[setup] Rewrite dpkg_install_from_wget in Python

This removes the special case logic for "remove bazel first", but
(1) now that we're installing with apt-get instead of dpkg, hopefully
that doesn't matter in practice, and (2) upstream bazel hasn't shipped
a new deb in several years and their apt site only goes up to 22.04,
so hopefully this isn't a problem anymore.

Author: jwnimmer-tri

setup/BUILD.bazel

@@ -9,6 +9,7 @@ package(default_visibility = ["//visibility:private"])
 PREREQUISITES_DATA = glob([
     "**/Brewfile*",
     "**/*.lock",
+    "**/*.json",
     "**/*.toml",
     "**/*.txt",
 ])

setup/install_prereqs.py

@@ -8,6 +8,8 @@
 
 import argparse
 import functools
+import hashlib
+import json
 import logging
 import os
 from pathlib import Path
@@ -16,7 +18,10 @@
 import shlex
 import subprocess
 import sys
+import tempfile
 import textwrap
+import urllib.parse
+import urllib.request
 
 _MY_DIR: Path = Path(__file__).parent
 """The directory containing this script, used to locate our data assets."""
@@ -38,38 +43,228 @@ def _workspace_dir() -> Path:
     return _MY_DIR.parent
 
 
+@functools.cache
+def _is_ubuntu() -> bool:
+    if platform.system() == "Linux":
+        os_release = platform.freedesktop_os_release()["ID"]
+        return os_release == "ubuntu"
+    return False
+
+
+@functools.cache
+def _os_codename() -> str:
+    if platform.system() == "Linux":
+        return platform.freedesktop_os_release()["VERSION_CODENAME"]
+    raise NotImplementedError(platform.system())
+
+
+def _check_sudo() -> None:
+    """Checks that 'sudo' has sufficient credentials."""
+    subprocess.check_call(["sudo", "-v"])
+
+
 def _run(
     *,
     args: list,
     cwd: Path | None = None,
+    check: bool = True,
+    superuser: bool = False,
     quiet: bool = False,
-) -> None:
-    """Runs a subprocess command given by `args`. Failure of the command is an
-    `_error`. When `quiet` is true, the command line will not be printed by
-    default.
-    """
+    interactive: bool = False,
+) -> subprocess.CompletedProcess:
+    """Runs a subprocess command given by `args`. When `check` is true, failure
+    of the command is an `_error`. When `superuser` is true, the command will
+    be run under 'sudo' unless the euid is already root. When `quiet` is
+    true, the command line will not be printed by default. When `interactive`
+    is true, input is allowed and output is unbuffered. Returns the completed
+    process object."""
     command = args[0]
+    if superuser and os.geteuid() != 0:
+        _check_sudo()
+        args = ["sudo"] + args
     logging.log(
         msg=f"Running: {shlex.join(args)} ...",
         level=logging.DEBUG if quiet else logging.INFO,
     )
     process = subprocess.run(
         args,
         cwd=cwd,
-        stdin=subprocess.DEVNULL,
-        stdout=subprocess.PIPE,
-        stderr=subprocess.STDOUT,
+        stdin=subprocess.DEVNULL if not interactive else None,
+        stdout=subprocess.PIPE if not interactive else None,
+        stderr=subprocess.STDOUT if not interactive else None,
         text=True,
     )
-    problem = process.returncode != 0
-    for line in process.stdout.splitlines():
-        logging.log(
-            msg=f"... from {command}: {line}",
-            level=logging.INFO if problem else logging.DEBUG,
-        )
+    problem = check and (process.returncode != 0)
+    if process.stdout is not None:
+        for line in process.stdout.splitlines():
+            logging.log(
+                msg=f"... from {command}: {line}",
+                level=logging.INFO if problem else logging.DEBUG,
+            )
     logging.debug(f"... finished {command}.")
     if problem:
         _error(f"{command} failed with returncode {process.returncode}")
+    return process
+
+
+def _get_dpkg_versions(package_names: list[str]) -> dict[str, str]:
+    """Returns the installed version of packages. The input is a list of
+    package names, and the return value is a dict mapping all of those
+    names to their installed version (or None, if not installed)."""
+    assert package_names
+    result = {}
+    for name in package_names:
+        result[name] = None
+    process = _run(
+        args=[
+            "dpkg-query",
+            "--show",
+            "--showformat=${Package} ${db:Status-Abbrev} ${Version}\n",
+        ]
+        + package_names,
+        check=False,
+        quiet=True,
+    )
+    for line in process.stdout.splitlines():
+        tokens = line.split()
+        if len(tokens) != 3:
+            continue
+        name, status, version = tokens
+        if status == "ii":
+            result[name] = version
+    logging.debug(f"dpkg_versions = {result!r}")
+    return result
+
+
+def _apt_install(*, package_names: list[str], yes: bool) -> None:
+    """Installs the given packages using 'apt-get'.
+    The `yes` flag is passed along to apt as `--yes`."""
+    assert package_names
+    args = [
+        "apt-get",
+        "install",
+        "--no-install-recommends",
+    ]
+    if yes:
+        args.append("--yes")
+    args.extend(package_names)
+    process = _run(args=args, superuser=True, check=yes)
+    if process.returncode == 0:
+        return
+    # We can only reach here when yes=False (i.e., check=False). The apt-get
+    # command didn't work, and the most likely reason is it needs Y/n input
+    # from the user, so we'll try it again allowing for user input.
+    _run(args=args, superuser=True, interactive=True, quiet=True)
+
+
+def _download(*, temp_dir: Path, package: dict) -> Path:
+    """Downloads a `*.deb` package a denoted by the given `package` entry loaded
+    from the setupo/ubuntu/packages.json file. Returns its path inside temp_dir.
+    """
+    name = package["name"]
+    version = package["version"]
+    urls = package["urls"]
+    sha256 = package["sha256"]
+
+    logging.info(f"Downloading {name} {version} ...")
+
+    # Try each url in turn.
+    errors = []
+    for url in urls:
+        logging.debug(f"Trying {url} ...")
+        basename = urllib.parse.urlparse(url).path.split("/")[-1]
+        temp_filename = temp_dir / basename
+        hasher = hashlib.sha256()
+        with temp_filename.open("wb") as f:
+            try:
+                with urllib.request.urlopen(url=url, timeout=30) as response:
+                    while True:
+                        data = response.read(4096)
+                        if not data:
+                            break
+                        hasher.update(data)
+                        f.write(data)
+            except OSError as e:
+                errors.append(f"Candidate {url} failed:\n{e}")
+                continue
+        download_sha256 = hasher.hexdigest()
+        if download_sha256 == sha256:
+            return temp_filename
+        errors.append(
+            f"Candidate {url} failed:\n"
+            f"Checksum mismatch; was {download_sha256} but wanted {sha256}."
+        )
+
+    # No downloads succeeded.
+    messages = "\n\n".join(errors)
+    _error(f"All downloads failed:\n\n{messages}")
+
+
+def _install_downloaded_debs(*, yes: bool) -> None:
+    """Downloads and installs required debs for --developer that are not
+    available in Ubuntu's apt site.
+    The `yes` flag is passed along to apt as `--yes`."""
+    deb_arch = {
+        "x86_64": "amd64",
+        "aarch64": "arm64",
+    }[platform.machine().lower()]
+
+    # Load the list of packages and filter for the relevant ones.
+    json_filename = _MY_DIR / "ubuntu/packages.json"
+    packages = {}
+    for package in json.loads(json_filename.read_text(encoding="utf-8")):
+        assert package["type"] == "download_deb"
+        name = package["name"]
+        if deb_arch not in package["arches"]:
+            continue
+        if _os_codename() not in package["codenames"]:
+            continue
+        assert name not in packages, name
+        packages[name] = package
+    if not packages:
+        return
+
+    # Check what's already installed in case we can skip some.
+    all_names = list(packages.keys())
+    for name, installed_version in _get_dpkg_versions(all_names).items():
+        desired_version = packages[name]["version"]
+        if installed_version is None:
+            continue
+
+        # Check if already installed at the exact version.
+        if installed_version == desired_version:
+            logging.debug(f"{name} already installed at the desired version.")
+            del packages[name]
+            continue
+
+        # Check if already installed at a newer version.
+        comparison = _run(
+            args=[
+                "dpkg",
+                "--compare-versions",
+                installed_version,
+                "gt",
+                desired_version,
+            ],
+            quiet=True,
+            check=False,
+        )
+        if comparison.returncode == 0:
+            logging.info(
+                f"Not downgrading {name} from {installed_version=} "
+                f"to {desired_version=}."
+            )
+            del packages[name]
+            continue
+
+    # Download and install the necessary file(s).
+    if packages:
+        with tempfile.TemporaryDirectory(prefix="drake_prereqs_") as temp:
+            paths = [
+                str(_download(temp_dir=Path(temp), package=package))
+                for package in packages.values()
+            ]
+            _apt_install(package_names=paths, yes=yes)
 
