fix(amazonq): codefix does not do error handling

[ctlai95]

Problem

Code fix errors are not handled correctly, only shows a generic error notification and webview is not updated.

Solution

Surface the server error to the UI

---

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[ashishrp-aws]

@ctlai95 can we use user friendly error messages instead passing the service error straight to user? Like how we handle code review errors.

[nkomonen-amazon]

Look to add in the following before to avoid needing to cast:

if (!(err instanceof Error)) {
  throw new Error('Unexpected non error', err) // modify this as needed
}

[justinmk3]

using isAwsError may be better:

aws-toolkit-vscode/packages/core/src/shared/errors.ts

Line 594 in 02f6d0b

export function isAwsError(error: unknown): error is AWSError & { error_description?: string } {

[nkomonen-amazon]

I think this should be good enough

Suggested change

	generateFixError?: string | null
	generateFixError?: string

[ctlai95]

I think null is required for this since I want to maintain this behavior where the following will remove the error from the webview:

updateSecurityIssueWebview({
  ...
  generateFixError: null
})

while the absence of the field should not remove it

updateSecurityIssueWebview({
  ...
  issue: newIssue
})

[nkomonen-amazon]

Can probably drop null

[nkomonen-amazon]

This should be good enough. I think the types upstream may need to be modified

Suggested change

	generateFixError: undefined as string | null | undefined,
	generateFixError: undefined

[nkomonen-amazon]

Try

Suggested change

	private generateFixError: string | null | undefined = undefined
	private generateFixError: string | undefined = undefined