path: root/python/mozbuild/mozbuild/vendor/vendor_rust.py

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, # You can obtain one at http://mozilla.org/MPL/2.0/.

import errno
import hashlib
import json
import logging
import os
import re
import subprocess
import typing
from collections import defaultdict
from itertools import dropwhile
from pathlib import Path

import mozpack.path as mozpath
import toml
from looseversion import LooseVersion
from mozboot.util import MINIMUM_RUST_VERSION

from mozbuild.base import BuildEnvironmentNotFoundException, MozbuildObject

if typing.TYPE_CHECKING:
    import datetime

# Type of a TOML value.
TomlItem = typing.Union[
    str,
    typing.List["TomlItem"],
    typing.Dict[str, "TomlItem"],
    bool,
    int,
    float,
    "datetime.datetime",
    "datetime.date",
    "datetime.time",
]


CARGO_CONFIG_TEMPLATE = """\
# This file contains vendoring instructions for cargo.
# It was generated by `mach vendor rust`.
# Please do not edit.

{config}

# Take advantage of the fact that cargo will treat lines starting with #
# as comments to add preprocessing directives. This file can thus by copied
# as-is to $topsrcdir/.cargo/config with no preprocessing to be used there
# (for e.g. independent tasks building rust code), or be preprocessed by
# the build system to produce a .cargo/config with the right content.
#define REPLACE_NAME {replace_name}
#define VENDORED_DIRECTORY {directory}
# We explicitly exclude the following section when preprocessing because
# it would overlap with the preprocessed [source."@REPLACE_NAME@"], and
# cargo would fail.
#ifndef REPLACE_NAME
[source.{replace_name}]
directory = "{directory}"
#endif

# Thankfully, @REPLACE_NAME@ is unlikely to be a legitimate source, so
# cargo will ignore it when it's here verbatim.
#filter substitution
[source."@REPLACE_NAME@"]
directory = "@top_srcdir@/@VENDORED_DIRECTORY@"
"""


CARGO_LOCK_NOTICE = """
NOTE: `cargo vendor` may have made changes to your Cargo.lock. To restore your
Cargo.lock to the HEAD version, run `git checkout -- Cargo.lock` or
`hg revert Cargo.lock`.
"""


WINDOWS_UNDESIRABLE_REASON = """\
The windows and windows-sys crates and their dependencies are too big to \
vendor, and is a risk of version duplication due to its current update \
cadence. Until this is worked out with upstream, we prefer to avoid them.\
"""

PACKAGES_WE_DONT_WANT = {
    "windows-sys": WINDOWS_UNDESIRABLE_REASON,
    "windows": WINDOWS_UNDESIRABLE_REASON,
    "windows_aarch64_msvc": WINDOWS_UNDESIRABLE_REASON,
    "windows_i686_gnu": WINDOWS_UNDESIRABLE_REASON,
    "windows_i686_msvc": WINDOWS_UNDESIRABLE_REASON,
    "windows_x86_64_gnu": WINDOWS_UNDESIRABLE_REASON,
    "windows_x86_64_msvc": WINDOWS_UNDESIRABLE_REASON,
}

PACKAGES_WE_ALWAYS_WANT_AN_OVERRIDE_OF = [
    "autocfg",
    "cmake",
    "vcpkg",
]


# Historically duplicated crates. Eventually we want this list to be empty.
# If you do need to make changes increasing the number of duplicates, please
# add a comment as to why.
TOLERATED_DUPES = {
    "mio": 2,
    # Transition from time 0.1 to 0.3 underway, but chrono is stuck on 0.1
    # and hasn't been updated in 1.5 years (an hypothetical update is
    # expected to remove the dependency on time altogether).
    "time": 2,
}


class VendorRust(MozbuildObject):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._issues = []

    def serialize_issues_json(self):
        return json.dumps(
            {
                "Cargo.lock": [
                    {
                        "path": "Cargo.lock",
                        "column": None,
                        "line": None,
                        "level": "error" if level == logging.ERROR else "warning",
                        "message": msg,
                    }
                    for (level, msg) in self._issues
                ]
            }
        )

    def log(self, level, action, params, format_str):
        if level >= logging.WARNING:
            self._issues.append((level, format_str.format(**params)))
        super().log(level, action, params, format_str)

