fix: truncate conversation variable description to 255 chars in draft prefill

[JasonOA888]

Summary

Fixes #33037 - Prevents StringDataRightTruncation error when conversation variable description exceeds 255 characters.

Problem

When a user sets a conversation variable description longer than 255 characters in the workflow editor, saving succeeds (stored in Workflow._conversation_variables as LongText JSON). However, when the variable inspection panel is opened:

1. prefill_conversation_variable_default_values copies the description
2. Into workflow_draft_variables.description (varchar(255))
3. PostgreSQL raises psycopg2.errors.StringDataRightTruncation

Solution

Truncate description to 255 characters in prefill_conversation_variable_default_values before passing to WorkflowDraftVariable.new_conversation_variable.

# Before
description=conv_var.description,

# After
truncated_description = conv_var.description[:255] if conv_var.description else ""
description=truncated_description,

Changes

File	Change
api/services/workflow_draft_variable_service.py	Truncate description to 255 chars

Notes

• This is a backend safeguard
• Frontend should also add validation (character counter + error toast)
• No database schema changes required
• No breaking changes

Testing

• Verified truncation logic is correct
• Existing tests should pass (no behavior change for descriptions ≤255 chars)

Closes #33037

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical backend issue where excessively long conversation variable descriptions could lead to a database error during the prefill process. By introducing a truncation mechanism, the system now gracefully handles descriptions that exceed the database column's character limit, ensuring data integrity and preventing application crashes. This change acts as a backend safeguard, complementing any future frontend validation.

Highlights

• Database Error Prevention: Implemented a fix to prevent psycopg2.errors.StringDataRightTruncation when a conversation variable description exceeds 255 characters during the prefill process.
• Description Truncation: Truncated conversation variable descriptions to 255 characters in prefill_conversation_variable_default_values before saving to WorkflowDraftVariable to match the database column constraint.

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Changelog

• api/services/workflow_draft_variable_service.py
  • Truncated conversation variable descriptions to 255 characters to prevent database errors.

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[gemini-code-assist]

Code Review

This pull request addresses a StringDataRightTruncation error by truncating conversation variable descriptions to the varchar(255) limit of the workflow_draft_variables.description column. The change correctly truncates the description before creating a WorkflowDraftVariable, which effectively resolves the described bug. The implementation is sound and I have no further feedback.

[github-actions]

Pyrefly Diff

No changes detected.