 
 def _setup_user_environment():
@@ -84,12 +279,9 @@ def _setup_user_environment():
     # Compute the bazel rcfile snippet. This is always created, but only needs
     # content for Drake Developers on Linux.
     bazelrc_content = ""
-    if sys.platform == "linux":
-        os_release = platform.freedesktop_os_release()
+    if _is_ubuntu():
         developer_txt = (
-            _MY_DIR
-            / "ubuntu"
-            / f"packages-{os_release['VERSION_CODENAME']}-developer.txt"
+            _MY_DIR / "ubuntu" / f"packages-{_os_codename()}-developer.txt"
         )
         clang_re = re.compile("^clang-([0-9]+)$")
         for line in developer_txt.read_text(encoding="utf-8").splitlines():
@@ -155,12 +347,17 @@ def main():
             "but don't install any system-wide packages."
         ),
     )
-    for name in ("--without-update", "-y"):
-        parser.add_argument(
-            name,
-            action="store_true",
-            help="Ignored for forwards compatibility.",
-        )
+    parser.add_argument(
+        "--without-update",
+        action="store_true",
+        help="Ignored for forwards compatibility.",
+    )
+    parser.add_argument(
+        "-y",
+        action="store_true",
+        dest="yes",
+        help="Install without prompting for confirmation.",
+    )
     parser.add_argument(
         "--verbose",
         action="store_true",
@@ -172,6 +369,8 @@ def main():
 
     # We are in the process of migrating our bash setup code into this file.
     # Anything not set up here was already setup by install_prereqs.sh.
+    if _is_ubuntu() and args.developer:
+        _install_downloaded_debs(yes=args.yes)
     if args.developer or args.user_environment_only:
         _setup_user_environment()
     if args.developer: