## Ant

### Description

Runs Apache Ant on a supplied buildfile. This can be used to build subprojects. This task must not be used outside of a `target` if it invokes the same build file it is part of.

When the antfile attribute is omitted, the file `build.xml` in the supplied directory (dir attribute) is used.

If no target attribute is supplied, the default target of the new project is used.

By default, all of the properties of the current project will be available in the new project. Alternatively, you can set the inheritAll attribute to false and only "user" properties (i.e., those passed on the command-line) will be passed to the new project. In either case, the set of properties passed to the new project will override the properties that are set in the new project (See also the property task).

You can also set properties in the new project from the old project by using nested `property` tags. These properties are always passed to the new project and any project created in that project regardless of the setting of inheritAll. This allows you to parameterize your subprojects.

When more than one nested `<property>` element would set a property of the same name, the one declared last will win. This is for backwards compatibility reasons even though it is different from the way `<property>` tasks in build files behave.

Properties defined on the command line cannot be overridden by nested `<property>` elements. Since Ant 1.8.0, the same is true for nested structures of `<ant>` tasks: if a build file A invokes B via an `<ant>` task setting a property with a nested `<property>` element and B contains an `<ant>` tasks invoking C, C will see the value set in A, even if B used a nested `<property>` element as well.

References to data types can also be passed to the new project, but by default they are not. If you set the inheritrefs attribute to true, all references will be copied, but they will not override references defined in the new project.

Nested `<reference>` elements can also be used to copy references from the calling project to the new project, optionally under a different id. References taken from nested elements will override existing references that have been defined outside of targets in the new project—but not those defined inside of targets.

### Parameters

Attribute | Description | Required
--- | --- | ---
antfile | the buildfile to use. This file is expected to be a filename relative to the dir attribute given. | No; defaults to build.xml
dir | the directory to use as a basedir for the new Ant project (unless useNativeBasedir is set to true). This will override the basedir setting of the called project. Also serves as the directory to resolve the antfile and output attribute's values (if any). | No; defaults to the current project's basedir, unless inheritall has been set to false, in which case it doesn't have a default value
target | the target of the new Ant project that should be executed. | No; defaults to the new project's default target
output | Filename to write the Ant output to. This is relative to the value of the dir attribute if it has been set or to the basedir of the current project otherwise. | No
inheritAll | If true, pass all properties to the new Ant project. | No; defaults to true
inheritRefs | If true, pass all references to the new Ant project. | No; defaults to false
useNativeBasedir | If set to true, the child build will use the same basedir as it would have used when run from the command line (i.e. the basedir one would expect when looking at the child build's buildfile). Since Ant 1.8.0 | No; defaults to false

### Parameters specified as nested elements

#### property

See the description of the property task.
These properties become equivalent to properties you define on the command line. These are special properties and they will always get passed down, even through additional `<*ant*>` tasks with inheritAll set to false (see above).
Note that the refid attribute points to a reference in the calling project, not in the new one.

#### reference

Used to choose references that shall be copied into the new project, optionally changing their id.

Attribute | Description | Required
--- | --- | ---
refid | The id of the reference in the calling project. | Yes
torefid | The id of the reference in the new project. | No; defaults to the value of refid

#### propertyset

Since Ant 1.6.

You can specify a set of properties to be copied into the new project with propertysets.

#### target

Since Ant 1.6.3.

You can specify multiple targets using nested `<target>` elements instead of using the target attribute. These will be executed as if Ant had been invoked with a single target whose dependencies are the targets so specified, in the order specified.

Attribute | Description | Required
--- | --- | ---
name | The name of the called target. | Yes

### Basedir of the new project

If you set useNativeBasedir to true, the basedir of the new project will be whatever the basedir attribute of the `<project>` element of the new project says (or the new project's directory if the there is no basedir attribute)—no matter what any other attribute of this task says and no matter how deeply nested into levels of `<ant>` invocations this task lives.

If you haven't set useNativeBasedir or set it to false, the following rules apply:

The basedir value of the new project is affected by the two attributes, dir and inheritall, as well as the `<ant>` task's history. The current behaviour is known to be confusing but cannot be changed without breaking backwards compatibility in subtle ways.

If the `<ant>` task is in a "top level" build file, i.e. the project containing the `<ant>` task has not itself been invoked as part of a different `<ant>` (or `<antcall>`) task "higher up", the following table shows the details:

dir attribute | inheritAll attribute | new project's basedir
--- | --- | ---
value provided | true | value of dir attribute
value provided | false | value of dir attribute
omitted | true | basedir of calling project (the one whose build file contains the `<ant>` task).
omitted | false | basedir attribute of the `<project>` element of the new project

If on the other hand the `<ant>` task is already nested into another invocation, the parent invocation's settings affect the outcome of the basedir value. The current task's dir attribute will always win, but if the dir attribute has been omitted an even more complex situation arises:

parent dir attribute | parent inheritAll attribute | current inheritAll attribute | new project's basedir
--- | --- | --- | ---
value provided | any | any | value of parent's dir attribute
omitted | true | true | basedir of parent project (the one whose build file called the build file that contains the current `<ant>` task).
omitted | true | false | basedir of parent project (the one whose build file called the build file that contains the current `<ant>` task).
omitted | false | true | basedir of calling project (the one whose build file contains the current `<ant>` task).
omitted | false | false | basedir attribute of the `<project>` element of the new project

If you add even deeper levels of nesting, things get even more complicated and you need to apply the above table recursively.

If the basedir of the outermost build has been specified as a property on the command line (i.e. `-Dbasedir=some-value` or a `-propertyfile` argument) the value provided will get an even higher priority. For any `<ant>` task that doesn't specify a dir attribute, the new project's basedir will be the value specified on the command line—no matter how deeply nested into layers of build files the task may be.

The same happens if the basedir is specified as a nested `<property>` of an `<ant>` task. The basedir of build files started at deeper levels will be set to the specified value of the property element unless the corresponding Ant tasks set the dir attribute explicitly.

### Examples

These are different ways of using the task:

    <ant antfile="subproject/subbuild.xml" target="compile"/>

    <ant dir="subproject"/>

    <ant antfile="subproject/property_based_subbuild.xml">
      <property name="param1" value="version 1.x"/>
      <property file="config/subproject/default.properties"/>
    </ant>

    <ant inheritAll="false" antfile="subproject/subbuild.xml">
      <property name="output.type" value="html"/>
    </ant>

These lines invoke the same build file:

    <ant antfile="sub1/sub2/build.xml"/>
    <ant antfile="sub2/build.xml" dir="sub1"/>
    <ant antfile="build.xml" dir="sub1/sub2"/>

The build file of the calling project defines some `<path>` elements like this:

    <path id="path1">
        ...
    </path>
    <path id="path2">
        ...
    </path>

and the called build file (`subbuild.xml`) also defines a `<path>` with the id `path1`, but `path2` is not defined; then

    <ant antfile="subbuild.xml" inheritrefs="true"/>

will not override `subbuild`'s definition of `path1`, but make the parent's definition of `path2` available in the `subbuild`, whereas

    <ant antfile="subbuild.xml"/>

as well as

    <ant antfile="subbuild.xml" inheritrefs="false"/>

will neither override `path1` nor copy `path2`, while

    <ant antfile="subbuild.xml" inheritrefs="false">
      <reference refid="path1"/>
    </ant>

will override `subbuild`'s definition of `path1`, and

    <ant antfile="subbuild.xml" inheritrefs="false">
      <reference refid="path1" torefid="path2"/>
    </ant>

will copy the parent's definition of `path1` into the new project using the id `path2`.