syntastic

Syntastic is a plugin for Vim, a text editor popular among developers, that checks your code for errors while you work. Instead of waiting until you try to run or compile a file, Syntastic runs the appropriate checking tool in the background and shows you any problems it finds directly inside the editor.

When an error is present, Syntastic can display it in several ways at once: a list of errors appears in a panel at the bottom of the window, a marker shows up in the left margin next to the problematic line, the error message appears at the bottom of the screen when your cursor lands on that line, and the erroneous text can be highlighted inline. You configure which of these visual cues you want active.

The plugin supports a very wide range of programming languages and file formats. The README lists over 100 supported languages including Python, JavaScript, Ruby, Go, C, C++, PHP, Rust, TypeScript, HTML, CSS, YAML, and many others. For each language it delegates the actual checking to an external tool that must be installed on your machine separately. Syntastic itself just runs that tool and collects the results.

Important context: the README prominently notes that this project is no longer maintained. The authors recommend switching to ALE, a newer plugin that covers similar functionality and takes a different architectural approach. Syntastic still works for many users who prefer to keep it, but no new development is happening here.

Installation follows the standard Vim plugin workflow using a plugin manager of your choice. The README includes basic setup instructions and recommended starting settings for new users.