meson: Cleanup our meson integration

Writing a proper "depfile" to follow depending files, based on depfiles
generated by rustc.

This is based on work done while working on gobject-examples-rs

cargo_wrapper.py

@@ -1,58 +1,91 @@
 #!/usr/bin/env python3
 
+import hashlib
+import re
 import glob
 import os
-import os.path
 import shutil
 import subprocess
 import sys
+from argparse import ArgumentParser
+from pathlib import Path as P
 
-PLUGIN_DIRS = ['audio', 'generic', 'net', 'text', 'utils', 'video']
+PARSER = ArgumentParser()
+PARSER.add_argument('command', choices=['build', 'test'])
+PARSER.add_argument('build_dir', type=P)
+PARSER.add_argument('src_dir', type=P)
+PARSER.add_argument('root_dir', type=P)
+PARSER.add_argument('target', choices=['release', 'debug'])
+PARSER.add_argument('include')
+PARSER.add_argument('extra_env')
+PARSER.add_argument('prefix', type=P)
+PARSER.add_argument('libdir', type=P)
+PARSER.add_argument('--version', default=None)
+PARSER.add_argument('--exts', nargs="+", default=[])
+PARSER.add_argument('--depfile')
 
-command, meson_build_dir, meson_current_source_dir, meson_build_root, target, include, extra_env, prefix, libdir = sys.argv[
-    1:10]
-include = include.split(',')
 
-cargo_target_dir = os.path.join(meson_build_dir, 'target')
+def generate_depfile_for(libfile):
+    file_stem = libfile.parent / libfile.stem
+    depfile_content = ""
+    with open(f"{file_stem}.d", 'r') as depfile:
+        for l in depfile.readlines():
+            if l.startswith(str(file_stem)):
+                output, srcs = l.split(":", maxsplit=2)
+                output = re.sub(f"^{file_stem}",
+                                f"{opts.build_dir / libfile.stem}", f)
+
+                all_deps = []
+                for src in srcs.split(" "):
+                    all_deps.append(src)
+                    src = P(src)
+                    if src.name == 'lib.rs':
+                        # `rustc` doesn't take `Cargo.toml` into account
+                        # but we need to
+                        cargo_toml = src.parent.parent / 'Cargo.toml'
+                        if cargo_toml.exists():
+                            all_deps.append(str(cargo_toml))
+
+                depfile_content += f"{output}: {' '.join(all_deps)}\n"
+
+    return depfile_content
+
+
+if __name__ == "__main__":
+    opts = PARSER.parse_args()
+
+    logfile = open(opts.root_dir / 'meson-logs' /
+                   f'{opts.src_dir.name}-cargo-wrapper.log', 'w')
+
+    print(opts, file=logfile)
+    cargo_target_dir = opts.build_dir / 'target'
 
     env = os.environ.copy()
-env['CARGO_TARGET_DIR'] = cargo_target_dir
+    env['CARGO_TARGET_DIR'] = str(cargo_target_dir)
 
     pkg_config_path = env.get('PKG_CONFIG_PATH', '').split(':')
-pkg_config_path.append(os.path.join(meson_build_root, 'meson-uninstalled'))
+    pkg_config_path.append(str(opts.root_dir / 'meson-uninstalled'))
     env['PKG_CONFIG_PATH'] = ':'.join(pkg_config_path)
 
-if len(extra_env) > 0:
+    if opts.extra_env:
-    for e in extra_env.split(','):
+        for e in opts.extra_env.split(','):
             k, v = e.split(':')
             env[k] = v
 
-if command == 'build':
+    if opts.command == 'build':
-    # cargo build
+        cargo_cmd = ['cargo', 'cbuild']
-    ext = sys.argv[10]
+        if opts.target == 'release':
-    # when using --default-library=both 2 extensions are passed
-    try:
-        ext2 = sys.argv[11]
-    except IndexError:
-        ext2 = None
-
-    # Build with the 'static' feature enforcing the minimal gst version required for static builds
-    cargo_cmd = ['cargo', 'cbuild', '--features', 'static']
-    if target == 'release':
             cargo_cmd.append('--release')
-elif command == 'test':
+    elif opts.command == 'test':
         # cargo test
         cargo_cmd = ['cargo', 'ctest', '--no-fail-fast', '--color=always']
     else:
-    print("Unknown command:", command)
+        print("Unknown command:", opts.command, file=logfile)
         sys.exit(1)
 
