# Profiles

In Leiningen 2.x you can change the configuration of your project by
applying various profiles. For instance, you may want to have a few
extra test data directories on the classpath during development
without including them in the jar, or you may want to have Swank
Clojure available in every project you hack on without modifying every
single project.clj you use.

By default the `:dev`, `:provided`, `:user`, and `:base` profiles are
activated for each task, but the settings they provide are not
propagated downstream to projects that depend upon yours. Each profile
is defined as a map which gets merged into your project map.

You can place any arbitrary defproject entries into a given profile
and they will be merged into the project map when that profile is
active.

The example below adds a "dummy-data" resources directory during
development and a dependency upon "midje" that's only used for tests.

```clj
(defproject myproject "0.5.0-SNAPSHOT"
  :description "A project for doing things."
  :dependencies [[org.clojure/clojure "1.4.0"]]
  :profiles {:dev {:resources-path ["dummy-data"]
                   :dependencies [[midje "1.4.0"]]}})
```


## Declaring Profiles

In addition to `project.clj`, profiles also can be specified in `profiles.clj`
within the project root. Profiles specified in `profiles.clj` will override
profiles in `project.clj`, so this can be used for project-specific overrides
that you don't want committed in version control.

Global profiles can also be specified in `~/.lein/profiles.clj`. These will be
available in all projects managed by Leiningen, though those profiles will be
overridden by profiles of the same name in the specified in the project.

The `:user` profile is separate from `:dev`; the latter is intended to be
specified in the project itself. In order to avoid collisions, the project
should never define a `:user` profile, nor should `~/.lein/profiles.clj` define
a `:dev` profile. Use the `show-profiles` task to see what's available.

If you want to access dependencies during development time for any
project place them in your `:user` profile. Your
`~/.lein/profiles.clj` file could look something like this:

```clj
{:user {:plugins [[lein-swank "1.4.0"]
                  [lein-pprint "1.1.1"]]}}
```

Profiles are merged by taking each key in the project map or profile
map, combining the value if it's a collection and replacing it if it's
not. Profiles specified earlier take precedence when replacing. The
dev profile takes precedence over user by default. Maps are merged
recursively, sets are combined with `clojure.set/union`, and
lists/vectors are concatenated. You can add hints via metadata that a
given value should take precedence (`:replace`) or defer to values
from a different profile (`:displace`) if you want to override this
logic:

```clj
{:profiles {:dev {:prep-tasks ^:replace ["clean" "compile"]
                  :aliases ^:displace {"launch" "run"}}}}
```

The exception to this merge logic is that plugins and dependencies
have custom de-duplication logic since they must be specified as
vectors even though they behave like maps (because it only makes sense
to have a single version of a given dependency present at once). The
replace/displace metadata hints still apply though.

## Activating Profiles

Another use of profiles is to test against various sets of dependencies:

```clj
(defproject swank-clojure "1.5.0-SNAPSHOT"
  :description "Swank server connecting Clojure to Emacs SLIME"
  :dependencies [[org.clojure/clojure "1.2.1"]
                 [clj-stacktrace "0.2.4"]
                 [cdt "1.2.6.2"]]
  :profiles {:1.3 {:dependencies [[org.clojure/clojure "1.3.0"]]}
             :1.4 {:dependencies [[org.clojure/clojure "1.4.0-beta1"]]}})
```

To activate other profiles for a given run, use the `with-profile`
higher-order task:

    $ lein with-profile 1.3 test :database

Multiple profiles may be combined with commas:

    $ lein with-profile qa,user test :database

Multiple profiles may be executed in series with colons:

    $ lein with-profile 1.3:1.4 test :database

## Composite Profiles

Sometimes it is useful to define a profile as a combination of other
profiles. To do this, just use a vector instead of a map as the profile value.
This can be used to avoid duplication:

```clj
{:shared {:port 9229, :protocol \"https\"}
 :qa [:shared {:servers [\"qa.mycorp.com\"]}]
 :stage [:shared {:servers [\"stage.mycorp.com\"]}]
 :production [:shared {:servers [\"prod1.mycorp.com\", \"prod1.mycorp.com\"]}]}
```

Composite profiles are used by Leiningen internally for the `:default`
profile, which is the profile used if you don't change it using
`with-profile`. The `:default` profile is defined to be a composite of
`[:dev :provided :user :base]`, but you can change this in your
`project.clj` just like any other profile.

## Debugging

To see how a given profile affects your project map, use the
[lein-pprint](https://github.com/technomancy/leiningen/tree/master/lein-pprint)
plugin:

    $ lein with-profile 1.4 pprint
    {:compile-path "/home/phil/src/leiningen/lein-pprint/classes",
     :group "lein-pprint",
     :source-path ("/home/phil/src/leiningen/lein-pprint/src"),
     :dependencies
     ([org.clojure/tools.nrepl "0.0.5" :exclusions [org.clojure/clojure]]
      [clojure-complete "0.1.4" :exclusions [org.clojure/clojure]]
      [org.thnetos/cd-client "0.3.3" :exclusions [org.clojure/clojure]]),
     :target-path "/home/phil/src/leiningen/lein-pprint/target",
     :name "lein-pprint",
     [...]
     :description "Pretty-print a representation of the project map."}

In order to prevent profile settings from being propagated to other
projects that depend upon yours, the `:default` profiles are removed from
your project when generating the pom, jar, and uberjar. Profiles
activated through an explicit `with-profile` invocation will be
preserved. The `repl` and `test` tasks use their own profile in order
to inject needed functionality.