crate_universe/defs.bzl - third_party/github/bazelbuild/rules_rust - Git at Google

 """A module defining the `crate_universe` rule"""

 load("//crate_universe/private:defaults.bzl", "DEFAULT_SHA256_CHECKSUMS", "DEFAULT_URL_TEMPLATE")
 load("//crate_universe/private:util.bzl", "get_cargo_and_rustc", "get_host_triple")
 load("//rust:defs.bzl", "rust_common")
 load("//rust:repositories.bzl", "DEFAULT_TOOLCHAIN_TRIPLES")
 load("//rust/platform:triple_mappings.bzl", "system_to_binary_ext", "triple_to_system")

 # The default template for download URLs from the default registry (i.e. crates.io).
 DEFAULT_DEFAULT_CRATE_DOWNLOAD_URL_TEMPLATE = "https://crates.io/api/v1/crates/{crate}/{version}/download"

 def _input_content_template(ctx, name, packages, cargo_toml_files, overrides, default_registry_download_url_template, additional_registries, targets, cargo_bin_path):
     """Generate json encoded dependency info for the crate resolver.

     Args:
         ctx (repository_ctx): The repository rule's context object.
         name (str): The name of the repository.
         packages (list): A list of json encoded `crate.spec` entries.
         cargo_toml_files (list): A list of `Label`s to Cargo manifests.
         overrides (dict): A dict of crate name (`str`) to json encoded `crate.override` data.
         default_registry_download_url_template (str): The URL template for downloading crates from the default registry.
         additional_registries (dict): Dict of registry name (`str`) to the URL of the index (`str`).
         targets (list): A list of target platform triples
         cargo_bin_path (path): The label of a Cargo binary.

     Returns:
         str: Json encoded config data for the resolver
     """

     # packages are expected to be json encoded, so we decode them
     # to ensure they are correctly re-encoded
     dcoded_pkgs = [json.decode(artifact) for artifact in packages]

     # Generate an easy to use map of `Cargo.toml` files
     encodable_cargo_toml_files = dict()
     for label in cargo_toml_files:
         encodable_cargo_toml_files.update({str(label): str(ctx.path(label))})

     # Overrides are passed as encoded json strings, so we decode
     # them to ensure they are correctly re-encoded
     encodable_overrides = dict()
     for key, value in overrides.items():
         encodable_overrides.update({key: json.decode(value)})

     return "{}\n".format(
         json.encode_indent(
             struct(
                 additional_registries = additional_registries,
                 cargo = str(cargo_bin_path),
                 cargo_toml_files = encodable_cargo_toml_files,
                 default_registry_download_url_template = default_registry_download_url_template,
                 overrides = encodable_overrides,
                 packages = dcoded_pkgs,
                 repository_name = name,
                 target_triples = targets,
             ),
             indent = " " * 4,
         ),
     )

 def _crate_universe_resolve_impl(repository_ctx):
     """Entry-point repository to manage rust dependencies.

     General flow is:
     - Serialize user-provided rule attributes into JSON
     - Call the Rust resolver script. It writes a `defs.bzl` file in this repo containing the
       transitive dependencies as repo rules in a `pinned_rust_install()` macro.
     - The user then calls defs.bzl%pinned_rust_install().
     """

     host_triple, resolver_triple = get_host_triple(repository_ctx)
     tools = get_cargo_and_rustc(repository_ctx, host_triple)
     extension = system_to_binary_ext(triple_to_system(host_triple))

     if repository_ctx.attr.resolver:
         resolver_path = repository_ctx.path(repository_ctx.attr.resolver)
     else:
         # Allow for an an override environment variable to define a url to a binary
         resolver_url = repository_ctx.os.environ.get("RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE", None)
         resolver_sha = repository_ctx.os.environ.get("RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE_SHA256", None)
         if resolver_url:
             if resolver_url.startswith("file://"):
                 sha256_result = repository_ctx.execute(["sha256sum", resolver_url[7:]])
                 resolver_sha = sha256_result.stdout[:64]
         else:
             resolver_url = repository_ctx.attr.resolver_download_url_template.format(
                 host_triple = resolver_triple,
                 extension = extension,
             )
             resolver_sha = repository_ctx.attr.resolver_sha256s.get(resolver_triple, None)

         resolver_path = repository_ctx.path("resolver")
         repository_ctx.download(
             url = resolver_url,
             sha256 = resolver_sha,
             output = resolver_path,
             executable = True,
         )

