update dev notes

docs/dev/development-notes.md

@@ -1,4 +1,18 @@
 # Development Notes
+## Main decisions
+1. Dependency resolving is async and sync:
+  - if resolving requires event loop in sync mode `RuntimeError` is raised;
+  - framework was developed mostly for usage with async python applications;
+  - sync resolving is also possible, but it will fail in runtime in case of unresolved async dependencies;
+2. Resources and singletons are safe for concurrent resolving:
+  - in async resolving `asyncio.Lock` is used;
+  - in sync resolving `threading.Lock` is used;
+3. No global state -> all state lives in containers:
+  - it's needed for scopes to work;
+4. Focus on maximum compatibility with mypy:
+  - no need for `# type: ignore`
+  - no need for `typing.cast`
+
 ## Base parts
 ### Scope
 - any int enum, starting from 1 with step 1;
@@ -9,6 +23,8 @@
   - resolved dependencies;
   - context stacks for resources;
   - overrides;
+- must have scope;
+- can have link to parent container;
 
 ### Providers
 - completely stateless
@@ -19,8 +35,7 @@
 ### Graph
 - Cannot be instantiated
 - Contains graph of `Providers`
-- Can initialize its resources and factories to container
+- Can initialize its resources and singletons to container
 
-### Questions
-1. Thread-safety
-2. Configuration without global object
+## Questions
+1. Is configuration needed inside DI or global object is OK?