Split into multiple examples, one for hybrid Cargo + Buck projects

examples/hybrid/.buckconfig

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+[repositories]
+root = .
+prelude = prelude
+toolchains = toolchains
+none = none
+
+[repository_aliases]
+config = prelude
+fbcode = none
+fbsource = none
+buck = none
+
+[external_cells]
+prelude = bundled
+
+[parser]
+target_platform_detector_spec = target:root//...->prelude//platforms:default
+
+[rust]
+default_edition = 2021
+remap_src_paths = yes

examples/hybrid/.buckversion

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+latest

examples/hybrid/.gitignore

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+/buck-out
+/target
+.cargo
+
+# You can also preserve config.toml, if you need to change cargo settings.
+# !.cargo/config.toml
+

examples/hybrid/Cargo.toml

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+[workspace]
+
+members = ["project"]
+resolver = "2"
+
+# Local patches - typically git references
+[patch.crates-io]

examples/hybrid/README.md

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+# Hybrid Cargo + Buck project
+
+This example is for using both Cargo and Buck on the same project. This is 
+useful if you want to:
+
+- use Cargo to do things like `cargo fmt`;
+- have it work out of the box with `rust-analyzer`, so it's easy to contribute;
+- ultimately build your code with Buck;
+- or support building with either.
+
+The key is the `reindeer.toml` in the root, which stitches together a Cargo 
+workspace and a Buck package (`third-party`) to buckify Cargo dependencies 
+into.
+
+## Running the example
+
+```sh
+cargo install --path .
+cd examples/hybrid
+
+# Add a dependency
+cargo add -p project serde --features derive
+
+# Buckify deps. Do this every time you modify the Cargo.tomls, in general.
+reindeer buckify
+
+# Note that both buck and cargo can build this project
+buck2 run //project:test
+cargo run -p project
+```
+
+## Missing from this example
+
+This example does no vendoring or anything fancy with fixups. You will have to 
+follow the other examples to get a non-trivial Cargo project built with Buck.
+

examples/hybrid/project/BUCK

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+rust_binary(
+    name = "test",
+    srcs = ["src/main.rs"],
+    deps = [
+        "//third-party:once_cell",
+    ],
+)

examples/hybrid/project/Cargo.toml

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+[package]
+# Pseudo-package whose dependencies are imported and buckified
+name = "project"
+version = "0.0.0"
+edition = "2021"
+publish = false
+
+# List of packages to be imported, with version constraints, features
+# and all options Cargo supports.
+[dependencies]
+once_cell = "1.4"
+
+# Local patches - typically git references
+[patch.crates-io]

examples/hybrid/project/src/main.rs

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+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+use once_cell::sync::Lazy;
+
+const MAGIC: &str = "this is a magic string";
+
+static SPECIAL: Lazy<String> = Lazy::new(|| MAGIC.to_string());
+
+fn main() {
+    println!("{}", &*SPECIAL);
+}

examples/hybrid/reindeer.toml

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+##
+## Reindeer Config for a hybrid Cargo + Buck project
+##
+
+# Paths
+#
+# This is a workspace Cargo.toml. For all default workspace members, it will
+# recursively buckify their dependencies to third-party/BUCK.
+manifest_path = "Cargo.toml"
+third_party_dir = "third-party"
+include_top_level = false
+fixup_templates = true
+
+# Platforms (see other examples)
+#
+[platform.linux-x86_64]
+x86_64-unknown-linux-gnu = []                      # true for a boolean test
+target_arch = ["x86_64"]
+target_endian = ["little"]
+target_env = ["gnu"]
+target_family = ["unix"]
+target_feature = ["fxsr", "sse", "sse2"]
+target_has_atomic = ["8", "16", "32", "64", "ptr"]
+target_os = ["linux"]
+target_pointer_width = ["64"]
+target_vendor = ["unknown"]
+
+# Fortanix SGX
+[platform.fortanix-sgx]
+x86_64-fortanix-unknown-sgx = []
+target_arch = ["x86_64"]
+target_endian = ["little"]
+target_env = ["sgx"]
+target_feature = ["fxsr", "rdrand", "rdseed", "sse", "sse2"]
+target_has_atomic = ["8", "16", "32", "64", "ptr"]
+target_os = ["unknown"]
+target_pointer_width = ["64"]
+target_vendor = ["fortanix"]
+
+# macOS - x86_64-apple-darwin
+[platform.macos]
+x86_64-apple-darwin = []
+target_arch = ["x86_64"]
+target_endian = ["little"]
+target_env = []
+target_family = ["unix"]
+target_feature = ["cmpxchg16b", "fxsr", "sse", "sse2", "sse3", "ssse3"]
+target_has_atomic = ["8", "16", "32", "64", "128", "ptr"]
+target_os = ["macos"]
+target_pointer_width = ["64"]
+target_vendor = ["apple"]
+
+# Windows with MSVC toolchain - x86_64-pc-windows-msvc
+[platform.windows]
+x86_64-pc-windows-msvc = []
+target_arch = ["x86_64"]
+target_endian = ["little"]
+target_env = ["msvc"]
+target_family = ["windows"]
+target_feature = ["fxsr", "sse", "sse2"]
+target_has_atomic = ["8", "16", "32", "64", "ptr"]
+target_os = ["windows"]
+target_pointer_width = ["64"]
+target_vendor = ["pc"]
+
+# Windows with GNU toolchain - x86_64-pc-windows-gnu
+[platform.windows-gnu]
+x86_64-pc-windows-gnu = []
+target_arch = ["x86_64"]
+target_endian = ["little"]
+target_env = ["gnu"]
+target_family = ["windows"]
+target_feature = ["fxsr", "sse", "sse2"]
+target_has_atomic = ["8", "16", "32", "64", "ptr"]
+target_os = ["windows"]
+target_pointer_width = ["64"]
+target_vendor = ["pc"]
+
+# Configuration for generated BUCK file
+# See other examples
+[buck]
+file_name = "BUCK"
+rust_library = "cargo.rust_library"
+rust_binary = "cargo.rust_binary"
+buildscript_genrule = "buildscript_run"
+buckfile_imports = """
+load("@prelude//rust:cargo_buildscript.bzl", "buildscript_run")
+load("@prelude//rust:cargo_package.bzl", "cargo")
+"""
+generated_file_header = """
+##
+## \u0040generated by reindeer
+## Do not edit by hand.
+##
+## See README.md for directions on how to update this.
+##
+"""

