From df5443129c63394b2d12feba64b08c6a7b6b392b Mon Sep 17 00:00:00 2001
From: Stefano Pigozzi <me@steffo.eu>
Date: Tue, 19 Apr 2022 01:01:55 +0200
Subject: [PATCH] :sparkles: Accumulate resolution errors

---
 cfig/config.py         | 38 ++++++++++++++++++++++++++++++--------
 cfig/errors.py         | 27 +++++++++++++++++++++++++--
 cfig/tests/test_all.py |  3 ++-
 3 files changed, 57 insertions(+), 11 deletions(-)

diff --git a/cfig/config.py b/cfig/config.py
index 30bb756..ad0ef0e 100644
--- a/cfig/config.py
+++ b/cfig/config.py
@@ -31,17 +31,39 @@ class Configuration:
         An extended :class:`dict` with methods to perform some actions on the contained proxies.
         """
 
-        def resolve(self):
+        def resolve(self) -> None:
             """
             Resolve all values of the proxies inside this dictionary.
+
+            :raises .errors.BatchResolutionFailure: If it was not possible to resolve at least one value.
             """
 
-            log.debug("Resolving and caching all values...")
-            for item in self.values():
-                log.debug(f"Resolving: {item!r}")
-                _ = item.__wrapped__
+            errors_dict = {}
 
-        def unresolve(self):
+            log.debug("Resolving and caching all proxied values...")
+            for key, proxy in self.items():
+                log.debug(f"Resolving: {proxy!r}")
+                try:
+                    _ = proxy.__wrapped__
+                except Exception as e:
+                    errors_dict[key] = e
+
+            if errors_dict:
+                raise errors.BatchResolutionFailure(errors=errors_dict)
+
+        def resolve_failfast(self) -> None:
+            """
+            Resolve all values of the proxies inside this dictionary, failing immediately if an error occurs during a resolution, and raising the error itself.
+
+            :raises Exception: The error occurred during the resolution.
+            """
+
+            log.debug("Resolving and caching all proxied values in failfast mode...")
+            for key, proxy in self.items():
+                log.debug(f"Resolving: {proxy!r}")
+                _ = proxy.__wrapped__
+
+        def unresolve(self) -> None:
             """
             Unresolve all values of the proxies inside this dictionary.
             """
@@ -98,7 +120,7 @@ class Configuration:
 
             if not key:
                 log.debug("Determining key...")
-                key: str = self._find_resolver_key(configurable)
+                key = self._find_resolver_key(configurable)
                 log.debug(f"Key is: {key!r}")
 
             log.debug("Creating required item...")
@@ -135,7 +157,7 @@ class Configuration:
 
             if not key:
                 log.debug("Determining key...")
-                key: str = self._find_resolver_key(configurable)
+                key = self._find_resolver_key(configurable)
                 log.debug(f"Key is: {key!r}")
 
             log.debug("Creating optional item...")
diff --git a/cfig/errors.py b/cfig/errors.py
index e47d0d3..fae59d7 100644
--- a/cfig/errors.py
+++ b/cfig/errors.py
@@ -1,6 +1,14 @@
-class DefinitionError(Exception):
+class CfigError(Exception):
+    """
+    Base class for all :mod:`cfig` errors.
+    """
+
+
+class DefinitionError(CfigError):
     """
     An error is present in the definition of a :class:`cfig.Configuration`.
+
+    This is a developer-side error: the user has no way to solve it.
     """
 
 
@@ -24,9 +32,11 @@ class DuplicateProxyNameError(ProxyRegistrationError):
     """
 
 
-class ConfigurationError(Exception):
+class ConfigurationError(CfigError):
     """
     An error is present in the configuration specified by the user.
+
+    This is a user-side error: the developer of the application has no way to solve it.
     """
 
 
@@ -36,6 +46,18 @@ class MissingValueError(ConfigurationError):
     """
 
 
+class BatchResolutionFailure(BaseException):
+    """
+    A cumulative error which sums the errors occurred while resolving proxied configuration values.
+    """
+
+    def __init__(self, errors: dict[str, Exception]):
+        self.errors: dict[str, Exception] = errors
+
+    def __repr__(self):
+        return f"<{self.__class__.__qualname__}: {len(self.errors)} errors>"
+
+
 __all__ = (
     "DefinitionError",
     "UnknownResolverNameError",
@@ -43,4 +65,5 @@ __all__ = (
     "DuplicateProxyNameError",
     "ConfigurationError",
     "MissingValueError",
+    "BatchResolutionFailure",
 )
diff --git a/cfig/tests/test_all.py b/cfig/tests/test_all.py
index 4280851..dd44d54 100644
--- a/cfig/tests/test_all.py
+++ b/cfig/tests/test_all.py
@@ -60,8 +60,9 @@ class TestConfig:
         assert not os.environ.get("FIRST_NUMBER")
         assert not os.environ.get("SECOND_NUMBER")
 
-        with pytest.raises(cfig.MissingValueError):
+        with pytest.raises(cfig.BatchResolutionFailure) as ei:
             numbers_config.proxies.resolve()
+            assert isinstance(ei.value.errors["FIRST_NUMBER"], cfig.MissingValueError)
 
     def test_resolve_required(self, numbers_config, monkeypatch):
         monkeypatch.setenv("FIRST_NUMBER", "1")