backends: choose whether to serialize in as_meson_exe_cmdline

This removes more duplicate code between custom targets and generators.
In addition, generators can now have arguments with newlines in them.

mesonbuild/backend/backends.py

@@ -323,26 +323,33 @@ class Backend:
                 raise MesonException('Unknown data type in object list.')
         return obj_list
 
-    def as_meson_exe_cmdline(self, tname, exe, cmd_args, workdir, env=None,
-                             extra_paths=None, capture=None):
+    def as_meson_exe_cmdline(self, tname, exe, cmd_args, workdir=None,
+                             for_machine=MachineChoice.BUILD,
+                             extra_bdeps=None, capture=None, force_serialize=False):
         '''
         Serialize an executable for running with a generator or a custom target
         '''
         import hashlib
-        if env is None:
-            env = {}
-        if extra_paths is None:
-            # The callee didn't check if we needed extra paths, so check it here
-            if mesonlib.is_windows() or mesonlib.is_cygwin():
-                extra_paths = self.determine_windows_extra_paths(exe, [])
-            else:
-                extra_paths = []
-        # Can't just use exe.name here; it will likely be run more than once
+        machine = self.environment.machines[for_machine]
+        if machine.is_windows() or machine.is_cygwin():
+            extra_paths = self.determine_windows_extra_paths(exe, extra_bdeps or [])
+        else:
+            extra_paths = []
+
+        force_serialize = force_serialize or extra_paths or capture or workdir or \
+            any('\n' in c for c in cmd_args)
+        if not force_serialize:
+            return None
+
+        workdir = workdir or self.environment.get_build_dir()
+        env = {}
         if isinstance(exe, (dependencies.ExternalProgram,
                             build.BuildTarget, build.CustomTarget)):
             basename = exe.name
         else:
             basename = os.path.basename(exe)
+
+        # Can't just use exe.name here; it will likely be run more than once
         # Take a digest of the cmd args, env, workdir, and capture. This avoids
         # collisions and also makes the name deterministic over regenerations
         # which avoids a rebuild by Ninja because the cmdline stays the same.

mesonbuild/backend/ninjabackend.py

@@ -658,32 +658,13 @@ int dummy;
             # Add a dependency on all the outputs of this target
             for output in d.get_outputs():
                 elem.add_dep(os.path.join(self.get_target_dir(d), output))
-        serialize = False
-        extra_paths = []
-        # If the target requires capturing stdout, then use the serialized
-        # executable wrapper to capture that output and save it to a file.
-        if target.capture:
-            serialize = True
-        # If the command line requires a newline, also use the wrapper, as
-        # ninja does not support them in its build rule syntax.
-        if any('\n' in c for c in cmd):
-            serialize = True
-        # Windows doesn't have -rpath, so for EXEs that need DLLs built within
-        # the project, we need to set PATH so the DLLs are found. We use
-        # a serialized executable wrapper for that and check if the
-        # CustomTarget command needs extra paths first.
-        machine = self.environment.machines[target.for_machine]
-        if machine.is_windows() or machine.is_cygwin():
-            extra_bdeps = target.get_transitive_build_target_deps()
-            extra_paths = self.determine_windows_extra_paths(target.command[0], extra_bdeps)
-            if extra_paths:
-                serialize = True
-        if serialize:
-            cmd = self.as_meson_exe_cmdline(target.name, target.command[0], cmd[1:],
-                                            # All targets are built from the build dir
-                                            self.environment.get_build_dir(),
-                                            extra_paths=extra_paths,
-                                            capture=ofilenames[0] if target.capture else None)
+
+        meson_exe_cmd = self.as_meson_exe_cmdline(target.name, target.command[0], cmd[1:],
+                                                  for_machine=target.for_machine,
+                                                  extra_bdeps=target.get_transitive_build_target_deps(),
+                                                  capture=ofilenames[0] if target.capture else None)
+        if meson_exe_cmd:
+            cmd = meson_exe_cmd
             cmd_type = 'meson_exe.py custom'
         else:
             cmd_type = 'custom'
@@ -1785,18 +1766,13 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
                 outfilelist = outfilelist[len(generator.outputs):]
             args = self.replace_paths(target, args, override_subdir=subdir)
             cmdlist = exe_arr + self.replace_extra_args(args, genlist)
-            if generator.capture:
-                cmd = self.as_meson_exe_cmdline(
-                    'generator ' + cmdlist[0],
-                    cmdlist[0],
-                    cmdlist[1:],
-                    self.environment.get_build_dir(),
-                    capture=outfiles[0]
-                )
-                abs_pdir = os.path.join(self.environment.get_build_dir(), self.get_target_dir(target))
-                os.makedirs(abs_pdir, exist_ok=True)
-            else:
-                cmd = cmdlist
+            meson_exe_cmd = self.as_meson_exe_cmdline('generator ' + cmdlist[0],
+                                                      cmdlist[0], cmdlist[1:],
+                                                      capture=outfiles[0] if generator.capture else None)
+            if meson_exe_cmd:
+                cmdlist = meson_exe_cmd
+            abs_pdir = os.path.join(self.environment.get_build_dir(), self.get_target_dir(target))
+            os.makedirs(abs_pdir, exist_ok=True)
 
             elem = NinjaBuildElement(self.all_outputs, outfiles, rulename, infilename)
             elem.add_dep([self.get_target_filename(x) for x in generator.depends])
@@ -1811,7 +1787,7 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
                 elem.add_item('DESC', 'Generating source from {!r}.'.format(sole_output))
             if isinstance(exe, build.BuildTarget):
                 elem.add_dep(self.get_target_filename(exe))
-            elem.add_item('COMMAND', cmd)
+            elem.add_item('COMMAND', cmdlist)
             self.add_build(elem)
 
     def scan_fortran_module_outputs(self, target):

mesonbuild/backend/vs2010backend.py

@@ -150,8 +150,9 @@ class Vs2010Backend(backends.Backend):
                         'generator ' + cmd[0],
                         cmd[0],
                         cmd[1:],
-                        tdir_abs,
-                        capture=outfiles[0] if generator.capture else None
+                        workdir=tdir_abs,
+                        capture=outfiles[0] if generator.capture else None,
+                        force_serialize=True
                     )
                     deps = cmd[-1:] + deps
                     abs_pdir = os.path.join(self.environment.get_build_dir(), self.get_target_dir(target))
@@ -559,12 +560,12 @@ class Vs2010Backend(backends.Backend):
         # there are many arguments.
         tdir_abs = os.path.join(self.environment.get_build_dir(), self.get_target_dir(target))
         extra_bdeps = target.get_transitive_build_target_deps()
-        extra_paths = self.determine_windows_extra_paths(target.command[0], extra_bdeps)
         wrapper_cmd = self.as_meson_exe_cmdline(target.name, target.command[0], cmd[1:],
                                                 # All targets run from the target dir
-                                                tdir_abs,
-                                                extra_paths=extra_paths,
-                                                capture=ofilenames[0] if target.capture else None)
+                                                workdir=tdir_abs,
+                                                extra_bdeps=extra_bdeps,
+                                                capture=ofilenames[0] if target.capture else None,
+                                                force_serialize=True)
         if target.build_always_stale:
             # Use a nonexistent file to always consider the target out-of-date.
             ofilenames += [self.nonexistent_file(os.path.join(self.environment.get_scratch_dir(),