ENHANCE: Make Config a singleton

surround/__init__.py

@@ -4,7 +4,7 @@
 from .state import State
 from .stage import Validator, Filter, Estimator
 from .visualiser import Visualiser
-from .config import Config
+from .config import Config, has_config
 from .assembler import Assembler
 from .runners import Runner, RunMode
 

surround/assembler.py

@@ -7,7 +7,7 @@
 from abc import ABC
 from datetime import datetime
 
-from .config import Config
+from .config import Config, has_config
 from .stage import Filter, Estimator, Validator
 from .visualiser import Visualiser
 
@@ -57,7 +57,8 @@ class Assembler(ABC):
     """
 
     # pylint: disable=too-many-instance-attributes
-    def __init__(self, assembler_name=""):
+    @has_config
+    def __init__(self, assembler_name="", config=None):
         """
         Constructor for an Assembler pipeline:
 
@@ -66,7 +67,7 @@ def __init__(self, assembler_name=""):
         """
 
         self.assembler_name = assembler_name
-        self.config = Config(auto_load=True)
+        self.config = config
         self.stages = None
         self.estimator = None
         self.validator = None

surround/config.py

@@ -1,5 +1,6 @@
 import ast
 import os
+import functools
 
 from pathlib import Path
 from collections.abc import Mapping
@@ -51,6 +52,19 @@ class Config(Mapping):
         SURRROUND_PREDICT_DEBUG=False
     """
 
+    __instance = None
+
+    @staticmethod
+    def instance():
+        """
+        Static method which returns the a singleton instance of Config.
+        """
+
+        if not Config.__instance:
+            Config.__instance = Config(auto_load=True)
+
+        return Config.__instance
+
     def __init__(self, project_root=None, package_path=None, auto_load=False):
         """
         Constructor of the Config class, loads the default YAML file into storage.
@@ -373,3 +387,40 @@ def __len__(self):
         """
 
         return len(self._storage)
+
+def has_config(func=None, name="config", filename=None):
+    """
+    Decorator that injects the singleton config instance into the arguments of the function.
+    e.g.
+    ```
+        @has_config
+        def some_func(config):
+            value = config.get_path("some.config")
+            ...
+
+        @has_config(name="global_config")
+        def other_func(global_config, new_config):
+            value = config.get_path("some.config")
+
+        @has_config(filename="override.yaml")
+        def some_func(config):
+            value = config.get_path("override.value")
+    ```
+    """
+
+    @functools.wraps(func)
+    def function_wrapper(*args, **kwargs):
+        config = Config.instance()
+        if filename:
+            path = os.path.join(config.get_path("package_path"), filename)
+            config.read_config_files([path])
+        kwargs[name] = config
+        return func(*args, **kwargs)
+
+    if func:
+        return function_wrapper
+
+    def recursive_wrapper(func):
+        return has_config(func, name, filename)
+
+    return recursive_wrapper

templates/new/batch_main.py.txt

@@ -5,7 +5,7 @@ Runners and assemblies are defined in here.
 
 import os
 import argparse
-from surround import Surround, Assembler, Config
+from surround import Surround, Assembler, has_config
 from .stages import Baseline, InputValidator, ReportGenerator
 from .file_system_runner import FileSystemRunner
 
@@ -20,8 +20,8 @@ ASSEMBLIES = [
         .set_visualiser(ReportGenerator())
 ]
 
-def main():
-    config = Config(auto_load=True)
+@has_config
+def main(config=None):
     default_runner = config.get_path('runner.default')
     default_assembler = config.get_path('assembler.default')
 

templates/new/web_main.py.txt

@@ -5,7 +5,7 @@ Runners and ASSEMBLIES are defined in here.
 
 import os
 import argparse
-from surround import Surround, Assembler, Config
+from surround import Surround, Assembler, has_config
 from .stages import Baseline, InputValidator, ReportGenerator
 from .file_system_runner import FileSystemRunner
 from .web_runner import WebRunner
@@ -22,8 +22,8 @@ ASSEMBLIES = [
         .set_visualiser(ReportGenerator())
 ]
 
-def main():
-    config = Config(auto_load=True)
+@has_config
+def main(config=None):
     default_runner = config.get_path('runner.default')
     default_assembler = config.get_path('assembler.default')