WIP: Draft iterable hooks implementation

Author: Tyler Goodlet

pluggy/callers.py

@@ -199,3 +199,60 @@ def _multicall(hook_impls, caller_kwargs, firstresult=False):
                 pass
 
         return outcome.get_result()
+
+
+def _itercall(hook_impls, caller_kwargs, specopts={}, hook=None):
+    """Execute a calls into multiple python functions/methods and yield
+    the result(s) lazily.
+
+    ``caller_kwargs`` comes from _HookCaller.__call__().
+    """
+    __tracebackhide__ = True
+    specopts = hook.spec_opts if hook else specopts
+    results = []
+    firstresult = specopts.get("firstresult")
+    excinfo = None
+    try:  # run impl and wrapper setup functions in a loop
+        teardowns = []
+        try:
+            for hook_impl in reversed(hook_impls):
+                try:
+                    args = [caller_kwargs[argname] for argname in hook_impl.argnames]
+                except KeyError:
+                    for argname in hook_impl.argnames:
+                        if argname not in caller_kwargs:
+                            raise HookCallError(
+                                "hook call must provide argument %r" % (argname,))
+
+                if hook_impl.hookwrapper:
+                    try:
+                        gen = hook_impl.function(*args)
+                        next(gen)   # first yield
+                        teardowns.append(gen)
+                    except StopIteration:
+                        _raise_wrapfail(gen, "did not yield")
+                else:
+                    res = hook_impl.function(*args)
+                    if res is not None:
+                        results.append(res)
+                        yield res
+                        if firstresult:  # halt further impl calls
+                            break
+        except BaseException:
+            excinfo = sys.exc_info()
+    finally:
+        if firstresult:  # first result hooks return a single value
+            outcome = _Result(results[0] if results else None, excinfo)
+        else:
+            outcome = _Result(results, excinfo)
+
+        # run all wrapper post-yield blocks
+        for gen in reversed(teardowns):
+            try:
+                gen.send(outcome)
+                _raise_wrapfail(gen, "has second yield")
+            except StopIteration:
+                pass
+
+        # raise any exceptions
+        outcome.get_result()

pluggy/hooks.py

@@ -168,16 +168,16 @@ def __init__(self, trace):
 
 
 class _HookCaller(object):
-    def __init__(self, name, hook_execute, specmodule_or_class=None,
-                 spec_opts=None):
+    def __init__(self, name, hook_execute, specmodule_or_class=None, spec_opts=None,
+                 iterate=False):
         self.name = name
         self._wrappers = []
         self._nonwrappers = []
         self._hookexec = hook_execute
         self._specmodule_or_class = None
         self.argnames = None
         self.kwargnames = None
-        self.multicall = _multicall
+        self.multicall = _multicall if not iterate else _itercall
         self.spec_opts = spec_opts or {}
         if specmodule_or_class is not None:
             self.set_specification(specmodule_or_class, spec_opts)