Add some basic examples

examples/.gitignore

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+buck-out

examples/cpp/.buckconfig

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+[buildfile]
+name=TARGETS
+
+[repositories]
+root = .

examples/cpp/hello-world/TARGETS

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+load("//:rules.bzl", "cpp_binary")
+load("//:toolchain.bzl", "cpp_local_toolchain")
+
+cpp_local_toolchain(
+    name = "clang",
+    command = "clang++",
+)
+
+cpp_binary(
+    name = "main",
+    srcs = glob(["src/**/*.cpp"]),
+    headers = glob(["src/**/*.hpp"]),
+    deps = [],
+    toolchain = ":clang",
+)

examples/cpp/hello-world/src/func.cpp

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+#include <iostream>
+
+void print_hello()
+{
+    std::cout << "hellp from cpp" << std::endl;
+}

examples/cpp/hello-world/src/func.hpp

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+void print_hello();

examples/cpp/hello-world/src/main.cpp

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+#include "func.hpp"
+
+int main()
+{
+    print_hello();
+}

examples/cpp/library/TARGETS

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+load("//:rules.bzl", "cpp_library")
+
+cpp_library(
+    name = "library",
+    visibility = ["//..."],
+    srcs = glob(["src/**/*.cpp"]),
+    headers = glob(["src/**/*.hpp"]),
+    deps = [],
+)

examples/cpp/library/src/library.cpp

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+#include <iostream>
+
+void print_hello()
+{
+    std::cout << "hello from library" << std::endl;
+}

examples/cpp/library/src/library.hpp

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+void print_hello();

examples/cpp/rules.bzl

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+load("//toolchain.bzl", "CxxCompilerInfo")
+
+CxxLibraryInfo = provider(fields = ["headers", "objects", "include_folders"])
+
+def _cpp_binary_impl(ctx: "context") -> ["provider"]:
+    sources = ctx.attr.srcs
+    out = ctx.actions.declare_output("main")
+
+    cmd = cmd_args([ctx.attr.toolchain[CxxCompilerInfo].compiler_path, "-o", out.as_output()] + sources)
+
+    ctx.actions.run(cmd, category = "compile")
+
+    return [
+        DefaultInfo(default_outputs = [out]),
+        RunInfo(args = cmd_args(out)),
+    ]
+
+cpp_binary = rule(
+    implementation = _cpp_binary_impl,
+    attrs = {
+        "srcs": attr.list(attr.source()),
+        "headers": attr.list(attr.source()),
+        "deps": attr.list(attr.dep()),
+        "toolchain": attr.dep(),
+    },
+)
+
+def _cpp_library_impl(ctx: "context") -> ["provider"]:
+    sources = ctx.attr.srcs
+    headers = ctx.attr.headers
+    out = ctx.actions.declare_output("lib.so")
+
+    cmd = cmd_args(["clang++", "-shared", "-undefined", "dynamic_lookup", "-o", out.as_output()] + sources)
+
+    ctx.actions.run(cmd, category = "compile")
+
+    return [DefaultInfo(default_outputs = [out]), CxxLibraryInfo(objects = [out], headers = headers)]
+
+cpp_library = rule(
+    implementation = _cpp_library_impl,
+    attrs = {
+        "srcs": attr.list(attr.source()),
+        "headers": attr.list(attr.source()),
+        "deps": attr.list(attr.dep()),
+    },
+)

examples/cpp/toolchain.bzl

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+CxxCompilerInfo = provider(
+    doc = "Information about how to invoke the cpp compiler.",
+    fields = ["compiler_path", "include_directories", "lib_directories"],
+)
+
+def _cpp_local_toolchain_impl(ctx):
+    return [DefaultInfo(), CxxCompilerInfo(compiler_path = ctx.attr.command)]
+
+cpp_local_toolchain = rule(
+    implementation = _cpp_local_toolchain_impl,
+    attrs = {
+        "command": attr.string(),
+    },
+)

examples/go/.buckconfig

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+[buildfile]
+name=TARGETS
+
+[repositories]
+root = .

