added $ escapes\n\nfor now only `$env:envname` is supported

3 files changed, 44 insertions, 3 deletions

diff --git a/configlib/model.py b/configlib/model.py
index 5f5c694..0bc94e1 100644
--- a/configlib/model.py
+++ b/configlib/model.py
@@ -11,6 +11,12 @@ from typing import Type, Union, AnyStr, TextIO
 from configlib.util import snake_case
 
 
+class InvalidConfigEscapeException(Exception):
+    """
+    Some config uses an invalid escape like `$invalidescapecode:argument`
+    """
+
+
 class InvalidConfigTypingException(Exception):
     """
     The typing found in the given class is missing arguments.
diff --git a/configlib/model_impl.py b/configlib/model_impl.py
index dc8cde0..d18611f 100644
--- a/configlib/model_impl.py
+++ b/configlib/model_impl.py
@@ -1,10 +1,11 @@
 """
 Implementations for the modules of :module:`configlib.model`
 """
-
+import os
 from typing import Type, Dict, List
 
-from .model import Config, ConfigValueMissingException, InvalidConfigTypingException
+from .model import Config, ConfigValueMissingException, InvalidConfigTypingException, \
+    InvalidConfigEscapeException
 from .util import snake_case
 
 
@@ -57,6 +58,23 @@ def parse_dict_impl(val_type: Type[object], val, path) -> dict:
     return dic
 
 
+_ESCAPES = {
+    'env': os.environ.get,
+}
+
+
+def _resolve_string(val: str):
+    if val[0] != '$':
+        return val
+    if val[1] == '$':
+        return val[1:]
+    descriptor, arg, *_ = val[1:].split(':', 2) + ['']
+    escape = _ESCAPES.get(descriptor)
+    if not escape:
+        raise InvalidConfigEscapeException(descriptor)
+    return escape(arg)
+
+
 # noinspection PyUnresolvedReferences
 def parse_single_item(val_type: Type[object], val, path):
     """
@@ -67,8 +85,13 @@ def parse_single_item(val_type: Type[object], val, path):
     :param path: the path inside the config. used for error reporting
     :return: the parsed something
     """
+    if isinstance(val, str):
+        if len(val) > 2 and val[0] == '$':
+            val = _resolve_string(val)
+
     if issubclass(val_type, (str, int, float)):
-        return val
+        # noinspection PyArgumentList
+        return val_type(val)
     if isinstance(val_type, List):
         if len(val_type.__args__) != 1:
             raise InvalidConfigTypingException(path + ': List must be supplied exactly one type')
diff --git a/tests/test_something.py b/tests/test_something.py
index 8091f46..7bb979a 100644
--- a/tests/test_something.py
+++ b/tests/test_something.py
@@ -1,4 +1,5 @@
 import json
+import os
 from unittest import TestCase
 
 from configlib.model_impl import BaseConfig
@@ -19,6 +20,12 @@ test_dict = {
         'a': 1
     }
 }
+env_dict = {
+    'something': '$env:ENVVAR',
+    'ye': {
+        'a': 1
+    }
+}
 
 
 def verify_test_dict(conf):
@@ -37,3 +44,8 @@ class TestSomething(TestCase):
     def test_text(self):
         conf: SomeConfig = SomeConfig.loads(json.dumps(test_dict))
         verify_test_dict(conf)
+
+    def test_environ(self):
+        os.environ['ENVVAR'] = 'hmm'
+        conf: SomeConfig = SomeConfig.parse_dict(env_dict)
+        verify_test_dict(conf)