fix(editor): Show an error when imported JSON is not a valid workflow

[hammadxcm]

Summary

Importing a workflow file (or URL/pasted JSON) that is syntactically valid JSON but not a workflow — i.e. it has no nodes/connections properties — silently resulted in an empty canvas with no feedback.

importWorkflowData in useCanvasOperations short-circuited with return {} when the data didn't look like a workflow, without notifying the user:

// If it is JSON check if it looks on the first look like data we can use
if (!workflowData.hasOwnProperty('nodes') || !workflowData.hasOwnProperty('connections')) {
	return {};
}

This PR shows the existing "Problem importing workflow" error toast with a new message — "The imported data does not contain valid workflow data ('nodes' and 'connections' are missing)" — before returning, matching the established convention of the invalid-nodes toast directly below this check.

How to test

1. Create a JSON file with valid syntax that is not a workflow, e.g. { "name": "hello" }.
2. In the editor, use the workflow menu → Import from File and select it.
   • Before: nothing happens (empty canvas, no message).
   • After: an error toast "Problem importing workflow — The imported data does not contain valid workflow data ('nodes' and 'connections' are missing)" is shown.

Unit tests cover both the invalid-shape path (toast shown, nothing imported) and the valid path (no toast).

Related Linear tickets, Github issues, and Community forum posts

Fixes #31646

Review / Merge checklist

• I have seen this code, I have run this code, and I take responsibility for this code.
• PR title and summary are descriptive.
• Tests included.

[cubic-dev-ai]

No issues found across 3 files

Architecture diagram

sequenceDiagram
    participant User as User
    participant Editor as Editor UI
    participant CanvasOp as useCanvasOperations
    participant I18n as i18n Service
    participant Toast as Toast Service

    User->>Editor: Import workflow (file / URL / paste)
    Editor->>CanvasOp: importWorkflowData(rawData, source)
    Note over CanvasOp: JSON already parsed here (existing)
    CanvasOp->>CanvasOp: Check hasOwnProperty('nodes') and hasOwnProperty('connections')
    alt Missing 'nodes' or 'connections'
        Note over CanvasOp: NEW: invalid structure detected
        CanvasOp->>I18n: baseText('invalidStructure')
        I18n-->>CanvasOp: localized message
        CanvasOp->>I18n: baseText('importError.title')
        I18n-->>CanvasOp: "Problem importing workflow"
        CanvasOp->>Toast: showError(Error(msg), title)
        Note over Toast: Error toast displayed
        CanvasOp-->>Editor: return {} (empty)
        Editor-->>User: Canvas unchanged, no workflow imported
    else Valid workflow structure
        Note over CanvasOp: Continue with existing import logic
        CanvasOp->>CanvasOp: Import nodes, connections, etc.
        CanvasOp-->>Editor: Workflow data
        Editor->>Editor: Update canvas
        Editor-->>User: Workflow displayed
    end

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_{Re-trigger cubic}

[n8n-assistant]

Hey @hammadxcm,

Thank you for your contribution. We appreciate the time and effort you’ve taken to submit this pull request.

Before we can proceed, please ensure the following:
• Tests are included for any new functionality, logic changes or bug fixes.
• The PR aligns with our contribution guidelines.

Regarding new nodes:
We no longer accept new nodes directly into the core codebase. Instead, we encourage contributors to follow our Community Node Submission Guide to publish nodes independently.

If your node integrates with an AI service that you own or represent, please email nodes@n8n.io and we will be happy to discuss the best approach.

About review timelines:
This PR has been added to our internal tracker as "GHC-8628". While we plan to review it, we are currently unable to provide an exact timeframe. Our goal is to begin reviews within a month, but this may change depending on team priorities. We will reach out when the review begins.

Thank you again for contributing to n8n.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[CharlieKolb]

Nice! 🚀

[n8n-assistant]

Got released with n8n@