Files
zed/docs
saberoueslati 1db5b3ae06 project: Prevent empty external formatter output from clearing buffers (#61276)
## Context

Zed runs external formatters as stdin/stdout filters: it writes the
current buffer to stdin and replaces the buffer with the formatter's
stdout. Commands such as `cargo fmt` instead rewrite files on disk and
exit successfully without producing stdout, causing Zed to interpret the
empty output as the formatted contents and clear a non-empty buffer.

The fix treats empty stdout from a successful external formatter as no
output when the original buffer is non-empty. Zed leaves the buffer
unchanged and displays a notification explaining that the formatter did
not return formatted contents. The formatter documentation now clarifies
the stdin/stdout contract and recommends using the Rust language server
or invoking `rustfmt` directly.

Closes #56344

Behavior before the fix :

[Screencast from 2026-07-19
02-58-29.webm](https://github.com/user-attachments/assets/61fc5bf9-4420-43f1-94a3-394bbbc4f2a0)


Behavior after the fix :

[Screencast from 2026-07-19
02-55-35.webm](https://github.com/user-attachments/assets/21062065-6b95-4cd4-8200-506f5681d98e)


## How to Review

**crates/project/src/lsp_store.rs**  
Start with `format_via_external_command`, which now checks whether a
successful formatter returned empty stdout while the input buffer was
non-empty. In that case, it returns `None` before constructing a diff,
preventing the buffer contents from being replaced with an empty string.
Then review the external formatter branch in `apply_formatter`: when it
receives `None`, it skips extending the formatting transaction, logs the
condition, and emits an `LspStoreEvent::Notification` explaining why the
buffer was left unchanged.

**crates/editor/src/editor_tests.rs**  
Adds a GPUI regression test that configures an external command to
consume stdin and return no stdout. It uses platform-specific commands
for Windows and Unix, invokes manual formatting on a non-empty Rust
buffer, and verifies that the buffer remains unchanged, the operation is
not recorded as a formatter failure, and a notification is emitted.

**docs/src/reference/all-settings.md**  
Extends the external formatter documentation to state that formatters
must return the formatted buffer through stdout. It calls out
file-rewriting tools such as `cargo fmt` as incompatible and recommends
using the Rust language server or `rustfmt --emit stdout`.

## Self-Review Checklist

- [x] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the UI/UX checklist
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- Fixed external formatters that produce no output clearing non-empty
buffers
2026-07-23 21:21:38 +00:00
..
2026-06-04 15:55:21 +00:00
2026-07-08 20:54:51 +00:00
2026-07-23 05:26:09 +00:00
2026-05-07 06:55:11 +00:00
2026-07-08 20:54:51 +00:00

Zed Docs

Welcome to Zed's documentation.

This is built on push to main and published automatically to https://zed.dev/docs.

To preview the docs locally you will need to install mdBook (cargo install mdbook@0.4.40), generate the action metadata, and then serve:

script/generate-action-metadata
mdbook serve docs

The first command dumps an action manifest to crates/docs_preprocessor/actions.json. Without it, the preprocessor cannot validate keybinding and action references in the docs and will report errors. You only need to re-run it when actions change.

If you use Nix, the development shell provides a pinned mdbook (0.4.40) and a prebuilt docs preprocessor, so you can build the docs without installing anything or compiling the preprocessor on every run:

nix develop -c mdbook build docs

(When actions.json has not been generated, action/keybinding validation is skipped with a warning rather than failing the build.)

It's important to note the version number above. For an unknown reason, as of 2025-04-23, running 0.4.48 will cause odd URL behavior that breaks things.

Before committing, verify that the docs are formatted in the way Prettier expects with:

cd docs && pnpm dlx prettier@3.5.0 . --write && cd ..

Preprocessor

We have a custom mdBook preprocessor for interfacing with our crates (crates/docs_preprocessor).

If for some reason you need to bypass the docs preprocessor, you can comment out [preprocessor.zed-docs-preprocessor] from the book.toml.

Images and videos

To add images or videos to the docs, upload them to another location (e.g., zed.dev, GitHub's asset storage) and then link out to them from the docs.

Putting binary assets such as images in the Git repository will bloat the repository size over time.

