From 8d83f698d1107b4557e91f0ef2c0f9fbb0adf207 Mon Sep 17 00:00:00 2001
From: Dag Brattli <dag@brattli.net>
Date: Sun, 20 Jan 2019 17:02:15 +0100
Subject: [PATCH] Make tracebacks more readable by avoiding AnonymousObserver
 for the common case and flattening AutoDetachObserver

---
 rx/core/autodetachobserver.py    | 50 ++++++++++++++++++++++--------
 rx/core/observable/observable.py | 52 +++++++++++++++-----------------
 2 files changed, 62 insertions(+), 40 deletions(-)

diff --git a/rx/core/autodetachobserver.py b/rx/core/autodetachobserver.py
index acd6e66c5..02e3c7f84 100644
--- a/rx/core/autodetachobserver.py
+++ b/rx/core/autodetachobserver.py
@@ -1,32 +1,48 @@
+from typing import Any
+
+from rx.internal import noop, default_error
 from rx.disposables import SingleAssignmentDisposable
 
-from .observerbase import ObserverBase
+from .typing import Observer
 
 
-class AutoDetachObserver(ObserverBase):
+class AutoDetachObserver(Observer):
 
-    def __init__(self, observer):
-        super(AutoDetachObserver, self).__init__()
+    def __init__(self, on_next=None, on_error=None, on_completed=None):
+        self._on_next = on_next or noop
+        self._on_error = on_error or default_error
+        self._on_completed = on_completed or noop
 
-        self._observer = observer
         self._subscription = SingleAssignmentDisposable()
+        self.is_stopped = False
+
+    def on_next(self, value: Any) -> None:
+        if self.is_stopped:
+            return
 
-    def _on_next_core(self, value):
         try:
-            self._observer.on_next(value)
+            self._on_next(value)
         except Exception:
             self.dispose()
             raise
 
-    def _on_error_core(self, error):
+    def on_error(self, error) -> None:
+        if self.is_stopped:
+            return
+        self.is_stopped = True
+
         try:
-            self._observer.on_error(error)
+            self._on_error(error)
         finally:
             self.dispose()
 
-    def _on_completed_core(self):
+    def on_completed(self) -> None:
+        if self.is_stopped:
+            return
+        self.is_stopped = True
+
         try:
-            self._observer.on_completed()
+            self._on_completed()
         finally:
             self.dispose()
 
@@ -35,6 +51,14 @@ def set_disposable(self, value):
 
     subscription = property(fset=set_disposable)
 
-    def dispose(self):
-        super().dispose()
+    def dispose(self) -> None:
+        self.is_stopped = True
         self._subscription.dispose()
+
+    def fail(self, exn: Exception) -> bool:
+        if self.is_stopped:
+            return False
+
+        self.is_stopped = True
+        self._on_error(exn)
+        return True
diff --git a/rx/core/observable/observable.py b/rx/core/observable/observable.py
index abfbf22b5..5ed55f7a9 100644
--- a/rx/core/observable/observable.py
+++ b/rx/core/observable/observable.py
@@ -125,34 +125,8 @@ def subscribe_(self,
             Disposable object representing an observer's subscription
             to the observable sequence.
         """
-        observer = AnonymousObserver(on_next, on_error, on_completed)
-        return self.subscribe(observer, scheduler)
 
-    def subscribe(self, observer: typing.Observer = None, scheduler: typing.Scheduler = None) -> typing.Disposable:
-        """Subscribe an observer to the observable sequence.
-
-        Examples:
-            >>> source.subscribe()
-            >>> source.subscribe(observer)
-
-        Args:
-            observer: [Optional] The object that is to receive
-                notifications. You may subscribe using an observer or
-                callbacks, not both.
-
-        Returns:
-            Disposable object representing an observer's subscription
-            to the observable sequence.
-        """
-
-        observer = observer or AnonymousObserver()
-        assert isinstance(observer, (abc.Observer, types.GeneratorType))
-
-        if isinstance(observer, types.GeneratorType):
-            if inspect.getgeneratorstate(observer) == inspect.GEN_CREATED:
-                observer.send(None)
-
-        auto_detach_observer = AutoDetachObserver(observer)
+        auto_detach_observer = AutoDetachObserver(on_next, on_error, on_completed)
 
         def fix_subscriber(subscriber):
             """Fixes subscriber to make sure it returns a Disposable instead
@@ -187,6 +161,30 @@ def set_disposable(_: abc.Scheduler = None, __: Any = None):
         # Hide the identity of the auto detach observer
         return Disposable.create(auto_detach_observer.dispose)
 
+
+    def subscribe(self, observer: typing.Observer = None, scheduler: typing.Scheduler = None) -> typing.Disposable:
+        """Subscribe an observer to the observable sequence.
+
+        Examples:
+            >>> source.subscribe()
+            >>> source.subscribe(observer)
+
+        Args:
+            observer: [Optional] The object that is to receive
+                notifications. You may subscribe using an observer or
+                callbacks, not both.
+
+        Returns:
+            Disposable object representing an observer's subscription
+            to the observable sequence.
+        """
+
+        observer = observer or AnonymousObserver()
+        assert isinstance(observer, abc.Observer)
+
+        return self.subscribe_(observer.on_next, observer.on_error, observer.on_completed, scheduler)
+
+
     def pipe(self, *operators: Callable[['Observable'], 'Observable']) -> 'Observable':
         """Compose multiple operators left to right.