src: rewrite driver impl checker in Python

As part of a goal to eliminate Perl from libvirt build tools,
rewrite the check-driverimpls.pl tool in Python.

This was a straight conversion, manually going line-by-line to
change the syntax from Perl to Python. Thus the overall structure
of the file and approach is the same.

Tested-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

scripts/check-driverimpls.py

@@ -0,0 +1,103 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2013-2019 Red Hat, Inc.
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library.  If not, see
+# <http://www.gnu.org/licenses/>.
+#
+
+from __future__ import print_function
+
+import re
+import sys
+
+
+def checkdriverimpls(filename):
+    intable = False
+    mainprefix = None
+
+    errs = False
+    with open(filename, "r") as fh:
+        lineno = 0
+        for line in fh:
+            lineno = lineno + 1
+            if intable:
+                if line.find("}") != -1:
+                    intable = False
+                    mainprefix = None
+                    continue
+
+                m = re.search(r'''\.(\w+)\s*=\s*(\w+),?''', line)
+                if m is not None:
+                    api = m.group(1)
+                    impl = m.group(2)
+
+                    if api in ["no", "name"]:
+                        continue
+                    if impl in ["NULL"]:
+                        continue
+
+                    suffix = impl
+                    prefix = re.sub(r'''^([a-z]+)(.*?)$''', r'''\1''', impl)
+
+                    if mainprefix is not None:
+                        if mainprefix != prefix:
+                            print(("%s:%d Bad prefix '%s' for API '%s', " +
+                                   "expecting '%s'") %
+                                  (filename, lineno, prefix, api, mainprefix),
+                                  file=sys.stderr)
+                            errs = True
+                    else:
+                        mainprefix = prefix
+
+                    if not api.startswith(mainprefix):
+                        suffix = re.sub(r'''^[a-z]+''', "", suffix)
+                        suffix = re.sub(r'''^([A-Z]+)''',
+                                        lambda m: m.group(1).lower(), suffix)
+
+                    if api != suffix:
+                        want = api
+                        if want.startswith("nwf"):
+                            want = "NWF" + want[3:]
+
+                        if not api.startswith(mainprefix):
+                            want = re.sub(r'''^([a-z])''',
+                                          lambda m: m.group(1).upper(), want)
+                            want = mainprefix + want
+
+                        print(("%s:%d Bad impl name '%s' for API " +
+                               "'%s', expecting '%s'") %
+                              (filename, lineno, impl, api, want),
+                              file=sys.stderr)
+                        errs = True
+            else:
+                m = re.search(r'''^(?:static\s+)?(vir(?:\w+)?Driver)''' +
+                              r'''\s+(?!.*;)''', line)
+                if m is not None:
+                    drv = m.group(1)
+                    if drv in [
+                            "virNWFilterCallbackDriver",
+                            "virNWFilterTechDriver",
+                            "virConnectDriver"]:
+                        continue
+                    intable = True
+
+    return errs
+
+
+status = 0
+for filename in sys.argv[1:]:
+    if checkdriverimpls(filename):
+        status = 1
+sys.exit(status)