     lockfile_path = None
     if repository_ctx.attr.lockfile:
         lockfile_path = repository_ctx.path(repository_ctx.attr.lockfile)

     input_content = _input_content_template(
         ctx = repository_ctx,
         name = repository_ctx.attr.name,
         packages = repository_ctx.attr.packages,
         cargo_toml_files = repository_ctx.attr.cargo_toml_files,
         overrides = repository_ctx.attr.overrides,
         default_registry_download_url_template = repository_ctx.attr.default_registry_download_url_template,
         additional_registries = repository_ctx.attr.additional_registries,
         targets = repository_ctx.attr.supported_targets,
         cargo_bin_path = tools.cargo,
     )

     input_path = "{name}.resolver_config.json".format(name = repository_ctx.attr.name)
     repository_ctx.file(input_path, content = input_content)

     args = [
         resolver_path,
         "--input_path",
         input_path,
         "--repository_dir",
         repository_ctx.path("."),
         "--repo-name",
         repository_ctx.attr.name,
     ]
     if lockfile_path != None:
         args.append("--lockfile")
         str(args.append(lockfile_path))
     env_var_names = repository_ctx.os.environ.keys()
     if "RULES_RUST_REPIN" in env_var_names or "REPIN" in env_var_names:
         args.append("--update-lockfile")

     result = repository_ctx.execute(
         args,
         environment = {
             # The resolver invokes `cargo metadata` which relies on `rustc` being on the $PATH
             # See https://github.com/rust-lang/cargo/issues/8219
             "CARGO": str(tools.cargo),
             "RUSTC": str(tools.rustc),
             "RUST_LOG": "info",
         },
         quiet = False,
     )
     if result.return_code != 0:
         fail("Error resolving crate_universe deps - see above output for more information")

     repository_ctx.file("BUILD.bazel")

 crate_universe = repository_rule(
     doc = """\
 A rule for downloading Rust dependencies (crates).

 __WARNING__: This rule experimental and subject to change without warning.

 Environment Variables:
 - `REPIN`: Re-pin the lockfile if set (useful for repinning deps from multiple rulesets).
 - `RULES_RUST_REPIN`: Re-pin the lockfile if set (useful for only repinning Rust deps).
 - `RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE`: Override URL to use to download resolver binary
     - for local paths use a `file://` URL.
 - `RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE_SHA256`: An optional sha256 value for the binary at the override url location.
 """,
     implementation = _crate_universe_resolve_impl,
     attrs = {
         "additional_registries": attr.string_dict(
             doc = """\
 Additional registries used by Cargo (see https://doc.rust-lang.org/cargo/reference/registries.html).

 Dict of registry_name: index_url.
 """,
         ),
         "cargo_toml_files": attr.label_list(
             doc = "A list of Cargo manifests (`Cargo.toml` files).",
             allow_files = True,
         ),
         "default_registry_download_url_template": attr.string(
             doc = "A template for where to download crates from for the default crate registry. This must contain `{version}` and `{crate}` templates.",
             default = DEFAULT_DEFAULT_CRATE_DOWNLOAD_URL_TEMPLATE,
         ),
         "iso_date": attr.string(
             doc = "The iso_date of cargo binary the resolver should use. Note: This can only be set if `version` is `beta` or `nightly`",
         ),
         "lockfile": attr.label(
             doc = (
                 "The path to a file which stores pinned information about the generated dependency graph. " +
                 "this target must be a file and will be updated by the repository rule when the `REPIN` " +
                 "environment variable is set. If this is not set, dependencies will be re-resolved more " +
                 "often, setting this allows caching resolves, but will error if the cache is stale."
             ),
             allow_single_file = True,
             mandatory = False,
         ),
         "overrides": attr.string_dict(
             doc = (
                 "Mapping of crate name to specification overrides. See [crate.override](#crateoverride) " +
                 " for more details."
             ),
         ),
         "packages": attr.string_list(
             doc = "A list of crate specifications. See [crate.spec](#cratespec) for more details.",
             allow_empty = True,
         ),
         "resolver": attr.label(
             doc = (
                 "The label of a `crate_universe` resolver. Resolvers can be built using `cargo_bootstrap_repository` " +
                 "but if possible, it's recommended to stick with downloading a resoler via `resolver_download_url_template`."
             ),
         ),
         "resolver_download_url_template": attr.string(
             doc = (
                 "URL template from which to download the resolver binary. {host_triple} and {extension} will be " +
                 "filled in according to the host platform."
             ),
             default = DEFAULT_URL_TEMPLATE,
         ),
         "resolver_sha256s": attr.string_dict(
             doc = "Dictionary of host_triple -> sha256 for resolver binary.",
             default = DEFAULT_SHA256_CHECKSUMS,
         ),
         "rust_toolchain_repository_template": attr.string(
             doc = (
                 "The template to use for finding the host `rust_toolchain` repository. `{version}` (eg. '1.53.0'), " +
                 "`{triple}` (eg. 'x86_64-unknown-linux-gnu'), `{system}` (eg. 'darwin'), and `{arch}` (eg. 'aarch64') " +
                 "will be replaced in the string if present."
             ),
             default = "rust_{system}_{arch}",
         ),
         "sha256s": attr.string_dict(
             doc = "The sha256 checksum of the desired rust artifacts",
         ),
         "supported_targets": attr.string_list(
             doc = (
                 "A list of supported [platform triples](https://doc.rust-lang.org/nightly/rustc/platform-support.html) " +
                 "to consider when resoliving dependencies."
             ),
             allow_empty = False,
             default = DEFAULT_TOOLCHAIN_TRIPLES.keys(),
         ),
         "version": attr.string(
             doc = "The version of cargo the resolver should use",
             default = rust_common.default_version,
         ),
     },
     environ = [
         "REPIN",
         "RULES_RUST_REPIN",
         "RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE",
         "RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE_SHA256",
     ],
 )