examples/go/binary-toolchain/TARGETS

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+load("//:rules.bzl", "go_binary")
+load("//:toolchain.bzl", "go_toolchain")
+
+go_toolchain(
+    name = "go_linux",
+    version = "1.18.3",
+    platform = "linux-amd64",
+    sha1 = "3511fcb34e0162abdcdeea0ab532f0264943e3d8",
+)
+
+go_binary(
+    name = "main",
+    srcs = glob(["*.go"]),
+    deps = [],
+    toolchain = ":go_linux",
+)

examples/go/binary-toolchain/main.go

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+package main
+
+import "fmt"
+
+func main() {
+    fmt.Println("hello from go toolchain")
+}

examples/go/rules.bzl

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+load("//toolchain.bzl", "GoCompilerInfo")
+
+def _go_binary_impl(ctx: "context") -> ["provider"]:
+    sources = ctx.attr.srcs
+    out = ctx.actions.declare_output("main")
+
+    cmd = cmd_args([ctx.attr.toolchain[GoCompilerInfo].compiler_path, "build", "-o", out.as_output()] + sources)
+
+    ctx.actions.run(cmd, category = "compile")
+
+    return [
+        DefaultInfo(default_outputs = [out]),
+        RunInfo(args = cmd_args(out)),
+    ]
+
+go_binary = rule(
+    implementation = _go_binary_impl,
+    attrs = {
+        "srcs": attr.list(attr.source()),
+        "deps": attr.list(attr.dep()),
+        "toolchain": attr.dep(),
+    },
+)

examples/go/toolchain.bzl

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+GoCompilerInfo = provider(
+    doc = "Information about how to invoke the go compiler.",
+    fields = ["compiler_path", "GOROOT"],
+)
+
+def _go_toolchain_impl(ctx):
+    url = "https://go.dev/dl/go" + ctx.attr.version + "." + ctx.attr.platform + ".tar.gz"
+
+    download = http_archive_impl(ctx, url, ctx.attr.sha1)
+
+    compiler_dst = ctx.actions.declare_output("compiler")
+    compiler_src = cmd_args(download[0].default_outputs[0], format = "{}/go/bin/go")
+    ctx.actions.run(["ln", "-srf", compiler_src, compiler_dst.as_output()], category = "cp_compiler")
+
+    # ctx.actions.symlink_file(compiler_dst, compiler_src)
+
+    return download + [GoCompilerInfo(compiler_path = compiler_dst, GOROOT = "")]
+
+go_toolchain = rule(
+    implementation = _go_toolchain_impl,
+    attrs = {
+        "version": attr.string(),
+        "platform": attr.string(),
+        "sha1": attr.string(),
+    },
+)
+
+def http_archive_impl(ctx: "context", url, sha1) -> ["provider"]:
+    # Download archive.
+    archive = ctx.actions.declare_output("archive.tar.gz")
+    ctx.actions.download_file(archive.as_output(), url, sha1 = sha1, is_deferrable = True)
+
+    # Unpack archive to output directory.
+    compress_flag = "-z"
+
+    output = ctx.actions.declare_output(ctx.label.name)
+    script, hidden = ctx.actions.write(
+        "unpack.sh",
+        [
+            cmd_args(output, format = "mkdir -p {}"),
+            cmd_args(output, format = "cd {}"),
+            cmd_args(["tar", compress_flag, "-x", "-f", archive], delimiter = " ").relative_to(output),
+        ],
+        is_executable = True,
+        allow_args = True,
+    )
+
+    print(dir(output), output.short_path, str(output))
+
+    ctx.actions.run(cmd_args(["/bin/sh", script])
+        .hidden(hidden + [archive, output.as_output()]), category = "http_archive")
+
+    return [DefaultInfo(default_outputs = [output])]

examples/readme.md

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+# buck2 examples
+
+In these folders are some examples on how to get buck2 working with
+your favorite languages and tools.

examples/rust/.buckconfig

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+[buildfile]
+name=TARGETS
+
+[repositories]
+root = .

examples/rust/rules.bzl

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+def _rust_binary_impl(ctx):
+    file = ctx.attr.file
+    out = ctx.actions.declare_output("main")
+
+    cmd = cmd_args(["rustc", "--crate-type=bin", file, "-o", out.as_output()])
+
+    ctx.actions.run(cmd, category = "compile")
+
+    return [DefaultInfo(default_outputs = [out]), RunInfo(args = cmd_args([out]))]
+
+rust_binary = rule(
+    implementation = _rust_binary_impl,
+    attrs = {
+        "file": attr.source(),
+    },
+)

examples/rust/rustc/TARGETS

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+load("//:rules.bzl", "rust_binary")
+
+rust_binary(
+    name = "main",
+    file = "./main.rs",
+)

examples/rust/rustc/main.rs

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+fn main() {
+    println!("hello from rustc");
+}