Always flatten include_directories lists

mesonbuild/interpreter.py

@@ -2209,7 +2209,7 @@ class Interpreter(InterpreterBase):
         version = kwargs.get('version', self.project_version)
         if not isinstance(version, str):
             raise InterpreterException('Version must be a string.')
-        incs = self.entries_to_incdirs(extract_as_list(kwargs, 'include_directories', unholder=True))
+        incs = self.extract_incdirs(kwargs)
         libs = extract_as_list(kwargs, 'link_with', unholder=True)
         libs_whole = extract_as_list(kwargs, 'link_whole', unholder=True)
         sources = extract_as_list(kwargs, 'sources')
@@ -3698,15 +3698,14 @@ This will become a hard error in the future.''' % kwargs['input'])
             self.build.data.append(build.Data([cfile], idir, install_mode))
         return mesonlib.File.from_built_file(self.subdir, output)
 
-    def entries_to_incdirs(self, prospectives):
-        if not isinstance(prospectives, list):
-            return self.entries_to_incdirs([prospectives])[0]
+    def extract_incdirs(self, kwargs):
+        prospectives = listify(kwargs.get('include_directories', []), unholder=True)
         result = []
         for p in prospectives:
-            if isinstance(p, (IncludeDirsHolder, build.IncludeDirs)):
+            if isinstance(p, build.IncludeDirs):
                 result.append(p)
             elif isinstance(p, str):
-                result.append(self.build_incdir_object([p]))
+                result.append(self.build_incdir_object([p]).held_object)
             else:
                 raise InterpreterException('Include directory objects can only be created from strings or include directories.')
         return result
@@ -4072,8 +4071,7 @@ Try setting b_lundef to false instead.'''.format(self.coredata.base_options['b_s
         # passed to library() when default_library == 'static'.
         kwargs = {k: v for k, v in kwargs.items() if k in targetclass.known_kwargs}
 
-        if 'include_directories' in kwargs:
-            kwargs['include_directories'] = self.entries_to_incdirs(kwargs['include_directories'])
+        kwargs['include_directories'] = self.extract_incdirs(kwargs)
         target = targetclass(name, self.subdir, self.subproject, is_cross, sources, objs, self.environment, kwargs)
 
         if is_cross:

test cases/common/19 includedir/src/meson.build

@@ -1,5 +1,5 @@
 exe = executable('prog', 'prog.c', 'func.c', include_directories : inc)
 test('inc test', exe)
 
-exe2 = executable('prog2', 'prog.c', 'func.c', include_directories : '../include')
+exe2 = executable('prog2', 'prog.c', 'func.c', include_directories : [['../include']])
 test('inc test 2', exe2)

test cases/common/84 declare dep/entity/meson.build

@@ -1,7 +1,7 @@
 entity_lib = static_library('entity', 'entity1.c')
 
 entity_dep = declare_dependency(link_with : [[entity_lib]],
-  include_directories : '.',
+  include_directories : [['.']],
   sources : 'entity2.c',
   compile_args : ['-DUSING_ENT=1'],
   version : '1.2.3',