 def _spec(
         name,
         semver,
         features = None):
     """A simple crate definition for use in the `crate_universe` rule.

     __WARNING__: This rule experimental and subject to change without warning.

     Example:

     ```python
     load("@rules_rust//crate_universe:defs.bzl", "crate_universe", "crate")

     crate_universe(
         name = "spec_example",
         packages = [
             crate.spec(
                 name = "lazy_static",
                 semver = "=1.4",
             ),
         ],
     )
     ```

     Args:
         name (str): The name of the crate as it would appear in a crate registry.
         semver (str): The desired version ([semver](https://semver.org/)) of the crate
         features (list, optional): A list of desired [features](https://doc.rust-lang.org/cargo/reference/features.html).

     Returns:
         str: A json encoded struct of crate info
     """
     return json.encode(struct(
         name = name,
         semver = semver,
         features = features or [],
     ))

 def _override(
         extra_bazel_data_deps = None,
         extra_bazel_deps = None,
         extra_build_script_bazel_data_deps = None,
         extra_build_script_bazel_deps = None,
         extra_build_script_env_vars = None,
         extra_rustc_env_vars = None,
         features_to_remove = []):
     """A map of overrides for a particular crate

     __WARNING__: This rule experimental and subject to change without warning.

     Example:

     ```python
     load("@rules_rust//crate_universe:defs.bzl", "crate_universe", "crate")

     crate_universe(
         name = "override_example",
         # [...]
         overrides = {
             "tokio": crate.override(
                 extra_rustc_env_vars = {
                     "MY_ENV_VAR": "MY_ENV_VALUE",
                 },
                 extra_build_script_env_vars = {
                     "MY_BUILD_SCRIPT_ENV_VAR": "MY_ENV_VALUE",
                 },
                 extra_bazel_deps = {
                     # Extra dependencies are per target. They are additive.
                     "cfg(unix)": ["@somerepo//:foo"],  # cfg() predicate.
                     "x86_64-apple-darwin": ["@somerepo//:bar"],  # Specific triple.
                     "cfg(all())": ["@somerepo//:baz"],  # Applies to all targets ("regular dependency").
                 },
                 extra_build_script_bazel_deps = {
                     # Extra dependencies are per target. They are additive.
                     "cfg(unix)": ["@buildscriptdep//:foo"],
                     "x86_64-apple-darwin": ["@buildscriptdep//:bar"],
                     "cfg(all())": ["@buildscriptdep//:baz"],
                 },
                 extra_bazel_data_deps = {
                     # ...
                 },
                 extra_build_script_bazel_data_deps = {
                     # ...
                 },
             ),
         },
     )
     ```

