Allow capturing command output of a custom target.

For commands that always output to stdout and don't have a "-o" or
"--output" or some other similar option, this 'capture' setting allows
the build to capture the result and place it in the output file.

mesonbuild/backend/backends.py

@@ -37,7 +37,7 @@ class InstallData():
 
 class ExecutableSerialisation():
     def __init__(self, name, fname, cmd_args, env, is_cross, exe_wrapper,
-                 workdir, extra_paths):
+                 workdir, extra_paths, capture):
         self.name = name
         self.fname = fname
         self.cmd_args = cmd_args
@@ -46,6 +46,7 @@ class ExecutableSerialisation():
         self.exe_runner = exe_wrapper
         self.workdir = workdir
         self.extra_paths = extra_paths
+        self.capture = capture
 
 class TestSerialisation:
     def __init__(self, name, suite, fname, is_cross, exe_wrapper, is_parallel, cmd_args, env,
@@ -176,7 +177,8 @@ class Backend():
                 raise MesonException('Unknown data type in object list.')
         return obj_list
 
-    def serialise_executable(self, exe, cmd_args, workdir, env={}):
+    def serialise_executable(self, exe, cmd_args, workdir, env={},
+                             capture=None):
         import uuid
         # Can't just use exe.name here; it will likely be run more than once
         if isinstance(exe, (dependencies.ExternalProgram,
@@ -207,7 +209,7 @@ class Backend():
                 extra_paths = []
             es = ExecutableSerialisation(basename, exe_fullpath, cmd_args, env,
                                          is_cross, exe_wrapper, workdir,
-                                         extra_paths)
+                                         extra_paths, capture)
             pickle.dump(es, f)
         return exe_data
 

mesonbuild/backend/ninjabackend.py

@@ -379,15 +379,19 @@ int dummy;
                 tmp = [tmp]
             for fname in tmp:
                 elem.add_dep(os.path.join(self.get_target_dir(d), fname))
+        # If the target requires capturing stdout, then use the serialized
+        # executable wrapper to capture that output and save it to a file.
+        #
         # 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.
-        if mesonlib.is_windows() and \
-           self.determine_windows_extra_paths(target.command[0]):
+        if target.capture or (mesonlib.is_windows() and
+                self.determine_windows_extra_paths(target.command[0])):
             exe_data = self.serialise_executable(target.command[0], cmd[1:],
                 # All targets are built from the build dir
-                self.environment.get_build_dir())
+                self.environment.get_build_dir(),
+                capture=ofilenames[0] if target.capture else None)
             cmd = [sys.executable, self.environment.get_build_command(),
                    '--internal', 'exe', exe_data]
             cmd_type = 'meson_exe.py custom'

mesonbuild/build.py

@@ -927,6 +927,7 @@ class CustomTarget:
     known_kwargs = {'input' : True,
                     'output' : True,
                     'command' : True,
+                    'capture' : False,
                     'install' : True,
                     'install_dir' : True,
                     'build_always' : True,
@@ -982,6 +983,10 @@ class CustomTarget:
                 raise InvalidArguments('Output argument not a string.')
             if '/' in i:
                 raise InvalidArguments('Output must not contain a path segment.')
+        self.capture = kwargs.get('capture', False)
+        if self.capture and len(self.output) != 1:
+            raise InvalidArguments(
+                'Capturing can only output to a single file.')
         if 'command' not in kwargs:
             raise InvalidArguments('Missing keyword argument "command".')
         cmd = kwargs['command']

mesonbuild/scripts/meson_exe.py

@@ -59,6 +59,11 @@ def run_exe(exe):
                          stderr=subprocess.PIPE,
                          env=child_env,
                          cwd=exe.workdir)
+    stdout, stderr = p.communicate()
+    if exe.capture and p.returncode == 0:
+        with open(exe.capture, 'wb') as output:
+            output.write(stdout)
+    return p.returncode
 
 def run(args):
     global options
@@ -68,7 +73,7 @@ def run(args):
         print(sys.argv[0] + ' [data file]')
     exe_data_file = options.args[0]
     exe = pickle.load(open(exe_data_file, 'rb'))
-    run_exe(exe)
+    return run_exe(exe)
 
 if __name__ == '__main__':
     sys.exit(run(sys.argv[1:]))

test cases/common/117 custom target capture/data_source.txt

@@ -0,0 +1 @@
+This is a text only input file.

test cases/common/117 custom target capture/installed_files.txt

@@ -0,0 +1 @@
+usr/subdir/data.dat

test cases/common/117 custom target capture/meson.build

@@ -0,0 +1,16 @@
+project('custom target', 'c')
+
+python = find_program('python3')
+
+# Note that this will not add a dependency to the compiler executable.
+# Code will not be rebuilt if it changes.
+comp = '@0@/@1@'.format(meson.current_source_dir(), 'my_compiler.py')
+
+mytarget = custom_target('bindat',
+output : 'data.dat',
+input : 'data_source.txt',
+capture : true,
+command : [python, comp, '@INPUT@'],
+install : true,
+install_dir : 'subdir'
+)

test cases/common/117 custom target capture/my_compiler.py

@@ -0,0 +1,13 @@
+#!/usr/bin/env python3
+
+import sys
+
+if __name__ == '__main__':
+    if len(sys.argv) != 2:
+        print(sys.argv[0], 'input_file')
+        sys.exit(1)
+    ifile = open(sys.argv[1]).read()
+    if ifile != 'This is a text only input file.\n':
+        print('Malformed input')
+        sys.exit(1)
+    print('This is a binary output file.')