TomlSmith for VS Code

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TOML diagnostics and formatting in VS Code.

TomlSmith for VS Code uses TomlSmith for .toml files and named TOML files such as Cargo.lock and Pipfile. It supports TOML 1.0 and 1.1.

Features

• View errors and warnings while editing TOML files, with stable diagnostic codes in VS Code's Problems panel.
• Format a document with VS Code's Format Document action. The extension applies the edits returned by the language server instead of replacing the whole document.
• Highlight keys, values, tables, comments, and literals with TextMate and semantic tokens. Regular tables, arrays of tables, scalar keys, array-valued keys, inline-table-valued keys, and member keys inside inline tables receive distinct classifications.
• View a key's path and TOML value kind on hover.
• Browse a hierarchical symbol tree for tables, arrays of tables, and keys through Outline, breadcrumbs, and Go to Symbol in Editor, including documents whose tables are declared out of order.
• Fold table regions, arrays of tables, multi-line arrays, and TOML 1.1 multi-line inline tables.
• Validate as TOML 1.1 by default, or select strict TOML 1.0 for files consumed by 1.0-only tools.
• Configure indentation, preferred line width, line endings, and whether generated files are formatted.

The extension does not provide rename refactors, completion, Schema integration, or code actions. Switching from Even Better TOML? See the migration notes.

Supported files

The extension registers TOML for .toml files and these filenames: Cargo.lock, Pipfile, uv.lock, poetry.lock, and pdm.lock.

Syntax colors

TomlSmith keeps keys and table headers on VS Code's standard property and namespace semantic token types, then adds TOML-specific modifiers for array-valued keys, inline-table-valued keys, member keys inside inline tables, and arrays of tables. Themes therefore retain their normal fallback colors while you can override each TOML structure independently.

With Dark+, TomlSmith gives inline-table member keys a cyan #4FC1FF default while outer property keys retain Dark+'s light blue and table headers retain its teal namespace color. The default is scoped to TOML and both the newer Dark+ and older Default Dark+ theme IDs; a user or workspace color setting still takes precedence. This example customizes the complete palette:

{
  "editor.semanticTokenColorCustomizations": {
    "[Dark+][Default Dark+]": {
      "enabled": true,
      "rules": {
        "property:toml": "#9CDCFE",
        "property.tomlArray:toml": "#569CD6",
        "property.tomlInlineTable:toml": "#9CDCFE",
        "property.tomlInlineTableMember:toml": "#4FC1FF",
        "property.tomlArray.tomlInlineTableMember:toml": "#4FC1FF",
        "property.tomlInlineTable.tomlInlineTableMember:toml": "#4FC1FF",
        "namespace:toml": "#4EC9B0",
        "namespace.tomlArrayTable:toml": "#569CD6",
        "tomlDateTime:toml": "#DCDCAA",
        "tomlInvalid:toml": {
          "foreground": "#F44747",
          "underline": true
        }
      }
    }
  }
}

Remove the [Dark+][Default Dark+] wrapper and place enabled and rules directly under editor.semanticTokenColorCustomizations to apply the palette to every theme. Matching TextMate scopes provide the same structural fallback before the language server starts or when semantic highlighting is disabled. Use Developer: Inspect Editor Tokens and Scopes to inspect the selector and winning color rule at the cursor.

Set up the language server

The Marketplace and GitHub Release provide platform-specific packages for macOS x64/arm64, non-Alpine Linux x64/arm64, and Windows x64. Each matching package includes a compatible tomlsmith-lsp, so no separate server setup is required. The same applies when VS Code installs the extension on the workspace side of a supported Remote-SSH, WSL, or Dev Container environment.

The Marketplace also provides an untargeted universal fallback for environments not covered above, including Alpine and Windows Arm64. The fallback deliberately contains no executable; install tomlsmith-lsp from crates.io and configure it explicitly or make it available on PATH as described below.

The extension talks to a tomlsmith-lsp executable, resolved in this order:

1. An explicitly configured tomlsmith.server.path setting.
2. A server binary bundled inside the extension package, when one is present for the current platform.
3. A tomlsmith-lsp found on PATH.

For extension development or an unsupported platform, if neither a bundled server binary nor one on PATH is available, install the published server crate:

1. Install the latest stable server from crates.io:

   cargo install tomlsmith-lsp --locked
   

2. Make it reachable — keep Cargo's bin directory on PATH, or point the setting at the binary:

   {
     "tomlsmith.server.path": "/absolute/path/to/tomlsmith-lsp"
   }
   

If the server fails to start, the extension reports the command that failed. Correcting tomlsmith.server.path takes effect without reloading the window.

Packagers can stage a built binary into a locally packaged VSIX with pnpm bundle-server --binary <path-to-tomlsmith-lsp>; see CONTRIBUTING.md for details.

For extension source development, follow CONTRIBUTING.md.

Settings

Changing any tomlsmith.server.* setting automatically restarts the language server; tomlsmith.toml.version and the tomlsmith.format.* settings are pushed to the running server and apply without a restart.

In Restricted Mode, workspace-level overrides of tomlsmith.server.path, tomlsmith.server.arguments, and tomlsmith.server.environment are ignored.

Formatting behavior

• By default, Format Document skips generated files: the lockfiles Cargo.lock, uv.lock, poetry.lock, and pdm.lock, and any file whose leading comments carry a marker such as @generated. Set tomlsmith.format.generatedFiles to format to format them anyway.
• A document with syntax errors is not formatted. The reason is written to the TomlSmith output log rather than shown as a popup.

Language status

While a TOML file is open, a TomlSmith entry in the language status area (the {} indicator in the status bar) shows the server state — starting, running, stopped, or failed with the failure detail — and offers a Restart Server action.

Commands

• TomlSmith: Restart Language Server — restart the current language-server process on demand.

Acknowledgements

Even Better TOML and its Taplo language tooling helped establish the TOML editor experience users expect and informed TomlSmith's feature-gap checklist for folding, symbol navigation, refactoring, and Schema intelligence. TomlSmith is an independent implementation; thanks to Tamás Fehér and every Taplo contributor for advancing TOML tooling.

Contributing

Read CONTRIBUTING.md before opening a pull request. Participation is governed by the Code of Conduct.

License

TomlSmith for VS Code is released under the MIT License.