Cache open blend files

This simplifies blend file handling, ensuring that blend files are only
opened once. Otherwise it would be harder to handle things like dependency
diamonds (libraries that are referenced via multiple paths through multiple
other libraries).

blender_asset_tracer/tracer/__init__.py

@@ -23,9 +23,9 @@ def deps(bfilepath: pathlib.Path) -> typing.Iterator[result.BlockUsage]:
     :param bfilepath: File to open.
     """
 
-    with blendfile.BlendFile(bfilepath) as bfile:
-        for block in asset_holding_blocks(file2blocks.iter_blocks(bfile)):
-            yield from blocks2assets.iter_assets(block)
+    bfile = blendfile.open_cached(bfilepath)
+    for block in asset_holding_blocks(file2blocks.iter_blocks(bfile)):
+        yield from blocks2assets.iter_assets(block)
 
 
 def asset_holding_blocks(blocks: typing.Iterable[blendfile.BlendFileBlock]) \

blender_asset_tracer/tracer/file2blocks.py

@@ -86,9 +86,8 @@ class _BlockIterator:
                 continue
 
             log.debug('Expanding %d blocks in %s', len(idblocks), lib_path)
-
-            with blendfile.BlendFile(lib_path) as libfile:
-                yield from self.iter_blocks(libfile, idblocks)
+            libfile = blendfile.open_cached(lib_path)
+            yield from self.iter_blocks(libfile, idblocks)
 
     def _queue_all_blocks(self, bfile: blendfile.BlendFile):
         log.debug('Queueing all blocks from file %s', bfile.filepath)