preservedQueryManager.test.ts

@@ -0,0 +1,73 @@
+import { beforeEach, describe, expect, it } from 'vitest'
+
+import {
+  capturePreservedQuery,
+  clearPreservedQuery,
+  hydratePreservedQuery,
+  mergePreservedQueryIntoQuery
+} from '@/platform/navigation/preservedQueryManager'
+import { PRESERVED_QUERY_NAMESPACES } from '@/platform/navigation/preservedQueryNamespaces'
+
+const NAMESPACE = PRESERVED_QUERY_NAMESPACES.TEMPLATE
+
+describe('preservedQueryManager', () => {
+  beforeEach(() => {
+    sessionStorage.clear()
+    clearPreservedQuery(NAMESPACE)
+  })
+
+  it('captures specified keys from the route query', () => {
+    capturePreservedQuery(NAMESPACE, { template: 'flux', source: 'custom' }, [
+      'template',
+      'source'
+    ])
+
+    hydratePreservedQuery(NAMESPACE)
+    const merged = mergePreservedQueryIntoQuery(NAMESPACE)
+
+    expect(merged).toEqual({ template: 'flux', source: 'custom' })
+    expect(sessionStorage.getItem('Comfy.PreservedQuery.template')).toBeTruthy()
+  })
+
+  it('hydrates cached payload from sessionStorage once', () => {
+    sessionStorage.setItem(
+      'Comfy.PreservedQuery.template',
+      JSON.stringify({ template: 'flux', source: 'default' })
+    )
+
+    hydratePreservedQuery(NAMESPACE)
+    const merged = mergePreservedQueryIntoQuery(NAMESPACE)
+
+    expect(merged).toEqual({ template: 'flux', source: 'default' })
+  })
+
+  it('merges stored payload only when query lacks the keys', () => {
+    capturePreservedQuery(NAMESPACE, { template: 'flux' }, ['template'])
+
+    const merged = mergePreservedQueryIntoQuery(NAMESPACE, {
+      foo: 'bar'
+    })
+
+    expect(merged).toEqual({ foo: 'bar', template: 'flux' })
+  })
+
+  it('returns undefined when merge does not change query', () => {
+    capturePreservedQuery(NAMESPACE, { template: 'flux' }, ['template'])
+
+    const merged = mergePreservedQueryIntoQuery(NAMESPACE, {
+      template: 'existing'
+    })
+
+    expect(merged).toBeUndefined()
+  })
+
+  it('clears cached payload', () => {
+    capturePreservedQuery(NAMESPACE, { template: 'flux' }, ['template'])
+
+    clearPreservedQuery(NAMESPACE)
+
+    const merged = mergePreservedQueryIntoQuery(NAMESPACE)
+    expect(merged).toBeUndefined()
+    expect(sessionStorage.getItem('Comfy.PreservedQuery.template')).toBeNull()
+  })
+})

tests-ui/tests/platform/workflow/templates/composables/useTemplateUrlLoader.test.ts

@@ -12,6 +12,10 @@ import { useTemplateUrlLoader } from '@/platform/workflow/templates/composables/
  * - Input validation for template and source parameters
  */
 
+const preservedQueryMocks = vi.hoisted(() => ({
+  clearPreservedQuery: vi.fn()
+}))
+
 // Mock vue-router
 let mockQueryParams: Record<string, string | undefined> = {}
 const mockRouterReplace = vi.fn()
@@ -25,6 +29,11 @@ vi.mock('vue-router', () => ({
   }))
 }))
 
+vi.mock(
+  '@/platform/navigation/preservedQueryManager',
+  () => preservedQueryMocks
+)
+
 // Mock template workflows composable
 const mockLoadTemplates = vi.fn().mockResolvedValue(true)
 const mockLoadWorkflowTemplate = vi.fn().mockResolvedValue(true)
@@ -88,6 +97,7 @@ describe('useTemplateUrlLoader', () => {
       'flux_simple',
       'default'
     )
+    expect(preservedQueryMocks.clearPreservedQuery).toHaveBeenCalledTimes(1)
   })
 
   it('uses default source when source param is not provided', async () => {