take override_option('unity=...') into account when allowing extract_objects()

A single target could be picked for unity build, and in that case
extract_objects() should not be allowed.

Likewise for the opposite case, where extract_objects() should be allowed
if unity build is disabled for a single target.  A test that covers that
case is added later.

mesonbuild/backend/backends.py

@@ -836,7 +836,7 @@ class Backend:
         # With unity builds, sources don't map directly to objects,
         # we only support extracting all the objects in this mode,
         # so just return all object files.
-        if self.is_unity(extobj.target):
+        if extobj.target.is_unity:
             compsrcs = classify_unity_sources(extobj.target.compilers.values(), sources)
             sources = []
             unity_size = extobj.target.get_option(OptionKey('unity_size'))
@@ -1280,10 +1280,6 @@ class Backend:
             libs.extend(self.get_custom_target_provided_by_generated_source(t))
         return libs
 
-    def is_unity(self, target: build.BuildTarget) -> bool:
-        optval = target.get_option(OptionKey('unity'))
-        return optval == 'on' or (optval == 'subprojects' and target.subproject != '')
-
     def get_custom_target_sources(self, target: build.CustomTarget) -> T.List[str]:
         '''
         Custom target sources can be of various object types; strings, File,

mesonbuild/backend/ninjabackend.py

@@ -792,7 +792,7 @@ class NinjaBackend(backends.Backend):
         # Generate rules for building the remaining source files in this target
         outname = self.get_target_filename(target)
         obj_list = []
-        is_unity = self.is_unity(target)
+        is_unity = target.is_unity
         header_deps = []
         unity_src = []
         unity_deps = [] # Generated sources that must be built before compiling a Unity target.
@@ -1527,7 +1527,7 @@ class NinjaBackend(backends.Backend):
             # Outputted header
             hname = os.path.join(self.get_target_dir(target), target.vala_header)
             args += ['--header', hname]
-            if self.is_unity(target):
+            if target.is_unity:
                 # Without this the declarations will get duplicated in the .c
                 # files and cause a build failure when all of them are
                 # #include-d in one .c file.

mesonbuild/backend/vs2010backend.py

@@ -878,7 +878,7 @@ class Vs2010Backend(backends.Backend):
         # Prefix to use to access the source tree's subdir from the vcxproj dir
         proj_to_src_dir = os.path.join(proj_to_src_root, self.get_target_dir(target))
         (sources, headers, objects, languages) = self.split_sources(target.sources)
-        if self.is_unity(target):
+        if target.is_unity:
             sources = self.generate_unity_files(target, sources)
         compiler = self._get_cl_compiler(target)
         build_args = compiler.get_buildtype_args(self.buildtype)

mesonbuild/build.py

@@ -753,8 +753,6 @@ class BuildTarget(Target):
                  sources: T.List['SourceOutputs'], structured_sources: T.Optional[StructuredSources],
                  objects, environment: environment.Environment, compilers: T.Dict[str, 'Compiler'], kwargs):
         super().__init__(name, subdir, subproject, True, for_machine, environment)
-        unity_opt = environment.coredata.get_option(OptionKey('unity'))
-        self.is_unity = unity_opt == 'on' or (unity_opt == 'subprojects' and subproject != '')
         self.all_compilers = compilers
         self.compilers = OrderedDict() # type: OrderedDict[str, Compiler]
         self.objects: T.List[T.Union[str, 'File', 'ExtractedObjects']] = []
@@ -810,6 +808,11 @@ class BuildTarget(Target):
     def __str__(self):
         return f"{self.name}"
 
+    @property
+    def is_unity(self) -> bool:
+        unity_opt = self.get_option(OptionKey('unity'))
+        return unity_opt == 'on' or (unity_opt == 'subprojects' and self.subproject != '')
+
     def validate_install(self):
         if self.for_machine is MachineChoice.BUILD and self.need_install:
             if self.environment.is_cross_build():

test cases/failing/126 extract from unity/meson.build

@@ -0,0 +1,4 @@
+project('extract nonexisting gen', 'c')
+
+lib1 = library('lib1', 'src1.c', 'src2.c', override_options: ['unity=on'])
+lib2 = library('lib2', objects: lib1.extract_objects('src1.c'))

test cases/failing/126 extract from unity/src1.c

@@ -0,0 +1,3 @@
+int sub_lib_method1() {
+    return 1337;
+}

test cases/failing/126 extract from unity/src2.c

@@ -0,0 +1,3 @@
+int sub_lib_method2() {
+    return 1337;
+}

test cases/failing/126 extract from unity/test.json

@@ -0,0 +1,7 @@
+{
+  "stdout": [
+    {
+      "line": "test cases/failing/126 extract from unity/meson.build:4:0: ERROR: Single object files can not be extracted in Unity builds. You can only extract all the object files for each compiler at once."
+    }
+  ]
+}