created_at2022-10-31 22:35:05.477295
updated_at2024-05-22 18:32:42.019185
descriptionBuild the documentation for the local package and all dependencies. The output is placed in `out/doc` in the same format as the project.



Forc Doc

The Sway language documenter.

Quick Start


  • Must have forc installed.
  • Must be in a directory, or parent directory containing a Forc.toml and some Sway code that successfully compiles
  • For documentation to appear you need only add doc attributes to documentable items, like so:
    /// Defines my contract ABI...
    abi MyContractABI {}
  • You may also document at the module level with the module level doc attribute syntax:

    Note: This will only work at the beginning of Sway files

    //! Library containing types used for...
    Check out the doc attribute section of the Sway reference for more information on how to document Sway code.

If you've installed a distributed toolchain via fuelup, you already have everything you need to run forc doc. Otherwise, you can install forc & forc doc via cargo install, or from fuelup directly.

The below commands check you have everything necessary to run forc doc.

$ cd my_fuel_project
$ ls # check Forc.toml exists
# src Forc.toml
$ forc --version # check forc is installed
$ forc doc --version # check forc doc is installed
$ forc doc --open # open docs in default browser

For usage, see the docs.

To install forc doc for development, see the Getting Started section under Contributing.


Welcome! We're glad you're here to help. Below is an overview of the program's design choices, as well as how to build forc doc and test your changes locally.

Build Requirements

  • cargo
  • forc
  • a default, modern browser (older browsers may cause issues)

Tip: If you see no changes take effect, it may be due to multiple forc doc binaries. To prevent this, remove any pre-existing versions that take precedence, such as a fuelup binary. You can also avoid this by executing the forc doc binary via cargo run, see Viewing Changes.

$ which forc-doc
# ~/.fuelup/bin/forc-doc
$ rm ~/.fuelup/bin/forc-doc
$ which forc-doc
# if it displays nothing, you're good to go!

Getting Started

Clone the sway repository into your preferred directory:

$ git clone

Then move into the newly created sway directory, and install forc doc:

$ cd sway
$ cargo install --path forc-plugins/forc-doc

Great! Let's check everything is working as intended. Try running forc doc on one of the test directories:

$ forc doc --manifest-path src/tests/data/impl_traits --open

If it succeeded, you should be seeing the test docs in your browser.


New language keyword? Want to add a feature? Updating CSS? forc doc is setup to make development easy.

Design Overview

Each section of the project is labeled to its corresponding functionality.

  • doc: The documenting phase. Handles analysis of a compiled typed Sway program and collects useful information into Documents that can be rendered to HTML. This is where to start if you are trying to implement a new Sway language feature, or make some information about an existing feature available for rendering.
  • render: Renders the information collected by the documenting phase into HTML and places them into the out/doc directory. This phase is intended to be especially friendly to those familiar with building static HTML webpages. The horrorshow library uses macros to write HTML that look strikingly similar to writing plain HTML.
  • licenses: Files that must be present in docs generated by forc doc for use of fonts, logos or anything pertaining to the project that requires a license.
  • static.files: Files that must be present in docs generated by forc doc in order for styling to take effect, eg CSS, icons & fonts.
  • tests/data: This is where edge case Sway code lives. If an edge case bug arises, write a minimal reproduction and place it here to start.

Try running cargo doc on the forc-doc project directory for an in-depth look at what each section is responsible for!

The Documenting Phase

Documentable Items

Adding new documentable items is very straight-forward. Documentable items take only two forms, declarations (TyDecls) and context (everything else).

Declarations can be added directly to the description phase of the analysis, found in Just add the new TyDecl to the match arm of from_typed_decl and fill in the necessary fields for the resulting Descriptor wrapped Document, then return it as Documentable.

Context items, eg fields on structs, variants of an enum etc, must be added to the ContextType enum, found in and collected at the time of its corresponding TyDecl's analysis. The ContextType is wrapped by a Context struct which is later sorted and rendered to the ItemContext of a RenderedDocument.


Let's say that we want to have a new declaration type called CoolNewDecl, modeled after the StructDecl but with some special purpose.