    def get_cargo_path(self):
        try:
            return self.substs["CARGO"]
        except (BuildEnvironmentNotFoundException, KeyError):
            if "MOZ_AUTOMATION" in os.environ:
                cargo = os.path.join(
                    os.environ["MOZ_FETCHES_DIR"], "rustc", "bin", "cargo"
                )
                assert os.path.exists(cargo)
                return cargo
            # Default if this tree isn't configured.
            from mozfile import which

            cargo = which("cargo")
            if not cargo:
                raise OSError(
                    errno.ENOENT,
                    (
                        "Could not find 'cargo' on your $PATH. "
                        "Hint: have you run `mach build` or `mach configure`?"
                    ),
                )
            return cargo

    def check_cargo_version(self, cargo):
        """
        Ensure that Cargo is new enough.
        """
        out = (
            subprocess.check_output([cargo, "--version"])
            .splitlines()[0]
            .decode("UTF-8")
        )
        if not out.startswith("cargo"):
            return False
        version = LooseVersion(out.split()[1])
        # Cargo 1.68.0 changed vendoring in a way that creates a lot of noise
        # if we go back and forth between vendoring with an older version and
        # a newer version. Only allow the newer versions.
        minimum_rust_version = MINIMUM_RUST_VERSION
        if LooseVersion("1.68.0") >= MINIMUM_RUST_VERSION:
            minimum_rust_version = "1.68.0"
        if version < minimum_rust_version:
            self.log(
                logging.ERROR,
                "cargo_version",
                {},
                "Cargo >= {0} required (install Rust {0} or newer)".format(
                    minimum_rust_version
                ),
            )
            return False
        self.log(logging.DEBUG, "cargo_version", {}, "cargo is new enough")
        return True

    def has_modified_files(self):
        """
        Ensure that there aren't any uncommitted changes to files
        in the working copy, since we're going to change some state
        on the user. Allow changes to Cargo.{toml,lock} since that's
        likely to be a common use case.
        """
        modified = [
            f
            for f in self.repository.get_changed_files("M")
            if os.path.basename(f) not in ("Cargo.toml", "Cargo.lock")
            and not f.startswith("supply-chain/")
        ]
        if modified:
            self.log(
                logging.ERROR,
                "modified_files",
                {},
                """You have uncommitted changes to the following files:

{files}

Please commit or stash these changes before vendoring, or re-run with `--ignore-modified`.
""".format(
                    files="\n".join(sorted(modified))
                ),
            )
        return modified

    def check_openssl(self):
        """
        Set environment flags for building with openssl.

        MacOS doesn't include openssl, but the openssl-sys crate used by
        mach-vendor expects one of the system. It's common to have one
        installed in /usr/local/opt/openssl by homebrew, but custom link
        flags are necessary to build against it.
        """

        test_paths = ["/usr/include", "/usr/local/include"]
        if any(
            [os.path.exists(os.path.join(path, "openssl/ssl.h")) for path in test_paths]
        ):
            # Assume we can use one of these system headers.
            return None

        if os.path.exists("/usr/local/opt/openssl/include/openssl/ssl.h"):
            # Found a likely homebrew install.
            self.log(
                logging.INFO, "openssl", {}, "Using OpenSSL in /usr/local/opt/openssl"
            )
            return {
                "OPENSSL_INCLUDE_DIR": "/usr/local/opt/openssl/include",
                "OPENSSL_LIB_DIR": "/usr/local/opt/openssl/lib",
            }

        self.log(logging.ERROR, "openssl", {}, "OpenSSL not found!")
        return None

    def _ensure_cargo(self):
        """
        Ensures all the necessary cargo bits are installed.

        Returns the path to cargo if successful, None otherwise.
        """
        cargo = self.get_cargo_path()
        if not self.check_cargo_version(cargo):
            return None
        return cargo

    # A whitelist of acceptable license identifiers for the
    # packages.license field from https://spdx.org/licenses/.  Cargo
    # documentation claims that values are checked against the above
    # list and that multiple entries can be separated by '/'.  We
    # choose to list all combinations instead for the sake of
    # completeness and because some entries below obviously do not
    # conform to the format prescribed in the documentation.
    #
    # It is insufficient to have additions to this whitelist reviewed
    # solely by a build peer; any additions must be checked by somebody
    # competent to review licensing minutiae.

