Add support for meson.options as a replacement for meson_options.txt

We will still try to load `meson_options.txt` if `meson.options` doesn't
exist. Because there are some advantages to using `meson.options` even
with older versions of meson (such as better text editor handling)
we will not warn about the existence of a `meson.options` file if a
`meson_options.txt` file or symlink also exists.

The name `meson.options` was picked instead of alternative proposals,
such as `meson_options.build` for a couple of reasons:

  1. meson.options is shorter
  2. While the syntax is the same, only the `option()` function may be
     called in meson.options, while, it may not be called in meson.build
  3. While the two files share a syntax and elementary types (strings,
     arrays, etc), they have different purposes: `meson.build` declares
     build targets, `meson.options` declares options. This is similar to
     the difference between C's `.c` and `.h` extensions.

As an implementation detail `Interpreter.option_file` has been removed,
as it is used exactly once, in the `project()` call to read the options,
and we can just calculate it there and not store it.

Fixes: #11176

1 files changed, 5 insertions, 3 deletions

diff --git a/mesonbuild/ast/introspection.py b/mesonbuild/ast/introspection.py
index 98f03fd..e811f11 100644
--- a/mesonbuild/ast/introspection.py
+++ b/mesonbuild/ast/introspection.py
@@ -76,7 +76,6 @@ class IntrospectionInterpreter(AstInterpreter):
             self.environment = env
         self.subproject_dir = subproject_dir
         self.coredata = self.environment.get_coredata()
-        self.option_file = os.path.join(self.source_root, self.subdir, 'meson_options.txt')
         self.backend = backend
         self.default_options = {OptionKey('backend'): self.backend}
         self.project_data = {}    # type: T.Dict[str, T.Any]
@@ -113,9 +112,12 @@ class IntrospectionInterpreter(AstInterpreter):
             proj_vers = 'undefined'
         self.project_data = {'descriptive_name': proj_name, 'version': proj_vers}
 
-        if os.path.exists(self.option_file):
+        optfile = os.path.join(self.source_root, self.subdir, 'meson.options')
+        if not os.path.exists(optfile):
+            optfile = os.path.join(self.source_root, self.subdir, 'meson_options.txt')
+        if os.path.exists(optfile):
             oi = optinterpreter.OptionInterpreter(self.subproject)
-            oi.process(self.option_file)
+            oi.process(optfile)
             self.coredata.update_project_options(oi.options)
 
         def_opts = self.flatten_args(kwargs.get('default_options', []))