Add a simple reproducibility test command.

docs/markdown/snippets/reprotester.md

@@ -0,0 +1,15 @@
+## Simple tool to test build reproducibility
+
+Meson now ships with a command for testing whether your project can be
+[built reprodicibly](https://reproducible-builds.org/). It can be used
+by running a command like the following in the source root of your
+project:
+
+    meson reprotest --intermediaries -- --buildtype=debugoptimized
+
+All command line options after the `--` are passed to the build
+invocations directly.
+
+This tool is not meant to be exhaustive, but instead easy and
+convenient to run. It will detect some but definitely not all
+reproducibility issues.

mesonbuild/mesonmain.py

@@ -65,7 +65,7 @@ class CommandLineParser:
     def __init__(self) -> None:
         # only import these once we do full argparse processing
         from . import mconf, mdist, minit, minstall, mintro, msetup, mtest, rewriter, msubprojects, munstable_coredata, mcompile, mdevenv, mformat
-        from .scripts import env2mfile
+        from .scripts import env2mfile, reprotest
         from .wrap import wraptool
         import shutil
 
@@ -103,6 +103,8 @@ def __init__(self) -> None:
                          help_msg='Run commands in developer environment')
         self.add_command('env2mfile', env2mfile.add_arguments, env2mfile.run,
                          help_msg='Convert current environment to a cross or native file')
+        self.add_command('reprotest', reprotest.add_arguments, reprotest.run,
+                         help_msg='Test if project builds reproducibly')
         self.add_command('format', mformat.add_arguments, mformat.run, aliases=['fmt'],
                          help_msg='Format meson source file')
         # Add new commands above this line to list them in help command

mesonbuild/scripts/reprotest.py

@@ -0,0 +1,130 @@
+# SPDX-License-Identifier: Apache-2.0
+# Copyright 2024 The Meson development team
+
+from __future__ import annotations
+
+import sys, os, subprocess, shutil
+import pathlib
+import typing as T
+
+if T.TYPE_CHECKING:
+    import argparse
+
+from ..mesonlib import get_meson_command
+
+# Note: when adding arguments, please also add them to the completion
+# scripts in $MESONSRC/data/shell-completions/
+def add_arguments(parser: 'argparse.ArgumentParser') -> None:
+    parser.add_argument('--intermediaries',
+                        default=False,
+                        action='store_true',
+                        help='Check intermediate files.')
+    parser.add_argument('mesonargs', nargs='*',
+                        help='Arguments to pass to "meson setup".')
+
+IGNORE_PATTERNS = ('.ninja_log',
+                   '.ninja_deps',
+                   'meson-private',
+                   'meson-logs',
+                   'meson-info',
+                   )
+
+INTERMEDIATE_EXTENSIONS = ('.gch',
+                           '.pch',
+                           '.o',
+                           '.obj',
+                           '.class',
+                           )
+
+class ReproTester:
+    def __init__(self, options: T.Any):
+        self.args = options.mesonargs
+        self.meson = get_meson_command()[:]
+        self.builddir = pathlib.Path('buildrepro')
+        self.storagedir = pathlib.Path('buildrepro.1st')
+        self.issues: T.List[str] = []
+        self.check_intermediaries = options.intermediaries
+
+    def run(self) -> int:
+        if not pathlib.Path('meson.build').is_file():
+            sys.exit('This command needs to be run at your project source root.')
+        self.check_ccache()
+        self.cleanup()
+        self.build()
+        self.check_output()
+        self.print_results()
+        if not self.issues:
+            self.cleanup()
+        return len(self.issues)
+
+    def check_ccache(self) -> None:
+        for evar in ('CC', 'CXX'):
+            evalue = os.environ.get(evar, '')
+            if 'ccache' in evalue:
+                print(f'Environment variable {evar} set to value "{evalue}".')
+                print('This implies using a compiler cache, which is incompatible with reproducible builds.')
+                sys.exit(1)
+
+    def cleanup(self) -> None:
+        if self.builddir.exists():
+            shutil.rmtree(self.builddir)
+        if self.storagedir.exists():
+            shutil.rmtree(self.storagedir)
+
+    def build(self) -> None:
+        setup_command: T.Sequence[T.Union[pathlib.Path, str]] = self.meson + ['setup', self.builddir] + self.args
+        build_command: T.Sequence[T.Union[pathlib.Path, str]] = self.meson + ['compile', '-C', self.builddir]
+        subprocess.check_call(setup_command)
+        subprocess.check_call(build_command)
+        self.builddir.rename(self.storagedir)
+        subprocess.check_call(setup_command)
+        subprocess.check_call(build_command)
+
+    def ignore_file(self, fstr: str) -> bool:
+        for p in IGNORE_PATTERNS:
+            if p in fstr:
+                return True
+        if not self.check_intermediaries:
+            for e in INTERMEDIATE_EXTENSIONS:
+                if fstr.endswith(e):
+                    return True
+        return False
+
+    def check_contents(self, fromdir: str, todir: str, check_contents: bool) -> None:
+        frompath = fromdir + '/'
+        topath = todir + '/'
+        for fromfile in pathlib.Path(fromdir).glob('**/*'):
+            if not fromfile.is_file():
+                continue
+            fstr = str(fromfile)
+            if self.ignore_file(fstr):
+                continue
+            assert fstr.startswith(frompath)
+            tofile = pathlib.Path(fstr.replace(frompath, topath, 1))
+            if not tofile.exists():
+                self.issues.append(f'Missing file: {tofile}')
+            elif check_contents:
+                fromdata = fromfile.read_bytes()
+                todata = tofile.read_bytes()
+                if fromdata != todata:
+                    self.issues.append(f'File contents differ: {fromfile}')
+
+    def print_results(self) -> None:
+        if self.issues:
+            print('Build differences detected')
+            for i in self.issues:
+                print(i)
+        else:
+            print('No differences detected.')
+
+    def check_output(self) -> None:
+        self.check_contents('buildrepro', 'buildrepro.1st', True)
+        self.check_contents('buildrepro.1st', 'buildrepro', False)
+
+def run(options: T.Any) -> None:
+    rt = ReproTester(options)
+    try:
+        sys.exit(rt.run())
+    except FileNotFoundError as e:
+        print(e)
+        sys.exit(1)