    # Licenses for code used at runtime. Please see the above comment before
    # adding anything to this list.
    RUNTIME_LICENSE_WHITELIST = [
        "Apache-2.0",
        "Apache-2.0 WITH LLVM-exception",
        # BSD-2-Clause and BSD-3-Clause are ok, but packages using them
        # must be added to the appropriate section of about:licenses.
        # To encourage people to remember to do that, we do not whitelist
        # the licenses themselves, and we require the packages to be added
        # to RUNTIME_LICENSE_PACKAGE_WHITELIST below.
        "CC0-1.0",
        "ISC",
        "MIT",
        "MPL-2.0",
        "Unicode-DFS-2016",
        "Unlicense",
        "Zlib",
    ]

    # Licenses for code used at build time (e.g. code generators). Please see the above
    # comments before adding anything to this list.
    BUILDTIME_LICENSE_WHITELIST = {
        "BSD-3-Clause": [
            "bindgen",
            "fuchsia-zircon",
            "fuchsia-zircon-sys",
            "fuchsia-cprng",
            "glsl",
            "instant",
        ]
    }

    # This whitelist should only be used for packages that use an acceptable
    # license, but that also need to explicitly mentioned in about:license.
    RUNTIME_LICENSE_PACKAGE_WHITELIST = {
        "BSD-2-Clause": [
            "arrayref",
            "cloudabi",
            "Inflector",
            "mach",
            "qlog",
        ],
        "BSD-3-Clause": [],
    }

    # ICU4X is distributed as individual crates that all share the same LICENSE
    # that will need to be individually added to the allow list below. We'll
    # define the SHA256 once here, to make the review process easier as new
    # ICU4X crates are vendored into the tree.
    ICU4X_LICENSE_SHA256 = (
        "02420cc1b4c26d9a3318d60fd57048d015831249a5b776a1ada75cd227e78630"
    )

    # This whitelist should only be used for packages that use a
    # license-file and for which the license-file entry has been
    # reviewed.  The table is keyed by package names and maps to the
    # sha256 hash of the license file that we reviewed.
    #
    # As above, it is insufficient to have additions to this whitelist
    # reviewed solely by a build peer; any additions must be checked by
    # somebody competent to review licensing minutiae.
    RUNTIME_LICENSE_FILE_PACKAGE_WHITELIST = {
        # MIT
        "deque": "6485b8ed310d3f0340bf1ad1f47645069ce4069dcc6bb46c7d5c6faf41de1fdb",
        # we're whitelisting this fuchsia crate because it doesn't get built in the final
        # product but has a license-file that needs ignoring
        "fuchsia-cprng": "03b114f53e6587a398931762ee11e2395bfdba252a329940e2c8c9e81813845b",
        # Old ICU4X crates for ICU4X 1.0, see comment above.
        "yoke-derive": ICU4X_LICENSE_SHA256,
        "zerofrom-derive": ICU4X_LICENSE_SHA256,
    }

    @staticmethod
    def runtime_license(package, license_string):
        """Cargo docs say:
        ---
        https://doc.rust-lang.org/cargo/reference/manifest.html

        This is an SPDX 2.1 license expression for this package.  Currently
        crates.io will validate the license provided against a whitelist of
        known license and exception identifiers from the SPDX license list
        2.4.  Parentheses are not currently supported.

        Multiple licenses can be separated with a `/`, although that usage
        is deprecated.  Instead, use a license expression with AND and OR
        operators to get more explicit semantics.
        ---
        But I have no idea how you can meaningfully AND licenses, so
        we will abort if that is detected. We'll handle `/` and OR as
        equivalent and approve is any is in our approved list."""

        # This specific AND combination has been reviewed for encoding_rs.
        if (
            license_string == "(Apache-2.0 OR MIT) AND BSD-3-Clause"
            and package == "encoding_rs"
        ):
            return True

        # This specific AND combination has been reviewed for unicode-ident.
        if (
            license_string == "(MIT OR Apache-2.0) AND Unicode-DFS-2016"
            and package == "unicode-ident"
        ):
            return True

        if re.search(r"\s+AND", license_string):
            return False

        license_list = re.split(r"\s*/\s*|\s+OR\s+", license_string)
        for license in license_list:
            if license in VendorRust.RUNTIME_LICENSE_WHITELIST:
                return True
            if package in VendorRust.RUNTIME_LICENSE_PACKAGE_WHITELIST.get(license, []):
                return True
        return False

    def _check_licenses(self, vendor_dir: str) -> bool:
        def verify_acceptable_license(package: str, license: str) -> bool:
            self.log(
                logging.DEBUG, "package_license", {}, "has license {}".format(license)
            )

            if not self.runtime_license(package, license):
                if license not in self.BUILDTIME_LICENSE_WHITELIST:
                    self.log(
                        logging.ERROR,
                        "package_license_error",
                        {},
                        """Package {} has a non-approved license: {}.

