Add new MavenPackage build system base class (#18185)

* Add new MavenPackage build system base class

* Fix flake8 and doc tests

* More specific regex

* Java 8 required for these packages

6 files changed, 155 insertions, 0 deletions

diff --git a/lib/spack/docs/build_systems.rst b/lib/spack/docs/build_systems.rst
index a68dd99911..84c608077f 100644
--- a/lib/spack/docs/build_systems.rst
+++ b/lib/spack/docs/build_systems.rst
@@ -29,6 +29,7 @@ on these ideas for each distinct build system that Spack supports:
    :maxdepth: 1
    :caption: Make-incompatible
 
+   build_systems/mavenpackage
    build_systems/sconspackage
    build_systems/wafpackage
 
diff --git a/lib/spack/docs/build_systems/mavenpackage.rst b/lib/spack/docs/build_systems/mavenpackage.rst
new file mode 100644
index 0000000000..e8a8a1b86c
--- /dev/null
+++ b/lib/spack/docs/build_systems/mavenpackage.rst
@@ -0,0 +1,84 @@
+.. Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
+   Spack Project Developers. See the top-level COPYRIGHT file for details.
+
+   SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+.. _mavenpackage:
+
+------------
+MavenPackage
+------------
+
+Apache Maven is a general-purpose build system that does not rely
+on Makefiles to build software. It is designed for building and
+managing and Java-based project.
+
+^^^^^^
+Phases
+^^^^^^
+
+The ``MavenPackage`` base class comes with the following phases:
+
+#. ``build`` - compile code and package into a JAR file
+#. ``install`` - copy to installation prefix
+
+By default, these phases run:
+
+.. code-block:: console
+
+   $ mvn package
+   $ install . <prefix>
+
+
+^^^^^^^^^^^^^^^
+Important files
+^^^^^^^^^^^^^^^
+
+Maven packages can be identified by the presence of a ``pom.xml`` file.
+This file lists dependencies and other metadata about the project.
+There may also be configuration files in the ``.mvn`` directory.
+
+^^^^^^^^^^^^^^^^^^^^^^^^^
+Build system dependencies
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Maven requires the ``mvn`` executable to build the project. It also
+requires Java at both build- and run-time. Because of this, the base
+class automatically adds the following dependencies:
+
+.. code-block:: python
+
+   depends_on('java', type=('build', 'run'))
+   depends_on('maven', type='build')
+
+
+In the ``pom.xml`` file, you may see sections like:
+
+.. code-block:: xml
+
+   <requireJavaVersion>
+      <version>[1.7,)</version>
+   </requireJavaVersion>
+   <requireMavenVersion>
+      <version>[3.5.4,)</version>
+   </requireMavenVersion>
+
+
+This specifies the versions of Java and Maven that are required to
+build the package. See
+https://docs.oracle.com/middleware/1212/core/MAVEN/maven_version.htm#MAVEN402
+for a description of this version range syntax. In this case, you
+should add:
+
+.. code-block:: python
+
+   depends_on('java@7:', type='build')
+   depends_on('maven@3.5.4:', type='build')
+
+
+^^^^^^^^^^^^^^^^^^^^^^
+External documentation
+^^^^^^^^^^^^^^^^^^^^^^
+
+For more information on the Maven build system, see:
+https://maven.apache.org/index.html
diff --git a/lib/spack/spack/build_systems/maven.py b/lib/spack/spack/build_systems/maven.py
new file mode 100644
index 0000000000..c7faaf2014
--- /dev/null
+++ b/lib/spack/spack/build_systems/maven.py
@@ -0,0 +1,55 @@
+# Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+
+from llnl.util.filesystem import install_tree, working_dir
+from spack.directives import depends_on
+from spack.package import PackageBase, run_after
+from spack.util.executable import which
+
+
+class MavenPackage(PackageBase):
+    """Specialized class for packages that are built using the
+    Maven build system. See https://maven.apache.org/index.html
+    for more information.
+
+    This class provides the following phases that can be overridden:
+
+    * build
+    * install
+    """
+    # Default phases
+    phases = ['build', 'install']
+
+    # To be used in UI queries that require to know which
+    # build-system class we are using
+    build_system_class = 'MavenPackage'
+
+    depends_on('java', type=('build', 'run'))
+    depends_on('maven', type='build')
+
+    @property
+    def build_directory(self):
+        """The directory containing the ``pom.xml`` file."""
+        return self.stage.source_path
+
+    def build(self, spec, prefix):
+        """Compile code and package into a JAR file."""
+
+        with working_dir(self.build_directory):
+            mvn = which('mvn')
+            if self.run_tests:
+                mvn('verify')
+            else:
+                mvn('package', '-DskipTests')
+
+    def install(self, spec, prefix):
+        """Copy to installation prefix."""
+
+        with working_dir(self.build_directory):
+            install_tree('.', prefix)
+
+    # Check that self.prefix is there after installation
+    run_after('install')(PackageBase.sanity_check_prefix)
diff --git a/lib/spack/spack/cmd/create.py b/lib/spack/spack/cmd/create.py
index 57d4bd7ded..a31b9537b6 100644
--- a/lib/spack/spack/cmd/create.py
+++ b/lib/spack/spack/cmd/create.py
@@ -204,6 +204,17 @@ class QMakePackageTemplate(PackageTemplate):
         return args"""
 
