ninjabackend: start adjusting for differences between rustc and rustdoc

Add functions to RustCompiler() to account for differences
between rustc and "rustdoc --test": rustdoc always generates
a binary, does not support -g, and does not need --emit.

Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

mesonbuild/backend/ninjabackend.py

@@ -2008,8 +2008,8 @@ class NinjaBackend(backends.Backend):
         # Rustc replaces - with _. spaces or dots are not allowed, so we replace them with underscores
         args += ['--crate-name', target.name.replace('-', '_').replace(' ', '_').replace('.', '_')]
         depfile = os.path.join(self.get_target_private_dir(target), target.name + '.d')
-        args += ['--emit', f'dep-info={depfile}']
-        args += ['--emit', f'link'={target_name}']
+        args += rustc.get_dependency_gen_args(target_name, depfile)
+        args += rustc.get_output_args(target_name)
         args += ['-C', 'metadata=' + target.get_id()]
         args += target.get_extra_args('rust')
 

mesonbuild/compilers/rust.py

@@ -170,7 +170,10 @@ class RustCompiler(Compiler):
         self.native_static_libs = [i for i in match.group(1).split() if i not in exclude]
 
     def get_dependency_gen_args(self, outtarget: str, outfile: str) -> T.List[str]:
-        return ['--dep-info', outfile]
+        return ['--emit', f'dep-info={outfile}']
+
+    def get_output_args(self, outputname: str) -> T.List[str]:
+        return ['--emit', f'link={outputname}']
 
     @functools.lru_cache(maxsize=None)
     def get_sysroot(self) -> str:
@@ -222,9 +225,6 @@ class RustCompiler(Compiler):
 
         return parameter_list
 
-    def get_output_args(self, outputname: str) -> T.List[str]:
-        return ['-o', outputname]
-
     @classmethod
     def use_linker_args(cls, linker: str, version: str) -> T.List[str]:
         return ['-C', f'linker={linker}']
@@ -324,3 +324,21 @@ class ClippyRustCompiler(RustCompiler):
     """
 
     id = 'clippy-driver rustc'
+
+
+class RustdocTestCompiler(RustCompiler):
+
+    """We invoke Rustdoc to run doctests.  Some of the flags
+       are different from rustc and some (e.g. --emit link) are
+       ignored."""
+
+    id = 'rustdoc --test'
+
+    def get_debug_args(self, is_debug: bool) -> T.List[str]:
+        return []
+
+    def get_dependency_gen_args(self, outtarget: str, outfile: str) -> T.List[str]:
+        return []
+
+    def get_output_args(self, outputname: str) -> T.List[str]:
+        return []