Add patching example

examples/crate_universe/DEVELOPMENT.md

@@ -10,6 +10,7 @@ bazel commands:
 bazel run //vendor_external:crates_vendor
 bazel run //vendor_local_manifests:crates_vendor
 bazel run //vendor_local_pkgs:crates_vendor
+bazel run //vendor_local_patching:vendor
 bazel run //vendor_remote_manifests:crates_vendor
 bazel run //vendor_remote_pkgs:crates_vendor
 ```

examples/crate_universe/vendor_local_patching/.gitignore

@@ -0,0 +1,3 @@
+# Ignore everything but the `BUILD` files within the vendored directories
+vendor/*/*
+!vendor/*/BUILD.bazel

examples/crate_universe/vendor_local_patching/BUILD.bazel

@@ -0,0 +1,31 @@
+load("@rules_rust//crate_universe:defs.bzl", "crates_vendor")
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_test")
+
+crates_vendor(
+    name = "vendor",
+    cargo_lockfile = ":Cargo.lock",
+    manifests = [":Cargo.toml"],
+    mode = "local",
+    vendor_path = "vendor",
+    # No wasi support
+    supported_platform_triples = [
+        "x86_64-unknown-linux-gnu",
+        "aarch64-unknown-linux-gnu",
+        "x86_64-apple-darwin",
+        "x86_64-pc-windows-msvc",
+        "x86_64-unknown-fuchsia",
+        "aarch64-unknown-fuchsia",
+    ],
+)
+
+rust_binary(
+    name = "bin",
+    srcs = ["src/main.rs"],
+    edition = "2021",
+    deps = ["//vendor_local_patching/vendor:rand"],
+)
+
+rust_test(
+    name = "test",
+    crate = ":bin",
+)

examples/crate_universe/vendor_local_patching/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "my_third_party"
+version = "0.1.0"
+
+[dependencies]
+rand = "0.8.5"
+
+[patch.crates-io]
+# We need to make sure that forked_getrandom/BUILD.bazel exposes the correct
+# filegroups so that the generated BUILD file in the vendor dir can point to them.
+getrandom = { path = "forked_getrandom" }
+
+# Since we know this crate is never used, we don't have to bother creating a BUILD
+# file for our empty stub crate we're using to patch it out
+wasi = { path = "empty_wasi" }

examples/crate_universe/vendor_local_patching/README.md

@@ -0,0 +1,19 @@
+# Local vendoring with patches
+
+This demonstrates patching out crates when using the "local" vendor mode. The
+example crate just depends on `rand`, and we patch out two of the transitive deps:
+
+- `getrandom` is forked. In `forked_getrandom/BUILD.bazel` the necessary
+filegroups are exposed so that the generated BUILD file at
+`vendor/getrandom-0.2.8/BUILD.bazel` can use them.
+- `wasi` is "empty-patched" because it's not actually used in the build. When
+using local vendoring, `crate_universe` runs `cargo vendor` which isn't aware
+of which target-triples you're using. The `wasi` crate is only used by `rand`
+when you're actually targeting `wasi` (which we're not), so we
+patch it out with a stub crate to avoid downloading and vendoring the source
+of the that crate. This can be helpful to avoid vendoring large crates or
+ones with conflicting licenses that aren't used in your build graph.
+
+The result of our `getrandom` patch is that the binary is always given the
+same value for seeding its RNG. Therefore we can test that `rand::random`
+returns the same value to check that the patching behavior is working correctly.

examples/crate_universe/vendor_local_patching/empty_wasi/Cargo.toml

@@ -0,0 +1,3 @@
+[package]
+name = "wasi"
+version = "0.11.0+wasi-snapshot-preview1"

examples/crate_universe/vendor_local_patching/forked_getrandom/BUILD.bazel

@@ -0,0 +1,23 @@
+filegroup(
+    name = "crate_root",
+    srcs = ["src/lib.rs"],
+    visibility = ["//vendor_local_patching/vendor:__subpackages__"],
+)
+
+filegroup(
+    name = "srcs",
+    srcs = glob(["**/*.rs"]),
+    visibility = ["//vendor_local_patching/vendor:__subpackages__"],
+)
+
+filegroup(
+    name = "compile_data",
+    srcs = glob(["**/*"]),
+    visibility = ["//vendor_local_patching/vendor:__subpackages__"],
+)
+
+filegroup(
+    name = "build_script_crate_root",
+    srcs = ["build.rs"],
+    visibility = ["//vendor_local_patching/vendor:__subpackages__"],
+)

examples/crate_universe/vendor_local_patching/forked_getrandom/Cargo.toml

@@ -0,0 +1,35 @@
+[package]
+edition = "2018"
+name = "getrandom"
+version = "0.2.15"
+authors = ["The Rand Project Developers"]
+exclude = [".*"]
+autobins = false
+autoexamples = false
+autotests = false
+autobenches = false
+description = "A small cross-platform library for retrieving random data from system source"
+documentation = "https://docs.rs/getrandom"
+readme = "README.md"
+categories = ["os", "no-std"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-random/getrandom"
+
+[lib]
+name = "getrandom"
+path = "src/lib.rs"
+
+[dependencies.cfg-if]
+version = "1"
+
+[dependencies.compiler_builtins]
+version = "0.1"
+optional = true
+
+[dependencies.core]
+version = "1.0"
+optional = true
+package = "rustc-std-workspace-core"
+
+[features]
+std = []

examples/crate_universe/vendor_local_patching/forked_getrandom/build.rs

@@ -0,0 +1,4 @@
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rustc-env=RANDOM_NUMBER=4");
+}

examples/crate_universe/vendor_local_patching/forked_getrandom/src/lib.rs

@@ -0,0 +1,23 @@
+use std::{fmt, num::NonZeroU32};
+
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+pub struct Error(NonZeroU32);
+impl std::error::Error for Error {}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Error({})", self.0.get())
+    }
+}
+
+pub fn getrandom(dest: &mut [u8]) -> Result<(), Error> {
+    if dest.is_empty() {
+        return Ok(());
+    }
+    let num = env!("RANDOM_NUMBER").parse().unwrap();
+    for n in dest {
+        *n = num; // chosen by fair dice roll.
