From 522d3bc5d94645cdb63abe3a9d55aac272ed573f Mon Sep 17 00:00:00 2001
From: Dima Gerasimov <karlicoss@gmail.com>
Date: Sat, 21 Dec 2019 10:58:45 +0000
Subject: [PATCH] Move error handling to common

---
 my/body/blood.py                  |  6 ++-
 my/{kython/kerror.py => error.py} | 65 ++++++++++++-------------------
 my/reading/polar.py               |  2 +-
 3 files changed, 30 insertions(+), 43 deletions(-)
 rename my/{kython/kerror.py => error.py} (60%)

diff --git a/my/body/blood.py b/my/body/blood.py
index 6f6c913..a24c3c4 100755
--- a/my/body/blood.py
+++ b/my/body/blood.py
@@ -4,9 +4,11 @@ from typing import Iterable, NamedTuple, Optional
 from itertools import chain
 
 import porg
-from kython import listify
+from .common import listify
+from ..error import Res, echain
+
+
 from kython.org import parse_org_date
-from kython.kerror import Res, echain
 
 from mycfg import paths
 
diff --git a/my/kython/kerror.py b/my/error.py
similarity index 60%
rename from my/kython/kerror.py
rename to my/error.py
index 7484de3..721cb63 100644
--- a/my/kython/kerror.py
+++ b/my/error.py
@@ -1,23 +1,20 @@
-from typing import Union, TypeVar, Iterator, Callable, Iterable, List, Tuple, Type
+"""
+Various error handling helpers
+See https://beepb00p.xyz/mypy-error-handling.html#kiss for more detail
+"""
+
+from itertools import tee
+from typing import Union, TypeVar, Iterable, List, Tuple, Type
 
 
 T = TypeVar('T')
-E = TypeVar('E', bound=Exception)
+E = TypeVar('E', bound=Exception) # TODO make covariant?
 
 ResT = Union[T, E]
 
 Res = ResT[T, Exception]
 
 
-# TODO make it a bit more typed??
-def is_error(res: Res[T]) -> bool:
-    return isinstance(res, Exception)
-
-
-def is_ok(res: Res[T]) -> bool:
-    return not is_error(res)
-
-
 def unwrap(res: Res[T]) -> T:
     if isinstance(res, Exception):
         raise res
@@ -25,38 +22,26 @@ def unwrap(res: Res[T]) -> T:
         return res
 
 
-def split_errors(l: Iterable[ResT[T, E]], ET=Exception) -> Tuple[List[T], List[E]]:
-    rl: List[T] = []
-    el: List[E] = []
-    for x in l:
-        if isinstance(x, ET):
-            el.append(x)
-        else:
-            rl.append(x) # type: ignore
-    return rl, el
-
-
-def ytry(cb) -> Iterator[Exception]:
-    try:
-        cb()
-    except Exception as e:
-        yield e
-
-
-# TODO experimental, not sure if I like it
 def echain(ex: E, cause: Exception) -> E:
     ex.__cause__ = cause
-    # TODO assert cause is none?
-    # TODO copy??
     return ex
-    # try:
-    #     # TODO is there a awy to get around raise from?
-    #     raise ex from cause
-    # except Exception as e:
-    #     if isinstance(e, type(ex)):
-    #         return e
-    #     else:
-    #         raise e
+
+
+def split_errors(l: Iterable[ResT[T, E]], ET: Type[E]) -> Tuple[Iterable[T], Iterable[E]]:
+    # TODO would be nice to have ET=Exception default?
+    vit, eit = tee(l)
+    # TODO ugh, not sure if I can reconcile type checking and runtime and convince mypy that ET and E are the same type?
+    values: Iterable[T] = (
+        r # type: ignore[misc]
+        for r in vit
+        if not isinstance(r, ET))
+    errors: Iterable[E] = (
+        r
+        for r in eit
+        if     isinstance(r, ET))
+    # TODO would be interesting to be able to have yield statement anywehere in code
+    # so there are multiple 'entry points' to the return value
+    return (values, errors)
 
 
 def sort_res_by(items: Iterable[ResT], key) -> List[ResT]:
diff --git a/my/reading/polar.py b/my/reading/polar.py
index 9594a78..ca4c140 100755
--- a/my/reading/polar.py
+++ b/my/reading/polar.py
@@ -9,7 +9,7 @@ import pytz
 
 from ..common import setup_logger
 
-from ..kython.kerror import ResT, echain, unwrap, sort_res_by
+from ..error import ResT, echain, unwrap, sort_res_by
 from ..kython.konsume import wrap, zoom, ignore