[VIPR] Parser for [ meta ] information (#517)

* parse_block_meta

* add comment

* change typo, add docstring, convert numeric value

* update docstring

* add test_meta , remove meta float parsing

* meta test done

* typo float docstring _parse_block_meta

vermouth/ffinput.py

@@ -222,6 +222,44 @@ def _block(self, line, lineno=0):
     def _block_atoms(self, line, lineno=0):
         tokens = collections.deque(_tokenize(line))
         _parse_block_atom(tokens, self.current_block)
+
+    @SectionLineParser.section_parser('moleculetype', 'meta')
+    def _parse_block_meta(self, line, lineno=0):
+        """
+        Parse the meta section and update the object current_block with meta information. 
+        Allow the dictionnary value to be None (in case of flag), string, int or float. 
+        
+        Example :
+            [meta]
+            flag1
+            key value
+            key2 value1 0.37 
+        
+            will give :
+                {   
+                    'flag1' : None, 
+                    'key': 'value', 
+                    'key2': ['value1' , '0.37']
+                }
+        
+        Parameters
+        ----------
+        line: str
+        lineno: str
+        """
+
+        split_line = line.split()
+        key = split_line[0]
+
+        # depend of the number of value(s) 
+        if len(split_line[1:]) == 0 : 
+            value = None
+        elif len(split_line[1:]) == 1 : 
+            value = split_line[1]
+        else: 
+            value = split_line[1:]
+
+        self.current_block.meta[key] = value
 
     @SectionLineParser.section_parser('moleculetype', 'edges',
                                       negate=False, context_type='block')

vermouth/tests/test_ff_files.py

@@ -80,6 +80,26 @@ def test_atoms():
                                       'charge_group': 3, 'custom': 4,
                                       'other': 'plop'}
 
+    @staticmethod
+    def test_meta():
+        lines = """
+        [ moleculetype ]
+        XXX 1
+        [ meta ]
+        flag
+        key1 0.15 ;test
+        key2 value1 value2
+        """
+        lines = textwrap.dedent(lines).splitlines()
+        ff = vermouth.forcefield.ForceField(name='test_ff')
+        vermouth.ffinput.read_ff(lines, ff)
+        block = ff.blocks['XXX']
+        assert len(block.meta) == 3
+        assert block.meta['flag'] == None 
+        assert block.meta['key1'] == '0.15' 
+        assert block.meta['key2'] ==  ['value1', 'value2']
+
+
     @staticmethod
     def test_fixed_number_interaction():
         """