Use when encountering frontend build errors, runtime JavaScript errors, or API call failures from the browser. Prevents @nextcloud/* version mismatches with server, using deprecated OC global, and missing CSRF requesttoken. Covers Vue/Webpack build failures, @nextcloud/* import path issues, CORS problems, CSRF token failures, missing dialog styles, deprecated OC global usage, version mismatches between @nextcloud packages and Nextcloud server, and initial state loading errors. Keywords: Webpack error, Vue build, @nextcloud version, OC global, CSRF, requesttoken, initial state, CORS, import path, build fails, Vue error, import error, white screen, CSRF token missing, styles broken..
license
MIT
compatibility
Designed for Claude Code. Requires Nextcloud 28+.
metadata
{"author":"OpenAEC-Foundation","version":"1.0"}
nextcloud-errors-frontend
Diagnostic Quick Reference
Build Errors
Symptom
Likely Cause
Fix
Module not found: @nextcloud/vue/components/NcButton
Wrong import path for library version
Use @nextcloud/vue/dist/Components/NcButton.js for v8.x
Can't resolve 'vue' in webpack build
Missing Vue dependency or wrong version
Install vue@^2.7 for NC 28-30, vue@^3 for NC 31+
vue-loader errors during build
Missing or wrong vue-loader version
Install vue-loader@legacy for Vue 2 projects
Module parse failed: Unexpected token in .vue file
webpack config missing vue-loader
Use @nextcloud/webpack-vue-config as base config
TypeError: Cannot read properties of undefined (reading 'component')
Vue 2 / Vue 3 API mismatch
Check @nextcloud/vue version matches your Vue version
Runtime Errors
Symptom
Likely Cause
Fix
Error: Could not find initial state thrown
loadState() called without fallback for missing key
ALWAYS pass a fallback as third argument
CSRF check failed on frontend API call
Using raw axios or fetch instead of @nextcloud/axios
Switch to import axios from '@nextcloud/axios'
Toasts render as unstyled text blobs
Missing @nextcloud/dialogs CSS import
Add import '@nextcloud/dialogs/style.css'
OC is not defined in console
Using legacy globals without checking existence
Use @nextcloud/router and @nextcloud/initial-state
OCA.Theming throws TypeError
Accessing theming object without existence check
ALWAYS check if (OCA.Theming) before access
CORS error in browser console
Backend controller extends Controller not ApiController
Extend ApiController for cross-origin endpoints
Version Mismatch Errors
Symptom
Likely Cause
Fix
Components render incorrectly or throw Vue warnings
@nextcloud/vue v9 used with Vue 2 project
Use @nextcloud/vue@^8 for NC 28-30 (Vue 2)
@nextcloud/files methods missing
Wrong major version for NC version
Use @nextcloud/files@^3 for NC 28-32, @^4 for NC 33+
createApp is not a function
Vue 3 bootstrap code in Vue 2 project
Use new Vue({...}) for Vue 2, createApp() for Vue 3
Error 1: Import Path Errors with @nextcloud/* Packages
What You See
Module not found: Error: Can't resolve '@nextcloud/vue/components/NcButton'
Build fails with unresolved module errors for @nextcloud/vue imports
Tree-shaking imports work in one version but break in another
Why It Happens
The @nextcloud/vue library changed its internal directory structure between major versions. Import paths that work in v9.x (Vue 3) do NOT work in v8.x (Vue 2), and vice versa. The barrel import (import { NcButton } from '@nextcloud/vue') works in all versions but increases bundle size.
How to Fix
ALWAYS check which @nextcloud/vue version your project uses before writing imports.
// For @nextcloud/vue v8.x (NC 28-30, Vue 2) -- direct importimportNcButtonfrom'@nextcloud/vue/dist/Components/NcButton.js'// For @nextcloud/vue v9.x (NC 31+, Vue 3) -- direct importimportNcButtonfrom'@nextcloud/vue/components/NcButton'// SAFE for ALL versions (but larger bundle) -- barrel importimport { NcButton } from'@nextcloud/vue'
NEVER assume import paths are stable across major versions. When upgrading @nextcloud/vue, ALWAYS verify all direct import paths still resolve.
Error 2: CSRF Token Missing on Frontend API Calls
What You See
HTTP 401 or 997 from API calls made in the browser
"CSRF check failed" in response
API calls work from curl but fail from your Vue component
Why It Happens
Nextcloud requires CSRF tokens for authenticated requests. Raw axios and fetch() do NOT include the CSRF token or the OCS-APIRequest header. The @nextcloud/axios wrapper adds both automatically.
How to Fix
ALWAYS use @nextcloud/axios for HTTP requests from Nextcloud frontend code.
