fix(nodes-langchain): handle primitive toolInput in intermediateSteps

[majiayu000]

Summary

When tools receive primitive values (strings, numbers) as input, the toolInput field in intermediateSteps was incorrectly set to an empty object {}. This fix wraps primitive values in an object with an input key, ensuring the tool input is properly exposed.

The issue: In buildSteps.ts, when toolInput.input is a primitive value (like a string "5*343"), the condition typeof toolInputForResult === 'object' fails, resulting in an empty {} being returned instead of the actual input.

The fix: Added logic to wrap primitive values in { input: value } format, making the input accessible in intermediateSteps.

Related Issue

Fixes #23501

Test plan

• Added test case for primitive string input ("5*343")
• Added test case for primitive number input (42)
• All existing tests pass
• TypeScript type check passes

[cubic-dev-ai]

1 issue found across 2 files

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="packages/@n8n/nodes-langchain/utils/agent-execution/buildSteps.ts">

<violation number="1" location="packages/@n8n/nodes-langchain/utils/agent-execution/buildSteps.ts:259">
P2: Rule violated: **Prefer Typeguards over Type casting**

Type narrowing with `as IDataObject` should use a type guard function instead. After the `typeof === &#39;object&#39;` check, TypeScript knows it&#39;s an object but not specifically `IDataObject`. Consider creating a type guard function or using assertion function to properly narrow the type.</violation>
</file>

_{Reply to cubic to teach it or ask questions. Re-run a review with @cubic-dev-ai review this PR}

[cubic-dev-ai]

P2: Rule violated: Prefer Typeguards over Type casting

Type narrowing with as IDataObject should use a type guard function instead. After the typeof === 'object' check, TypeScript knows it's an object but not specifically IDataObject. Consider creating a type guard function or using assertion function to properly narrow the type.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At packages/@n8n/nodes-langchain/utils/agent-execution/buildSteps.ts, line 259:

<comment>Type narrowing with `as IDataObject` should use a type guard function instead. After the `typeof === &#39;object&#39;` check, TypeScript knows it&#39;s an object but not specifically `IDataObject`. Consider creating a type guard function or using assertion function to properly narrow the type.</comment>

<file context>
@@ -250,13 +250,24 @@ export function buildSteps(
+			// - Otherwise, return empty object
+			let resultToolInput: IDataObject;
+			if (toolInputForResult &amp;&amp; typeof toolInputForResult === &#39;object&#39;) {
+				resultToolInput = toolInputForResult as IDataObject;
+			} else if (toolInputForResult !== undefined &amp;&amp; toolInputForResult !== null) {
+				// Handle primitive values like strings or numbers
</file context>