This chapter describes OCamldoc, a tool that generates documentation from special comments embedded in source files. The comments used by OCamldoc are of the form (**…*) and follow the format described in section 16.2.
OCamldoc can produce documentation in various formats: HTML, LATEX, TeXinfo, Unix man pages, and dot dependency graphs. Moreover, users can add their own custom generators, as explained in section 16.3.
In this chapter, we use the word element to refer to any of the following parts of an OCaml source file: a type declaration, a value, a module, an exception, a module type, a type constructor, a record field, a class, a class type, a class method, a class value or a class inheritance clause.
OCamldoc is invoked via the command ocamldoc, as follows:
ocamldoc options sourcefiles
The following options determine the format for the generated documentation.
OCamldoc calls the OCaml type-checker to obtain type information. The following options impact the type-checking phase. They have the same meaning as for the ocamlc and ocamlopt commands.
The following options apply in conjunction with the -html option:
module M : functor (A:Module) -> functor (B:Module2) -> sig .. endis displayed as:
module M (A:Module) (B:Module2) : sig .. end
The following options apply in conjunction with the -latex option:
These options are useful when you have, for example, a type and a value with the same name. If you do not specify prefixes, LATEX will complain about multiply defined labels.
The following options apply in conjunction with the -texi option:
The following options apply in conjunction with the -dot option:
The following options apply in conjunction with the -man option:
Information on a module can be extracted either from the .mli or .ml file, or both, depending on the files given on the command line. When both .mli and .ml files are given for the same module, information extracted from these files is merged according to the following rules:
The following rules must be respected in order to avoid name clashes resulting in cross-reference errors:
Comments containing documentation material are called special comments and are written between (** and *). Special comments must start exactly with (**. Comments beginning with ( and more than two * are ignored.
OCamldoc can associate comments to some elements of the language encountered in the source files. The association is made according to the locations of comments with respect to the language elements. The locations of comments in .mli and .ml files are different.
A special comment is associated to an element if it is placed before or
after the element.
A special comment before an element is associated to this element if :
A special comment after an element is associated to this element if there is no blank line or comment between the special comment and the element.
There are two exceptions: for constructors and record fields in type definitions, the associated comment can only be placed after the constructor or field definition, without blank lines or other comments between them. The special comment for a constructor with another constructor following must be placed before the ’|’ character separating the two constructors.
The following sample interface file foo.mli illustrates the placement rules for comments in .mli files.
A special comment is associated to an element if it is placed before the element and there is no blank line between the comment and the element. Meanwhile, there can be a simple comment between the special comment and the element. There are two exceptions, for constructors and record fields in type definitions, whose associated comment must be placed after the constructor or field definition, without blank line between them. The special comment for a constructor with another constructor following must be placed before the ’|’ character separating the two constructors.
The following example of file toto.ml shows where to place comments in a .ml file.
The special comment (**/**) tells OCamldoc to discard elements placed after this comment, up to the end of the current class, class type, module or module type, or up to the next stop comment. For instance:
The -no-stop option to ocamldoc causes the Stop special comments to be ignored.
The inside of documentation comments (**…*) consists of free-form text with optional formatting annotations, followed by optional tags giving more specific information about parameters, version, authors, … The tags are distinguished by a leading @ character. Thus, a documentation comment has the following shape:
(** The comment begins with a description, which is text formatted according to the rules described in the next section. The description continues until the first non-escaped '@' character. @author Mr Smith @param x description for parameter x *)
Some elements support only a subset of all @-tags. Tags that are not relevant to the documented element are simply ignored. For instance, all tags are ignored when documenting type constructors, record fields, and class inheritance clauses. Similarly, a @param tag on a class instance variable is ignored.
At last, (**) is the empty documentation comment.
