fix(EmailSend Node): Support binary data expressions in attachments

[nsouzaco]

Fixes #20832

Users can now use expressions like ={{ $('NodeName').item.binary.data }} in the attachments parameter, in addition to the existing comma-separated string format.

Changes:

• Enhanced attachment processing to handle string, IBinaryData object, or array
• Updated EmailSendOptions type to accept string | IBinaryData | IBinaryData[]
• Added comprehensive unit tests (12 tests) covering backward compatibility and new expression functionality
• Maintained full backward compatibility with existing workflows

Summary

Fixes a bug where users cannot use expressions to reference binary data from other nodes in the EmailSend node's attachments parameter. Previously, only comma-separated string property names were supported (e.g., "data, file1"). Now users can also use expressions like ={{ $('Read File').item.binary.data }} to dynamically reference binary data.

What changed

• Enhanced attachment processing to detect and handle both string and object/array inputs
• Updated type definitions to accept string | IBinaryData | IBinaryData[]
• Added comprehensive unit tests (12 tests) covering all scenarios
• Fully backward compatible - existing workflows continue to work unchanged

How to test

1. Create a workflow with a node that outputs binary data (e.g., "Read/Write Files from Disk")
2. Add an EmailSend node
3. In the attachments field, use an expression: ={{ $('Read/Write Files from Disk').item.binary.data }}
4. Execute the workflow
5. Verify that the email is sent with the attachment

Before this fix: Attachment would not be sent (expression resolved to object, code expected string)
After this fix: Attachment is correctly attached to the email

Test Coverage

• ✅ Backward compatibility with string property names ("data", "data, file1, file2")
• ✅ Expression-resolved IBinaryData objects
• ✅ Arrays of binary data objects
• ✅ All email formats (HTML, text, both)
• ✅ Edge cases (no attachments, no binary data, whitespace handling)

Related Linear tickets, Github issues, and Community forum posts

Fixes #20832
Linear: https://linear.app/n8n/issue/GHC-5047

Review / Merge checklist

• PR title and summary are descriptive
• Docs updated or follow-up ticket created
• Tests included (12 unit tests)
• PR Labeled with release/backport (not applicable - this is not an urgent fix)

Additional Notes

Breaking Changes: None - fully backward compatible

Files Changed:

• packages/nodes-base/nodes/EmailSend/v2/send.operation.ts - Core fix
• packages/nodes-base/nodes/EmailSend/v2/utils.ts - Type definitions
• packages/nodes-base/nodes/EmailSend/test/v2/send.operation.test.ts - Test coverage (NEW)

Code Quality:

• ✅ All tests passing (13/13)
• ✅ Lint passed
• ✅ Typecheck passed
• ✅ No ts-ignore usage
• ✅ Follows n8n coding conventions

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[n8n-assistant]

Hey @nsouzaco,

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 [email protected] and we will be happy to discuss the best approach.

About review timelines:
This PR has been added to our internal tracker as "GHC-5618". 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.

[cubic-dev-ai]

1 issue found across 3 files

Prompt for AI agents (all 1 issues)

Understand the root cause of the following 1 issues and fix them.


<file name="packages/nodes-base/nodes/EmailSend/v2/send.operation.ts">

<violation number="1" location="packages/nodes-base/nodes/EmailSend/v2/send.operation.ts:240">
Expression-based attachments remain disabled because the new handling only runs when the current item already has binary data; drop the `item.binary` guard so IBinaryData objects returned from expressions are processed.</violation>
</file>

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[cubic-dev-ai]

Expression-based attachments remain disabled because the new handling only runs when the current item already has binary data; drop the item.binary guard so IBinaryData objects returned from expressions are processed.

Prompt for AI agents

Address the following comment on packages/nodes-base/nodes/EmailSend/v2/send.operation.ts at line 240:

<comment>Expression-based attachments remain disabled because the new handling only runs when the current item already has binary data; drop the `item.binary` guard so IBinaryData objects returned from expressions are processed.</comment>

<file context>
@@ -235,18 +236,44 @@ export async function execute(this: IExecuteFunctions): Promise&lt;INodeExecutionDa
 
-				for (const propertyName of attachmentProperties) {
-					const binaryData = this.helpers.assertBinaryData(itemIndex, propertyName);
+				// Handle both string property names and expression-resolved binary data
+				let attachmentItems: Array&lt;string | IBinaryData&gt; = [];
+
</file context>