+                  // guaranteed to be random.
+    }
+    Ok(())
+}

examples/crate_universe/vendor_local_patching/src/main.rs

@@ -0,0 +1,11 @@
+fn main() {
+    println!("\"random\" number: {}", rand::random::<f32>());
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn not_actually_random() {
+        assert_eq!(rand::random::<u32>(), 34253218);
+    }
+}

examples/crate_universe/vendor_local_patching/vendor/BUILD.bazel

@@ -0,0 +1,37 @@
+###############################################################################
+# @generated
+# DO NOT MODIFY: This file is auto-generated by a crate_universe tool. To
+# regenerate this file, run the following:
+#
+#     bazel run @//vendor_local_patching:vendor
+###############################################################################
+
+package(default_visibility = ["//visibility:public"])
+
+exports_files(
+    [
+        "cargo-bazel.json",
+        "defs.bzl",
+    ] + glob(
+        include = ["*.bazel"],
+        allow_empty = True,
+    ),
+)
+
+filegroup(
+    name = "srcs",
+    srcs = glob(
+        include = [
+            "*.bazel",
+            "*.bzl",
+        ],
+        allow_empty = True,
+    ),
+)
+
+# Workspace Member Dependencies
+alias(
+    name = "rand",
+    actual = "//vendor_local_patching/vendor/rand-0.8.5:rand",
+    tags = ["manual"],
+)

examples/crate_universe/vendor_local_patching/vendor/alias_rules.bzl

@@ -0,0 +1,47 @@
+"""Alias that transitions its target to `compilation_mode=opt`.  Use `transition_alias="opt"` to enable."""
+
+load("@rules_cc//cc:defs.bzl", "CcInfo")
+load("@rules_rust//rust:rust_common.bzl", "COMMON_PROVIDERS")
+
+def _transition_alias_impl(ctx):
+    # `ctx.attr.actual` is a list of 1 item due to the transition
+    providers = [ctx.attr.actual[0][provider] for provider in COMMON_PROVIDERS]
+    if CcInfo in ctx.attr.actual[0]:
+        providers.append(ctx.attr.actual[0][CcInfo])
+    return providers
+
+def _change_compilation_mode(compilation_mode):
+    def _change_compilation_mode_impl(_settings, _attr):
+        return {
+            "//command_line_option:compilation_mode": compilation_mode,
+        }
+
+    return transition(
+        implementation = _change_compilation_mode_impl,
+        inputs = [],
+        outputs = [
+            "//command_line_option:compilation_mode",
+        ],
+    )
+
+def _transition_alias_rule(compilation_mode):
+    return rule(
+        implementation = _transition_alias_impl,
+        provides = COMMON_PROVIDERS,
+        attrs = {
+            "actual": attr.label(
+                mandatory = True,
+                doc = "`rust_library()` target to transition to `compilation_mode=opt`.",
+                providers = COMMON_PROVIDERS,
+                cfg = _change_compilation_mode(compilation_mode),
+            ),
+            "_allowlist_function_transition": attr.label(
+                default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
+            ),
+        },
+        doc = "Transitions a Rust library crate to the `compilation_mode=opt`.",
+    )
+
+transition_alias_dbg = _transition_alias_rule("dbg")
+transition_alias_fastbuild = _transition_alias_rule("fastbuild")
+transition_alias_opt = _transition_alias_rule("opt")

examples/crate_universe/vendor_local_patching/vendor/cfg-if-1.0.0/BUILD.bazel

@@ -0,0 +1,53 @@
+###############################################################################
+# @generated
+# DO NOT MODIFY: This file is auto-generated by a crate_universe tool. To
+# regenerate this file, run the following:
+#
+#     bazel run @//vendor_local_patching:vendor
+###############################################################################
+
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+package(default_visibility = ["//visibility:public"])
+
+rust_library(
+    name = "cfg_if",
+    srcs = glob(
+        include = ["**/*.rs"],
+        allow_empty = False,
+    ),
+    crate_root = "src/lib.rs",
+    data = glob(
+        include = [],
+        allow_empty = True,
+        exclude = [
+            "**/* *",
+            ".tmp_git_root/**/*",
+            "BUILD",
+            "BUILD.bazel",
+            "WORKSPACE",
+            "WORKSPACE.bazel",
+        ],
+    ),
+    edition = "2018",
+    rustc_flags = [
+        "--cap-lints=allow",
+    ],
+    tags = [
+        "cargo-bazel",
+        "crate-name=cfg-if",
+        "manual",
+        "noclippy",
+        "norustfmt",
+    ],
+    target_compatible_with = select({
+        "@rules_rust//rust/platform:aarch64-unknown-fuchsia": [],
+        "@rules_rust//rust/platform:aarch64-unknown-linux-gnu": [],
+        "@rules_rust//rust/platform:x86_64-apple-darwin": [],
+        "@rules_rust//rust/platform:x86_64-pc-windows-msvc": [],
+        "@rules_rust//rust/platform:x86_64-unknown-fuchsia": [],
+        "@rules_rust//rust/platform:x86_64-unknown-linux-gnu": [],
+        "//conditions:default": ["@platforms//:incompatible"],
+    }),
+    version = "1.0.0",
+)