---
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title: References
description: |
    References and documentation of the SVGU public API.
---

# SVGU References

This document presents the exposed API of SVGU for use within Starlark
configurations.

## index

```python
index(domain)
```

Index initializes the module registry to host at the given domain.
This function must be called before any [`module()`](#module) function.

Parameters:

- `domain` (str): the domain name the repository will be hosted at, e.g.
  [go.nc0.fr](https://go.nc0.fr).

```python
# Modules hosted at example.com`
index(domain="example.com")

# ...
```

## module

```python
module(name, vcs, repo, dir, file)
```

Module registers a module inside the index. A module is defined by its `name`.
Two modules with the same name cannot exist at the same time in the same index.

A module name must be a valid URL path segment, it cannot be empty, nor
contains dots (`.`), slashes (`/`), backslashes (`\`), colons (`:`),
asterisks (`*`), or ASCII control characters (i.e. `\x00` through `\x1f`)
(required to avoid issues with file systems and URLs).

The module name cannot also be simply `index`. This is a limitation of the
file generation system.

Parameters:

- `name` (str): the name of the module (without the domain and the prefixing
  slash), e.g. `"foo/v2"`;
- `vcs` (str): the version control system used to host the code supported by
  the standard Go toolchain. Must be one of `"bzr"` ([Bazaar][bzr]), `"fossil"`
  ([Fossil][fossil]), `"git"` ([Git][git]), `"hg"` ([Mercurial][hg]), or
  `"svn"` ([Subversion][svn]);
- `repo`: the URL of the code repository, e.g. `"https://github.com/foo/bar"`;
- `dir`: a Go template forming the URL to a page listing the various files
  inside a directory, e.g. `"https://github.com/foo/bar/tree/main{/dir}"`.
  Please refers to the [`go-source`][go-source] for more information about the
 - `file`: a Go template forming the URL to a page listing the lines of code
  inside a file, and links to a specific line if needed, e.g. 
  `"https://github.com/foo/bar/blob/main{/dir}/{file}#{line}"`. Please refers to
  the [`go-source`][go-source] for more information about the
  template template.

[go-source]: https://github.com/golang/gddo/wiki/Source-Code-Links
[bzr]: https://www.gnu.org/software/bazaar/
[fossil]: https://www2.fossil-scm.org/home/doc/trunk/www/index.wiki
[git]: https://git-scm.com
[hg]: https://www.mercurial-scm.org
[svn]: https://subversion.apache.org

Here are valid templates for a few popular hosting services:

- **GitHub (Git):** `https://<instance>/<user>/<repo>/tree/<ref>{/dir}` (dir)
  and`https://<instance>/<user>/<repo>/blob/<ref>{/dir}/{file}#{line}` (file);
- **GitLab (Git):** `https://<instance>/<user>/<repo>/-/tree/<ref>{/dir}` (dir)
  and `https://<instance>/<user>/<repo>/-/blob/<ref>{/dir}/{file}#L{line}`
  (file);
- **Source Hut (Git):** `https://<instance>/~<user>/<repo>/tree/<ref>{/dir}`
  (dir) and
  `https://<instance>/~<user>/<repo>/tree/<ref>/item{/dir}/{file}#L{line}`
  (file);
- **Bitbucket (Git):** `https://<instance>/<workspace>/<repo>/src/<ref>{/dir}`
  (dir) and
  `https://<instance/<workspace>/<repo>/src/<ref>{/dir}/{file}#{file}-{file}`
  (file);
- **Gitiles (Git):** `https://<instance>/<repo>/+/refs/heads/<ref>{/dir}` (dir)
  and `https://<instance>/<repo>/+/refs/heads/<ref>{/dir}/{file}#{line}` (file);
- **Launchpad (Bazaar):**
  `https://<instance>/~<user>/<repo>/<branch>/files/<rev>{/dir}` (dir) and
  `https://<instance>/~<user>/<repo>/<branch>/view/<rev>{/dir}/{file}#L{line}`
  (file);
- **Source Hut (Mercurial):**
  `https://<instance>/~<user>/<repo>/browse{/dir}?rev=<rev>` (dir) and
  `https://<instance>/~<user>/<repo>/browse{/dir}/{file}?rev=<rev>#L{line}`
  (file).

> Do not forget to replace `<variables>` with the expected value.

```python
index(domain="example.com")

SUBVERSION = "svn"

# Will be usable in Go as "example.com/foo".
module(name="foo", vcs=SUBVERSION, repo="https://src.example.com/foo",
        dir="https://src.example.com/tree/master{/dir}",
        file="https://src.example.com/tree/master{/dir}/{file}#{line}")
```

## Helpers

In previous versions of SVGU, a set of Starlark modules (`@svgu/bzr`...) was
exposing a set of macros to help writing configurations for modules hosted
on popular platforms, such as GitHub.

We decided to remove them due to the burden of maintaining them with the
rational that they are trivial to write. Indeed, the old `git.github()` macro
can be implemented as such:

```python
def github(name, user, repo, ref = "main", instance = "github.com"):
    repo = "https://%s/%s/%s" % (instance, user, repo)
    dir = "%s/tree/%s{/dir} % (repo, ref)

    module(
        name=name,
        vcs="git",
        repo=repo,
        dir=dir,
        file="%s/{file}#{line}" % dir,
    )
```

> The same applies to other macro inside other modules, such as
>`bzr.launchpad()` and `hg.sourcehut()`.

And constants, such as `git.GIT` and `fossil.FOSSIL` are simple variables:

```python
BAZAAR = "bzr"
FOSSIL = "fossil"
GIT = "git"
MERCURIAL = "hg"
SUBVERSION = "svn"
```

It is encouraged to write your own helper functions and constants at the
beginning of your configuration file.