Here is the BNF grammar for the simple markup language used to format text descriptions.
|
| text-element | ::= |
| ∣ | { { 0 … 9 }+ text } | format text as a section header; the integer following { indicates the sectioning level. |
| ∣ | { { 0 … 9 }+ : label text } | same, but also associate the name label to the current point. This point can be referenced by its fully-qualified label in a {! command, just like any other element. |
| ∣ | {b text } | set text in bold. |
| ∣ | {i text } | set text in italic. |
| ∣ | {e text } | emphasize text. |
| ∣ | {C text } | center text. |
| ∣ | {L text } | left align text. |
| ∣ | {R text } | right align text. |
| ∣ | {ul list } | build a list. |
| ∣ | {ol list } | build an enumerated list. |
| ∣ | {{: string } text } | put a link to the given address (given as string) on the given text. |
| ∣ | [ string ] | set the given string in source code style. |
| ∣ | {[ string ]} | set the given string in preformatted source code style. |
| ∣ | {v string v} | set the given string in verbatim style. |
| ∣ | {% string %} | target-specific content (LATEX code by default, see details in 16.2.4.4) |
| ∣ | {! string } | insert a cross-reference to an element (see section 16.2.4.2 for the syntax of cross-references). |
| ∣ | {!modules: string string ... } | insert an index table for the given module names. Used in HTML only. |
| ∣ | {!indexlist} | insert a table of links to the various indexes (types, values, modules, ...). Used in HTML only. |
| ∣ | {^ text } | set text in superscript. |
| ∣ | {_ text } | set text in subscript. |
| ∣ | escaped-string | typeset the given string as is; special characters (’{’, ’}’, ’[’, ’]’ and ’@’) must be escaped by a ’\’ |
| ∣ | blank-line | force a new line. |
A shortcut syntax exists for lists and enumerated lists:
(** Here is a {b list}
- item 1
- item 2
- item 3
The list is ended by the blank line.*)
is equivalent to:
(** Here is a {b list}
{ul {- item 1}
{- item 2}
{- item 3}}
The list is ended by the blank line.*)
The same shortcut is available for enumerated lists, using ’+’ instead of ’-’. Note that only one list can be defined by this shortcut in nested lists.
Cross-references are fully qualified element names, as in the example {!Foo.Bar.t}. This is an ambiguous reference as it may designate a type name, a value name, a class name, etc. It is possible to make explicit the intended syntactic class, using {!type:Foo.Bar.t} to designate a type, and {!val:Foo.Bar.t} a value of the same name.
The list of possible syntactic class is as follows:
| tag | syntactic class |
| module: | module |
| modtype: | module type |
| class: | class |
| classtype: | class type |
| val: | value |
| type: | type |
| exception: | exception |
| attribute: | attribute |
| method: | class method |
| section: | ocamldoc section |
| const: | variant constructor |
| recfield: | record field |
In the case of variant constructors or record field, the constructor or field name should be preceded by the name of the correspond type – to avoid the ambiguity of several types having the same constructor names. For example, the constructor Node of the type tree will be referenced as {!tree.Node} or {!const:tree.Node}, or possibly {!Mod1.Mod2.tree.Node} from outside the module.
In the description of a value, type, exception, module, module type, class or class type, the first sentence is sometimes used in indexes, or when just a part of the description is needed. The first sentence is composed of the first characters of the description, until
outside of the following text formatting : {ul list } , {ol list } , [ string ] , {[ string ]} , {v string v} , {% string %} , {! string } , {^ text } , {_ text } .
The content inside {%foo: ... %} is target-specific and will only be interpreted by the backend foo, and ignored by the others. The backends of the distribution are latex, html, texi and man. If no target is specified (syntax {% ... %}), latex is chosen by default. Custom generators may support their own target prefix.
The HTML tags <b>..</b>, <code>..</code>, <i>..</i>, <ul>..</ul>, <ol>..</ol>, <li>..</li>, <center>..</center> and <h[0-9]>..</h[0-9]> can be used instead of, respectively, {b ..} , [..] , {i ..} , {ul ..} , {ol ..} , {li ..} , {C ..} and {[0-9] ..}.
The following table gives the list of predefined @-tags, with their
syntax and meaning.
| @author string | The author of the element. One author per @author tag. There may be several @author tags for the same element. |
| @deprecated text | The text should describe when the element was deprecated, what to use as a replacement, and possibly the reason for deprecation. |
| @param id text | Associate the given description (text) to the given parameter name id. This tag is used for functions, methods, classes and functors. |
| @raise Exc text | Explain that the element may raise the exception Exc. |
| @return text | Describe the return value and its possible values. This tag is used for functions and methods. |
| @see < URL > text | Add a reference to the URL with the given text as comment. |
| @see 'filename' text | Add a reference to the given file name (written between single quotes), with the given text as comment. |
| @see "document-name" text | Add a reference to the given document name (written between double quotes), with the given text as comment. |
| @since string | Indicate when the element was introduced. |
| @before version text | Associate the given description (text) to the given version in order to document compatibility issues. |
| @version string | The version number for the element. |
You can use custom tags in the documentation comments, but they will have no effect if the generator used does not handle them. To use a custom tag, for example foo, just put @foo with some text in your comment, as in:
(** My comment to show you a custom tag. @foo this is the text argument to the [foo] custom tag. *)
To handle custom tags, you need to define a custom generator, as explained in section 16.3.2.