-cargo_cmd.extend(
+    cargo_cmd.extend(['--manifest-path', opts.src_dir / 'Cargo.toml'])
-    ['--manifest-path', os.path.join(meson_current_source_dir, 'Cargo.toml')])
+    cargo_cmd.extend(['--prefix', opts.prefix, '--libdir',
-
+                     opts.prefix / opts.libdir])
-cargo_cmd.extend(['--prefix', prefix, '--libdir',
-                  os.path.join(prefix, libdir)])
-
 
     def run(cargo_cmd, env):
         try:
@@ -60,30 +93,46 @@ def run(cargo_cmd, env):
         except subprocess.SubprocessError:
             sys.exit(1)
 
-
+    for p in opts.include.split(','):
-for p in include:
         cargo_cmd.extend(['-p', p])
     run(cargo_cmd, env)
 
-if command == 'build':
+    if opts.command == 'build':
-    target_dir = os.path.join(cargo_target_dir, '**', target)
+        target_dir = cargo_target_dir / '**' / opts.target
+
         # Copy so files to build dir
-    for f in glob.glob(os.path.join(target_dir, '*.' + ext), recursive=True):
+        depfile_content = ""
-        shutil.copy(f, meson_build_dir)
+        for ext in opts.exts:
-    if ext2:
+            for f in glob.glob(str(target_dir / f'*.{ext}'), recursive=True):
-        for f in glob.glob(os.path.join(target_dir, '*.' + ext2), recursive=True):
+                libfile = P(f)
-            shutil.copy(f, meson_build_dir)
+
+                depfile_content += generate_depfile_for(libfile)
+
+                copied_file = (opts.build_dir / libfile.name)
+                try:
+                    if copied_file.stat().st_mtime == libfile.stat().st_mtime:
+                        print(f"{copied_file} has not changed.", file=logfile)
+                        continue
+                except FileNotFoundError:
+                    pass
+
+                print(f"Copying {copied_file}", file=logfile)
+                shutil.copy2(f, opts.build_dir)
+
+        with open(opts.depfile, 'w') as depfile:
+            depfile.write(depfile_content)
+
         # Copy generated pkg-config files
-    for f in glob.glob(os.path.join(target_dir, '*.pc'), recursive=True):
+        for f in glob.glob(str(target_dir / '*.pc'), recursive=True):
-        shutil.copy(f, meson_build_dir)
+            shutil.copy(f, opts.build_dir)
 
         # Move -uninstalled.pc to meson-uninstalled
-    uninstalled = os.path.join(meson_build_dir, 'meson-uninstalled')
+        uninstalled = opts.build_dir / 'meson-uninstalled'
-    if not os.path.exists(uninstalled):
+        os.makedirs(uninstalled, exist_ok=True)
-        os.mkdir(uninstalled)
+
-    for f in glob.glob(os.path.join(meson_build_dir, '*-uninstalled.pc')):
+        for f in opts.build_dir.glob('*-uninstalled.pc'):
             # move() does not allow us to update the file so remove it if it already exists
-        dest = os.path.join(uninstalled, os.path.basename(f))
+            dest = uninstalled / P(f).name
-        if os.path.exists(dest):
+            if dest.exists():
-            os.unlink(dest)
+                dest.unlink()
             shutil.move(f, uninstalled)

meson.build

@@ -176,32 +176,16 @@ extra_env_str = ','.join(extra_env_list)
 plugins_install_dir = get_option('libdir') / 'gstreamer-1.0'
 pkgconfig_install_dir = get_option('libdir') / 'pkgconfig'
 
-# Use all files checked in git to  figure out when to rebuild
-git = find_program('git', required: false)
-files = []
-if git.found()
-  tmp = run_command([git, 'ls-files', '.'])
-  if tmp.returncode() == 0
-    files = tmp.stdout().split()
-  endif
-endif
-
-if files.length() > 0
-  build_always_stale = false
-else
-  warning('Could not retrieve list of files, always building the target')
-  build_always_stale = true
-endif
 
+python = import('python').find_installation()
 rs_plugins = custom_target('gst-plugins-rs',
   build_by_default: true,
   output: output,
   console: true,
   install: true,
   install_dir: plugins_install_dir,
-  input: files,
-  build_always_stale: build_always_stale,
   depends: depends,
+  depfile: 'gst-plugins-rs.dep',
   command: [cargo_wrapper,
     'build',
     meson.current_build_dir(),
@@ -212,14 +196,15 @@ rs_plugins = custom_target('gst-plugins-rs',
     extra_env_str,
     get_option('prefix'),
     get_option('libdir'),
-    extensions])
+    '--depfile', '@DEPFILE@',
+    '--exts', extensions,
+  ])
 
 plugins = rs_plugins.to_list()
 
 # We don't need to pass a command as we depends on the target above
 # but it is currently mandatory ( https://github.com/mesonbuild/meson/issues/8059 )
 # so use python as it's guaranteed to be present on any setup
-python = import('python').find_installation()
 custom_target('gst-plugins-rs-pc-files',
   build_by_default: true,
   output: pc_files,