    Please request license review on the package's license.  If the package's license
    is approved, please add it to the whitelist of suitable licenses.
    """.format(
                            package, license
                        ),
                    )
                    return False
                elif package not in self.BUILDTIME_LICENSE_WHITELIST[license]:
                    self.log(
                        logging.ERROR,
                        "package_license_error",
                        {},
                        """Package {} has a license that is approved for build-time dependencies:
    {}
    but the package itself is not whitelisted as being a build-time only package.

    If your package is build-time only, please add it to the whitelist of build-time
    only packages. Otherwise, you need to request license review on the package's license.
    If the package's license is approved, please add it to the whitelist of suitable licenses.
    """.format(
                            package, license
                        ),
                    )
                    return False
            return True

        def check_package(package_name: str) -> bool:
            self.log(
                logging.DEBUG,
                "package_check",
                {},
                "Checking license for {}".format(package_name),
            )

            toml_file = os.path.join(vendor_dir, package_name, "Cargo.toml")
            with open(toml_file, encoding="utf-8") as fh:
                toml_data = toml.load(fh)

            package_entry: typing.Dict[str, TomlItem] = toml_data["package"]
            license = package_entry.get("license", None)
            license_file = package_entry.get("license-file", None)

            if license is not None and type(license) is not str:
                self.log(
                    logging.ERROR,
                    "package_invalid_license_format",
                    {},
                    "package {} has an invalid `license` field (expected a string)".format(
                        package_name
                    ),
                )
                return False

            if license_file is not None and type(license_file) is not str:
                self.log(
                    logging.ERROR,
                    "package_invalid_license_format",
                    {},
                    "package {} has an invalid `license-file` field (expected a string)".format(
                        package_name
                    ),
                )
                return False

            # License information is optional for crates to provide, but
            # we require it.
            if not license and not license_file:
                self.log(
                    logging.ERROR,
                    "package_no_license",
                    {},
                    "package {} does not provide a license".format(package_name),
                )
                return False

            # The Cargo.toml spec suggests that crates should either have
            # `license` or `license-file`, but not both.  We might as well
            # be defensive about that, though.
            if license and license_file:
                self.log(
                    logging.ERROR,
                    "package_many_licenses",
                    {},
                    "package {} provides too many licenses".format(package_name),
                )
                return False

            if license:
                return verify_acceptable_license(package_name, license)

            # otherwise, it's a custom license in a separate file
            assert license_file is not None
            self.log(
                logging.DEBUG,
                "package_license_file",
                {},
                "package has license-file {}".format(license_file),
            )

            if package_name not in self.RUNTIME_LICENSE_FILE_PACKAGE_WHITELIST:
                self.log(
                    logging.ERROR,
                    "package_license_file_unknown",
                    {},
                    """Package {} has an unreviewed license file: {}.

Please request review on the provided license; if approved, the package can be added
to the whitelist of packages whose licenses are suitable.
""".format(
                        package_name, license_file
                    ),
                )
                return False

            approved_hash = self.RUNTIME_LICENSE_FILE_PACKAGE_WHITELIST[package_name]

            with open(
                os.path.join(vendor_dir, package_name, license_file), "rb"
            ) as license_buf:
                current_hash = hashlib.sha256(license_buf.read()).hexdigest()

            if current_hash != approved_hash:
                self.log(
                    logging.ERROR,
                    "package_license_file_mismatch",
                    {},
                    """Package {} has changed its license file: {} (hash {}).