First, we would add the context of the declaration to the ContextType as a variant:

// in
pub(crate) enum ContextType {
    // Add in the new declaration's context type
    /* ... */

Then, match for the new declaration and return the Document.

// in
pub(crate) enum Descriptor {
impl Descriptor {
    pub(crate) fn from_typed_decl(/* ... */) -> Result<Self> {
        match ty_decl {
            // Add the new declaration to the match arm
            ty::TyDecl::CoolNewDecl(ty::CoolNewDecl { decl_id, .. }) => {
                let decl = decl_engine.get_cool_new_decl(decl_id);
                if !document_private_items && decl.visibility.is_private() {
                } else {
                    let item_name = decl.call_path.suffix;
                    let attrs_opt = (!decl.attributes.is_empty())
                        .then(|| decl.attributes.to_html_string());
                    // Fill in the context of the new declaration
                    let context = (!decl.fields.is_empty()).then_some(Context::new(

                    Ok(Descriptor::Documentable(Document {
                        module_info: module_info.clone(),
                        item_header: ItemHeader {
                            module_info: module_info.clone(),
                            friendly_name: ty_decl.friendly_type_name(),
                            item_name: item_name.clone(),
                        item_body: ItemBody {
                            ty_decl: ty_decl.clone(),
                            code_str: swayfmt::parse::parse_format::<sway_ast::ItemCoolNew>(
                            attrs_opt: attrs_opt.clone(),
                            item_context: ItemContext {
                                context_opt: context,
                                impl_traits: None,
                        raw_attributes: attrs_opt,
            /* ... */
            _ => Ok(Descriptor::NonDocumentable),

Once the declarations are collected into a Document, the Document can then be rendered. Refer to the from_raw_docs method on RenderedDocumentation found in render/ for the beginning of the rendering phase. There you can find plenty of examples on how to render Documents into RenderedDocuments if you are adding in a new documentable item.

Index File Generation

Index files, such as the AllDocIndex, ProjectIndex and ModuleIndexs, are rendered using only the information gathered from Sway modules. The process for their rendering can also be found in the RenderedDocumentation::from_raw_docs method. ModuleInfo is gathered from at point of generating the Documentation from a TyProgram, found in doc/ This is the starting point of the entire analytical process, where a TyProgram is compiled and passed to Documentation::from_ty_program.

The Rendering Phase

As stated before, rendering is fairly straight-forward in forc doc, as the HTML is that of a generic webpage.

Let's try writing a small render-side example together, using the horrorshow library.

Here is the HTML for the search bar on

<nav class="sub">
  <form class="search-form">
    <div class="search-container">
        placeholder="Click or press ‘S’ to search, ‘?’ for more options…"
      <div id="help-button" title="help" tabindex="-1">
        <a href="../help.html">?</a>
      <div id="settings-menu" tabindex="-1">
        <a href="../settings.html" title="settings">
            alt="change settings"

Here is the corresponding horrorshow code that produces the same HTML:

mod search {
    use horrorshow::{box_html, RenderBox};

    pub(crate) fn generate_searchbar() -> Box<dyn RenderBox> {
        box_html! {
            nav(class="sub") {
                form(class="search-form") {
                    div(class="search-container") {
                            placeholder="Click or press ‘S’ to search, ‘?’ for more options…",
                        div(id="help-button", title="help", tabindex="-1") {
                            a(href="../help.html") { : "?" }
                        div(id="settings-menu", tabindex="-1") {
                            a(href="../settings.html", title="settings") {
                                    alt="change settings",

Now we can call this function anytime we need to generate a searchbar for our webpage!

Viewing Changes

Once you've made some changes, run the forc doc binary, passing it a path containing a Forc.toml:

cargo run -- --manifest-path path/to/manifest --open

Tip: VS Code user? Try the Live Server plugin to make viewing changes even easier. It will reload a webpage on updates, so you only need to rebuild the docs (cargo run -- --manifest-path path/to/manifest). Just right click the index file of docs produced by forc doc which can be found in the out/doc directory, and choose the option "open with Live Server". Voila!

Commit count: 2829

cargo fmt