Support dict with MultiFileTileSource

[banesullivan-kobold]

Resolves #1638

[manthey]

There are some petty formatting complaints from flake8, and a minor change is needed to not break the Girder use of the source, plus we can add a test. You can apply this diff to get CI to pass:

diff --git a/sources/multi/large_image_source_multi/__init__.py b/sources/multi/large_image_source_multi/__init__.py
index da0e48b0..c6838d57 100644
--- a/sources/multi/large_image_source_multi/__init__.py
+++ b/sources/multi/large_image_source_multi/__init__.py
@@ -419,7 +419,7 @@ class MultiFileTileSource(FileTileSource, metaclass=LruCacheMetaclass):
     _defaultTileSize = 256
     _maxOpenHandles = 6
 
-    def __init__(self, path, **kwargs):
+    def __init__(self, path, **kwargs):  # noqa
         """
         Initialize the tile class.  See the base class for other available
         parameters.
@@ -434,10 +434,10 @@ class MultiFileTileSource(FileTileSource, metaclass=LruCacheMetaclass):
         self._lastOpenSourceLock = threading.RLock()
         # 'c' must be first as channels are special because they can have names
         self._axesList = ['c', 'z', 't', 'xy']
-        if isinstance(path, dict):
+        if isinstance(path, dict) and 'sources' in path:
             self._info = path.copy()
-            self._basePath = "."
-            self._largeImagePath = "."
+            self._basePath = '.'
+            self._largeImagePath = '.'
             try:
                 self._validator.validate(self._info)
             except jsonschema.ValidationError:
diff --git a/test/test_source_multi.py b/test/test_source_multi.py
index fbf74903..8f856b11 100644
--- a/test/test_source_multi.py
+++ b/test/test_source_multi.py
@@ -126,6 +126,22 @@ def testTilesFromMultiString():
         large_image_source_multi.open('invalid' + sourceString)
 
 
+def testTilesFromMultiDict():
+    sourceString = {'sources': [{
+        'sourceName': 'test', 'path': '__none__', 'params': {'sizeX': 10000, 'sizeY': 10000}}]}
+    source = large_image_source_multi.open(sourceString)
+    tileMetadata = source.getMetadata()
+    assert tileMetadata['tileWidth'] == 256
+    assert tileMetadata['tileHeight'] == 256
+    assert tileMetadata['sizeX'] == 10000
+    assert tileMetadata['sizeY'] == 10000
+    assert tileMetadata['levels'] == 7
+    utilities.checkTilesZXY(source, tileMetadata)
+
+    with pytest.raises(Exception):
+        large_image_source_multi.open({'invalid': True})
+
+
 def testTilesFromNonschemaMultiString():
     sourceString = json.dumps({
         'sources': [{

[banesullivan-kobold]

Thank you for taking this over the finish line @manthey!