coredata: Set default options as cmdline args that override each other

The previous code was assuming that options do not depend on each
other, and that you can set defaults using `dict.setdefault()`. This
is not true for `buildtype` + `optimization`/`debug`, so we add
defaults + overrides in the right order and use the options parsing
code later to compute the values.

Includes a test.

Closes https://github.com/mesonbuild/meson/issues/6752

mesonbuild/coredata.py

@@ -718,13 +718,8 @@ class CoreData:
             self.copy_build_options_from_regular_ones()
 
     def set_default_options(self, default_options, subproject, env):
-        # Set defaults first from conf files (cross or native), then
-        # override them as nec as necessary.
-        for k, v in env.paths.host:
-            if v is not None:
-                env.cmd_line_options.setdefault(k, v)
-
-        # Set default options as if they were passed to the command line.
+        cmd_line_options = OrderedDict()
+        # Set project default_options as if they were passed to the cmdline.
         # Subprojects can only define default for user options and not yielding
         # builtin option.
         from . import optinterpreter
@@ -734,7 +729,17 @@ class CoreData:
                         and optinterpreter.is_invalid_name(k, log=False):
                     continue
                 k = subproject + ':' + k
-            env.cmd_line_options.setdefault(k, v)
+            cmd_line_options[k] = v
+
+        # Override project default_options using conf files (cross or native)
+        for k, v in env.paths.host:
+            if v is not None:
+                cmd_line_options[k] = v
+
+        # Override all the above defaults using the command-line arguments
+        # actually passed to us
+        cmd_line_options.update(env.cmd_line_options)
+        env.cmd_line_options = cmd_line_options
 
         # Create a subset of cmd_line_options, keeping only options for this
         # subproject. Also take builtin options if it's the main project.

run_unittests.py

@@ -3825,6 +3825,24 @@ recommended as it is not supported on some platforms''')
         self.assertEqual(opts['debug'], True)
         self.assertEqual(opts['optimization'], '0')
 
+        # Command-line parsing of buildtype settings should be the same as
+        # setting with `meson configure`.
+        #
+        # Setting buildtype should set optimization/debug
+        self.new_builddir()
+        self.init(testdir, extra_args=['-Dbuildtype=debugoptimized'])
+        opts = self.get_opts_as_dict()
+        self.assertEqual(opts['debug'], True)
+        self.assertEqual(opts['optimization'], '2')
+        self.assertEqual(opts['buildtype'], 'debugoptimized')
+        # Setting optimization/debug should set buildtype
+        self.new_builddir()
+        self.init(testdir, extra_args=['-Doptimization=2', '-Ddebug=true'])
+        opts = self.get_opts_as_dict()
+        self.assertEqual(opts['debug'], True)
+        self.assertEqual(opts['optimization'], '2')
+        self.assertEqual(opts['buildtype'], 'debugoptimized')
+
     @skipIfNoPkgconfig
     @unittest.skipIf(is_windows(), 'Help needed with fixing this test on windows')
     def test_native_dep_pkgconfig(self):

test cases/common/1 trivial/meson.build

@@ -1,7 +1,7 @@
 # Comment on the first line
 project('trivial test',
   # Comment inside a function call + array for language list
-  ['c'],
+  ['c'], default_options: ['buildtype=debug'],
   meson_version : '>=0.52.0')
 #this is a comment
 sources = 'trivial.c'