     Args:
         extra_bazel_data_deps (dict, optional): Targets to add to the `data` attribute
             of the generated target (eg: [rust_library.data](./defs.md#rust_library-data)).
         extra_bazel_deps (dict, optional): Targets to add to the `deps` attribute
             of the generated target (eg: [rust_library.deps](./defs.md#rust_library-data)).
         extra_rustc_env_vars (dict, optional): Environment variables to add to the `rustc_env`
             attribute for the generated target (eg: [rust_library.rustc_env](./defs.md#rust_library-rustc_env)).
         extra_build_script_bazel_data_deps (dict, optional): Targets to add to the
             [data](./cargo_build_script.md#cargo_build_script-data) attribute of the generated
             `cargo_build_script` target.
         extra_build_script_bazel_deps (dict, optional): Targets to add to the
             [deps](./cargo_build_script.md#cargo_build_script-deps) attribute of the generated
             `cargo_build_script` target.
         extra_build_script_env_vars (dict, optional): Environment variables to add to the
             [build_script_env](./cargo_build_script.md#cargo_build_script-build_script_env)
             attribute of the generated `cargo_build_script` target.
         features_to_remove (list, optional): A list of features to remove from a generated target.

     Returns:
         str: A json encoded struct of crate overrides
     """
     for (dep_key, dep_val) in [
         (extra_bazel_deps, extra_bazel_deps),
         (extra_build_script_bazel_deps, extra_build_script_bazel_deps),
         (extra_bazel_data_deps, extra_bazel_data_deps),
         (extra_build_script_bazel_data_deps, extra_build_script_bazel_data_deps),
     ]:
         if dep_val != None:
             if not type(dep_val) == "dict":
                 fail("The {} attribute should be a dictionary".format(dep_key))

             for target, deps in dep_val.items():
                 if not type(deps) == "list" or any([type(x) != "string" for x in deps]):
                     fail("The {} values should be lists of strings".format(dep_key))

     return json.encode(struct(
         extra_rustc_env_vars = extra_rustc_env_vars or {},
         extra_build_script_env_vars = extra_build_script_env_vars or {},
         extra_bazel_deps = extra_bazel_deps or {},
         extra_build_script_bazel_deps = extra_build_script_bazel_deps or {},
         extra_bazel_data_deps = extra_bazel_data_deps or {},
         extra_build_script_bazel_data_deps = extra_build_script_bazel_data_deps or {},
         features_to_remove = features_to_remove,
     ))

 crate = struct(
     spec = _spec,
     override = _override,
 )
	"""A module defining the `crate_universe` rule"""

	load("//crate_universe/private:defaults.bzl", "DEFAULT_SHA256_CHECKSUMS", "DEFAULT_URL_TEMPLATE")
	load("//crate_universe/private:util.bzl", "get_cargo_and_rustc", "get_host_triple")
	load("//rust:defs.bzl", "rust_common")
	load("//rust:repositories.bzl", "DEFAULT_TOOLCHAIN_TRIPLES")
	load("//rust/platform:triple_mappings.bzl", "system_to_binary_ext", "triple_to_system")

	# The default template for download URLs from the default registry (i.e. crates.io).
	DEFAULT_DEFAULT_CRATE_DOWNLOAD_URL_TEMPLATE = "https://crates.io/api/v1/crates/{crate}/{version}/download"

	def _input_content_template(ctx, name, packages, cargo_toml_files, overrides, default_registry_download_url_template, additional_registries, targets, cargo_bin_path):
	"""Generate json encoded dependency info for the crate resolver.

	Args:
	ctx (repository_ctx): The repository rule's context object.
	name (str): The name of the repository.
	packages (list): A list of json encoded `crate.spec` entries.
	cargo_toml_files (list): A list of `Label`s to Cargo manifests.
	overrides (dict): A dict of crate name (`str`) to json encoded `crate.override` data.
	default_registry_download_url_template (str): The URL template for downloading crates from the default registry.
	additional_registries (dict): Dict of registry name (`str`) to the URL of the index (`str`).
	targets (list): A list of target platform triples
	cargo_bin_path (path): The label of a Cargo binary.

