# Package Guide

Documenter is designed to do one thing -- combine markdown files and inline docstrings from
Julia's docsystem into a single inter-linked document. What follows is a step-by-step guide
to creating a simple document.


## Installation

Documenter can be installed using the Julia package manager.
From the Julia REPL, type `]` to enter the Pkg REPL mode and run

```
pkg> add Documenter
```


## Setting up the Folder Structure

!!! note
    The function [`DocumenterTools.generate`](@ref) from the `DocumenterTools` package
    can generate the basic structure that Documenter expects.

Firstly, we need a Julia module to document. This could be a package generated via
`PkgDev.generate` or a single `.jl` script accessible via Julia's `LOAD_PATH`. For this
guide we'll be using a package called `Example.jl` that has the following directory layout:

```
Example/
    src/
        Example.jl
    ...
```

Note that the `...` just represent unimportant files and folders.

We must decide on a location where we'd like to store the documentation for this package.
It's recommended to use a folder named `docs/` in the toplevel of the package, like so

```
Example/
    docs/
        ...
    src/
        Example.jl
    ...
```

Inside the `docs/` folder we need to add two things. A source folder which will contain the
markdown files that will be used to build the finished document and a Julia script that will
be used to control the build process. The following names are recommended

```
docs/
    src/
    make.jl
```


## Building an Empty Document

With our `docs/` directory now setup we're going to build our first document. It'll just be
a single empty file at the moment, but we'll be adding to it later on.

Add the following to your `make.jl` file

```julia
using Documenter, Example

makedocs(sitename="My Documentation")
```

This assumes you've installed Documenter as discussed in [Installation](@ref) and that your
`Example.jl` package can be found by Julia.

!!! note

    If your source directory is not accessible through Julia's LOAD_PATH, you might wish to
    add the following line at the top of make.jl

    ```julia
    push!(LOAD_PATH,"../src/")
    ```

Now add an `index.md` file to the `src/` directory. The name has no particular significance
though and you may name it whatever you like. We'll stick to `index.md` for this guide.

Leave the newly added file empty and then run the following command from the `docs/` directory

```sh
$ julia make.jl
```

Note that `$` just represents the prompt character. You don't need to type that.

If you'd like to see the output from this command in color use

```sh
$ julia --color=yes make.jl
```

When you run that you should see the following output

```
Documenter: setting up build directory.
Documenter: expanding markdown templates.
Documenter: building cross-references.
Documenter: running document checks.
 > checking for missing docstrings.
 > running doctests.
 > checking footnote links.
Documenter: populating indices.
Documenter: rendering document.
```

The `docs/` folder should contain a new directory -- called `build/`. It's structure should
look like the following

```
build/
    assets/
        arrow.svg
        documenter.css
        documenter.js
        search.js
    index.html
    search.html
    search_index.js
```

!!! warning

    **Never** `git commit` the contents of `build` (or any other content generated by
    Documenter) to your repository's `master` branch. Always commit generated files to the
    `gh-pages` branch of your repository. This helps to avoid including unnecessary changes
    for anyone reviewing commits that happen to include documentation changes.

    See the [Hosting Documentation](@ref) section for details regarding how you should go
    about setting this up correctly.

At this point `build/index.html` should be an empty page since `src/index.md` is empty. You
can try adding some text to `src/index.md` and re-running the `make.jl` file to see the
changes.


## Adding Some Docstrings

Next we'll splice a docstring defined in the `Example` module into the `index.md` file. To
do this first document a function in that module:

```julia
module Example

export func

"""
    func(x)

Returns double the number `x` plus `1`.
"""
func(x) = 2x + 1

end
```

Then in the `src/index.md` file add the following

````markdown
# Example.jl Documentation

```@docs
func(x)
```
````

When we next run `make.jl` the docstring for `Example.func(x)` should appear in place of
the `@docs` block in `build/index.md`. Note that *more than one* object can be referenced
inside a `@docs` block -- just place each one on a separate line.

Note that a `@docs` block is evaluated in the `Main` module. This means that each object
listed in the block must be visible there. The module can be changed to something else on
a per-page basis with a `@meta` block as in the following

````markdown
# Example.jl Documentation

```@meta
CurrentModule = Example
```

```@docs
func(x)
```
````

### Filtering included docstrings

In some cases you may want to include a docstring for a `Method` that extends a
`Function` from a different module -- such as `Base`. In the following example we extend
`Base.length` with a new definition for the struct `T` and also add a docstring:

```julia
struct T
    # ...
end

"""
Custom `length` docs for `T`.
"""
Base.length(::T) = 1
```

When trying to include this docstring with

````markdown
```@docs
length
```
````

all the docs for `length` will be included -- even those from other modules. There are two
ways to solve this problem. Either include the type in the signature with

````markdown
```@docs
length(::T)
```
````

or declare the specific modules that [`makedocs`](@ref) should include with

```julia
makedocs(
    # options
    modules = [MyModule]
)
```


## Cross Referencing

It may be necessary to refer to a particular docstring or section of your document from
elsewhere in the document. To do this we can make use of Documenter's cross-referencing
syntax which looks pretty similar to normal markdown link syntax. Replace the contents of
`src/index.md` with the following

````markdown
# Example.jl Documentation

```@docs
func(x)
```

- link to [Example.jl Documentation](@ref)
- link to [`func(x)`](@ref)
````

So we just have to replace each link's url with `@ref` and write the name of the thing we'd
link to cross-reference. For document headers it's just plain text that matches the name of
the header and for docstrings enclose the object in backticks.

This also works across different pages in the same way. Note that these sections and
docstrings must be unique within a document.


## Navigation

Documenter can auto-generate tables of contents and docstring indexes for your document with
the following syntax. We'll illustrate these features using our `index.md` file from the
previous sections. Add the following to that file

````markdown
# Example.jl Documentation

```@contents
```

## Functions

```@docs
func(x)
```

## Index

```@index
```
````

The `@contents` block will generate a nested list of links to all the section headers in
the document. By default it will gather all the level 1 and 2 headers from every page in the
document, but this can be adjusted using `Pages` and `Depth` settings as in the following

````markdown
```@contents
Pages = ["foo.md", "bar.md"]
Depth = 3
```
````

The `@index` block will generate a flat list of links to all the docs that that have been
spliced into the document using `@docs` blocks. As with the `@contents` block the pages to
be included can be set with a `Pages = [...]` line. Since the list is not nested `Depth` is
not supported for `@index`.


## Pages in the Sidebar

By default all the pages (`.md` files) in your source directory get added to the sidebar,
sorted by their filenames. However, in most cases you want to use the `pages` argument to
[`makedocs`](@ref) to control how the sidebar looks like. The basic usage is as follows:

```julia
makedocs(
    ...,
    pages = [
        "page.md",
        "Page title" => "page2.md",
        "Subsection" => [
            ...
        ]
    ]
)
```

Using the `pages` argument you can organize your pages into subsections and hide some pages
from the sidebar with the help of the [`hide`](@ref) functions.