Please request review on the provided license; if approved, please update the
license file's hash.
""".format(
                        package_name, license_file, current_hash
                    ),
                )
                return False
            return True

        # Force all of the packages to be checked for license information
        # before reducing via `all`, so all license issues are found in a
        # single `mach vendor rust` invocation.
        results = [
            check_package(p)
            for p in os.listdir(vendor_dir)
            if os.path.isdir(os.path.join(vendor_dir, p))
        ]
        return all(results)

    def _check_build_rust(self, cargo_lock):
        ret = True
        crates = {}
        for path in Path(self.topsrcdir).glob("build/rust/**/Cargo.toml"):
            with open(path) as fh:
                cargo_toml = toml.load(fh)
                path = path.relative_to(self.topsrcdir)
                package = cargo_toml["package"]
                key = (package["name"], package["version"])
                if key in crates:
                    self.log(
                        logging.ERROR,
                        "build_rust",
                        {
                            "path": crates[key],
                            "path2": path,
                            "crate": key[0],
                            "version": key[1],
                        },
                        "{path} and {path2} both contain {crate} {version}",
                    )
                    ret = False
                crates[key] = path

        for package in cargo_lock["package"]:
            key = (package["name"], package["version"])
            if key in crates and "source" not in package:
                crates.pop(key)

        for ((name, version), path) in crates.items():
            self.log(
                logging.ERROR,
                "build_rust",
                {"path": path, "crate": name, "version": version},
                "{crate} {version} has an override in {path} that is not used",
            )
            ret = False
        return ret

    def vendor(
        self, ignore_modified=False, build_peers_said_large_imports_were_ok=False
    ):
        from mozbuild.mach_commands import cargo_vet

        self.populate_logger()
        self.log_manager.enable_unstructured()
        if not ignore_modified and self.has_modified_files():
            return False

        cargo = self._ensure_cargo()
        if not cargo:
            self.log(logging.ERROR, "cargo_not_found", {}, "Cargo was not found.")
            return False

        relative_vendor_dir = "third_party/rust"
        vendor_dir = mozpath.join(self.topsrcdir, relative_vendor_dir)

        # We use check_call instead of mozprocess to ensure errors are displayed.
        # We do an |update -p| here to regenerate the Cargo.lock file with minimal
        # changes. See bug 1324462
        res = subprocess.run([cargo, "update", "-p", "gkrust"], cwd=self.topsrcdir)
        if res.returncode:
            self.log(logging.ERROR, "cargo_update_failed", {}, "Cargo update failed.")
            return False

        with open(os.path.join(self.topsrcdir, "Cargo.lock")) as fh:
            cargo_lock = toml.load(fh)
            failed = False
            for package in cargo_lock.get("patch", {}).get("unused", []):
                self.log(
                    logging.ERROR,
                    "unused_patch",
                    {"crate": package["name"]},
                    """Unused patch in top-level Cargo.toml for {crate}.""",
                )
                failed = True

            if not self._check_build_rust(cargo_lock):
                failed = True

            grouped = defaultdict(list)
            for package in cargo_lock["package"]:
                if package["name"] in PACKAGES_WE_ALWAYS_WANT_AN_OVERRIDE_OF:
                    # When the in-tree version is used, there is `source` for
                    # it in Cargo.lock, which is what we expect.
                    if package.get("source"):
                        self.log(
                            logging.ERROR,
                            "non_overridden",
                            {
                                "crate": package["name"],
                                "version": package["version"],
                                "source": package["source"],
                            },
                            "Crate {crate} v{version} must be overridden but isn't "
                            "and comes from {source}.",
                        )
                        failed = True
                elif package["name"] in PACKAGES_WE_DONT_WANT:
                    self.log(
                        logging.ERROR,
                        "undesirable",
                        {
                            "crate": package["name"],
                            "version": package["version"],
                            "reason": PACKAGES_WE_DONT_WANT[package["name"]],
                        },
                        "Crate {crate} is not desirable: {reason}",
                    )
                    failed = True
                grouped[package["name"]].append(package)

