main: inline matchnodes() into collect()

Now all of the logic is in one place and may be simplified and
refactored in more sensible way.

src/_pytest/main.py

@@ -707,8 +707,53 @@ class Session(nodes.FSCollector):
                     col = collect_root._collectfile(argpath, handle_dupes=False)
                     if col:
                         self._collection_node_cache1[argpath] = col
-                m = self.matchnodes(col, names)
+
-                if not m:
+                matching = []
+                work = [
+                    (col, names)
+                ]  # type: List[Tuple[Sequence[Union[nodes.Item, nodes.Collector]], Sequence[str]]]
+                while work:
+                    self.trace("matchnodes", col, names)
+                    self.trace.root.indent += 1
+
+                    matchnodes, matchnames = work.pop()
+                    for node in matchnodes:
+                        if not matchnames:
+                            matching.append(node)
+                            continue
+                        if not isinstance(node, nodes.Collector):
+                            continue
+                        key = (type(node), node.nodeid)
+                        if key in self._collection_matchnodes_cache:
+                            rep = self._collection_matchnodes_cache[key]
+                        else:
+                            rep = collect_one_node(node)
+                            self._collection_matchnodes_cache[key] = rep
+                        if rep.passed:
+                            submatchnodes = []
+                            for r in rep.result:
+                                # TODO: Remove parametrized workaround once collection structure contains
+                                # parametrization.
+                                if (
+                                    r.name == matchnames[0]
+                                    or r.name.split("[")[0] == matchnames[0]
+                                ):
+                                    submatchnodes.append(r)
+                            if submatchnodes:
+                                work.append((submatchnodes, matchnames[1:]))
+                            # XXX Accept IDs that don't have "()" for class instances.
+                            elif len(rep.result) == 1 and rep.result[0].name == "()":
+                                work.append((rep.result, matchnames))
+                        else:
+                            # Report collection failures here to avoid failing to run some test
+                            # specified in the command line because the module could not be
+                            # imported (#134).
+                            node.ihook.pytest_collectreport(report=rep)
+
+                    self.trace("matchnodes finished -> ", len(matching), "nodes")
+                    self.trace.root.indent -= 1
+
+                if not matching:
                     report_arg = "::".join((str(argpath), *names))
                     self._notfound.append((report_arg, col))
                     continue
@@ -718,16 +763,17 @@ class Session(nodes.FSCollector):
                 # Module itself, so just use that. If this special case isn't taken, then all
                 # the files in the package will be yielded.
                 if argpath.basename == "__init__.py":
-                    assert isinstance(m[0], nodes.Collector)
+                    assert isinstance(matching[0], nodes.Collector)
                     try:
-                        yield next(iter(m[0].collect()))
+                        yield next(iter(matching[0].collect()))
                     except StopIteration:
                         # The package collects nothing with only an __init__.py
                         # file in it, which gets ignored by the default
                         # "python_files" option.
                         pass
                     continue
-                yield from m
+
+                yield from matching
 
             self.trace.root.indent -= 1
         self._collection_node_cache1.clear()
@@ -735,51 +781,6 @@ class Session(nodes.FSCollector):
         self._collection_matchnodes_cache.clear()
         self._collection_pkg_roots.clear()
 
-    def matchnodes(
-        self,
-        matching: Sequence[Union[nodes.Item, nodes.Collector]],
-        names: Sequence[str],
-    ) -> Sequence[Union[nodes.Item, nodes.Collector]]:
-        result = []
-        work = [(matching, names)]
-        while work:
-            self.trace("matchnodes", matching, names)
-            self.trace.root.indent += 1
-
-            matching, names = work.pop()
-            for node in matching:
-                if not names:
-                    result.append(node)
-                    continue
-                if not isinstance(node, nodes.Collector):
-                    continue
-                key = (type(node), node.nodeid)
-                if key in self._collection_matchnodes_cache:
-                    rep = self._collection_matchnodes_cache[key]
-                else:
-                    rep = collect_one_node(node)
-                    self._collection_matchnodes_cache[key] = rep
-                if rep.passed:
-                    submatching = []
-                    for x in rep.result:
-                        # TODO: Remove parametrized workaround once collection structure contains parametrization.
-                        if x.name == names[0] or x.name.split("[")[0] == names[0]:
-                            submatching.append(x)
-                    if submatching:
-                        work.append((submatching, names[1:]))
-                    # XXX Accept IDs that don't have "()" for class instances.
-                    elif len(rep.result) == 1 and rep.result[0].name == "()":
-                        work.append((rep.result, names))
-                else:
-                    # Report collection failures here to avoid failing to run some test
-                    # specified in the command line because the module could not be
-                    # imported (#134).
-                    node.ihook.pytest_collectreport(report=rep)
-
-            self.trace("matchnodes finished -> ", len(result), "nodes")
-            self.trace.root.indent -= 1
-        return result
-
     def genitems(
         self, node: Union[nodes.Item, nodes.Collector]
     ) -> Iterator[nodes.Item]: