build: Throw an error instead of warning for sourceless targets

We might run into an assertion failure down the road, if we don't fail
here. Specifically
    project('proj')
    executable('bin', 'header.h')
will throw during the ninja generation.

7 files changed, 10 insertions, 12 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 041cb1972..cfba92380 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -760,9 +760,7 @@ class BuildTarget(Target):
 
         if not any([[src for src in self.sources if not is_header(src)], self.generated, self.objects,
                     self.link_whole_targets, self.structured_sources, kwargs.pop('_allow_no_sources', False)]):
-            mlog.warning(f'Build target {name} has no sources. '
-                         'This was never supposed to be allowed but did because of a bug, '
-                         'support will be removed in a future release of Meson')
+            raise MesonException(f'Build target {name} has no sources.')
         self.check_unknown_kwargs(kwargs)
         self.validate_install()
         self.check_module_linking()
diff --git a/test cases/common/44 pkgconfig-gen/meson.build b/test cases/common/44 pkgconfig-gen/meson.build
index fd6371ef4..624126cb1 100644
--- a/test cases/common/44 pkgconfig-gen/meson.build
+++ b/test cases/common/44 pkgconfig-gen/meson.build
@@ -189,7 +189,7 @@ endtestcase
 # Make sure the -uninstalled.pc file contains both include directories.
 # See dependencies/test2.c that gets built against both simple7.pc and
 # simple7-uninstalled.pc.
-simple7 = library('simple7', include_directories: 'inc1')
+simple7 = library('simple7', 'simple7.c', include_directories: 'inc1')
 dep = declare_dependency(include_directories: 'inc2')
 install_headers('inc1/inc1.h', 'inc2/inc2.h')
 pkgg.generate(simple7, libraries: dep)
diff --git a/test cases/common/44 pkgconfig-gen/simple7.c b/test cases/common/44 pkgconfig-gen/simple7.c
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/test cases/common/44 pkgconfig-gen/simple7.c
diff --git a/test cases/warning/8 target with no sources/meson.build b/test cases/failing/136 target with no sources/meson.build
index 2a8ee110b..2a8ee110b 100644
--- a/test cases/warning/8 target with no sources/meson.build
+++ b/test cases/failing/136 target with no sources/meson.build
diff --git a/test cases/failing/136 target with no sources/test.json b/test cases/failing/136 target with no sources/test.json
new file mode 100644
index 000000000..9cef75524
--- /dev/null
+++ b/test cases/failing/136 target with no sources/test.json
@@ -0,0 +1,7 @@
+{
+  "stdout": [
+    {
+      "line": "test cases/failing/136 target with no sources/meson.build:3:0: ERROR: Build target no sources has no sources."
+    }
+  ]
+}
diff --git a/test cases/warning/8 target with no sources/test.json b/test cases/warning/8 target with no sources/test.json
deleted file mode 100644
index 30e5b05f1..000000000
--- a/test cases/warning/8 target with no sources/test.json
+++ /dev/null
@@ -1,7 +0,0 @@
-{
-  "stdout": [
-    {
-      "line": "WARNING: Build target no sources has no sources. This was never supposed to be allowed but did because of a bug, support will be removed in a future release of Meson"
-    }
-  ]
-}
diff --git a/unittests/allplatformstests.py b/unittests/allplatformstests.py
index 04cbfc690..ebcb1f53c 100644
--- a/unittests/allplatformstests.py
+++ b/unittests/allplatformstests.py
@@ -4819,7 +4819,7 @@ class AllPlatformTests(BasePlatformTests):
                            for_machine=MachineChoice.HOST, sources=[],
                            structured_sources=None,
                            objects=[], environment=env, compilers=env.coredata.compilers[MachineChoice.HOST],
-                           kwargs={})
+                           kwargs={'_allow_no_sources': True})
             target.process_compilers_late()
             return target.filename