Add runfiles example with more levels of indirection (#3628)

#3399 changed the behavior
of runfiles. Due to this change a few cases no longer work with `bazel
run` that did work before. I tried to create a more complex runfiles
example since rules_rust does not have anyone yet + we can use it for
discussing what should be the correct behavior.

```shell
# Everything with bazel test still works
bazel test //...

# bazel run no longer works for all cases that work with bazel test
bazel run //pkg_a:pkg_a_binary
bazel run //pkg_b:pkg_b_binary
```

I added a comment to the few cases that still work with `bazel test` but
no longer work with `bazel run`. In particular, this happens when
requesting a folder through runfiles instead of an individual file.

Co-authored-by: UebelAndre <github@uebelandre.com>

Author: hofbi

.bazelci/presubmit.yml

@@ -777,6 +777,17 @@ tasks:
       - "//..."
     test_targets:
       - "//..."
+  example_runfiles:
+    name: Runfiles example
+    platform: ubuntu2204
+    working_directory: examples/runfiles
+    build_targets:
+      - "//..."
+    test_targets:
+      - "//..."
+    run_targets:
+      - "//pkg_a:pkg_a_binary"
+      - "//pkg_b:pkg_b_binary"
   ubuntu2204_bzlmod_bcr:
     name: bzlmod BCR presubmit
     platform: ubuntu2204

examples/runfiles/.gitignore

@@ -0,0 +1,2 @@
+/bazel-*
+user.bazelrc

examples/runfiles/MODULE.bazel

@@ -0,0 +1,16 @@
+module(
+    name = "runfiles_example",
+    version = "0.0.0",
+)
+
+###############################################################################
+# B A Z E L  C E N T R A L  R E G I S T R Y # https://registry.bazel.build/
+###############################################################################
+# https://github.com/bazelbuild/rules_rust/releases
+bazel_dep(name = "rules_rust", version = "0.0.0")
+local_path_override(
+    module_name = "rules_rust",
+    path = "../..",
+)
+
+bazel_dep(name = "rules_shell", version = "0.6.1")

examples/runfiles/MODULE.bazel.lock

@@ -0,0 +1,34 @@
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_library", "rust_test")
+load("@rules_shell//shell:sh_binary.bzl", "sh_binary")
+
+sh_binary(
+    name = "say_hello",
+    srcs = ["src/say_hello.sh"],
+    visibility = ["//visibility:public"],
+)
+
+rust_library(
+    name = "pkg_a_library",
+    srcs = ["src/lib.rs"],
+    data = [":say_hello"],
+    rustc_env = {
+        "SAY_HELLO_BIN": "$(rlocationpath :say_hello)",
+    },
+    visibility = ["//visibility:public"],
+    deps = [
+        "@rules_rust//rust/runfiles",
+    ],
+)
+
+rust_binary(
+    name = "pkg_a_binary",
+    srcs = ["src/main.rs"],
+    visibility = ["//visibility:public"],
+    deps = [":pkg_a_library"],
+)
+
+rust_test(
+    name = "pkg_a_test",
+    srcs = ["src/test.rs"],
+    deps = [":pkg_a_library"],
+)

examples/runfiles/pkg_a/BUILD.bazel

@@ -0,0 +1,50 @@
+use runfiles::{rlocation, Runfiles};
+use std::process;
+use std::path::PathBuf;
+
+pub fn invoke_binary(bin: PathBuf) {
+    let child = process::Command::new(bin)
+        .stdin(process::Stdio::piped())
+        .stdout(process::Stdio::piped())
+        .spawn()
+        .expect("Failed to spawn command");
+    let output = child.wait_with_output().expect("Failed to read stdout");
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    println!("say_hello binary output: {}", stdout.trim());
+}
+
+pub fn invoke_say_hello_binary_with_path() {
+    let r = Runfiles::create().unwrap();
+    let bin = rlocation!(r, "_main/pkg_a/say_hello").unwrap();
+    println!("Invoking say_hello binary with path:    {}", bin.display());
+
+    invoke_binary(bin);
+}
+
+pub fn invoke_say_hello_binary_with_env_var() {
+    let r = Runfiles::create().unwrap();
+    let bin = rlocation!(r, env!("SAY_HELLO_BIN")).unwrap();
+    println!("Invoking say_hello binary with env var: {}", bin.display());
+
+    invoke_binary(bin);
+}
+
+pub fn invoke_say_hello_with_late_join() {
+    let r = Runfiles::create().unwrap();
+    let bin_folder = rlocation!(r, "_main/pkg_a").unwrap();
+
+    let bin = bin_folder.join("say_hello");
+    println!("Invoking pkg_a binary with late join: {}", bin.display());
+
+    invoke_binary(bin);
+}
+
+pub fn invoke_say_hello_with_late_join_parent() {
+    let r = Runfiles::create().unwrap();
+    let bin_folder = rlocation!(r, "_main/pkg_a/say_hello").unwrap();
+
+    let bin = bin_folder.parent().unwrap().join("say_hello");
+    println!("Invoking pkg_a binary with late join parent: {}", bin.display());
+
+    invoke_binary(bin);
+}

examples/runfiles/pkg_a/src/lib.rs

@@ -0,0 +1,8 @@
+use pkg_a_library;
+
+fn main() {
+    pkg_a_library::invoke_say_hello_binary_with_path();
+    pkg_a_library::invoke_say_hello_binary_with_env_var();
+    // pkg_a_library::invoke_say_hello_with_late_join(); // This fails with bazel run, will be added in a follow up PR
+    pkg_a_library::invoke_say_hello_with_late_join_parent();
+}

examples/runfiles/pkg_a/src/main.rs

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+
+echo "Hello, world from $(pwd)"
+echo "========================"

examples/runfiles/pkg_a/src/say_hello.sh

@@ -0,0 +1,21 @@
+use pkg_a_library;
+
+#[test]
+fn test_invoke_say_hello_binary_with_path() {
+    pkg_a_library::invoke_say_hello_binary_with_path();
+}
+
+#[test]
+fn test_invoke_say_hello_binary_with_env_var() {
+    pkg_a_library::invoke_say_hello_binary_with_env_var();
+}
+
+#[test]
+fn test_invoke_say_hello_with_late_join() {
+    pkg_a_library::invoke_say_hello_with_late_join();
+}
+
+#[test]
+fn test_invoke_say_hello_with_late_join_parent() {
+    pkg_a_library::invoke_say_hello_with_late_join_parent();
+}

examples/runfiles/pkg_a/src/test.rs

@@ -0,0 +1,36 @@
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_library", "rust_test")
+
+rust_library(
+    name = "pkg_b_library",
+    srcs = ["src/lib.rs"],
+    data = [
+        "//pkg_a:pkg_a_binary",
+        "//pkg_a:say_hello",
+    ],
+    rustc_env = {
+        "PKG_A_BINARY_BIN": "$(rlocationpath //pkg_a:pkg_a_binary)",
+        "SAY_HELLO_BIN": "$(rlocationpath //pkg_a:say_hello)",
+    },
+    deps = [
+        "//pkg_a:pkg_a_library",
+        "@rules_rust//rust/runfiles",
+    ],
+)
+
+rust_binary(
+    name = "pkg_b_binary",
+    srcs = ["src/main.rs"],
+    deps = [
+        ":pkg_b_library",
+        "//pkg_a:pkg_a_library",
+    ],
+)
+
+rust_test(
+    name = "pkg_b_test",
+    srcs = ["src/test.rs"],
+    deps = [
+        ":pkg_b_library",
+        "//pkg_a:pkg_a_library",
+    ],
+)