	Returns:
	str: Json encoded config data for the resolver
	"""

	# packages are expected to be json encoded, so we decode them
	# to ensure they are correctly re-encoded
	dcoded_pkgs = [json.decode(artifact) for artifact in packages]

	# Generate an easy to use map of `Cargo.toml` files
	encodable_cargo_toml_files = dict()
	for label in cargo_toml_files:
	encodable_cargo_toml_files.update({str(label): str(ctx.path(label))})

	# Overrides are passed as encoded json strings, so we decode
	# them to ensure they are correctly re-encoded
	encodable_overrides = dict()
	for key, value in overrides.items():
	encodable_overrides.update({key: json.decode(value)})

	return "{}\n".format(
	json.encode_indent(
	struct(
	additional_registries = additional_registries,
	cargo = str(cargo_bin_path),
	cargo_toml_files = encodable_cargo_toml_files,
	default_registry_download_url_template = default_registry_download_url_template,
	overrides = encodable_overrides,
	packages = dcoded_pkgs,
	repository_name = name,
	target_triples = targets,
	),
	indent = " " * 4,
	),
	)

	def _crate_universe_resolve_impl(repository_ctx):
	"""Entry-point repository to manage rust dependencies.

	General flow is:
	- Serialize user-provided rule attributes into JSON
	- Call the Rust resolver script. It writes a `defs.bzl` file in this repo containing the
	transitive dependencies as repo rules in a `pinned_rust_install()` macro.
	- The user then calls defs.bzl%pinned_rust_install().
	"""

	host_triple, resolver_triple = get_host_triple(repository_ctx)
	tools = get_cargo_and_rustc(repository_ctx, host_triple)
	extension = system_to_binary_ext(triple_to_system(host_triple))

	if repository_ctx.attr.resolver:
	resolver_path = repository_ctx.path(repository_ctx.attr.resolver)
	else:
	# Allow for an an override environment variable to define a url to a binary
	resolver_url = repository_ctx.os.environ.get("RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE", None)
	resolver_sha = repository_ctx.os.environ.get("RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE_SHA256", None)
	if resolver_url:
	if resolver_url.startswith("file://"):
	sha256_result = repository_ctx.execute(["sha256sum", resolver_url[7:]])
	resolver_sha = sha256_result.stdout[:64]
	else:
	resolver_url = repository_ctx.attr.resolver_download_url_template.format(
	host_triple = resolver_triple,
	extension = extension,
	)
	resolver_sha = repository_ctx.attr.resolver_sha256s.get(resolver_triple, None)

	resolver_path = repository_ctx.path("resolver")
	repository_ctx.download(
	url = resolver_url,
	sha256 = resolver_sha,
	output = resolver_path,
	executable = True,
	)

	lockfile_path = None
	if repository_ctx.attr.lockfile:
	lockfile_path = repository_ctx.path(repository_ctx.attr.lockfile)

	input_content = _input_content_template(
	ctx = repository_ctx,
	name = repository_ctx.attr.name,
	packages = repository_ctx.attr.packages,
	cargo_toml_files = repository_ctx.attr.cargo_toml_files,
	overrides = repository_ctx.attr.overrides,
	default_registry_download_url_template = repository_ctx.attr.default_registry_download_url_template,
	additional_registries = repository_ctx.attr.additional_registries,
	targets = repository_ctx.attr.supported_targets,
	cargo_bin_path = tools.cargo,
	)

	input_path = "{name}.resolver_config.json".format(name = repository_ctx.attr.name)
	repository_ctx.file(input_path, content = input_content)

	args = [
	resolver_path,
	"--input_path",
	input_path,
	"--repository_dir",
	repository_ctx.path("."),
	"--repo-name",
	repository_ctx.attr.name,
	]
	if lockfile_path != None:
	args.append("--lockfile")
	str(args.append(lockfile_path))
	env_var_names = repository_ctx.os.environ.keys()
	if "RULES_RUST_REPIN" in env_var_names or "REPIN" in env_var_names:
	args.append("--update-lockfile")

	result = repository_ctx.execute(
	args,
	environment = {
	# The resolver invokes `cargo metadata` which relies on `rustc` being on the $PATH
	# See https://github.com/rust-lang/cargo/issues/8219
	"CARGO": str(tools.cargo),
	"RUSTC": str(tools.rustc),
	"RUST_LOG": "info",
	},
	quiet = False,
	)
	if result.return_code != 0:
	fail("Error resolving crate_universe deps - see above output for more information")

	repository_ctx.file("BUILD.bazel")

	crate_universe = repository_rule(
	doc = """\
	A rule for downloading Rust dependencies (crates).