examples/hybrid/third-party/.gitignore

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+# Ignore Cargo-related stuff
+.cargo/registry
+.cargo/git
+/registry
+/git
+.package-cache
+
+# Various cruft in vendored packages
+vendor/*/target
+vendor/*/Cargo.lock
+vendor/**/.buckconfig
+vendor/**/BUCK
+vendor/**/OWNERS
+vendor/**/*~
+vendor/**/*.bzl
+vendor/*/.github/**
+vendor/*/.appveyor.yml
+vendor/*/.travis.yml
+/target/**
+
+# Bad Windows names - oh for case-insensitive regex matching!
+vendor/**/[Aa][Uu][Xx]
+vendor/**/[Aa][Uu][Xx].*
+vendor/**/[Cc][Oo][Mm][1-9]
+vendor/**/[Cc][Oo][Mm][1-9].*
+vendor/**/[Cc][Oo][Nn]
+vendor/**/[Cc][Oo][Nn].*
+vendor/**/[Ll][Pp][Tt][1-9]
+vendor/**/[Ll][Pp][Tt][1-9].*
+vendor/**/[Nn][Uu][Ll]
+vendor/**/[Nn][Uu][Ll].*

examples/hybrid/third-party/BUCK

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+##
+## @generated by reindeer
+## Do not edit by hand.
+##
+## See README.md for directions on how to update this.
+##
+
+load("@prelude//rust:cargo_buildscript.bzl", "buildscript_run")
+load("@prelude//rust:cargo_package.bzl", "cargo")
+
+alias(
+    name = "once_cell",
+    actual = ":once_cell-1.20.2",
+    visibility = ["PUBLIC"],
+)
+
+http_archive(
+    name = "once_cell-1.20.2.crate",
+    sha256 = "1261fe7e33c73b354eab43b1273a57c8f967d0391e80353e51f764ac02cf6775",
+    strip_prefix = "once_cell-1.20.2",
+    urls = ["https://static.crates.io/crates/once_cell/1.20.2/download"],
+    visibility = [],
+)
+
+cargo.rust_library(
+    name = "once_cell-1.20.2",
+    srcs = [":once_cell-1.20.2.crate"],
+    crate = "once_cell",
+    crate_root = "once_cell-1.20.2.crate/src/lib.rs",
+    edition = "2021",
+    features = [
+        "alloc",
+        "default",
+        "race",
+        "std",
+    ],
+    visibility = [],
+)
+
+cargo.rust_binary(
+    name = "project-0.0.0-project",
+    srcs = ["../project/src/main.rs"],
+    crate = "project",
+    crate_root = "../project/src/main.rs",
+    edition = "2021",
+    visibility = [],
+    deps = [":once_cell-1.20.2"],
+)

examples/hybrid/toolchains/BUCK

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+load("@prelude//toolchains:demo.bzl", "system_demo_toolchains")
+system_demo_toolchains()

examples/hybrid/top/main.rs

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+// Dummy source to keep Cargo happy
+
+fn main() {}