Export istaskfailed (#32300)

* Export istaskfailed

* Add docstring for istaskfailed

* Add news for istaskfailed

NEWS.md

@@ -25,6 +25,7 @@ New library functions
 * `findfirst`, `findlast`, `findnext` and `findprev` now accept a character as first argument
   to search for that character in a string passed as the second argument ([#31664]).
 * New `findall(pattern, string)` method where `pattern` is a string or regex ([#31834]).
+* `istaskfailed` is now documented and exported, like its siblings `istaskdone` and `istaskstarted` ([#32300]).
 
 Standard library changes
 ------------------------

base/exports.jl

@@ -646,6 +646,7 @@ export
     islocked,
     istaskdone,
     istaskstarted,
+    istaskfailed,
     lock,
     notify,
     ReentrantLock,

base/task.jl

@@ -135,6 +135,28 @@ false
 """
 istaskstarted(t::Task) = ccall(:jl_is_task_started, Cint, (Any,), t) != 0
 
+"""
+    istaskfailed(t::Task) -> Bool
+
+Determine whether a task has exited because an exception was thrown.
+
+# Examples
+```jldoctest
+julia> a4() = error("task failed");
+
+julia> b = Task(a4);
+
+julia> istaskfailed(b)
+false
+
+julia> schedule(b);
+
+julia> yield();
+
+julia> istaskfailed(b)
+true
+```
+"""
 istaskfailed(t::Task) = (t.state == :failed)
 
 Threads.threadid(t::Task) = Int(ccall(:jl_get_task_tid, Int16, (Any,), t)+1)

doc/src/base/parallel.md

@@ -11,6 +11,7 @@ Base.fetch(t::Task)
 Base.current_task
 Base.istaskdone
 Base.istaskstarted
+Base.istaskfailed
 Base.task_local_storage(::Any)
 Base.task_local_storage(::Any, ::Any)
 Base.task_local_storage(::Function, ::Any, ::Any)