4.3.2 Documenting Modules

Each documented module specified as either a module-path (in the sense of require), in which case the module path is typeset using racketmodname, or by a content-expr. The latter case is triggered by the presence of a #:module-paths clause, which provides a plain module-path for each module-spec, and the plain module-path is used for cross-referencing.

If a #:require-form clause is provided and if #:lang and #:reader are not provided, the given expression produces content to use instead of require for the declaration of the module. The #:require-form clause is useful to suggest a different way of accessing the module instead of through require.

Besides generating text, unless #:no-declare appears as an option, this form expands to a use of declare-exporting with module-paths; the #:use-sources clause, if provided, is propagated to declare-exporting. Consequently, defmodule should be used at most once in a section without #:no-declare, though it can be shadowed with defmodules in sub-sections. Use #:no-declare form when you want to provide a more specific list of modules (e.g., to name both a specific module and one that combines several modules) via your own declare-exporting declaration

Unless #:link-target? is specified with an expression that produces a true value, then the module-paths are also declared as link targets though a part-tag-decl (which means that the defmodule form must appear before any sub-parts). These link targets are referenced via racketmodname, which thus points to the enclosing section, rather than the individual module-paths.

If #:lang is provided as an option, then the module name is shown after #lang (instead of in a require form) to indicate that the module-paths are suitable for use by either require or #lang. If the module path for require is syntactically different from the #lang form, use #:module-paths to provide the require variant (and make each module-spec a content-expr).

If #:reader is provided, then the module name is shown after #reader to indicate that the module path is intended for use as a reader module.

Each option form can appear at most once, and #:lang and #:reader are mutually exclusive.

The decoded pre-flows introduce the module, but need not include all of the module content.

More significantly, the first module-path before #:use-sources plus the module-paths after #:use-sources determine the binding that is documented by each defform, defproc, or similar form within the section that contains the declare-exporting declaration:

• If no #:use-sources clause is supplied, then the documentation applies to the given name as exported by the first module-path.

• If #:use-sources module-paths are supplied, then they are tried in order before the first module-path. The module-path that provides an export with the same symbolic name and free-label-identifier=? to the given name is used as the documented binding. This binding is assumed to be the same as the identifier as exported by the first module-path in the declare-exporting declaration.

Use #:use-sources sparingly, but it is needed when

• bindings are documented as originating from a module M, but the bindings are actually re-exported from some module P; and

• other documented modules also re-export the bindings from P, but they are documented as re-exporting from M.

For example, the parameterize binding of mzscheme is documented as re-exported from racket/base, but parameterize happens to be implemented in a private module and re-exported by both racket/base and mzscheme. Importing parameterize from mzscheme does not go through racket/base, so a search for documentation on parameterize in mzscheme would not automatically connect to the documentation of racket/base. To make the connection, the documentation of racket/base declares the private module to be a source through #:use-sources, so that any re-export of parameterize from the private module connects to the documentation for racket/base (unless a re-export has its own documentation, which would override the automatic connection when searching for documentation).

The initial module-paths sequence can be empty if module-paths are given with #:use-sources. In that case, the rendered documentation never reports an exporting module for identifiers that are documented within the section, but the module-paths in #:use-sources provide a binding context for connecting (via hyperlinks) definitions and uses of identifiers.

The declare-exporting form should be used no more than once per section, since the declaration applies to the entire section, although overriding declare-exporting forms can appear in sub-sections.