cargo_build_script can use rustc_env_files (#2276)

Fixes #2248

Author: illicitonion

cargo/private/cargo_build_script_wrapper.bzl

@@ -26,6 +26,7 @@ def cargo_build_script(
         links = None,
         rundir = None,
         rustc_env = {},
+        rustc_env_files = [],
         rustc_flags = [],
         visibility = None,
         tags = None,
@@ -113,6 +114,8 @@ def cargo_build_script(
 
             If set to `.`, the cargo build script will run in the exec root.
         rustc_env (dict, optional): Environment variables to set in rustc when compiling the build script.
+        rustc_env_files (list of label, optional): Files containing additional environment variables to set for rustc
+            when building the build script.
         rustc_flags (list, optional): List of compiler flags passed to `rustc`.
         visibility (list of label, optional): Visibility to apply to the generated build script output.
         tags: (list of str, optional): Tags to apply to the generated build script output.
@@ -149,6 +152,7 @@ def cargo_build_script(
         data = data,
         compile_data = compile_data,
         rustc_env = rustc_env,
+        rustc_env_files = rustc_env_files,
         rustc_flags = rustc_flags,
         edition = edition,
         tags = binary_tags,

docs/cargo.md

@@ -66,7 +66,7 @@ A rule for generating variables for dependent `cargo_build_script`s without a bu
 <pre>
 cargo_build_script(<a href="#cargo_build_script-name">name</a>, <a href="#cargo_build_script-edition">edition</a>, <a href="#cargo_build_script-crate_name">crate_name</a>, <a href="#cargo_build_script-crate_root">crate_root</a>, <a href="#cargo_build_script-srcs">srcs</a>, <a href="#cargo_build_script-crate_features">crate_features</a>, <a href="#cargo_build_script-version">version</a>, <a href="#cargo_build_script-deps">deps</a>,
                    <a href="#cargo_build_script-link_deps">link_deps</a>, <a href="#cargo_build_script-proc_macro_deps">proc_macro_deps</a>, <a href="#cargo_build_script-build_script_env">build_script_env</a>, <a href="#cargo_build_script-data">data</a>, <a href="#cargo_build_script-compile_data">compile_data</a>, <a href="#cargo_build_script-tools">tools</a>, <a href="#cargo_build_script-links">links</a>,
-                   <a href="#cargo_build_script-rundir">rundir</a>, <a href="#cargo_build_script-rustc_env">rustc_env</a>, <a href="#cargo_build_script-rustc_flags">rustc_flags</a>, <a href="#cargo_build_script-visibility">visibility</a>, <a href="#cargo_build_script-tags">tags</a>, <a href="#cargo_build_script-aliases">aliases</a>, <a href="#cargo_build_script-kwargs">kwargs</a>)
+                   <a href="#cargo_build_script-rundir">rundir</a>, <a href="#cargo_build_script-rustc_env">rustc_env</a>, <a href="#cargo_build_script-rustc_env_files">rustc_env_files</a>, <a href="#cargo_build_script-rustc_flags">rustc_flags</a>, <a href="#cargo_build_script-visibility">visibility</a>, <a href="#cargo_build_script-tags">tags</a>, <a href="#cargo_build_script-aliases">aliases</a>, <a href="#cargo_build_script-kwargs">kwargs</a>)
 </pre>
 
 Compile and execute a rust build script to generate build attributes
@@ -149,6 +149,7 @@ The `hello_lib` target will be build with the flags and the environment variable
 | <a id="cargo_build_script-links"></a>links |  Name of the native library this crate links against.   |  `None` |
 | <a id="cargo_build_script-rundir"></a>rundir |  A directory to <code>cd</code> to before the cargo_build_script is run. This should be a path relative to the exec root.<br><br>The default behaviour (and the behaviour if rundir is set to the empty string) is to change to the relative path corresponding to the cargo manifest directory, which replicates the normal behaviour of cargo so it is easy to write compatible build scripts.<br><br>If set to <code>.</code>, the cargo build script will run in the exec root.   |  `None` |
 | <a id="cargo_build_script-rustc_env"></a>rustc_env |  Environment variables to set in rustc when compiling the build script.   |  `{}` |
+| <a id="cargo_build_script-rustc_env_files"></a>rustc_env_files |  Files containing additional environment variables to set for rustc when building the build script.   |  `[]` |
 | <a id="cargo_build_script-rustc_flags"></a>rustc_flags |  List of compiler flags passed to <code>rustc</code>.   |  `[]` |
 | <a id="cargo_build_script-visibility"></a>visibility |  Visibility to apply to the generated build script output.   |  `None` |
 | <a id="cargo_build_script-tags"></a>tags |  (list of str, optional): Tags to apply to the generated build script output.   |  `None` |

