New subproject macos-bison-binary to provide bison on macOS

The version of bison that ships with macOS is too old, so we need to
provide our own version of it.

Fixes https://gitlab.freedesktop.org/gstreamer/gst-build/-/issues/174

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-build/-/merge_requests/257>

meson.build

@@ -91,6 +91,8 @@ os.symlink(os.path.join('@1@', 'subprojects', '@0@'),
 if build_system == 'windows'
   subproject('win-flex-bison-binaries')
   subproject('win-nasm')
+elif build_system == 'darwin'
+  subproject('macos-bison-binary')
 endif
 
 orc_subproject = subproject('orc', required: get_option('orc'))

subprojects/macos-bison-binary/.gitignore

@@ -0,0 +1,4 @@
+*.sw[op]
+*~
+*.tar.*
+bison-3.7.6-macos-x86_64/

subprojects/macos-bison-binary/README.md

@@ -0,0 +1,14 @@
+## How to generate binaries and update build files
+
+1. Download the latest bison source tarball
+1. Extract, then build it with --prefix=/
+1. Install into some dir using `DESTDIR`
+1. Delete all files except the following subdirs: `bin` `lib` `share/bison` `share/aclocal`
+1. Rename installdir to `bison-$version-macos-$arch` where `$arch` follows Meson's CPU families list:
+   https://mesonbuild.com/Reference-tables.html#cpu-families
+1. `tar -cvjf bison-$version-macos-$arch.tar.bz2 bison-$version-macos-$arch/`
+1. Fetch sha256sum: `shasum -256 bison-$version-macos-$arch.tar.bz2`
+1. Update sha256sum in `meson.build`
+1. Update `project()` version in `meson.build`
+
+That's it!

subprojects/macos-bison-binary/bison.py.in

@@ -0,0 +1,14 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import pathlib
+import subprocess
+
+srcdir = pathlib.Path("@SRCDIR@")
+extractdir = pathlib.Path("@EXTRACTDIR@")
+bison_path = srcdir / extractdir / 'bin/bison'
+env = os.environ.copy()
+env['BISON_PKGDATADIR'] = str(srcdir / extractdir / 'share/bison')
+ret = subprocess.run([str(bison_path)] + sys.argv[1:], check=False, env=env)
+sys.exit(ret.returncode)

subprojects/macos-bison-binary/download-binary.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import ssl
+import tarfile
+import hashlib
+import urllib.request
+import urllib.error
+
+# Disable certificate checking because it requires custom Python setup on macOS
+ctx = ssl.create_default_context()
+ctx.check_hostname = False
+ctx.verify_mode = ssl.CERT_NONE
+
+EXTRACTDIR = 'bison-{}-macos-{}'
+BASENAME = '{}.tar.bz2'.format(EXTRACTDIR)
+GSTREAMER_URL = 'https://gstreamer.freedesktop.org/src/mirror/{}'
+
+version = sys.argv[1]
+arch = sys.argv[2]
+tar_sha256 = sys.argv[3]
+source_dir = os.path.join(os.environ['MESON_SOURCE_ROOT'], os.environ['MESON_SUBDIR'])
+dest = BASENAME.format(version, arch)
+dest_path = os.path.join(source_dir, dest)
+extract_path = EXTRACTDIR.format(version, arch)
+
+def get_sha256(tarf):
+    hasher = hashlib.sha256()
+    with open(tarf, 'rb') as f:
+        hasher.update(f.read())
+    return hasher.hexdigest()
+
+def download():
+    for url in (GSTREAMER_URL.format(dest),):
+        print('Downloading {} to {}'.format(url, dest), file=sys.stderr)
+        try:
+            with open(dest_path, 'wb') as d:
+                f = urllib.request.urlopen(url, context=ctx)
+                d.write(f.read())
+            break
+        except urllib.error.URLError as ex:
+            print(ex, file=sys.stderr)
+            print('Failed to download from {!r}, trying mirror...'.format(url), file=sys.stderr)
+            continue
+    else:
+        curdir = os.path.dirname(sys.argv[0])
+        print('Couldn\'t download {!r}! Try downloading it manually and '
+              'placing it into {!r}'.format(dest, curdir), file=sys.stderr)
+
+def print_extract_dir():
+    'Print the extracted directory name'
+    print(extract_path, end='')
+
+if os.path.isfile(dest_path):
+    found_sha256 = get_sha256(dest_path)
+    if found_sha256 == tar_sha256:
+        if os.path.isdir(os.path.join(source_dir, extract_path)):
+            print('{} already downloaded and extracted'.format(dest), file=sys.stderr)
+            print_extract_dir()
+            sys.exit(0)
+    else:
+        print('{} checksum mismatch, redownloading'.format(dest), file=sys.stderr)
+        download()
+else:
+    download()
+
+found_sha256 = get_sha256(dest_path)
+if found_sha256 != tar_sha256:
+    print('SHA256 of downloaded file {} was {} instead of {}'
+          ''.format(dest, found_sha256, tar_sha256), file=sys.stderr)
+    sys.exit(1)
+
+print('Extracting {}'.format(dest), file=sys.stderr)
+tf = tarfile.open(dest_path, "r")
+tf.extractall(path=source_dir)
+print_extract_dir()

subprojects/macos-bison-binary/meson.build

@@ -0,0 +1,28 @@
+project('win-flex-bison-binary', version : '3.7.6')
+
+py3 = import('python3').find_python()
+
+message('Downloading and extracting bison for macOS x64...')
+
+arch = host_machine.cpu_family()
+tar_hash = '932f91d7c7fa0121abc3e5f8e54a7234b03d3de468c254ab8063ff8e6eb92a09'
+if arch != 'x86_64'
+  warning('bison binary is untested on non-x86_64, please report whether this worked or not')
+  arch = 'x86_64'
+endif
+
+ret = run_command(py3, files('download-binary.py'), meson.project_version(), arch, tar_hash)
+if ret.returncode() != 0
+  message(ret.stdout())
+  error(ret.stderr())
+endif
+
+conf = configuration_data()
+conf.set('SRCDIR', meson.project_source_root())
+conf.set('EXTRACTDIR', ret.stdout())
+bison_py = configure_file(
+    input: 'bison.py.in',
+    output: 'bison.py',
+    configuration: conf)
+
+meson.override_find_program('bison', find_program(bison_py))