Implemented Application.get_file_in_previous_generation.

2 files changed, 40 insertions, 0 deletions

diff --git a/obnam/app.py b/obnam/app.py
index 19e2cc54..a84ea939 100644
--- a/obnam/app.py
+++ b/obnam/app.py
@@ -241,6 +241,14 @@ class Application:
         
         return unchanged
 
+    def get_file_in_previous_generation(self, pathname):
+        """Return non-directory file in previous generation, or None."""
+        gen = self.get_previous_generation()
+        if gen:
+            return self.get_store().lookup_file(gen, pathname)
+        else:
+            return None
+
     def add_to_filegroup(self, fg, filename):
         """Add a file to a filegroup."""
         self._context.progress.update_current_action(filename)
diff --git a/obnam/appTests.py b/obnam/appTests.py
index 290b4850..4e6629f0 100644
--- a/obnam/appTests.py
+++ b/obnam/appTests.py
@@ -426,6 +426,38 @@ class ApplicationGetDirInPreviousGenerationTests(unittest.TestCase):
         self.failUnlessEqual(dir.get_name(), "pink")
 
 
+class ApplicationGetFileInPreviousGenerationTests(unittest.TestCase):
+
+    class MockStore:
+    
+        def __init__(self):
+            self.dict = {
+                "pink": obnam.cmp.Component(obnam.cmp.FILE, [])
+            }
+    
+        def lookup_file(self, gen, pathname):
+            return self.dict.get(pathname, None)
+
+    def setUp(self):
+        context = obnam.context.Context()
+        self.app = obnam.Application(context)
+        self.app._store = self.MockStore()
+        self.app.set_previous_generation("prevgen")
+
+    def testReturnsNoneIfPreviousGenerationIsUnset(self):
+        self.app.set_previous_generation(None)
+        self.failUnlessEqual(self.app.get_file_in_previous_generation("xx"),
+                             None)
+
+    def testReturnsNoneIfFileDidNotExist(self):
+        self.failUnlessEqual(self.app.get_file_in_previous_generation("xx"),
+                             None)
+
+    def testReturnsFileComponentIfFileDidExist(self):
+        cmp = self.app.get_file_in_previous_generation("pink")
+        self.failUnlessEqual(cmp.get_kind(), obnam.cmp.FILE)
+
+
 class ApplicationSelectFilesToBackUpTests(unittest.TestCase):
 
     class MockStore: