fix(chat): fix shell command execution output markdown block issue

[yueny2020]

Problem

• fix shell command execution output markdown block issue
• When the child process of bash command execution writes to both stdout and stderr, we need to main the output is processed in the exact order it was generated by the child process.

Solution

• Before this change
  

• After this change
  

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[justinmk3]

? javascript is single-thread, what is the purpose of this?

[yueny2020]

yes, javascript is single-thread, but we have the use case that one process can send bash command execution output to stdout and stderr, which the streaming of stdout and stderr is async.

[justinmk3]

javascript has a lot of asynchrony, but each async execution context is executed fully until a async call, and is not "preemptible". getAndSet() is not doing anything useful here.

[justinmk3]

see https://github.com/aws/aws-toolkit-vscode/pull/6995/files#r2037764657

[justinmk3]

oh, I see that you are using this as a shared lock. That's different than an atomic boolean.

If you want a shared lock, use AsyncLock:

aws-toolkit-vscode/packages/core/src/amazonq/messages/chatMessageDuration.ts

Line 14 in 1da77e7

private static _asyncLock = new AsyncLock()

But this risks deadlock. It would be less risky to collect stdout and stderr separately, then combine them later, if that's important to you.

[yueny2020]

I think as the javascript event loop is a single thread, we can use a simple boolean variable(isFirstChunk) in closure to replace the AsyncLock in my use case.

1. The onStdout and onStderr callbacks are never truly executing simultaneously for one bash command execution - they're queued and executed one after another on the event loop.

2. The only shared state is the simple boolean flag (isFirstChunk) that's only set once from true to false. and there is no any other async operations.

Overall, the usage of AsyncLock adds unnecessary overhead for such a simple operation.

I can remove the atomic inner class(as it causes confusion). just use var and a function.

            // Use a closure boolean value firstChunk and a function to get and set its value
            let isFirstChunk = true
            const getAndSetFirstChunk = (newValue: boolean): boolean => {
                const oldValue = isFirstChunk
                isFirstChunk = newValue
                return oldValue
            }

[justinmk3]

set its value atomically

what is the purpose of mentioning this? there is no atomicity provided by this function.

[yueny2020]

OK, remove it from the comment.

[yueny2020]

the function getAndSetFirstChunk can avoid duplicate code in line 260 and line 271.

[justinmk3]

This entire comment is likely to cause confusion. The only really purpose of this function in this codebase is to save a few lines of code. That's fine, but that is different than what this comment says.

[justinmk3]

this would be a field that actually needs a brief comment that gives insight into its purpose.

[justinmk3]

LGTM after comments are fixed