OCamldoc operates in two steps:
Users can provide their own documentation generator to be used during step 2 instead of the default generators. All the information retrieved during the analysis step is available through the Odoc_info module, which gives access to all the types and functions representing the elements found in the given modules, with their associated description.
The files you can use to define custom generators are installed in the ocamldoc sub-directory of the OCaml standard library.
The type of a generator module depends on the kind of generated documentation. Here is the list of generator module types, with the name of the generator class in the module :
That is, to define a new generator, one must implement a module with the expected signature, and with the given generator class, providing the generate method as entry point to make the generator generates documentation for a given list of modules :
method generate : Odoc_info.Module.t_module list -> unit
This method will be called with the list of analysed and possibly merged Odoc_info.t_module structures.
It is recommended to inherit from the current generator of the same kind as the one you want to define. Doing so, it is possible to load various custom generators to combine improvements brought by each one.
This is done using first class modules (see chapter 8.5).
The easiest way to define a custom generator is the following this example, here extending the current HTML generator. We don’t have to know if this is the original HTML generator defined in ocamldoc or if it has been extended already by a previously loaded custom generator :
module Generator (G : Odoc_html.Html_generator) =
struct
class html =
object(self)
inherit G.html as html
(* ... *)
method generate module_list =
(* ... *)
()
(* ... *)
end
end;;
let _ = Odoc_args.extend_html_generator (module Generator : Odoc_gen.Html_functor);;
To know which methods to override and/or which methods are available, have a look at the different base implementations, depending on the kind of generator you are extending :
Making a custom generator handle custom tags (see 16.2.5) is very simple.
Here is how to develop a HTML generator handling your custom tags.
The class Odoc_html.Generator.html inherits from the class Odoc_html.info, containing a field tag_functions which is a list pairs composed of a custom tag (e.g. "foo") and a function taking a text and returning HTML code (of type string). To handle a new tag bar, extend the current HTML generator and complete the tag_functions field:
module Generator (G : Odoc_html.Html_generator) =
struct
class html =
object(self)
inherit G.html
(** Return HTML code for the given text of a bar tag. *)
method html_of_bar t = (* your code here *)
initializer
tag_functions <- ("bar", self#html_of_bar) :: tag_functions
end
end
let _ = Odoc_args.extend_html_generator (module Generator : Odoc_gen.Html_functor);;
Another method of the class Odoc_html.info will look for the function associated to a custom tag and apply it to the text given to the tag. If no function is associated to a custom tag, then the method prints a warning message on stderr.
You can act the same way for other kinds of generators.
The command line analysis is performed after loading the module containing the documentation generator, thus allowing command line options to be added to the list of existing ones. Adding an option can be done with the function
Odoc_args.add_option : string * Arg.spec * string -> unit
Note: Existing command line options can be redefined using this function.
Let custom.ml be the file defining a new generator class. Compilation of custom.ml can be performed by the following command :
ocamlc -I +ocamldoc -c custom.ml
The file custom.cmo is created and can be used this way :
ocamldoc -g custom.cmo other-options source-files
Options selecting a built-in generator to ocamldoc, such as -html, have no effect if a custom generator of the same kind is provided using -g. If the kinds do not match, the selected built-in generator is used and the custom one is ignored.
It is possible to define a generator class in several modules, which are defined in several files file1.ml[i], file2.ml[i], ..., filen.ml[i]. A .cma library file must be created, including all these files.
The following commands create the custom.cma file from files file1.ml[i], ..., filen.ml[i] :
ocamlc -I +ocamldoc -c file1.ml[i]
ocamlc -I +ocamldoc -c file2.ml[i]
...
ocamlc -I +ocamldoc -c filen.ml[i]
ocamlc -o custom.cma -a file1.cmo file2.cmo ... filen.cmo
Then, the following command uses custom.cma as custom generator:
ocamldoc -g custom.cma other-options source-files