            for name, packages in grouped.items():
                # Allow to have crates of the same name when one depends on the other.
                num = len(
                    [
                        p
                        for p in packages
                        if all(d.split()[0] != name for d in p.get("dependencies", []))
                    ]
                )
                expected = TOLERATED_DUPES.get(name, 1)
                if num > expected:
                    self.log(
                        logging.ERROR,
                        "duplicate_crate",
                        {
                            "crate": name,
                            "num": num,
                            "expected": expected,
                            "file": Path(__file__).relative_to(self.topsrcdir),
                        },
                        "There are {num} different versions of crate {crate} "
                        "(expected {expected}). Please avoid the extra duplication "
                        "or adjust TOLERATED_DUPES in {file} if not possible "
                        "(but we'd prefer the former).",
                    )
                    failed = True
                elif num < expected and num > 1:
                    self.log(
                        logging.ERROR,
                        "less_duplicate_crate",
                        {
                            "crate": name,
                            "num": num,
                            "expected": expected,
                            "file": Path(__file__).relative_to(self.topsrcdir),
                        },
                        "There are {num} different versions of crate {crate} "
                        "(expected {expected}). Please adjust TOLERATED_DUPES in "
                        "{file} to reflect this improvement.",
                    )
                    failed = True
                elif num < expected and num > 0:
                    self.log(
                        logging.ERROR,
                        "less_duplicate_crate",
                        {
                            "crate": name,
                            "file": Path(__file__).relative_to(self.topsrcdir),
                        },
                        "Crate {crate} is not duplicated anymore. "
                        "Please adjust TOLERATED_DUPES in {file} to reflect this improvement.",
                    )
                    failed = True
                elif name in TOLERATED_DUPES and expected <= 1:
                    self.log(
                        logging.ERROR,
                        "broken_allowed_dupes",
                        {
                            "crate": name,
                            "file": Path(__file__).relative_to(self.topsrcdir),
                        },
                        "Crate {crate} is not duplicated. Remove it from "
                        "TOLERATED_DUPES in {file}.",
                    )
                    failed = True

            for name in TOLERATED_DUPES:
                if name not in grouped:
                    self.log(
                        logging.ERROR,
                        "outdated_allowed_dupes",
                        {
                            "crate": name,
                            "file": Path(__file__).relative_to(self.topsrcdir),
                        },
                        "Crate {crate} is not in Cargo.lock anymore. Remove it from "
                        "TOLERATED_DUPES in {file}.",
                    )
                    failed = True

        # Only emit warnings for cargo-vet for now.
        env = os.environ.copy()
        env["PATH"] = os.pathsep.join(
            (
                str(Path(cargo).parent),
                os.environ["PATH"],
            )
        )
        flags = ["--output-format=json"]
        if "MOZ_AUTOMATION" in os.environ:
            flags.append("--locked")
            flags.append("--frozen")
        res = cargo_vet(
            self,
            flags,
            stdout=subprocess.PIPE,
            env=env,
        )
        if res.returncode:
            vet = json.loads(res.stdout)
            logged_error = False
            for failure in vet.get("failures", []):
                failure["crate"] = failure.pop("name")
                self.log(
                    logging.ERROR,
                    "cargo_vet_failed",
                    failure,
                    "Missing audit for {crate}:{version} (requires {missing_criteria})."
                    " Run `./mach cargo vet` for more information.",
                )
                logged_error = True
            # NOTE: This could log more information, but the violation JSON
            # output isn't super stable yet, so it's probably simpler to tell
            # the caller to run `./mach cargo vet` directly.
            for key in vet.get("violations", {}).keys():
                self.log(
                    logging.ERROR,
                    "cargo_vet_failed",
                    {"key": key},
                    "Violation conflict for {key}. Run `./mach cargo vet` for more information.",
                )
                logged_error = True
            if "error" in vet:
                # NOTE: The error format produced by cargo-vet is from the
                # `miette` crate, and can include a lot of metadata and context.
                # If we want to show more details in the future, we can expand
                # this rendering to also include things like source labels and
                # related error metadata.
                error = vet["error"]
                self.log(
                    logging.ERROR,
                    "cargo_vet_failed",
                    error,
                    "Vet {severity}: {message}",
                )
                if "help" in error:
                    self.log(logging.INFO, "cargo_vet_failed", error, " help: {help}")
                for cause in error.get("causes", []):
                    self.log(
                        logging.INFO,
                        "cargo_vet_failed",
                        {"cause": cause},
                        " cause: {cause}",
                    )
                for related in error.get("related", []):
                    self.log(
                        logging.INFO,
                        "cargo_vet_failed",
                        related,
                        " related {severity}: {message}",
                    )
                self.log(
                    logging.INFO,
                    "cargo_vet_failed",
                    {},
                    "Run `./mach cargo vet` for more information.",
                )
                logged_error = True
            if not logged_error:
                self.log(
                    logging.ERROR,
                    "cargo_vet_failed",
                    {},
                    "Unknown vet error. Run `./mach cargo vet` for more information.",
                )
            failed = True