// WRONG: Raw axios -- no CSRF token, no OCS-APIRequest headerimport axios from'axios'const resp = await axios.get('/ocs/v2.php/cloud/capabilities')
// WRONG: Raw fetch -- same problemconst resp = awaitfetch('/apps/myapp/api/items')
// CORRECT: @nextcloud/axios handles auth automaticallyimport axios from'@nextcloud/axios'import { generateUrl } from'@nextcloud/router'const resp = await axios.get(generateUrl('/apps/myapp/api/items'))
If you MUST use raw axios (e.g., for external API calls that should NOT include Nextcloud auth), create a separate instance:
NEVER use raw axios or fetch() for requests to Nextcloud endpoints.
Error 3: Missing @nextcloud/dialogs Styles
What You See
Toast notifications appear as unstyled plain text
Dialog components render without backgrounds, borders, or proper positioning
File picker looks broken or partially styled
Why It Happens
The @nextcloud/dialogs package ships its CSS separately. Importing only the JavaScript functions does NOT include the styles. This is by design to allow tree-shaking, but causes invisible/broken UI when the CSS import is forgotten.
How to Fix
ALWAYS import the styles alongside the dialog functions.
// WRONG: Functions work but toasts have no stylingimport { showSuccess, showError } from'@nextcloud/dialogs'// CORRECT: Import styles ONCE at app entry point (main.js/main.ts)import'@nextcloud/dialogs/style.css'import { showSuccess, showError } from'@nextcloud/dialogs'
Import the CSS file ONCE in your app's entry point (main.js or main.ts). Do NOT import it in every component -- one import per app is sufficient.
Error 4: Deprecated OC Global Usage
What You See
ReferenceError: OC is not defined in bundled JavaScript
TypeError: Cannot read properties of undefined (reading 'generateUrl') on OC.generateUrl
Console warnings about deprecated OC/OCA globals
Why It Happens
The OC and OCA global objects are legacy APIs from before Nextcloud adopted npm packages. In webpack-bundled apps, these globals may not be available at module scope. Even when available, they are deprecated in favor of @nextcloud/* packages.
How to Fix
ALWAYS use the corresponding @nextcloud/* package instead of OC globals.
Deprecated Global
Modern Replacement
OC.generateUrl()
import { generateUrl } from '@nextcloud/router'
OC.generateOcsUrl()
import { generateOcsUrl } from '@nextcloud/router'
OC.generateFilePath()
import { generateFilePath } from '@nextcloud/router'
OC.requestToken
Use @nextcloud/axios (handles tokens automatically)
OC.getCurrentUser()
import { getCurrentUser } from '@nextcloud/auth'
OCA.Theming.color
Use CSS variable var(--color-primary-element)
t() / n() global
import { translate as t, translatePlural as n } from '@nextcloud/l10n'
// WRONG: Legacy globalsconst url = OC.generateUrl('/apps/myapp/api/items')
const user = OC.getCurrentUser()
// CORRECT: Modern packagesimport { generateUrl } from'@nextcloud/router'import { getCurrentUser } from'@nextcloud/auth'const url = generateUrl('/apps/myapp/api/items')
const user = getCurrentUser()
If you MUST access OCA.Theming (no npm equivalent for all properties):
// WRONG: Crashes if theming app is disabledconst color = OCA.Theming.color// CORRECT: Guard with existence checkconst color = OCA?.Theming?.color ?? '#0082C9'
NEVER use OC.generateUrl() in new code. NEVER access OCA.Theming without a null check.
Error 5: loadState() Throws on Missing Key
What You See
Error: Could not find initial state "myapp" "some_key" thrown at page load
App crashes before Vue mounts because loadState() fails
Works in development but crashes in production (missing state registration)
Why It Happens
loadState() from @nextcloud/initial-state throws an Error when the requested key does not exist in the DOM. This happens when: (A) the PHP controller forgot to call provideInitialState(), (B) the key name has a typo, or (C) the state is conditionally provided but the frontend always expects it.
How to Fix
ALWAYS provide a fallback value as the third argument to loadState().
import { loadState } from'@nextcloud/initial-state'// WRONG: Throws if key is missingconst config = loadState('myapp', 'app_config')
// CORRECT: Falls back to default on missing keyconst config = loadState('myapp', 'app_config', { refreshInterval: 15000 })
// CORRECT with TypeScript: Typed fallbackinterfaceAppConfig {
refreshInterval: numbermaxItems: number
}
const config = loadState<AppConfig>('myapp', 'app_config', {
refreshInterval: 15000,
maxItems: 50,
})
Ensure the PHP controller registers the state for EVERY route that loads the frontend:
NEVER call loadState() without a fallback for any state that might be absent.