	__WARNING__: This rule experimental and subject to change without warning.

	Environment Variables:
	- `REPIN`: Re-pin the lockfile if set (useful for repinning deps from multiple rulesets).
	- `RULES_RUST_REPIN`: Re-pin the lockfile if set (useful for only repinning Rust deps).
	- `RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE`: Override URL to use to download resolver binary
	- for local paths use a `file://` URL.
	- `RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE_SHA256`: An optional sha256 value for the binary at the override url location.
	""",
	implementation = _crate_universe_resolve_impl,
	attrs = {
	"additional_registries": attr.string_dict(
	doc = """\
	Additional registries used by Cargo (see https://doc.rust-lang.org/cargo/reference/registries.html).

	Dict of registry_name: index_url.
	""",
	),
	"cargo_toml_files": attr.label_list(
	doc = "A list of Cargo manifests (`Cargo.toml` files).",
	allow_files = True,
	),
	"default_registry_download_url_template": attr.string(
	doc = "A template for where to download crates from for the default crate registry. This must contain `{version}` and `{crate}` templates.",
	default = DEFAULT_DEFAULT_CRATE_DOWNLOAD_URL_TEMPLATE,
	),
	"iso_date": attr.string(
	doc = "The iso_date of cargo binary the resolver should use. Note: This can only be set if `version` is `beta` or `nightly`",
	),
	"lockfile": attr.label(
	doc = (
	"The path to a file which stores pinned information about the generated dependency graph. " +
	"this target must be a file and will be updated by the repository rule when the `REPIN` " +
	"environment variable is set. If this is not set, dependencies will be re-resolved more " +
	"often, setting this allows caching resolves, but will error if the cache is stale."
	),
	allow_single_file = True,
	mandatory = False,
	),
	"overrides": attr.string_dict(
	doc = (
	"Mapping of crate name to specification overrides. See [crate.override](#crateoverride) " +
	" for more details."
	),
	),
	"packages": attr.string_list(
	doc = "A list of crate specifications. See [crate.spec](#cratespec) for more details.",
	allow_empty = True,
	),
	"resolver": attr.label(
	doc = (
	"The label of a `crate_universe` resolver. Resolvers can be built using `cargo_bootstrap_repository` " +
	"but if possible, it's recommended to stick with downloading a resoler via `resolver_download_url_template`."
	),
	),
	"resolver_download_url_template": attr.string(
	doc = (
	"URL template from which to download the resolver binary. {host_triple} and {extension} will be " +
	"filled in according to the host platform."
	),
	default = DEFAULT_URL_TEMPLATE,
	),
	"resolver_sha256s": attr.string_dict(
	doc = "Dictionary of host_triple -> sha256 for resolver binary.",
	default = DEFAULT_SHA256_CHECKSUMS,
	),
	"rust_toolchain_repository_template": attr.string(
	doc = (
	"The template to use for finding the host `rust_toolchain` repository. `{version}` (eg. '1.53.0'), " +
	"`{triple}` (eg. 'x86_64-unknown-linux-gnu'), `{system}` (eg. 'darwin'), and `{arch}` (eg. 'aarch64') " +
	"will be replaced in the string if present."
	),
	default = "rust_{system}_{arch}",
	),
	"sha256s": attr.string_dict(
	doc = "The sha256 checksum of the desired rust artifacts",
	),
	"supported_targets": attr.string_list(
	doc = (
	"A list of supported [platform triples](https://doc.rust-lang.org/nightly/rustc/platform-support.html) " +
	"to consider when resoliving dependencies."
	),
	allow_empty = False,
	default = DEFAULT_TOOLCHAIN_TRIPLES.keys(),
	),
	"version": attr.string(
	doc = "The version of cargo the resolver should use",
	default = rust_common.default_version,
	),
	},
	environ = [
	"REPIN",
	"RULES_RUST_REPIN",
	"RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE",
	"RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE_SHA256",
	],
	)

	def _spec(
	name,
	semver,
	features = None):
	"""A simple crate definition for use in the `crate_universe` rule.

	__WARNING__: This rule experimental and subject to change without warning.

	Example:

	```python
	load("@rules_rust//crate_universe:defs.bzl", "crate_universe", "crate")

	crate_universe(
	name = "spec_example",
	packages = [
	crate.spec(
	name = "lazy_static",
	semver = "=1.4",
	),
	],
	)
	```

	Args:
	name (str): The name of the crate as it would appear in a crate registry.
	semver (str): The desired version ([semver](https://semver.org/)) of the crate
	features (list, optional): A list of desired [features](https://doc.rust-lang.org/cargo/reference/features.html).