 
+class MavenPackageTemplate(PackageTemplate):
+    """Provides appropriate overrides for Maven-based packages"""
+
+    base_class_name = 'MavenPackage'
+
+    body_def = """\
+    def build(self, spec, prefix):
+        # FIXME: If not needed delete this function
+        pass"""
+
+
 class SconsPackageTemplate(PackageTemplate):
     """Provides appropriate overrides for SCons-based packages"""
 
@@ -430,6 +441,7 @@ templates = {
     'cmake':      CMakePackageTemplate,
     'bundle':     BundlePackageTemplate,
     'qmake':      QMakePackageTemplate,
+    'maven':      MavenPackageTemplate,
     'scons':      SconsPackageTemplate,
     'waf':        WafPackageTemplate,
     'bazel':      BazelPackageTemplate,
@@ -515,6 +527,7 @@ class BuildSystemGuesser:
             (r'/configure$',          'autotools'),
             (r'/configure\.(in|ac)$', 'autoreconf'),
             (r'/Makefile\.am$',       'autoreconf'),
+            (r'/pom\.xml$',           'maven'),
             (r'/SConstruct$',         'scons'),
             (r'/waf$',                'waf'),
             (r'/setup\.py$',          'python'),
diff --git a/lib/spack/spack/pkgkit.py b/lib/spack/spack/pkgkit.py
index 5ffec6caef..ac0a7eee0d 100644
--- a/lib/spack/spack/pkgkit.py
+++ b/lib/spack/spack/pkgkit.py
@@ -21,6 +21,7 @@ from spack.build_systems.autotools import AutotoolsPackage
 from spack.build_systems.cmake import CMakePackage
 from spack.build_systems.cuda import CudaPackage
 from spack.build_systems.qmake import QMakePackage
+from spack.build_systems.maven import MavenPackage
 from spack.build_systems.scons import SConsPackage
 from spack.build_systems.waf import WafPackage
 from spack.build_systems.octave import OctavePackage
diff --git a/lib/spack/spack/test/build_system_guess.py b/lib/spack/spack/test/build_system_guess.py
index 64b37e546e..6c2e3c6be5 100644
--- a/lib/spack/spack/test/build_system_guess.py
+++ b/lib/spack/spack/test/build_system_guess.py
@@ -16,6 +16,7 @@ import spack.stage
         ('configure',      'autotools'),
         ('CMakeLists.txt', 'cmake'),
         ('project.pro',    'qmake'),
+        ('pom.xml',        'maven'),
         ('SConstruct',     'scons'),
         ('waf',            'waf'),
         ('setup.py',       'python'),