Error 6: Vue 2 vs Vue 3 Compatibility Errors
What You See
createApp is not a function or Vue.component is not a function
@nextcloud/vue components render incorrectly or throw internal errors
Composition API (ref, computed) unavailable or behaving differently
Why It Happens
Nextcloud supports two Vue versions depending on the server version. Mixing Vue 2 code with Vue 3 libraries (or vice versa) causes runtime failures. The @nextcloud/vue component library ships separate major versions for each Vue version.
How to Fix
Match ALL dependencies to your target Nextcloud version.
Target
Vue
@nextcloud/vue
vue-loader
Entry Point Pattern
NC 28-30
vue@^2.7
@nextcloud/vue@^8
vue-loader@legacy
new Vue({ render: h => h(App) }).$mount('#content')
NC 31+
vue@^3
@nextcloud/vue@^9
vue-loader@^17
createApp(App).mount('#content')
// Vue 2 entry point (NC 28-30)importVuefrom'vue'importAppfrom'./App.vue'newVue({
el: '#content',
render: h =>h(App),
})
// Vue 3 entry point (NC 31+)import { createApp } from'vue'importAppfrom'./App.vue'createApp(App).mount('#content')
NEVER install @nextcloud/vue@^9 in a project targeting NC 28-30. NEVER install @nextcloud/vue@^8 in a project targeting NC 31+.
Error 7: Webpack Configuration Errors
What You See
Build fails with cryptic webpack errors
Module parse failed on .vue files
Entry point not found or wrong output directory
Why It Happens
Custom webpack configs often break because they override settings that @nextcloud/webpack-vue-config expects to control. Common causes: wrong entry point path, missing vue-loader, or conflicting loader rules.
How to Fix
ALWAYS start from @nextcloud/webpack-vue-config and extend, NEVER write from scratch.
// package.json scripts{"scripts":{"build":"webpack --node-env production --progress","dev":"webpack --node-env development --progress","watch":"webpack --node-env development --progress --watch"}}
NEVER write a webpack config from scratch for a Nextcloud app. NEVER override the module.rules array entirely -- extend it with push() if you need custom loaders.
Error 8: CORS Errors on Frontend API Calls
What You See
Browser console: Access to XMLHttpRequest blocked by CORS policy
API works from curl but fails from JavaScript on a different origin
Preflight OPTIONS request returns 405 or has no CORS headers
Why It Happens
Standard Controller and OCSController do NOT set CORS headers. Only ApiController includes CORS support. This error ONLY occurs when JavaScript runs on a different origin than the Nextcloud server.
For same-origin requests (your app's JavaScript running inside Nextcloud), CORS is NOT needed. ALWAYS use @nextcloud/axios for same-origin calls -- it handles authentication automatically.
For cross-origin requests, the backend controller MUST extend ApiController. This is a backend fix, not a frontend fix.
Decision Tree: Diagnosing Frontend Errors
Frontend error occurs
|
+-- Is it a BUILD error (webpack/npm)?
| |
| +-- "Module not found" for @nextcloud/* import?
| | --> Check import path matches @nextcloud/vue version (v8 vs v9)
| | --> Try barrel import as fallback: import { X } from '@nextcloud/vue'
| |
| +-- "Can't resolve 'vue'"?
| | --> Install correct Vue version: vue@^2.7 (NC 28-30) or vue@^3 (NC 31+)
| |
| +-- "Module parse failed" on .vue files?
| | --> Use @nextcloud/webpack-vue-config as base
| | --> Install vue-loader@legacy for Vue 2 projects
| |
| +-- Other webpack error?
| --> Start from @nextcloud/webpack-vue-config, extend minimally
|
+-- Is it a RUNTIME error (browser console)?
| |
| +-- "Could not find initial state"?
| | --> Add fallback to loadState(): loadState('app', 'key', defaultValue)
| | --> Verify PHP controller calls provideInitialState()
| |
| +-- "OC is not defined" or "OCA is not defined"?
| | --> Replace OC globals with @nextcloud/* packages
| | --> See Error 4 replacement table
| |
| +-- "CSRF check failed" or HTTP 997?
| | --> Use @nextcloud/axios instead of raw axios/fetch
| |
| +-- Toasts/dialogs unstyled?
| | --> Add: import '@nextcloud/dialogs/style.css'
| |
| +-- CORS error?
| --> Backend must extend ApiController (not Controller)
| --> Same-origin? Use @nextcloud/axios, no CORS needed
|
+-- Is it a VERSION MISMATCH error?
|
+-- Check @nextcloud/vue version matches Vue version
+-- Check @nextcloud/files version matches NC version
+-- Check entry point pattern matches Vue version
