Issue with CKEditorError: ckeditor-duplicated-modules after updating to CKEditor 42.0.0

[w-beom]

After updating CKEditor to version 42.0.0, I encounter the following error when bundling with UMD: Uncaught CKEditorError: ckeditor-duplicated-modules. There are no plugins being called twice.

Below is the configuration file I used:

import {
    ClassicEditor as ClassicEditorBase,
    Alignment,
    AutoImage,
    Autoformat,
    AutoLink,
    BlockQuote,
    Bold,
    CKFinder,
    Code,
    CodeBlock,
    Essentials,
    FindAndReplace,
    Font,
    GeneralHtmlSupport,
    Heading,
    HeadingButtonsUI,
    HorizontalLine,
    HtmlEmbed,
    ImageCaption,
    ImageInsert,
    ImageResize,
    ImageStyle,
    ImageToolbar,
    ImageBlock,
    Image,
    ImageEditing,
    IndentBlock,
    Indent,
    Italic,
    LinkImage,
    Link,
    ListProperties,
    List,
    MediaEmbedToolbar,
    MediaEmbed,
    PageBreak,
    Paragraph,
    ParagraphButtonUI,
    PasteFromOffice,
    RemoveFormat,
    SelectAll,
    SimpleUploadAdapter,
    SourceEditing,
    SpecialCharactersArrows,
    SpecialCharactersCurrency,
    SpecialCharactersEssentials,
    SpecialCharactersLatin,
    SpecialCharactersMathematical,
    SpecialCharactersText,
    SpecialCharacters,
    StandardEditingMode,
    Strikethrough,
    Subscript,
    Superscript,
    TableCaption,
    TableCellProperties,
    TableColumnResize,
    TableProperties,
    TableToolbar,
    Table,
    TextTransformation,
    Title,
    TodoList,
    Underline,
    Mention,
    TextPartLanguage
} from 'ckeditor5'

import {
    DocumentOutline,
    FormatPainter,
    PasteFromOfficeEnhanced,
    SlashCommand,
    TableOfContents,
    CaseChange,
    Template
} from 'ckeditor5-premium-features'

export default class ClassicEditor extends ClassicEditorBase {
}

ClassicEditor.builtinPlugins = [

    Essentials, 
    Autoformat, 
    Heading,  
    HeadingButtonsUI, 
    Paragraph,  
    ParagraphButtonUI, 
    Bold,
    Code,
    Italic,
    Strikethrough,
    Subscript,
    Superscript,
    Underline,
    Font,   
    BlockToolbar, 
    Link,
    List,
    ListProperties,
    CodeBlock,
    BlockQuote,
    Indent,
    IndentBlock,
    SourceEditing,
    TableCaption,
    TableCellProperties,
    TableColumnResize,
    TableProperties,
    TableToolbar,
    Table,
    Alignment, 
    HorizontalLine,
    SelectAll, 
    Link,
    AutoLink,
    MediaEmbed,
    MediaEmbedToolbar,
    PasteFromOffice,
    Image,
    LinkImage,
    ImageEditing,
    AutoImage
    PageBreak, 
    TextTransformation, 
    RemoveFormat, 
    FindAndReplace, 
    TodoList,
    SimpleUploadAdapter,
    ImageCaption,
    ImageInsert,
    ImageToolbar,
    ImageResize,
    ImageStyle,
    ImageBlock,
    SpecialCharacters,
    SpecialCharactersArrows,
    SpecialCharactersCurrency,
    SpecialCharactersEssentials,
    SpecialCharactersLatin,
    SpecialCharactersMathematical,
    SpecialCharactersText,
    HtmlEmbed,
    Mention,
    TextPartLanguage,
    DocumentOutline,
    FormatPainter,
    PasteFromOfficeEnhanced,
    SlashCommand,
    TableOfContents,
    CaseChange,
    Template
];

[filipsobol]

Hi @w-beom 👋. This problem can be caused by old packages (in a different version) still being installed.

Can you share the dependencies from your package.json file?

[w-beom]

Hi @filipsobol Here is the package.json:

{
  "main": "./build/ckeditor.js",
  "scripts": {
    "dev": "vite",
    "build": "vite build",
    "serve": "vite preview"
  },
  "author": "",
  "devDependencies": {
    "ckeditor5": "^42.0.0",
    "ckeditor5-premium-features": "^42.0.0",
    "vite": "^5.3.1"
  }
}

[filipsobol]

Unfortunately this doesn't seem enough to find the cause of this issue. My guess would be some other other imports from @ckeditor/ckeditor5-* or ckeditor5/src/*.

Could you prepare a minimal reproduction that we can use to debug this, please?

[ogsmith]

Hi! We're also trying to solve for this:

We've downgraded back to 42.1.2, our dependencies are the same as the below, and we remove package-lock.json but some sub dependencies are upgrading themselves to 42

"@ckeditor/ckeditor5-alignment": "41.2.1",
"@ckeditor/ckeditor5-basic-styles": "41.2.1",
"@ckeditor/ckeditor5-build-classic": "41.2.1",
"@ckeditor/ckeditor5-editor-classic": "41.2.1",
"@ckeditor/ckeditor5-essentials": "41.2.1",
"@ckeditor/ckeditor5-font": "41.2.1",
"@ckeditor/ckeditor5-heading": "41.2.1",
"@ckeditor/ckeditor5-horizontal-line": "41.2.1",
"@ckeditor/ckeditor5-html-embed": "41.2.1",
"@ckeditor/ckeditor5-image": "41.2.1",
"@ckeditor/ckeditor5-link": "41.2.1",
"@ckeditor/ckeditor5-media-embed": "41.2.1",
"@ckeditor/ckeditor5-paragraph": "41.2.1",
"@ckeditor/ckeditor5-react": "6.2.0",
"@ckeditor/ckeditor5-theme-lark": "41.2.1",
"@ckeditor/ckeditor5-upload": "41.2.1",
"@ckeditor/vite-plugin-ckeditor5": "0.1.3",

[w-beom]

Oh, I'm sorry. The issue was caused by the import statement in the custom plugin I created. I referred to the custom plugin documentation and fixed it. The issue no longer occurs. Thank you, everyone.

[jjroelofs]

@w-beom Hi, I'm having the same problem and cannot find the documentation related to fixing it. Can you help me out? :)
I tried installing some other random plugin "ckeditor5-diagrams" to compare and it generates the same error.

[filipsobol]

Hi @jjroelofs. Have you seen our updated documentation for the ckeditor-duplicated-modules error? https://ckeditor.com/docs/ckeditor5/latest/support/error-codes.html#error-ckeditor-duplicated-modules

[jjroelofs]

@filipsobol Yes I have. We are building the plugin on a Custom Package Generator project that we cloned a couple of months ago, so it's on CKEditor 43. Our plugin works fine using yarn run start and yarn run dll:serve. When loading it in a simple custom build we run into problem.

I didn't study the docs in-depth to be honest, maybe I'll have another go at it next week.

Our plugin has 83 imports in source, and I'm not the main developer, so it's a bit tiring to debug. Would be great if the error could tell us what plugins are duplicated.

[jjroelofs]

@filipsobol ok I managed by matching the major version after all. Now my next problem is: Drupal 10.3 is on CKEditor 41. My plugin is on 43 and loading it in a 41 environment triggers the duplicate plugin error. How do I produce a release for 41? My project was built on the CK43 Plugin Generator.
I'll create a new issue if I can't figure it out.

[filipsobol]

I'm not sure if I can help more without some example. Could you create a new issue and provide a minimal reproduction?

[amitjangid12]

Hi @w-beom, I get this error when I use a custom plugin, how to solve this