add method to compute recursive cache id

The cache id will be used as a prefix in filenames in the cache
directory. The new way of computing it includes the cache ids of
any components so that if chunk A is included in stratum B, and
A changes, the new version of A has a new cache id, which means
that when we compute cache id for B, it also changes. This will
allow us to easily find out if we need to rebuild B.

The test repository is split into two: one for the chunk, one for
the stratum and system morphologies. This is so that the rebuild
test can modify just the chunk, and does not need to trigger both builds.

Signed-off-by: Lars Wirzenius <liw@liw.fi>

1 files changed, 38 insertions, 21 deletions

diff --git a/morphlib/builder.py b/morphlib/builder.py
index 86785e68..4f7dc432 100644
--- a/morphlib/builder.py
+++ b/morphlib/builder.py
@@ -46,9 +46,6 @@ class BinaryBlob(object):
         # Stopwatch to measure build times
         self.build_watch = morphlib.stopwatch.Stopwatch()
 
-    def dict_key(self):
-        return {}
-    
     def needs_built(self):
         return []
 
@@ -485,10 +482,9 @@ class Builder(object):
             raise Exception('Unknown kind of morphology: %s' % morph.kind)
         self.dump_memory_profile('after creating Chunk/Stratum/...')
 
-        dict_key = blob.dict_key()
-        self.complete_dict_key(dict_key, morph.name, repo, ref)
-        logging.debug('completed dict_key:\n%s' % repr(dict_key))
-        self.dump_memory_profile('after completing cache key')
+        cache_id = self.get_cache_id(repo, ref, filename)
+        logging.debug('cachae id: %s' % repr(cache_id))
+        self.dump_memory_profile('after computing cache id')
 
         blob.builddir = self.tempdir.join('%s.build' % morph.name)
         blob.destdir = self.tempdir.join('%s.inst' % morph.name)
@@ -497,7 +493,7 @@ class Builder(object):
             os.mkdir(blob.staging)
         blob.settings = self.settings
         blob.msg = self.msg
-        blob.cache_prefix = self.cachedir.name(dict_key)
+        blob.cache_prefix = self.cachedir.name(cache_id)
         blob.tempdir = self.tempdir
         blob.dump_memory_profile = self.dump_memory_profile
 
@@ -553,19 +549,6 @@ class Builder(object):
             self.msg('Unpacking chunk %s into staging' % chunk_name)
             morphlib.bins.unpack_binary(chunk_filename, staging_dir)
             
-    def complete_dict_key(self, dict_key, name, repo, ref):
-        '''Fill in default fields of a cache's dict key.'''
-
-        if repo and ref:
-            abs_ref = morphlib.git.get_commit_id(repo, ref)
-        else:
-            abs_ref = ''
-
-        dict_key['name'] = name
-        dict_key['arch'] = morphlib.util.arch()
-        dict_key['repo'] = repo
-        dict_key['ref'] = abs_ref
-
     def get_morph_from_git(self, repo, ref, filename):
         morph_text = morphlib.git.get_morph_text(repo, ref, filename)
         f = StringIO.StringIO(morph_text)
@@ -574,3 +557,37 @@ class Builder(object):
                                                self.settings['git-base-url'])
         return morph
 
+    def get_cache_id(self, repo, ref, morph_filename):
+        logging.debug('get_cache_id(%s, %s, %s)' %
+                      (repo, ref, morph_filename))
+        morph = self.get_morph_from_git(repo, ref, morph_filename)
+        if morph.kind == 'chunk':
+            kids = []
+        elif morph.kind == 'stratum':
+            kids = []
+            for source in morph.sources:
+                kid_repo = source['repo']
+                kid_ref = source['ref']
+                kid_filename = (source['morph'] 
+                                if 'morph' in source 
+                                else source['name'])
+                kid_filename = '%s.morph' % kid_filename
+                kid_cache_id = self.get_cache_id(kid_repo, kid_ref, 
+                                                 kid_filename)
+                kids.append(kid_cache_id)
+        elif morph.kind == 'system':
+            kids = []
+            for stratum in morph.strata:
+                kid_filename = '%s.morph' % stratum
+                kid_cache_id = self.get_cache_id(repo, ref, kid_filename)
+                kids.append(kid_cache_id)
+        else:
+            raise NotImplementedError('unknown morph kind %s' % morph.kind)
+        dict_key = {
+            'name': morph.name,
+            'arch': morphlib.util.arch(),
+            'ref': morphlib.git.get_commit_id(repo, ref),
+            'kids': ''.join(self.cachedir.key(k) for k in kids),
+        }
+        return dict_key
+