        # If we failed when checking the crates list and/or running `cargo vet`,
        # stop before invoking `cargo vendor`.
        if failed:
            return False

        res = subprocess.run(
            [cargo, "vendor", vendor_dir], cwd=self.topsrcdir, stdout=subprocess.PIPE
        )
        if res.returncode:
            self.log(logging.ERROR, "cargo_vendor_failed", {}, "Cargo vendor failed.")
            return False
        output = res.stdout.decode("UTF-8")

        # Get the snippet of configuration that cargo vendor outputs, and
        # update .cargo/config with it.
        # XXX(bug 1576765): Hopefully do something better after
        # https://github.com/rust-lang/cargo/issues/7280 is addressed.
        config = "\n".join(
            dropwhile(lambda l: not l.startswith("["), output.splitlines())
        )

        # The config is toml; parse it as such.
        config = toml.loads(config)

        # For each replace-with, extract their configuration and update the
        # corresponding directory to be relative to topsrcdir.
        replaces = {
            v["replace-with"] for v in config["source"].values() if "replace-with" in v
        }

        # We only really expect one replace-with
        if len(replaces) != 1:
            self.log(
                logging.ERROR,
                "vendor_failed",
                {},
                """cargo vendor didn't output a unique replace-with. Found: %s."""
                % replaces,
            )
            return False

        replace_name = replaces.pop()
        replace = config["source"].pop(replace_name)
        replace["directory"] = mozpath.relpath(
            mozpath.normsep(os.path.normcase(replace["directory"])),
            mozpath.normsep(os.path.normcase(self.topsrcdir)),
        )

        cargo_config = os.path.join(self.topsrcdir, ".cargo", "config.in")
        with open(cargo_config, "w", encoding="utf-8", newline="\n") as fh:
            fh.write(
                CARGO_CONFIG_TEMPLATE.format(
                    config=toml.dumps(config),
                    replace_name=replace_name,
                    directory=replace["directory"],
                )
            )

        if not self._check_licenses(vendor_dir):
            self.log(
                logging.ERROR,
                "license_check_failed",
                {},
                """The changes from `mach vendor rust` will NOT be added to version control.

{notice}""".format(
                    notice=CARGO_LOCK_NOTICE
                ),
            )
            self.repository.clean_directory(vendor_dir)
            return False

        self.repository.add_remove_files(vendor_dir)

        # 100k is a reasonable upper bound on source file size.
        FILESIZE_LIMIT = 100 * 1024
        large_files = set()
        cumulative_added_size = 0
        for f in self.repository.get_changed_files("A"):
            path = mozpath.join(self.topsrcdir, f)
            size = os.stat(path).st_size
            cumulative_added_size += size
            if size > FILESIZE_LIMIT:
                large_files.add(f)

        # Forcefully complain about large files being added, as history has
        # shown that large-ish files typically are not needed.
        if large_files and not build_peers_said_large_imports_were_ok:
            self.log(
                logging.ERROR,
                "filesize_check",
                {},
                """The following files exceed the filesize limit of {size}:

{files}

If you can't reduce the size of these files, talk to a build peer (on the #build
channel at https://chat.mozilla.org) about the particular large files you are
adding.

The changes from `mach vendor rust` will NOT be added to version control.

{notice}""".format(
                    files="\n".join(sorted(large_files)),
                    size=FILESIZE_LIMIT,
                    notice=CARGO_LOCK_NOTICE,
                ),
            )
            self.repository.forget_add_remove_files(vendor_dir)
            self.repository.clean_directory(vendor_dir)
            return False

        # Only warn for large imports, since we may just have large code
        # drops from time to time (e.g. importing features into m-c).
        SIZE_WARN_THRESHOLD = 5 * 1024 * 1024
        if cumulative_added_size >= SIZE_WARN_THRESHOLD:
            self.log(
                logging.WARN,
                "filesize_check",
                {},
                """Your changes add {size} bytes of added files.

Please consider finding ways to reduce the size of the vendored packages.
For instance, check the vendored packages for unusually large test or
benchmark files that don't need to be published to crates.io and submit
a pull request upstream to ignore those files when publishing.""".format(
                    size=cumulative_added_size
                ),
            )
        return True