Add test case for OUT_DIR in tests. (#954)

* Add test case for OUT_DIR in tests.

* Add some env printing, and make the test fail on purpose.

* Passing when OUT_DIR is used in a macro.

* Cleanup

* Remove Cargo.lock

* Buildifier warnings=all

* Remove Cargo.toml

Author: sayrer

test/out_dir_in_tests/BUILD.bazel

@@ -0,0 +1,34 @@
+load("//cargo:cargo_build_script.bzl", "cargo_build_script")
+load("//rust:defs.bzl", "rust_test_suite")
+load(
+    "//rust:rust.bzl",
+    "rust_library",
+    "rust_test",
+)
+
+cargo_build_script(
+    name = "build_script",
+    srcs = ["build.rs"],
+)
+
+rust_library(
+    name = "demo_lib",
+    srcs = [
+        "src/lib.rs",
+    ],
+    deps = [":build_script"],
+)
+
+rust_test(
+    name = "demo_lib_test",
+    crate = ":demo_lib",
+)
+
+rust_test_suite(
+    name = "suite",
+    srcs = glob(["tests/**"]),
+    # Add the 'crate' argument, which will be passed as a kwarg
+    # to the underlying rust_test rules. This will make OUT_DIR
+    # available when compiling integration tests.
+    crate = ":demo_lib",
+)

test/out_dir_in_tests/build.rs

@@ -0,0 +1,11 @@
+use std::env;
+use std::fs::File;
+use std::io::prelude::*;
+use std::path::PathBuf;
+
+fn main() -> std::io::Result<()> {
+    let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
+    let mut file = File::create(out_path.join("test_content.txt"))?;
+    file.write_all(b"Test content")?;
+    Ok(())
+}

test/out_dir_in_tests/src/lib.rs

@@ -0,0 +1,18 @@
+#[cfg(test)]
+mod tests {
+    use std::env;
+
+    #[test]
+    fn can_find_the_out_dir_file() {
+        // The file contents must be included via a macro.
+        let contents = include_str!(concat!(env!("OUT_DIR"), "/test_content.txt"));
+        assert_eq!("Test content", contents);
+    }
+
+    #[test]
+    fn no_out_dir_at_runtime() {
+        // Cargo seems to set this at runtime as well, although the documentation
+        // says it's only available at compile time.
+        assert!(env::var("OUT_DIR").is_err());
+    }
+}

test/out_dir_in_tests/tests/out_dir_reader.rs

@@ -0,0 +1,15 @@
+use std::env;
+
+#[test]
+fn can_find_the_out_dir_file() {
+    // The file contents must be included via a macro.
+    let contents = include_str!(concat!(env!("OUT_DIR"), "/test_content.txt"));
+    assert_eq!("Test content", contents);
+}
+
+#[test]
+fn no_out_dir_at_runtime() {
+    // Cargo seems to set this at runtime as well, although the documentation
+    // says it's only available at compile time.
+    assert!(env::var("OUT_DIR").is_err());
+}