qt module: add depfile support to moc as well

We currently enable this only for rcc (where this really really matters)
but it can often matter for moc as well, and is just generally more
correct.

Really, this should have been added in #7451 too, but I neglected it
since the module warned about inaccurate dependencies only for rcc...

1 files changed, 11 insertions, 1 deletions

diff --git a/mesonbuild/modules/qt.py b/mesonbuild/modules/qt.py
index 269656250..e548a0d1b 100644
--- a/mesonbuild/modules/qt.py
+++ b/mesonbuild/modules/qt.py
@@ -98,6 +98,7 @@ if T.TYPE_CHECKING:
 class QtBaseModule(ExtensionModule):
     _tools_detected = False
     _rcc_supports_depfiles = False
+    _moc_supports_depfiles = False
 
     def __init__(self, interpreter: 'Interpreter', qt_version: int = 5):
         ExtensionModule.__init__(self, interpreter)
@@ -170,6 +171,10 @@ class QtBaseModule(ExtensionModule):
             # Get all tools and then make sure that they are the right version
             self.compilers_detect(state, qt)
             if version_compare(qt.version, '>=5.14.0'):
+                self._moc_supports_depfiles = True
+            else:
+                mlog.warning('moc dependencies will not work properly until you move to Qt >= 5.15', fatal=False)
+            if version_compare(qt.version, '>=5.14.0'):
                 self._rcc_supports_depfiles = True
             else:
                 mlog.warning('rcc dependencies will not work properly until you move to Qt >= 5.14:',
@@ -434,15 +439,20 @@ class QtBaseModule(ExtensionModule):
 
         output: T.List[build.GeneratedList] = []
 
-        arguments = kwargs['extra_args'] + inc + compile_args + ['@INPUT@', '-o', '@OUTPUT@']
+        # depfile arguments (defaults to <output-name>.d)
+        DEPFILE_ARGS: T.List[str] = ['--output-dep-file'] if self._moc_supports_depfiles else []
+
+        arguments = kwargs['extra_args'] + DEPFILE_ARGS + inc + compile_args + ['@INPUT@', '-o', '@OUTPUT@']
         if kwargs['headers']:
             moc_gen = build.Generator(
                 self.tools['moc'], arguments, ['moc_@BASENAME@.cpp'],
+                depfile='moc_@BASENAME@.cpp.d',
                 name=f'Qt{self.qt_version} moc header')
             output.append(moc_gen.process_files(kwargs['headers'], state))
         if kwargs['sources']:
             moc_gen = build.Generator(
                 self.tools['moc'], arguments, ['@BASENAME@.moc'],
+                depfile='@BASENAME.moc.d@',
                 name=f'Qt{self.qt_version} moc source')
             output.append(moc_gen.process_files(kwargs['sources'], state))