Use file object directly in temporary_config() (#1598)

The context manager uses `NamedTemporaryFile` to store the current
configuration, to later restore them. Instead of passing the file object
directly to the save function, it just passes the file name, i.e. the
save (and the load function) will open the file again, which is in
itself not a problem. However, on the Github Windows image this leads to
a permission error (using the created file object is fine).

This commit solves this by adding the `file` argument to `Config.save()`
that allows to pass a file object directly to the function. The same
change is applied to the load function of the config object.

dace/config.py

@@ -3,6 +3,7 @@
 import os
 import platform
 import tempfile
+import io
 from typing import Any, Dict
 import yaml
 import warnings
@@ -39,10 +40,11 @@ def temporary_config():
             Config.set("optimizer", "autooptimize", value=True)
             foo()
     """
-    with tempfile.NamedTemporaryFile() as fp:
-        Config.save(fp.name)
+    with tempfile.NamedTemporaryFile(mode='w+t') as fp:
+        Config.save(file=fp)
         yield
-        Config.load(fp.name)
+        fp.seek(0)  # rewind to the beginning of the file.
+        Config.load(file=fp)
 
 
 def _env2bool(envval):
@@ -157,19 +159,21 @@ def initialize():
             Config.save(all=False)
 
     @staticmethod
-    def load(filename=None):
+    def load(filename=None, file=None):
         """
         Loads a configuration from an existing file.
         
         :param filename: The file to load. If unspecified,
                          uses default configuration file.
+        :param file: Load the configuration from the file object.
         """
-        if filename is None:
-            filename = Config._cfg_filename
 
-        # Read configuration file
-        with open(filename, 'r') as f:
-            Config._config = yaml.load(f.read(), Loader=yaml.SafeLoader)
+        if file is not None:
+            assert filename is None
+            Config._config = yaml.load(file.read(), Loader=yaml.SafeLoader)
+        else:
+            with open(filename if filename else Config._cfg_filename, 'r') as f:
+                Config._config = yaml.load(f.read(), Loader=yaml.SafeLoader)
 
         if Config._config is None:
             Config._config = {}
@@ -191,16 +195,17 @@ def load_schema(filename=None):
             Config._config_metadata = yaml.load(f.read(), Loader=yaml.SafeLoader)
 
     @staticmethod
-    def save(path=None, all: bool = False):
+    def save(path=None, all: bool = False, file=None):
         """
         Saves the current configuration to a file.
 
         :param path: The file to save to. If unspecified,
                      uses default configuration file.
         :param all: If False, only saves non-default configuration entries.
                     Otherwise saves all entries.
+        :param file: A file object to use directly.
         """
-        if path is None:
+        if path is None and file is None:
             path = Config._cfg_filename
             if path is None:
                 # Try to create a new config file in reversed priority order, and if all else fails keep config in memory
@@ -217,8 +222,11 @@ def save(path=None, all: bool = False):
                 return
 
         # Write configuration file
-        with open(path, 'w') as f:
-            yaml.dump(Config._config if all else Config.nondefaults(), f, default_flow_style=False)
+        if file is not None:
+            yaml.dump(Config._config if all else Config.nondefaults(), file, default_flow_style=False)
+        else:
+            with open(path, 'w') as f:
+                yaml.dump(Config._config if all else Config.nondefaults(), f, default_flow_style=False)
 
     @staticmethod
     def get_metadata(*key_hierarchy):

tests/config_test.py

@@ -1,5 +1,5 @@
 # Copyright 2019-2021 ETH Zurich and the DaCe authors. All rights reserved.
-from dace.config import set_temporary, Config
+from dace.config import Config, set_temporary, temporary_config
 
 
 def test_set_temporary():
@@ -10,5 +10,15 @@ def test_set_temporary():
     assert Config.get(*path) == current_value
 
 
+def test_temporary_config():
+    path = ["compiler", "build_type"]
+    current_value = Config.get(*path)
+    with temporary_config():
+        Config.set(*path, value="I'm not a build type")
+        assert Config.get(*path) == "I'm not a build type"
+    assert Config.get(*path) == current_value
+
+
 if __name__ == '__main__':
     test_set_temporary()
+    test_temporary_config()