# The documentation subsystem¶

The documentation is available online at tezos.gitlab.io, and always up to date with branch master on GitLab.

## Building instructions¶

To build the documentation, you need to install the Python package manager Poetry. For instructions on how to obtain Python and Poetry, see the installation instructions for the python testing framework. Once this is done, you can install the needed dependencies locally:

# in the "docs" directory
poetry install
make


The output is generated and available in docs/_build. It is built by Sphinx, and uses the Read The Docs theme.

### OCaml documentation¶

As part of the above procedure, Odoc is used for OCaml API generation. You can install Odoc with:

opam install odoc


Tezos generates the API documentation for all libraries in HTML format. The generated HTML pages are put in _build/<context>/_doc. It creates one sub-directory per public library and generates an index.html file in each sub-directory.

The documentation is not installed on the system by Tezos. It is meant to be read locally while developing and then published on the www when releasing packages.

## Writing documentation¶

Online documentation is written in reStructuredText format, also known as RST. reStructuredText is the default plaintext markup language used by Sphinx, which is the tool used to compile this format into plain web pages in HTML format.

For the RST syntax, see the Sphinx RST primer.

### Line breaking¶

When writing documentation in text formats such as RST, it is not required to respect a maximal line width, such as 80 columns. Therefore, you may choose between the different line breaking policies your text editor proposes. However, you should be aware that file comparison tools such as diff tend to output large differences for a paragraph that has been reformatted after only a small change in one phrase. Also, reviewing tools such as the one in the GitLab user interface associate comments and change suggestions to lines, while these comments and suggestions are usually logically associated to whole phrases.

For such reasons:

• Some contributors use one line per complete phrase, which allows to make rephrasing suggestions more easily in gitlab, associated to this (possibly long) line; and which allows diff to isolate modified phrases, instead of showing the whole container paragraph as modified.

• Other contributors, whose editor breaks lines at a fixed width, introduce an extra line break at the end of each phrase. This also allows diff to isolate modified phrases.

Thus, you may choose your own formatting style, while tolerating different styles from other contributors.

### Sphinx extensions¶

Some ad-hoc reference kinds are supported.

• :package-src:name or :package-src:text<name> points to the gitlab source tree viewer where the .opam for the package is located

• :package:name or :package:text<name> now points either to the odoc page, or if it doesn’t exist, to the gitlab source tree viewer

• :package-name:name or :package-name:text<name> just displays the package name (no link), checking that the package exists

• :src:/path/to/file/or/dir or :src:text</path/to/file/or/dir> points to the gitlab source tree viewer. It is possible to refer to a particular line in a file by adding a line number suffix of the form #Lnnn.

• :opam:package or :opam:text<package> points to the package page on opam.ocaml.org, version number is supported (package.version)

• :gl:<special gitlab reference> or :opam:text<special gitlab reference> expands and links GitLab special reference, like for merge requests tezos/tezos!123, issues tezos/tezos#999 and commits 28309c81. The default project and namespace is tezos/tezos. In other words, tezos/tezos#999, tezos#999 and #999 all refer to the same thing. Currently supports usernames, projects, issues, merge requests, snippets, milestone ids, commits and commit ranges. This is implemented in docs/_extensions/gitlab_custom_role.py.

### Writing protocol documentation¶

Writing protocol documentation is a special case because protocol-related documentation pages are duplicated for several protocol versions (under directories named NNN/, where NNN is either a protocol number or “alpha”), and possibly also in a protocol-independent part (typically under directory shell/).

Besides the need of maintaining several versions of these pages, this duplication introduces the need to carefully handle documentation cross-references, in particular to avoid duplicate labels (i.e., multiple labels with the same name in different pages) and wrong references (i.e., escaping from one protocol version into another).

The following rules promote a systematic way of handling documentation cross-references that avoids introducing such errors.

#### Definitions¶

First let us introduce the following definitions:

• A label is an identifier defining a specific position in a documentation page (typically, before a section name). A reference is a link to a label, in the same or another page. In Sphinx, labels are written .. _label: and references are written :ref: textual description <label>, or :ref: label. Labels and references are case-insensitive.

• A versioned label bears a protocol version in it (e.g. label_NNN); an unversioned label doesn’t (i.e. just label)

• A local reference is a link from a protocol-specific page to the same page or to another protocol-specific page. An external reference is a reference from a protocol-independent page to a label in a protocol-specific page.

#### Rules¶

The following simple rules are proposed for safely managing cross-references:

1. In all but the current protocol, any defined label must be versioned:

.. _<label>_NNN:

2. In the current protocol, labels may be versioned (as targets of local references), unversioned (as targets of external references), or both. The last case is done by defining two labels for such location:

..  _<label>:
..  _<label>_NNN:

3. Any local reference in protocol NNN must be versioned NNN. This includes references appearing in the currently active protocol.

4. External references must be unversioned.

The rationale of the above rules:

• Any label defined in a protocol-specific page must be versioned to avoid name conflicts (as by definition the containing page is duplicated).

• External references must be unversioned to avoid modifying protocol-independent pages when the current protocol is changed.

• Local references in the current protocol could also work if unversioned, but when the protocol is changed, they should be rewritten as versioned. It is much simpler to enforce the rule that all local references in a page for any protocol NNN must be versioned NNN.

#### Protocol changes¶

When a new protocol is adopted, its pages must be “linked” with the protocol-independent pages:

• remove in the old protocol all the unversioned labels (this operation is unnecessary if the pages of the old protocol are removed altogether)

• add in the new protocol an unversioned label before each versioned label

NB no rewriting of any reference is needed on protocol changes.

On creating a new protocol proposal version NNN out of alpha:

• rename all versioned labels AND references _alpha in its pages to version _NNN

#### Rules automation¶

To help enforcing the above cross-referencing rules in protocol-specific pages, the following scripts are provided under docs/scripts:

• check_proto_xrefs.py: checks the references, and optionally the labels, in all pages of a given protocol version

• can be used at any time, e.g. when changing a protocol-specific page

• add_labels_without_proto.py: adds unversioned labels before each versioned label in a protocol-specific page

• can be used when a new protocol is adopted, to “link” its documentation into protocol-independent pages

• remove_labels_without_proto.py: removes unversioned labels in a protocol-specific page

• can be used when a new protocol is adopted for “unlinking” the pages of the old protocol, only if those pages are not removed altogether

Moreover, the script scripts/snapshot_alpha.sh, used to create a new protocol proposal version NNN out of alpha is planned to integrate renaming of labels and references.

#### Documenting protocols¶

Due to the duplication of the documentation for multiple protocol versions, the following extra guidelines should be observed.

• In principle, protocol-independent pages should only refer to the currently active protocol. Indeed, until newer protocols are adopted, there is no guarantee that their features will be part of Tezos someday.

• When modifying the pages of a given protocol version, you might have to also modify it for later versions. Otherwise, when newer protocols are adopted, your changes will vanish! In particular, when fixing a problem in the documentation of the current protocol (e.g. adding a term in the glossary), you might have to fix it also for the candidate protocol (if there is one under the voting procedure) and for the Alpha protocol under development (assuming that the features of the candidate protocol will be inherited by or proposed in another form in Alpha).

• As there is a considerable overhead for maintaining protocol-specific pages, think twice before duplicating a page as protocol-specific. Does this page really refer to the protocol? If yes, does all the page refer to the protocol? If the answer to the last question is “no”, consider splitting the page in two parts, respectively protocol-specific and protocol-independent.