fix(client): prevent panics

[jkoelker]

The type assertation should be checked to prevent panicing allowing the caller to handle gracefully.

Summary by CodeRabbit

• Bug Fixes

  • Improved error handling to prevent crashes when accessing the standard error stream if unavailable.

• Tests

  • Updated tests to safely handle cases where the standard error stream may not be accessible.

[coderabbitai[bot]]

Walkthrough

The changes update the GetStderr function in the client package to safely handle cases where the client's transport is not of type *transport.Stdio. The function now returns a tuple consisting of an io.Reader and a boolean indicating availability, instead of panicking on a failed type assertion. Corresponding tests have been updated to check the boolean result before proceeding with operations on the stderr stream.

Changes

Files/Paths	Change Summary
client/stdio.go	Modified GetStderr to return (io.Reader, bool) and handle non-Stdio transports safely.
client/stdio_test.go	Updated tests to check the boolean from GetStderr before using the stderr reader.

Possibly related PRs

• mark3labs/mcp-go#72: Introduced the Stderr() method for StdioMCPClient, which is directly utilized and extended by the changes in this PR.

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📜 Recent review details

Configuration used: CodeRabbit UI Review profile: CHILL Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 781b7327ad04888293d38d0bf0a9cd0588d3af79 and 14e99ea86f17b89d72dce8665d6649cacb1113fc.

📒 Files selected for processing (2)

• client/stdio.go (1 hunks)
• client/stdio_test.go (1 hunks)

🧰 Additional context used

🧬 Code Graph Analysis (2)

client/stdio_test.go (1)

client/stdio.go (1)

• GetStderr (34-43)

client/stdio.go (2)

client/client.go (1)

• Client (16-25)

client/transport/stdio.go (1)

• Stdio (20-34)

🔇 Additional comments (2)

client/stdio.go (1)

34-43: Improved error handling by returning a boolean flag instead of panicking

This change properly handles the case when a client's transport is not a Stdio transport. Instead of potentially panicking on a failed type assertion, the function now returns a boolean flag to indicate whether the operation was successful. This is a good practice in Go and aligns with the language's error handling patterns.

-func GetStderr(c *Client) io.Reader {
+func GetStderr(c *Client) (io.Reader, bool) {
 	t := c.GetTransport()
-	
-	return t.(*transport.Stdio).Stderr()
+
+	stdio, ok := t.(*transport.Stdio)
+	if !ok {
+		return nil, false
+	}
+
+	return stdio.Stderr(), true
}

client/stdio_test.go (1)

50-56: Test updated to handle new GetStderr return signature

The test code has been correctly updated to handle the new function signature of GetStderr that now returns a boolean flag. The code now properly checks if the stderr reader is available before attempting to use it, which prevents potential panics during testing.

✨ Finishing Touches

• [ ] 📝 Generate Docstrings

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