docs(blog): bash rprompt deprecation statement

website/blog/2024-07-22-bash-rprompt.mdx

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+---
+title: "Deprecating the bash rprompt"
+description: "Deprecating the bash rprompt"
+slug: deprecating-bash-rprompt
+authors:
+- name: Jan De Dobbeleer
+  title: Maintainer
+  url: https://github.com/jandedobbeleer
+  image_url: https://avatars.githubusercontent.com/u/2492783?v=4
+tags: [breaking, ohmyposh]
+hide_table_of_contents: false
+---
+
+After careful consideration, it was decided to remove support for the [`rprompt`][rprompt] in bash. If you are
+interested in the reasons behind this decision, please read on.
+
+<!--truncate-->
+## Context
+
+[`rprompt`][rprompt] is a feature that allows you to display a prompt at the right side of the terminal, on
+the same line as your cursor. This feature is available natively on a lot of shells, but not on bash.
+To work around this limitation, Oh My Posh has a **custom implementation** we use for both bash and PowerShell.
+
+## History
+
+### First implementation
+
+There were two evolutions of bash' custom [`rprompt`][rprompt] in Oh My Posh. The first one printed the [`rprompt`][rprompt]
+together with the primany prompt in the `PS1` variable, so we only need one CLI call to visualize the prompt.
+
+The challenge is that, as the [`rprompt`][rprompt] is printed together with the primary prompt, we need to make sure
+bash' readline can interprete the prompt correctly. In bash, every character that isn't a printable character,
+like color codes, needs to be wrapped in `\[` and `\]`. This is necessary to make sure bash can **calculate the length**
+of the prompt and ultimately **position the cursor** correctly.
+
+It turned out that for [`rprompt`][rprompt], this _needed to be done differently_. The [`rprompt`][rprompt] is printed after what
+bash interpretes as the end of the prompt. We found out that we need to wrap the entire [`rprompt`][rprompt] in `\[` and `\]`,
+and not escape individual non-printable characters.
+
+We did that for a while, but apparently this approach was **not very robust**. It was easy to break readline's
+cursor position calculation, and it was hard to debug. The behaviour of this was also different cross platform,
+so we had to go back to the drawing board.
+
+### Second implementation
+
+The second implementation of the [`rprompt`][rprompt] was a lot more robust. We decided to print the [`rprompt`][rprompt] in a separate
+CLI call, so we could control the output more easily. It leveraged the use of the `PROMPT_COMMAND` variable in bash, which
+is a hook that is executed before the prompt is printed. We would first print the [`rprompt`][rprompt] in the `PROMPT_COMMAND`,
+and then set the primary prompt in the `PS1` variable so bash would not bother about the [`rprompt`][rprompt] being there.
+
+This approach was a lot **cleaner from an achitectural point of view**, but it had some downsides.
+The biggest downside was needing two CLI calls to print the prompt, which is not a big issue,
+but it was a bit slower than the first implementation.
+
+Additionally, as we print before `PS1` is evaluated, it introduced the following issues:
+
+1. when the output of the previous command didn't end with a newline, the [`rprompt`][rprompt] would be printed on the same line
+  as the output of the previous command
+2. when the prompt was at the bottom of the terminal buffer, the [`rprompt`][rprompt] would be printed on the same line as the
+  prompt, which would break the prompt
+3. depending on the platform, it would still break command history navigation
+4. it required different logic for multiline prompts as we print before `PS1` and need to reposition the cursor correctly
+
+Of these issues, **only bullet 4 could be fixed**. Everything else was out of our control.
+
+## Conclusion
+
+Oh My Posh is a tool that needs to be easy to use, maintain and be 100% reliable. One of the core principles of Oh My Posh is that it should
+**never break the shell**. The [`rprompt`][rprompt] feature in bash has never been reliable enough, and it was _hard to debug_ when it broke.
+I have spent countless hours debugging issues with the [`rprompt`][rprompt] in bash, but it's **time to move on**. If you
+want to use the [`rprompt`][rprompt] feature, I would recommend using a shell that supports it natively, like [nushell], [zsh] or [fish].
+
+## What about Powershell?
+
+The [`rprompt`][rprompt] feature in PowerShell is **100% reliable**, even if it's not natively supported. PowerShell doesn't
+have the same challenges calculating the actual prompt width like bash, there's _no need to escape anything_.
+We can use the first implementation mentioned above, and it works like a charm.
+
+[rprompt]: /docs/configuration/block#type
+[nushell]: https://www.nushell.sh/
+[zsh]: https://www.zsh.org/
+[fish]: https://fishshell.com/