Warn on unknown command line arguments

I have a tendency to typo things. Humans in general are bad at spotting
spelling mistakes, computers are not. This patches prints the bad
options and provides the generic meson "This will be a hard error
someday" message.

1 files changed, 9 insertions, 0 deletions

diff --git a/mesonbuild/optinterpreter.py b/mesonbuild/optinterpreter.py
index f8ccbe6..df945ab 100644
--- a/mesonbuild/optinterpreter.py
+++ b/mesonbuild/optinterpreter.py
@@ -15,6 +15,7 @@
 import os, re
 import functools
 
+from . import mlog
 from . import mparser
 from . import coredata
 from . import mesonlib
@@ -146,6 +147,14 @@ class OptionInterpreter:
                 e.colno = cur.colno
                 e.file = os.path.join('meson_options.txt')
                 raise e
+        bad = [o for o in sorted(self.cmd_line_options) if not
+               (o in list(self.options) + forbidden_option_names or
+                any(o.startswith(p) for p in forbidden_prefixes))]
+        if bad:
+            sub = 'In subproject {}: '.format(self.subproject) if self.subproject else ''
+            mlog.warning(
+                '{}Unknown command line options: "{}"\n'
+                'This will become a hard error in a future Meson release.'.format(sub, ', '.join(bad)))
 
     def reduce_single(self, arg):
         if isinstance(arg, str):