fix: Windows prompt cursor positioning issue with ANSI escape sequences

[thebristolsound]

Fix Windows prompt cursor positioning issue with ANSI escape sequences

Overview

This PR addresses a Windows-specific bug where ANSI escape sequences in the Goose CLI prompt cause incorrect cursor positioning and visual artifacts. This is a follow-up to the draft PR #3989 originally started by another contributor, with a refined implementation focused on simplicity and reliability.

Problem Description

On Windows, the Goose CLI prompt uses ANSI escape sequences for styling (cyan and bold colors):

let prompt = format!("{} ", console::style("( O)>").cyan().bold());

However, rustyline on Windows has a known issue with ANSI escape sequence width calculation that causes:

• Cursor positioning to be offset from the actual text
• Visual artifacts when editing commands
• A poor user experience with input handling

Root Cause

This is a known issue in the rustyline library where ANSI escape sequences are not properly accounted for in width calculations on Windows terminals. The issue affects how rustyline positions the cursor relative to the displayed text.

Related Issues:

• Upstream rustyline issue: Colored prompts behave incorrectly on Windows kkawakam/rustyline#562
• Fix pending in rustyline: On windows, check that prompt is not styled kkawakam/rustyline#890

Solution

This PR implements a Windows-specific workaround with a simple, direct approach:

Platform-Specific Prompt Generation: The get_input_prompt_string() function uses a compile-time cfg! check to determine the operating system:

• Windows: Returns plain text prompt "( O)> " without ANSI escape sequences
• Other platforms: Returns styled prompt with ANSI colors (preserving existing behavior)

Code Changes

• Simple Implementation: Uses cfg!(target_os = "windows") directly in the prompt generation function to conditionally return styled or plain text
• Comprehensive Comments: Added detailed explanation of the Windows-specific workaround and references to upstream issues
• Platform-Specific Testing: Updated unit tests to use conditional compilation (#[cfg]) to test only the behavior that runs on each platform, avoiding CI/CD environment issues

Testing

The test_get_input_prompt_string test uses conditional compilation to validate platform-specific behavior:

• On Windows builds: Tests that the prompt is plain text without ANSI codes
• On non-Windows builds: Tests that the prompt contains ANSI styling
• Both: Verify basic structure and formatting

This approach ensures tests are reliable across different environments and CI/CD systems.

Future Considerations

This workaround should be removed once the repository updates to a version of rustyline that includes the fix from kkawakam/rustyline#890 and the fix has been verified to resolve the cursor positioning issues on Windows.

Credit

This work builds upon the draft PR #3989 originally created by another contributor. The implementation has been simplified for reliability and maintainability. #3989

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Before screenshot:

After (fixed):

Screenshots taken in Windows 11 Terminal Preview, PowerShell 7

[thebristolsound]

Bump

[michaelneale]

looks good to me, can't test on windows myself but downside risk is low. And I learned that you can use "not" in platform macros, very cool! thanks @thebristolsound

[thebristolsound]

Thanks! Taking a look at these test failures, they were passing locally but something looks a bit off.

[Copilot]

Pull Request Overview

This PR fixes a Windows-specific bug where ANSI escape sequences in the Goose CLI prompt cause incorrect cursor positioning and visual artifacts in terminals. The solution implements platform-specific prompt generation to use plain text on Windows while preserving styled prompts on other platforms.

• Extracted prompt generation into a reusable get_input_prompt_string() function with conditional compilation
• Added Windows-specific workaround to use plain text prompts without ANSI escape sequences
• Included comprehensive unit tests to verify platform-specific behavior and prompt consistency

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[Copilot]

Pull Request Overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

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[michaelneale]

thanks @thebristolsound you will need to also follow instructions for the DCO Check: https://github.com/block/goose/pull/4464/checks?check_run_id=50117009096

[Copilot]

Pull Request Overview

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[Copilot]

Pull Request Overview

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[Copilot]

Pull Request Overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

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[thebristolsound]

Okay, sorry for the notification spam on this one, but I think we're all green in the pipeline now. I've re-requested review as I made some minor adjustments to the unit tests in this PR. Let me know if anything else comes up or you want additional changes. cc @michaelneale

[thebristolsound]

bump. Any chance we can get this merged in?

[DOsinga]

yes!