[Feature] Script Task Virtual Documents with Language Support & AI Writeback

[peterhnm]

Motivation

When editing script tasks in the BPMN properties panel, users are limited to a small text area without syntax highlighting, IntelliSense, or AI assistant support. This makes writing and maintaining non-trivial scripts painful — especially for Camunda 7 projects that rely on inline Groovy or JavaScript.

Feature Description

Virtual Documents via FileSystemProvider

When a user selects a scripting language on a script task and clicks an "Open in Editor" button, the extension opens a virtual document (bpmn-script://<taskId>/script.<ext>) in a full VS Code editor tab. Using FileSystemProvider (not TextDocumentContentProvider) ensures the document is writable, so:

• Users get full syntax highlighting and IntelliSense
• AI coding assistants (e.g. Claude in VS Code) can read and write the document
• Edits are synced back to the <script> element in the BPMN XML automatically

Autocompletion for Camunda 7 APIs

Provide autocompletion for the Camunda execution context (execution, task, connector) across supported script languages:

Language	Approach
JavaScript	.d.ts type declaration stubs — full IntelliSense out of the box
Python (Jython)	.pyi stub files — picked up by Pylance automatically
Groovy	Custom CompletionItemProvider scoped to bpmn-script scheme
Ruby (JRuby)	Custom CompletionItemProvider (lower priority)
JUEL	Custom CompletionItemProvider (lower priority)

Phased Rollout

Phase 1 — Virtual Documents + JS/Python stubs (high value, low effort)

• Implement FileSystemProvider for bpmn-script:// URI scheme
• Ship .d.ts stubs for the Camunda 7 execution context (e.g. execution.getVariable(), task.getAssignee())
• Ship .pyi stubs for Python/Jython equivalent
• Map BPMN properties panel language selection → VS Code languageId
• Sync virtual document edits back to BPMN XML <script> content

Phase 2 — Groovy autocompletion

• Register a CompletionItemProvider for Groovy scoped to the bpmn-script scheme
• Cover execution.*, task.*, and connector.* API surfaces

Phase 3 — Ruby / JUEL (lower priority)

• Same CompletionItemProvider pattern for remaining languages

Acceptance Criteria

• FileSystemProvider registered for bpmn-script:// scheme; virtual documents are read/write
• Opening a script task in the editor sets the correct languageId based on the selected script language
• Edits in the virtual document are synced back to the BPMN XML model
• JavaScript .d.ts stubs provide IntelliSense for execution, task, and connector objects
• Python .pyi stubs provide equivalent autocompletion via Pylance
• AI tools (e.g. Claude for VS Code) can read and edit virtual script documents
• Groovy CompletionItemProvider offers completions for execution.* methods

References

• Design doc: docs/features/advanced-scripting.md
• Camunda 7 scripting docs: https://docs.camunda.org/manual/7.22/user-guide/process-engine/scripting/