Make string additions work for file path completion

With this most simple cases of file path completions should be working now, fixes #493

jedi/api/completion.py

@@ -100,9 +100,11 @@ class Completion:
 
     def completions(self):
         leaf = self._module_node.get_leaf_for_position(self._position, include_prefixes=True)
-        string = _extract_string_while_in_string(leaf, self._position)
+        string, start_leaf = _extract_string_while_in_string(leaf, self._position)
         if string is not None:
-            completions = list(file_name_completions(self._evaluator, string, self._like_name))
+            completions = list(file_name_completions(
+                self._evaluator, self._module_context, start_leaf, string, self._like_name
+            ))
             if completions:
                 return completions
 
@@ -307,15 +309,15 @@ def _extract_string_while_in_string(leaf, position):
         match = re.match(r'^\w*(\'{3}|"{3}|\'|")', leaf.value)
         quote = match.group(1)
         if leaf.line == position[0] and position[1] < leaf.column + match.end():
-            return None
+            return None, None
         if leaf.end_pos[0] == position[0] and position[1] > leaf.end_pos[1] - len(quote):
-            return None
+            return None, None
-        return cut_value_at_position(leaf, position)[match.end():]
+        return cut_value_at_position(leaf, position)[match.end():], leaf
 
     leaves = []
     while leaf is not None and leaf.line == position[0]:
         if leaf.type == 'error_leaf' and ('"' in leaf.value or "'" in leaf.value):
-            return ''.join(l.get_code() for l in leaves)
+            return ''.join(l.get_code() for l in leaves), leaf
         leaves.insert(0, leaf)
         leaf = leaf.get_previous_leaf()
-    return None
+    return None, None

jedi/api/file_name.py

@@ -3,13 +3,15 @@ import os
 from jedi._compatibility import FileNotFoundError
 from jedi.evaluate.names import AbstractArbitraryName
 from jedi.api import classes
+from jedi.evaluate.helpers import get_str_or_none
 
 
-def file_name_completions(evaluator, string, like_name):
+def file_name_completions(evaluator, module_context, start_leaf, string, like_name):
     base_name = os.path.basename(string)
     like_name = base_name + like_name
     string = os.path.dirname(string)
 
+    string = _get_string_additions(module_context, start_leaf) + string
     base_path = os.path.join(evaluator.project._path, string)
     try:
         listed = os.listdir(base_path)
@@ -29,6 +31,35 @@ def file_name_completions(evaluator, string, like_name):
             )
 
 
+def _get_string_additions(module_context, start_leaf):
+    addition = start_leaf.get_previous_leaf()
+    if addition != '+':
+        return ''
+    node = addition.parent
+    string = ''
+    was_addition = True
+    for child_node in reversed(node.children[:node.children.index(addition)]):
+        if was_addition:
+            was_addition = False
+            context = module_context.create_context(node)
+            contexts = context.eval_node(child_node)
+            if len(contexts) != 1:
+                return string
+            c, = contexts
+            s = get_str_or_none(c)
+            if s is None:
+                return string
+            string = s + string
+            continue
+
+        if child_node != '+':
+            break
+        was_addition = True
+        child_node
+    module_context
+    return string
+
+
 class FileName(AbstractArbitraryName):
     api_type = u'path'
     is_context_name = False

test/test_api/test_completion.py

@@ -185,6 +185,11 @@ def test_keyword_completion(Script, code, has_keywords):
         ('example.py', 'r"""\ntest', None, []),
         ('example.py', 'u"""tes\n', (1, 7), ['t' + s]),
         ('example.py', '"""test%stest_cache.p"""' % s, 20, ['y']),
+
+        # Adding
+        ('example.py', '"test" + "%stest_cac' % s, None, ['he.py']),
+        ('example.py', '"test" + "%s" + "test_cac' % s, None, ['he.py']),
+        ('example.py', 'x = 1 + "test', None, [s]),
     ]
 )
 def test_file_path_completions(Script, file, code, column, expected):