dependencies: allow get_variable to expose files from subprojects

There are somewhat common, reasonable and legitimate use cases for a
dependency to provide data files installed to /usr which are used as
command inputs. When getting a dependency from a subproject, however,
the attempt to directly construct an input file from a subproject
results in a sandbox violation. This means not all dependencies can be
wrapped as a subproject.

One example is wayland-protocols XML files which get scanned and used to
produce C source files.

Teach Meson to recognize when a string path is the result of fetching a
dep.get_variable(), and special case this to be exempt from subproject
violations.

A requirement of this is that the file must be installed by
install_data() or install_subdir() because otherwise it is not actually
representative of what a pkg-config dependency would provide.

1 files changed, 27 insertions, 1 deletions

diff --git a/mesonbuild/interpreter/interpreter.py b/mesonbuild/interpreter/interpreter.py
index b31b7a8..5bac8ba 100644
--- a/mesonbuild/interpreter/interpreter.py
+++ b/mesonbuild/interpreter/interpreter.py
@@ -420,6 +420,7 @@ class Interpreter(InterpreterBase, HoldableObject):
             bool: P_OBJ.BooleanHolder,
             str: P_OBJ.StringHolder,
             P_OBJ.MesonVersionString: P_OBJ.MesonVersionStringHolder,
+            P_OBJ.DependencyVariableString: P_OBJ.DependencyVariableStringHolder,
 
             # Meson types
             mesonlib.File: OBJ.FileHolder,
@@ -2716,7 +2717,12 @@ external dependencies (including libraries) must go to "dependencies".''')
     @typed_pos_args('join_paths', varargs=str, min_varargs=1)
     @noKwargs
     def func_join_paths(self, node: mparser.BaseNode, args: T.Tuple[T.List[str]], kwargs: 'TYPE_kwargs') -> str:
-        return os.path.join(*args[0]).replace('\\', '/')
+        parts = args[0]
+        ret = os.path.join(*parts).replace('\\', '/')
+        if isinstance(parts[0], P_OBJ.DependencyVariableString):
+            return P_OBJ.DependencyVariableString(ret)
+        else:
+            return ret
 
     def run(self) -> None:
         super().run()
@@ -2759,6 +2765,26 @@ Try setting b_lundef to false instead.'''.format(self.coredata.options[OptionKey
     # declare_dependency).
     def validate_within_subproject(self, subdir, fname):
         srcdir = Path(self.environment.source_dir)
+        builddir = Path(self.environment.build_dir)
+        if isinstance(fname, P_OBJ.DependencyVariableString):
+            def validate_installable_file(fpath: Path) -> bool:
+                installablefiles: T.Set[Path] = set()
+                for d in self.build.data:
+                    for s in d.sources:
+                        installablefiles.add(Path(s.absolute_path(srcdir, builddir)))
+                installabledirs = [str(Path(srcdir, s.source_subdir)) for s in self.build.install_dirs]
+                if fpath in installablefiles:
+                    return True
+                for d in installabledirs:
+                    if str(fpath).startswith(d):
+                        return True
+                return False
+
+            norm = Path(fname)
+            # variables built from a dep.get_variable are allowed to refer to
+            # subproject files, as long as they are scheduled to be installed.
+            if norm.is_absolute() and '..' not in norm.parts and validate_installable_file(norm):
+                return
         norm = Path(srcdir, subdir, fname).resolve()
         if os.path.isdir(norm):
             inputtype = 'directory'