This Leiningen plugin
provides the benefits of Maven
multi-module projects
without setting your hair on fire. It works well for a related suite
of Leiningen projects stored in a single SCM repository.
Features include the building of automatically-discovered "child"
projects in dependency order, flexible project inheritance based on
Leiningen profiles, a simple dependency management mechanism, and
automatic checkout dependencies.
Simply include [lein-modules "0.3.11"] in the :plugins vector of
every associated module's project.clj.
Minimum supported versions:
Leiningen: 2.3.4
Clojure: 1.5.1
Usage
From any "parent" project, use the modules higher-order task to
build its "child" projects in the correct order. When you first create
a project that has inter-dependent modules, you must install them to
your local repo prior to running any task that may attempt to resolve
them. You can do this easily from your root project:
$ lein modules install
Once installed, you can run any task you like, e.g.:
$ lein modules test
$ lein modules deps :tree
$ lein modules do clean, jar
$ lein modules analias
By default, the task is not applied to the project in which you run
the modules task, only the child projects it finds. You can override
this behavior by adding "." to the :dirs vector.
In a child module, just use lein as you normally would, relying on
the plugin's implicit middleware to:
merge all ancestors' profiles
update the child's :dependencies from its ancestors' :versions
maps.
See the Configuration section for more details on
the supported options.
Checkout Dependencies
Run the following command to automatically create
checkout dependencies
for each related module:
$ lein modules :checkouts
Comparison to lein-sub
Both lein-modules and
lein-sub support project
aggregation. The modules task is feature-compatible with the sub
task.
$ lein sub install
$ lein sub -s "foo:bar" jar
$ lein modules install
$ lein modules :dirs "foo:bar" jar
But there are some important differences:
lein-sub builds the modules in the order listed in the :sub
vector, but lein-modules always builds them in dependency order,
regardless of the order of its :dirs vector
lein-sub runs the tasks for each module in the same Leiningen
process, while lein-modules spawns a new process identified by the
:subprocess config option, which defaults to "lein"
lein-modules supports automatic discovery of child modules so that
you don't have to set :dirs at all
lein-modules simplifies your release process by eliminating the
redundant references to your project's current version in
interdependent modules, e.g.
[:dependencies [[your-project/common :version]], resolving the
:version keyword to the value from the dependent's own project map
Release Management
Leiningen 2.4.0 provides a
new release task.
To use it with lein-modules, some configuration of its
:release-tasks vector is required.
Invoking lein modules release isn't feasible because all the modules
reside in the same repo. Only the first would succeed and subsequent
modules would error due to the release tag already existing. The
version in each modules' project.clj must be changed before
committing and tagging the release. So instead of lein modules release, we run lein release in the parent project and adjust its
:release-tasks to invoke the "change" and "deploy" tasks for the
modules:
We set :subprocess to nil because the release task binds a dynamic
variable to the value of its optional level argument that will be
lost in a new subprocess.
We also take advantage of the :inherited profile so we don't have
to redundantly configure the "releases" repo in every child module.
Configuration
The modules task will attempt to discover child projects
automatically, making the default assumption that each child project
resides in an immediate subdirectory of its parent.
Optionally, a :modules map may be added to your project, containing
any of the following keys:
:inherited - This is just a Leiningen profile. You could
alternatively put it in :profiles to emphasize that point. The
implicit plugin middleware will create composite profiles for all
the profile maps found among a project's ancestors, with the most
immediate taking precedence, i.e. a parent profile will be applied
after a grandparent. If found, the :inherited profiles will be
applied before the :default ones, but profile inheritance occurs
whether you define an :inherited profile or not, because all
profile maps from ancestors are automatically added to the child
(excluding :base, :system, :user and any in the leiningen
namespace). Therefore, ancestor profiles such as :dev,
:provided, :production or :whatever are [un]merged in the
child as appropriate for the task at hand.
:versions - A mapping of dependency symbols to version strings. As
a simpler alternative to Maven's dependency management, versions for
child module dependencies and parent vectors will be expanded from
this map. It is recursively searched -- values may be keys in the
same map -- for a version string using the following elements of the
dependency vector, in order:
the fully-qualified id field, group-id/artifact-id
the version field
the artifact id
the group id
The first non-nil value is returned, otherwise the dependency's
version is returned. This allows you to concisely maintain the
versions of your child modules' shared dependencies in a single
place. And like the :inherited profile, when multiple :versions
maps are found among ancestors, the most immediate take precedence.
The project map's :version is automatically included in the
:versions map, so your interdependent modules may use that without
configuring this option at all.
:dirs - A vector of strings denoting the relative paths to the
project's child modules. Normally, they're discovered automatically
by searching for project.clj files beneath the project's :root
with a related parent, but this vector can override that behavior by
specifying exactly which directories contain child modules. This
vector is only required when your module hierarchy doesn't match
your directory hierarchy, e.g. when a parent module is in a sibling
directory. Regardless of this option, build order is always
determined by module interdependence.
:parent - A string denoting the relative path to the parent
project's directory. If unset, the value of the :relative-path of
Leiningen's :parent vector will be used, and if that's unset, the
default value is "..". You can explicitly set it to nil to
signify that the project has no parent.
:subprocess - The name of the executable invoked by the modules
subtask for each child module in a separate process. Its default
value is "lein". You can optionally set it to nil, which will
speed up your build considerably since it runs every child module's
task in the same process that invoked lein modules. This should be
ok for most tasks, but can sometimes lead to surprises, e.g. hooks
from one project can infect others, and the current working
directory won't match the :root of the child project. Still, for
common tasks like clean it can be convenient to configure a
:fast profile that sets :subprocess to nil for projects with
lots of child modules.
Example
Hopefully, an example will clarify the above.
Note the underscores in the dependency vectors, which serve as a
placeholder for the string returned from the :versions map. Whatever
you set the version to in your dependency vector will be overwritten
if a version is found in :versions. Otherwise, whatever is there
will remain there. And if a mapping for the symbol can't be found, the
version itself will be tried as a key.
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