Add version attribute to force fields

foyer/forcefield.py

@@ -342,6 +342,8 @@ def __init__(self, forcefield_files=None, name=None, validation=True, debug=Fals
         self.atomTypeElements = dict()
         self._included_forcefields = dict()
         self.non_element_types = dict()
+        self._version = None
+        self._name = None
 
         all_files_to_load = []
         if forcefield_files is not None:
@@ -368,9 +370,25 @@ def __init__(self, forcefield_files=None, name=None, validation=True, debug=Fals
         finally:
             for ff_file_name in preprocessed_files:
                 os.remove(ff_file_name)
+
+        if isinstance(forcefield_files, str):
+            self._version = self._parse_version_number(forcefield_files)
+            self._name = self._parse_name(forcefield_files)
+        elif isinstance(forcefield_files, list):
+            self._version = [self._parse_version_number(f) for f in forcefield_files]
+            self._name = [self._parse_name(f) for f in forcefield_files]
+
         self.parser = smarts.SMARTS(self.non_element_types)
         self._SystemData = self._SystemData()
 
+    @property
+    def version(self):
+        return self._version
+
+    @property
+    def name(self):
+        return self._name
+
     @property
     def included_forcefields(self):
         if any(self._included_forcefields):
@@ -385,6 +403,30 @@ def included_forcefields(self):
             self._included_forcefields[basename] = ff_filepath
         return self._included_forcefields
 
+    def _parse_version_number(self, forcefield_file):
+        with open(forcefield_file, 'r') as f:
+            tree = ET.parse(f)
+            root = tree.getroot()
+            try:
+                return root.attrib['version']
+            except KeyError:
+                warnings.warn(
+                    'No force field version number found in force field XML file.'
+                )
+                return None
+
+    def _parse_name(self, forcefield_file):
+        with open(forcefield_file, 'r') as f:
+            tree = ET.parse(f)
+            root = tree.getroot()
+            try:
+                return root.attrib['name']
+            except KeyError:
+                warnings.warn(
+                    'No force field name found in force field XML file.'
+                )
+                return None
+
     def _create_element(self, element, mass):
         if not isinstance(element, elem.Element):
             try:

foyer/forcefields/ff.xsd

@@ -255,6 +255,8 @@
         <xs:element ref="CustomTorsionForce" minOccurs="0"/>
         <xs:element ref="NonbondedForce" minOccurs="0"/>
       </xs:all>
+      <xs:attribute type="xs:string" name="version" use="optional"/>
+      <xs:attribute type="xs:string" name="name" use="optional"/>
     </xs:complexType>
     <xs:key name="atomtype_name_key">
       <xs:selector xpath="AtomTypes/Type" />

foyer/tests/files/lj.xml

@@ -0,0 +1,8 @@
+<ForceField version="0.4.1" name="LJ">
+ <AtomTypes>
+   <Type name="LJ" class="" element="_LJ" mass="1.0" def="[_LJ]" desc="Generic LJ particle"/>
+ </AtomTypes>
+ <NonbondedForce coulomb14scale="0.5" lj14scale="0.5">
+  <Atom type="LJ" charge="0" sigma="1.0" epsilon="1.0"/>
+ </NonbondedForce>
+</ForceField>

foyer/tests/files/lj2.xml

@@ -0,0 +1,8 @@
+<ForceField version="4.8.2" name="JL">
+ <AtomTypes>
+   <Type name="JL" class="" element="_JL" mass="1.0" def="[_JL]" desc="Generic JL particle"/>
+ </AtomTypes>
+ <NonbondedForce coulomb14scale="0.5" lj14scale="0.5">
+  <Atom type="JL" charge="0" sigma="1.0" epsilon="1.0"/>
+ </NonbondedForce>
+</ForceField>

foyer/tests/test_forcefield.py

@@ -504,3 +504,12 @@ def test_write_xml_overrides():
         elif attributes['name'] == 'opls_146':
             assert attributes['overrides'] == 'opls_144'
             assert str(item.xpath('comment()')) == '[<!--Note: original overrides="opls_144"-->]'
+
+def test_load_metadata():
+    lj_ff = Forcefield(get_fn('lj.xml'))
+    assert lj_ff.version == '0.4.1'
+    assert lj_ff.name == 'LJ'
+
+    lj_ff = Forcefield(forcefield_files=[get_fn('lj.xml'), get_fn('lj2.xml')])
+    assert lj_ff.version == ['0.4.1', '4.8.2']
+    assert lj_ff.name == ['LJ', 'JL']