From: Vladimír Vondruš <mosra@centrum.cz>
Date: Fri, 27 Sep 2019 18:19:09 +0000 (+0200)
Subject: documentation: fix a crashy corner case with the typing module.
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~cjwatson/git?a=commitdiff_plain;h=0d63ac9045568bfb3f8455caac0aab6db32546fc;p=blog.git

documentation: fix a crashy corner case with the typing module.

WHY IS IT SUCH A DUMPSTER FIRE
---

diff --git a/documentation/python.py b/documentation/python.py
index ece774ee..21bb2e9a 100755
--- a/documentation/python.py
+++ b/documentation/python.py
@@ -1094,8 +1094,11 @@ def extract_annotation(state: State, referrer_path: List[str], annotation) -> Tu
     elif (hasattr(annotation, '__module__') and annotation.__module__ == 'typing'):
         # Optional or Union, handle those first
         if hasattr(annotation, '__origin__') and annotation.__origin__ is typing.Union:
-            # FOR SOME REASON `annotation.__args__[1] is None` is always False
-            if len(annotation.__args__) == 2 and isinstance(None, annotation.__args__[1]):
+            # FOR SOME REASON `annotation.__args__[1] is None` is always False,
+            # so we have to use isinstance(). HOWEVER, we *can't* use
+            # isinstance if it's a "bracketed" type -- it'll die. So check that
+            # first.
+            if len(annotation.__args__) == 2 and not hasattr(annotation.__args__[1], '__args__') and isinstance(None, annotation.__args__[1]):
                 name = 'typing.Optional'
                 args = annotation.__args__[:1]
             else:
diff --git a/documentation/test_python/inspect_annotations/inspect_annotations.html b/documentation/test_python/inspect_annotations/inspect_annotations.html
index 393138c1..70c0960a 100644
--- a/documentation/test_python/inspect_annotations/inspect_annotations.html
+++ b/documentation/test_python/inspect_annotations/inspect_annotations.html
@@ -105,6 +105,10 @@
               <span class="m-doc-wrap-bumper">def <a href="#annotation_union" class="m-doc-self">annotation_union</a>(</span><span class="m-doc-wrap">a: typing.Union[float, int])</span>
             </dt>
             <dd>Annotation with the Union type</dd>
+            <dt id="annotation_union_second_bracketed">
+              <span class="m-doc-wrap-bumper">def <a href="#annotation_union_second_bracketed" class="m-doc-self">annotation_union_second_bracketed</a>(</span><span class="m-doc-wrap">a: typing.Union[float, typing.List[int]])</span>
+            </dt>
+            <dd>Annotation with the Union type and second type bracketed, where we can&#x27;t use isinstance</dd>
             <dt id="args_kwargs">
               <span class="m-doc-wrap-bumper">def <a href="#args_kwargs" class="m-doc-self">args_kwargs</a>(</span><span class="m-doc-wrap">a, b, *args, **kwargs)</span>
             </dt>
diff --git a/documentation/test_python/inspect_annotations/inspect_annotations.py b/documentation/test_python/inspect_annotations/inspect_annotations.py
index bc38f81b..e4b65973 100644
--- a/documentation/test_python/inspect_annotations/inspect_annotations.py
+++ b/documentation/test_python/inspect_annotations/inspect_annotations.py
@@ -63,6 +63,9 @@ def annotation_generic(a: List[_T]) -> _T:
 def annotation_optional(a: Optional[float]):
     """Annotation with the Optional type"""
 
+def annotation_union_second_bracketed(a: Union[float, List[int]]):
+    """Annotation with the Union type and second type bracketed, where we can't use isinstance"""
+
 def annotation_callable(a: Callable[[float, int], str]):
     """Annotation with the Callable type"""