docs/flatten.md

@@ -1547,7 +1547,7 @@ A collection of files either found within the `rust-stdlib` artifact or generate
 <pre>
 cargo_build_script(<a href="#cargo_build_script-name">name</a>, <a href="#cargo_build_script-edition">edition</a>, <a href="#cargo_build_script-crate_name">crate_name</a>, <a href="#cargo_build_script-crate_root">crate_root</a>, <a href="#cargo_build_script-srcs">srcs</a>, <a href="#cargo_build_script-crate_features">crate_features</a>, <a href="#cargo_build_script-version">version</a>, <a href="#cargo_build_script-deps">deps</a>,
                    <a href="#cargo_build_script-link_deps">link_deps</a>, <a href="#cargo_build_script-proc_macro_deps">proc_macro_deps</a>, <a href="#cargo_build_script-build_script_env">build_script_env</a>, <a href="#cargo_build_script-data">data</a>, <a href="#cargo_build_script-compile_data">compile_data</a>, <a href="#cargo_build_script-tools">tools</a>, <a href="#cargo_build_script-links">links</a>,
-                   <a href="#cargo_build_script-rundir">rundir</a>, <a href="#cargo_build_script-rustc_env">rustc_env</a>, <a href="#cargo_build_script-rustc_flags">rustc_flags</a>, <a href="#cargo_build_script-visibility">visibility</a>, <a href="#cargo_build_script-tags">tags</a>, <a href="#cargo_build_script-aliases">aliases</a>, <a href="#cargo_build_script-kwargs">kwargs</a>)
+                   <a href="#cargo_build_script-rundir">rundir</a>, <a href="#cargo_build_script-rustc_env">rustc_env</a>, <a href="#cargo_build_script-rustc_env_files">rustc_env_files</a>, <a href="#cargo_build_script-rustc_flags">rustc_flags</a>, <a href="#cargo_build_script-visibility">visibility</a>, <a href="#cargo_build_script-tags">tags</a>, <a href="#cargo_build_script-aliases">aliases</a>, <a href="#cargo_build_script-kwargs">kwargs</a>)
 </pre>
 
 Compile and execute a rust build script to generate build attributes
@@ -1630,6 +1630,7 @@ The `hello_lib` target will be build with the flags and the environment variable
 | <a id="cargo_build_script-links"></a>links |  Name of the native library this crate links against.   |  `None` |
 | <a id="cargo_build_script-rundir"></a>rundir |  A directory to <code>cd</code> to before the cargo_build_script is run. This should be a path relative to the exec root.<br><br>The default behaviour (and the behaviour if rundir is set to the empty string) is to change to the relative path corresponding to the cargo manifest directory, which replicates the normal behaviour of cargo so it is easy to write compatible build scripts.<br><br>If set to <code>.</code>, the cargo build script will run in the exec root.   |  `None` |
 | <a id="cargo_build_script-rustc_env"></a>rustc_env |  Environment variables to set in rustc when compiling the build script.   |  `{}` |
+| <a id="cargo_build_script-rustc_env_files"></a>rustc_env_files |  Files containing additional environment variables to set for rustc when building the build script.   |  `[]` |
 | <a id="cargo_build_script-rustc_flags"></a>rustc_flags |  List of compiler flags passed to <code>rustc</code>.   |  `[]` |
 | <a id="cargo_build_script-visibility"></a>visibility |  Visibility to apply to the generated build script output.   |  `None` |
 | <a id="cargo_build_script-tags"></a>tags |  (list of str, optional): Tags to apply to the generated build script output.   |  `None` |

examples/hello_world/example_test.sh

@@ -0,0 +1,31 @@
+load("@bazel_skylib//rules:write_file.bzl", "write_file")
+load("//cargo:defs.bzl", "cargo_build_script")
+load("//rust:defs.bzl", "rust_library", "rust_test")
+
+write_file(
+    name = "generate_rustc_env_file",
+    out = "rustc_env_file",
+    content = [
+        "GREETING=Howdy",
+        "",
+    ],
+)
+
+cargo_build_script(
+    name = "cargo_build_script",
+    srcs = ["build.rs"],
+    edition = "2018",
+    rustc_env_files = [":generate_rustc_env_file"],
+)
+
+rust_library(
+    name = "test_lib",
+    srcs = ["test_lib.rs"],
+    edition = "2018",
+    deps = [":cargo_build_script"],
+)
+
+rust_test(
+    name = "consume_build_script",
+    crate = ":test_lib",
+)

test/cargo_build_script/rustc_env_files/BUILD.bazel

@@ -0,0 +1,3 @@
+fn main() {
+    println!("cargo:rustc-env=FROM_BUILD_SCRIPT={}", env!("GREETING"));
+}

test/cargo_build_script/rustc_env_files/build.rs

@@ -0,0 +1,4 @@
+#[test]
+fn check_env_set() {
+    assert_eq!("Howdy", env!("FROM_BUILD_SCRIPT"));
+}