Internal notes:

  • We have a Cloudflare router called docs-proxy that intercepts requests to zed.dev/docs and forwards them to the "docs" Cloudflare Pages project.
  • The CI uploads a new version to the Cloudflare Pages project from .github/workflows/deploy_docs.yml on every push to main.

Table of Contents

The table of contents files (theme/page-toc.js and theme/page-doc.css) were initially generated by mdbook-pagetoc.

Since all this preprocessor does is generate the static assets, we don't need to keep it around once they have been generated.

Referencing Keybindings and Actions

When referencing keybindings or actions, use the following formats:

Keybindings

{#kb scope::Action} - e.g., {#kb zed::OpenSettings}.

This will output a code element like: <code>Cmd + , | Ctrl + ,</code>. We then use a client-side plugin to show the actual keybinding based on the user's platform.

By using the action name, we can ensure that the keybinding is always up-to-date rather than hardcoding the keybinding.

Keymap Overlays

{#kb:keymap_name scope::Action} - e.g., {#kb:jetbrains editor::GoToDefinition}.

This resolves the keybinding from a keymap overlay (e.g., JetBrains) first, falling back to the default keymap if the overlay doesn't define a binding for that action. This is useful for sections where the documentation expects a special base keymap to be configured.

Supported overlays: jetbrains.

Actions

{#action scope::Action} - e.g., {#action zed::OpenSettings}.

This will render a human-readable version of the action name, e.g., "zed: open settings", and will allow us to implement things like additional context on hover, etc.

Creating New Templates

Templates are functions that modify the source of the docs pages (usually with a regex match and replace). You can see how the actions and keybindings are templated in crates/docs_preprocessor/src/main.rs for reference on how to create new templates.

We pre-bundle the c15t package because the docs pipeline does not include a JS bundler. If you need to update c15t and rebuild the bundle, use:

mkdir c15t-bundle && cd c15t-bundle
npm init -y
npm install c15t@<version> esbuild
echo "import { getOrCreateConsentRuntime } from 'c15t'; window.c15t = { getOrCreateConsentRuntime };" > entry.js
npx esbuild entry.js --bundle --format=iife --minify --outfile=c15t@<version>.js
cp c15t@<version>.js ../theme/c15t@<version>.js
cd .. && rm -rf c15t-bundle

Replace <version> with the new version of c15t you are installing. Then update book.toml to reference the new bundle filename.

References

  • Template Trait: crates/docs_preprocessor/src/templates.rs
  • Example template: crates/docs_preprocessor/src/templates/keybinding.rs
  • Client-side plugins: docs/theme/plugins.js

Postprocessor

A postprocessor is implemented as a sub-command of docs_preprocessor that wraps the built-in HTML renderer and applies post-processing to the HTML files, to add support for page-specific title and meta tag description values.

An example of the syntax can be found in git.md, as well as below:

---
title: Some more detailed title for this page
description: A page-specific description
---

# Editor

The above code will be transformed into (with non-relevant tags removed):

<head>
  <title>Editor | Some more detailed title for this page</title>
  <meta name="description" contents="A page-specific description" />
</head>
<body>
  <h1>Editor</h1>
</body>

If no front matter is provided, or if one or both keys aren't provided, the title and description will be set based on the default-title and default-description keys in book.toml respectively.

Implementation details

Unfortunately, mdBook does not support post-processing like it does pre-processing, and only supports defining one description to put in the meta tag per book rather than per file. So in order to apply post-processing (necessary to modify the HTML head tags) the global book description is set to a marker value #description# and the HTML renderer is replaced with a sub-command of docs_preprocessor that wraps the built-in HTML renderer and applies post-processing to the HTML files, replacing the marker value and the <title>(.*)</title> with the contents of the front matter if there is one.

Known limitations

The front matter parsing is extremely simple, which avoids needing to take on an additional dependency, or implement full YAML parsing.

  • Double quotes and multi-line values are not supported, i.e. Keys and values must be entirely on the same line, with no double quotes around the value.

The following will not work:

---
title: Some
  Multi-line
  Title
---

neither this:

---
title: "Some title"
---
  • The front matter must be at the top of the file, with only white-space preceding it.
  • The contents of the title and description will not be HTML escaped. They should be simple ASCII text with no unicode or emoji characters.