nandi.uk
Gleam-inspired typed configuration language (POC)
Document why editors/zed still has Rust.
Explain that Zed Install Dev Extension always cargo-builds a Rust guest, so
src/glint.rs is temporary; pure Gleam remains the target via the wasm fork.
author
nandi
date
(Jul 26, 2026, 1:20 AM -0700)
commit
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README.md
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README.md
···
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**Zed** (dev extension in this repo — see also [`editors/zed/README.md`](editors/zed/README.md)):
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#### Why is there Rust under `editors/zed/`?
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Not because we want the extension authored in Rust. **Zed forces it today.**
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On **Install Dev Extension**, when `extension.toml` has `[lib] kind = "Rust"`
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(the only allowed kind), Zed always runs roughly:
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```text
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cargo build --target wasm32-wasip2
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```
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and writes `extension.wasm` from that crate. There is **no** install path that
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only loads a prebuilt component from `gleam export zed-extension`. Without
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`Cargo.toml` + `src/*.rs` you get `failed to compile Rust extension`.
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So `editors/zed/src/glint.rs` is a **thin temporary guest** (same behaviour as
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`zed_glint.gleam`: resolve `glint`, start LSP). Direction of travel is pure
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Gleam via our [wasm fork](https://tangled.org/nandi.uk/gleam); the `.rs` crate
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can go once Zed accepts prebuilt guests (or we use another install path).
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| Path | Role |
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|------|------|
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| `editors/zed/src/glint.rs` | What Zed can compile and install **now** |
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| `editors/zed/src/zed_glint.gleam` | Target authoring surface (pure Gleam) |
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| [nandi.uk/gleam](https://tangled.org/nandi.uk/gleam) `wasm` | Compiler that builds a real `zed:extension` component |
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### 1. Build the glint binary
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```sh
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editors/zed/README.md
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editors/zed/README.md
···
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Zed extension for Glint — language config, tree-sitter highlighting (via
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tree-sitter-gleam), and the glint language server.
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## Why is there Rust code here?
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Not because we want the extension authored in Rust. **Zed forces it today.**
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On **Install Dev Extension**, when `extension.toml` has:
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```toml
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[lib]
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kind = "Rust"
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```
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(`"Rust"` is the only allowed `kind`.) Zed always runs roughly:
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```text
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cargo build --target wasm32-wasip2
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```
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and writes `extension.wasm` from that crate. There is **no** install path that
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only loads a prebuilt Wasm from `gleam export zed-extension`.
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Without `Cargo.toml` + `src/*.rs` you get:
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- `failed to compile Rust extension` (no Cargo.toml), or
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- invalid `kind` if you try anything other than `"Rust"`.
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So `src/glint.rs` is a **thin temporary guest** that implements the same idea
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as `src/zed_glint.gleam` (resolve `glint` on PATH / fallback, start the LSP).
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It is a **host/toolchain constraint**, not the product direction.
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| Path | Role |
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|------|------|
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| `src/glint.rs` | What Zed can compile and install **now** |
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| `src/zed_glint.gleam` | Target authoring surface (pure Gleam) |
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| [nandi.uk/gleam](https://tangled.org/nandi.uk/gleam) (`wasm` branch) | Compiler that builds a real `zed:extension` component |
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Once Zed accepts a prebuilt component (or we stop using Install Dev’s cargo
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path), the `.rs` crate can go away and the Gleam export path can own the guest.
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## Compile
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### Glint binary (LSP)
···
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nix build # → result/bin/glint
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```
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### Zed guest (Rust — what Install Dev Extension builds)
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Zed always runs `cargo build --target wasm32-wasip2` when
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`[lib] kind = "Rust"`. Local check:
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### Zed guest (Rust — required for Install Dev Extension today)
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```sh
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cd /home/nandi/code/glint/editors/zed
···
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```
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See `docs/compiler/wasm-zed-extensions.md` in that repo. Until Zed can load a
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prebuilt guest without cargo, **Install Dev Extension still uses the Rust
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crate** (`src/glint.rs`). `src/zed_glint.gleam` is the pure-Gleam sketch.
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prebuilt guest without cargo, **Install Dev Extension still overwrites with the
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Rust build**.
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## Install in Zed
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···
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| Path | Role |
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|------|------|
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| `extension.toml` | Zed manifest |
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| `src/glint.rs` | Installable guest (`zed_extension_api`) |
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| `src/glint.rs` | Temporary installable guest (Zed cargo path) |
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| `src/zed_glint.gleam` | Pure-Gleam authoring sketch |
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| `languages/glint/` | Tree-sitter queries + language config |
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| `extension.wasm` | Built component (Zed / cargo) |