cython: wire up support for emitting and using depfiles

This solves rebuild issues when e.g. importing a .pxd header from a .pyx
file, just like C/C++ source headers. The transpiler needs to run again
in this case.

This functionality is present in the 3.0.0 alphas of cython, and is also
backported to 0.29.33.

Fixes #9049

mesonbuild/backend/ninjabackend.py

@@ -2234,10 +2234,14 @@ class NinjaBackend(backends.Backend):
         description = 'Compiling Cython source $in'
         command = compiler.get_exelist()
 
-        args = ['$ARGS', '$in']
+        depargs = compiler.get_dependency_gen_args('$out', '$DEPFILE')
+        depfile = '$out.dep' if depargs else None
+
+        args = depargs + ['$ARGS', '$in']
         args += NinjaCommandArg.list(compiler.get_output_args('$out'), Quoting.none)
         self.add_rule(NinjaRule(rule, command + args, [],
                                 description,
+                                depfile=depfile,
                                 extra='restat = 1'))
 
     def generate_rust_compile_rules(self, compiler):

mesonbuild/compilers/cython.py

@@ -7,7 +7,7 @@ from __future__ import annotations
 import typing as T
 
 from .. import coredata
-from ..mesonlib import EnvironmentException, OptionKey
+from ..mesonlib import EnvironmentException, OptionKey, version_compare
 from .compilers import Compiler
 
 if T.TYPE_CHECKING:
@@ -40,6 +40,14 @@ class CythonCompiler(Compiler):
         # compiler might though
         return []
 
+    def get_dependency_gen_args(self, outtarget: str, outfile: str) -> T.List[str]:
+        if version_compare(self.version, '>=0.29.33'):
+            return ['-M']
+        return []
+
+    def get_depfile_suffix(self) -> str:
+        return 'dep'
+
     def sanity_check(self, work_dir: str, environment: 'Environment') -> None:
         code = 'print("hello world")'
         with self.cached_compile(code, environment.coredata) as p: