doc: Add mix-build-system.

* doc/guix.texi: Document mix-build-system and its most common keyword
arguments.
* gnu/build-system/mix.scm: Update links to documentation without hard
coding an Elixir version.

Change-Id: I68eb76efaaf5639f0eac2d9b674cdb05008e15a4
Reviewed-by: Hartmut Goebel <h.goebel@crazy-compilers.com>
Signed-off-by: Sharlatan Hellseher <sharlatanus@gmail.com>

2 files changed, 32 insertions, 4 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 8ce1492a3b4..95e9ebb35bb 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -10116,6 +10116,34 @@ directory, the parameter @code{#:javascript-files} can be used to
 specify a list of file names to feed to the minifier.
 @end defvar
 
+@defvar mix-build-system
+This is a variable exported by @code{guix build-system mix}.  It implements
+the standard build procedure used by Elixr programs with
+@url{https://hexdocs.pm/mix/Mix.html,Mix}, which consists
+of running @command{mix compile}, thereby creating bytecode.
+
+The API is similar to the @var{gnu-build-system}, with some specifics for
+Elixir:
+@itemize
+@item
+@code{#:tests?} is a boolean, @code{#true} by default, determining whether tests
+for the current build have to be run or not.
+@item
+@code{#:test-flags} is a list of arguments append to the @command{mix test}
+invocation.  It defaults to @code{'()}.
+@item
+@code{#:mix-exs}, changes the full path to the @code{mix.exs}
+file.  It defaults to @code{"mix.exs"}.  Please refer to
+@url{https://hexdocs.pm/mix/Mix.html#module-environment-variables,upstream}
+documentation for more details.
+@item
+@code{#:mix-path}, appends extra code paths.  It
+defaults to @code{#f}.  Please refer to
+@url{https://hexdocs.pm/mix/Mix.html#module-environment-variables,upstream}
+documentation for more details.
+@end itemize
+@end defvar
+
 @defvar mozilla-build-system
 This variable is exported by @code{(guix build-system mozilla)}.  It
 sets the @code{--target} and @code{--host} configuration flags to what
diff --git a/guix/build-system/mix.scm b/guix/build-system/mix.scm
index 4bfa4dcf0cb..e929e1df526 100644
--- a/guix/build-system/mix.scm
+++ b/guix/build-system/mix.scm
@@ -66,9 +66,9 @@ See: https://github.com/hexpm/specifications/blob/main/endpoints.md"
 
 ;; A number of environment variables specific to the Mix build system are
 ;; reflected here.  They are documented at
-;; https://hexdocs.pm/mix/1.15.7/Mix.html#module-environment-variables.  Other
+;; https://hexdocs.pm/mix/Mix.html#module-environment-variables.  Other
 ;; parameters located in mix.exs are defined at
-;; https://hexdocs.pm/mix/1.15.7/Mix.Project.html#module-configuration
+;; https://hexdocs.pm/mix/Mix.Project.html#module-configuration
 (define* (mix-build name
                     inputs
                     #:key
@@ -90,9 +90,9 @@ See: https://github.com/hexpm/specifications/blob/main/endpoints.md"
   "Build SOURCE using Elixir, and with INPUTS."
 
   ;; Check the documentation of :build_per_environment here:
-  ;; https://hexdocs.pm/mix/1.15.7/Mix.Project.html#module-configuration And
+  ;; https://hexdocs.pm/mix/Mix.Project.html#module-configuration And
   ;; "Environments" here:
-  ;; https://hexdocs.pm/mix/1.15.7/Mix.html#module-environments
+  ;; https://hexdocs.pm/mix/Mix.html#module-environments
   (define mix-environments
     (if build-per-environment
         `("prod" ,@(if tests? '("test") '()))