run_command: Add new kwarg 'capture'

capture: false means we won't try to read the stdout at all.

Closes https://github.com/mesonbuild/meson/issues/3364

docs/markdown/snippets/run_command_check.md

@@ -1,4 +1,9 @@
-## New 'check' keyword argument for the run_command function
+## New keyword arguments: 'check' and 'capture' for run_command()
 
-If `check` is `true`, then the configuration will fail if the command returns a
+If `check:` is `true`, then the configuration will fail if the command returns a
 non-zero exit status. The default value is `false` for compatibility reasons.
+
+`run_command()` used to always capture the output and stored it for use in
+build files. However, sometimes the stdout is in a binary format which is meant
+to be discarded. For that case, you can now set the `capture:` keyword argument
+to `false`.

mesonbuild/interpreter.py

@@ -33,6 +33,7 @@ from .modules import ModuleReturnValue
 
 import os, sys, shutil, uuid
 import re, shlex
+import subprocess
 from collections import namedtuple
 from pathlib import PurePath
 
@@ -144,10 +145,11 @@ class TryRunResultHolder(InterpreterObject):
 
 class RunProcess(InterpreterObject):
 
-    def __init__(self, cmd, args, source_dir, build_dir, subdir, mesonintrospect, in_builddir=False, check=False):
+    def __init__(self, cmd, args, source_dir, build_dir, subdir, mesonintrospect, in_builddir=False, check=False, capture=True):
         super().__init__()
         if not isinstance(cmd, ExternalProgram):
             raise AssertionError('BUG: RunProcess must be passed an ExternalProgram')
+        self.capture = capture
         pc, self.stdout, self.stderr = self.run_command(cmd, args, source_dir, build_dir, subdir, mesonintrospect, in_builddir, check)
         self.returncode = pc.returncode
         self.methods.update({'returncode': self.returncode_method,
@@ -168,12 +170,17 @@ class RunProcess(InterpreterObject):
             cwd = os.path.join(source_dir, subdir)
         child_env = os.environ.copy()
         child_env.update(env)
+        stdout = subprocess.PIPE if self.capture else subprocess.DEVNULL
         mlog.debug('Running command:', ' '.join(command_array))
         try:
-            p, o, e = Popen_safe(command_array, env=child_env, cwd=cwd)
-            mlog.debug('--- stdout----')
-            mlog.debug(o)
-            mlog.debug('----stderr----')
+            p, o, e = Popen_safe(command_array, stdout=stdout, env=child_env, cwd=cwd)
+            if self.capture:
+                mlog.debug('--- stdout ---')
+                mlog.debug(o)
+            else:
+                o = ''
+                mlog.debug('--- stdout disabled ---')
+            mlog.debug('--- stderr ---')
             mlog.debug(e)
             mlog.debug('')
 
@@ -1796,7 +1803,7 @@ permitted_kwargs = {'add_global_arguments': {'language'},
                     'install_subdir': {'exclude_files', 'exclude_directories', 'install_dir', 'install_mode', 'strip_directory'},
                     'jar': build.known_jar_kwargs,
                     'project': {'version', 'meson_version', 'default_options', 'license', 'subproject_dir'},
-                    'run_command': {'check'},
+                    'run_command': {'check', 'capture'},
                     'run_target': {'command', 'depends'},
                     'shared_library': build.known_shlib_kwargs,
                     'shared_module': build.known_shmod_kwargs,
@@ -2080,7 +2087,7 @@ external dependencies (including libraries) must go to "dependencies".''')
                 if not isinstance(actual, wanted):
                     raise InvalidArguments('Incorrect argument type.')
 
-    @FeatureNewKwargs('run_command', '0.47.0', ['check'])
+    @FeatureNewKwargs('run_command', '0.47.0', ['check', 'capture'])
     @permittedKwargs(permitted_kwargs['run_command'])
     def func_run_command(self, node, args, kwargs):
         return self.run_command_impl(node, args, kwargs)
@@ -2090,6 +2097,7 @@ external dependencies (including libraries) must go to "dependencies".''')
             raise InterpreterException('Not enough arguments')
         cmd = args[0]
         cargs = args[1:]
+        capture = kwargs.get('capture', True)
         srcdir = self.environment.get_source_dir()
         builddir = self.environment.get_build_dir()
 
@@ -2149,7 +2157,8 @@ external dependencies (including libraries) must go to "dependencies".''')
                     if a not in self.build_def_files:
                         self.build_def_files.append(a)
         return RunProcess(cmd, expanded_args, srcdir, builddir, self.subdir,
-                          self.environment.get_build_command() + ['introspect'], in_builddir, check)
+                          self.environment.get_build_command() + ['introspect'],
+                          in_builddir=in_builddir, check=check, capture=capture)
 
     @stringArgs
     def func_gettext(self, nodes, args, kwargs):

mesonbuild/mesonlib.py

@@ -796,22 +796,19 @@ def expand_arguments(args):
             return None
     return expended_args
 
-def Popen_safe(args, write=None, stderr=subprocess.PIPE, **kwargs):
+def Popen_safe(args, write=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE, **kwargs):
     import locale
     encoding = locale.getpreferredencoding()
     if sys.version_info < (3, 6) or not sys.stdout.encoding or encoding.upper() != 'UTF-8':
-        return Popen_safe_legacy(args, write=write, stderr=stderr, **kwargs)
-    p = subprocess.Popen(args, universal_newlines=True,
-                         close_fds=False,
-                         stdout=subprocess.PIPE,
-                         stderr=stderr, **kwargs)
+        return Popen_safe_legacy(args, write=write, stdout=stdout, stderr=stderr, **kwargs)
+    p = subprocess.Popen(args, universal_newlines=True, close_fds=False,
+                         stdout=stdout, stderr=stderr, **kwargs)
     o, e = p.communicate(write)
     return p, o, e
 
-def Popen_safe_legacy(args, write=None, stderr=subprocess.PIPE, **kwargs):
+def Popen_safe_legacy(args, write=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE, **kwargs):
     p = subprocess.Popen(args, universal_newlines=False,
-                         stdout=subprocess.PIPE,
-                         stderr=stderr, **kwargs)
+                         stdout=stdout, stderr=stderr, **kwargs)
     if write is not None:
         write = write.encode('utf-8')
     o, e = p.communicate(write)

test cases/common/38 run program/meson.build

@@ -55,3 +55,19 @@ if c.returncode() != 0
   error('Using files() in argument failed.')
 endif
 
+py3 = import('python3').find_python()
+
+ret = run_command(py3, '-c', 'print("some output")')
+assert(ret.returncode() == 0, 'failed to run python3: ' + ret.stderr())
+assert(ret.stdout() == 'some output\n', 'failed to run python3')
+
+ret = run_command(py3, '-c', 'print("some output")', capture : false)
+assert(ret.returncode() == 0, 'failed to run python3: ' + ret.stderr())
+assert(ret.stdout() == '', 'stdout is "@0@" instead of empty'.format(ret.stdout()))
+
+dd = find_program('dd', required : false)
+if dd.found()
+  ret = run_command(dd, 'if=/dev/urandom', 'bs=10', 'count=1', capture: false)
+  assert(ret.returncode() == 0, 'failed to run dd: ' + ret.stderr())
+  assert(ret.stdout() == '', 'stdout is "@0@" instead of empty'.format(ret.stdout()))
+endif