	Returns:
	str: A json encoded struct of crate info
	"""
	return json.encode(struct(
	name = name,
	semver = semver,
	features = features or [],
	))

	def _override(
	extra_bazel_data_deps = None,
	extra_bazel_deps = None,
	extra_build_script_bazel_data_deps = None,
	extra_build_script_bazel_deps = None,
	extra_build_script_env_vars = None,
	extra_rustc_env_vars = None,
	features_to_remove = []):
	"""A map of overrides for a particular crate

	__WARNING__: This rule experimental and subject to change without warning.

	Example:

	```python
	load("@rules_rust//crate_universe:defs.bzl", "crate_universe", "crate")

	crate_universe(
	name = "override_example",
	# [...]
	overrides = {
	"tokio": crate.override(
	extra_rustc_env_vars = {
	"MY_ENV_VAR": "MY_ENV_VALUE",
	},
	extra_build_script_env_vars = {
	"MY_BUILD_SCRIPT_ENV_VAR": "MY_ENV_VALUE",
	},
	extra_bazel_deps = {
	# Extra dependencies are per target. They are additive.
	"cfg(unix)": ["@somerepo//:foo"], # cfg() predicate.
	"x86_64-apple-darwin": ["@somerepo//:bar"], # Specific triple.
	"cfg(all())": ["@somerepo//:baz"], # Applies to all targets ("regular dependency").
	},
	extra_build_script_bazel_deps = {
	# Extra dependencies are per target. They are additive.
	"cfg(unix)": ["@buildscriptdep//:foo"],
	"x86_64-apple-darwin": ["@buildscriptdep//:bar"],
	"cfg(all())": ["@buildscriptdep//:baz"],
	},
	extra_bazel_data_deps = {
	# ...
	},
	extra_build_script_bazel_data_deps = {
	# ...
	},
	),
	},
	)
	```

	Args:
	extra_bazel_data_deps (dict, optional): Targets to add to the `data` attribute
	of the generated target (eg: [rust_library.data](./defs.md#rust_library-data)).
	extra_bazel_deps (dict, optional): Targets to add to the `deps` attribute
	of the generated target (eg: [rust_library.deps](./defs.md#rust_library-data)).
	extra_rustc_env_vars (dict, optional): Environment variables to add to the `rustc_env`
	attribute for the generated target (eg: [rust_library.rustc_env](./defs.md#rust_library-rustc_env)).
	extra_build_script_bazel_data_deps (dict, optional): Targets to add to the
	[data](./cargo_build_script.md#cargo_build_script-data) attribute of the generated
	`cargo_build_script` target.
	extra_build_script_bazel_deps (dict, optional): Targets to add to the
	[deps](./cargo_build_script.md#cargo_build_script-deps) attribute of the generated
	`cargo_build_script` target.
	extra_build_script_env_vars (dict, optional): Environment variables to add to the
	[build_script_env](./cargo_build_script.md#cargo_build_script-build_script_env)
	attribute of the generated `cargo_build_script` target.
	features_to_remove (list, optional): A list of features to remove from a generated target.

	Returns:
	str: A json encoded struct of crate overrides
	"""
	for (dep_key, dep_val) in [
	(extra_bazel_deps, extra_bazel_deps),
	(extra_build_script_bazel_deps, extra_build_script_bazel_deps),
	(extra_bazel_data_deps, extra_bazel_data_deps),
	(extra_build_script_bazel_data_deps, extra_build_script_bazel_data_deps),
	]:
	if dep_val != None:
	if not type(dep_val) == "dict":
	fail("The {} attribute should be a dictionary".format(dep_key))

	for target, deps in dep_val.items():
	if not type(deps) == "list" or any([type(x) != "string" for x in deps]):
	fail("The {} values should be lists of strings".format(dep_key))

	return json.encode(struct(
	extra_rustc_env_vars = extra_rustc_env_vars or {},
	extra_build_script_env_vars = extra_build_script_env_vars or {},
	extra_bazel_deps = extra_bazel_deps or {},
	extra_build_script_bazel_deps = extra_build_script_bazel_deps or {},
	extra_bazel_data_deps = extra_bazel_data_deps or {},
	extra_build_script_bazel_data_deps = extra_build_script_bazel_data_deps or {},
	features_to_remove = features_to_remove,
	))

	crate = struct(
	spec = _spec,
	override = _override,
	)