Add tools attr with exec transition for cargo_build_script (#885)

If tools are passed in `data`, they must be built in the `exec` configuration in order to run on the host machine when the target != host.

I _think_ this should be a fairly safe change, unless someone is doing something with the tools passed to the build script that would require them to run on the target configuration, but short of copying these tools into the out_dir I don't know what that would be. And -- that would be better handled by depending directly on these tools in the data attr of the library or binary anyway.

Author: djmarcin

cargo/cargo_build_script.bzl

@@ -120,15 +120,16 @@ def _build_script_impl(ctx):
         ctx,
         ctx.attr.build_script_env,
         getattr(ctx.attr, "data", []) +
-        getattr(ctx.attr, "compile_data", []),
+        getattr(ctx.attr, "compile_data", []) +
+        getattr(ctx.attr, "tools", []),
     ))
 
     tools = depset(
         direct = [
             script,
             ctx.executable._cargo_build_script_runner,
             toolchain.rustc,
-        ] + ctx.files.data + ([toolchain.target_json] if toolchain.target_json else []),
+        ] + ctx.files.data + ctx.files.tools + ([toolchain.target_json] if toolchain.target_json else []),
         transitive = toolchain_tools,
     )
 
@@ -195,7 +196,7 @@ _build_script_run = rule(
             doc = "The list of rust features that the build script should consider activated.",
         ),
         "data": attr.label_list(
-            doc = "Data or tools required by the build script.",
+            doc = "Data required by the build script.",
             allow_files = True,
         ),
         "deps": attr.label_list(
@@ -214,6 +215,11 @@ _build_script_run = rule(
             mandatory = True,
             cfg = "exec",
         ),
+        "tools": attr.label_list(
+            doc = "Tools required by the build script.",
+            allow_files = True,
+            cfg = "exec",
+        ),
         "version": attr.string(
             doc = "The semantic version (semver) of the crate",
         ),
@@ -242,6 +248,7 @@ def cargo_build_script(
         deps = [],
         build_script_env = {},
         data = [],
+        tools = [],
         links = None,
         rustc_env = {},
         visibility = None,
@@ -311,7 +318,8 @@ def cargo_build_script(
         version (str, optional): The semantic version (semver) of the crate.
         deps (list, optional): The dependencies of the crate.
         build_script_env (dict, optional): Environment variables for build scripts.
-        data (list, optional): Files or tools needed by the build script.
+        data (list, optional): Files needed by the build script.
+        tools (list, optional): Tools (executables) needed by the build script.
         links (str, optional): Name of the native library this crate links against.
         rustc_env (dict, optional): Environment variables to set in rustc when compiling the build script.
         visibility (list of label, optional): Visibility to apply to the generated build script output.
@@ -346,6 +354,7 @@ def cargo_build_script(
         links = links,
         deps = deps,
         data = data,
+        tools = tools,
         visibility = visibility,
         tags = tags,
     )

docs/cargo.md

@@ -37,8 +37,8 @@ A rule for bootstrapping a Rust binary using [Cargo](https://doc.rust-lang.org/c
 ## cargo_build_script
 
 <pre>
-cargo_build_script(<a href="#cargo_build_script-name">name</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-build_script_env">build_script_env</a>, <a href="#cargo_build_script-data">data</a>, <a href="#cargo_build_script-links">links</a>, <a href="#cargo_build_script-rustc_env">rustc_env</a>,
-                   <a href="#cargo_build_script-visibility">visibility</a>, <a href="#cargo_build_script-tags">tags</a>, <a href="#cargo_build_script-kwargs">kwargs</a>)
+cargo_build_script(<a href="#cargo_build_script-name">name</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-build_script_env">build_script_env</a>, <a href="#cargo_build_script-data">data</a>, <a href="#cargo_build_script-tools">tools</a>, <a href="#cargo_build_script-links">links</a>,
+                   <a href="#cargo_build_script-rustc_env">rustc_env</a>, <a href="#cargo_build_script-visibility">visibility</a>, <a href="#cargo_build_script-tags">tags</a>, <a href="#cargo_build_script-kwargs">kwargs</a>)
 </pre>
 
 Compile and execute a rust build script to generate build attributes
@@ -109,7 +109,8 @@ The `hello_lib` target will be build with the flags and the environment variable
 | <a id="cargo_build_script-version"></a>version |  The semantic version (semver) of the crate.   |  <code>None</code> |
 | <a id="cargo_build_script-deps"></a>deps |  The dependencies of the crate.   |  <code>[]</code> |
 | <a id="cargo_build_script-build_script_env"></a>build_script_env |  Environment variables for build scripts.   |  <code>{}</code> |
-| <a id="cargo_build_script-data"></a>data |  Files or tools needed by the build script.   |  <code>[]</code> |
+| <a id="cargo_build_script-data"></a>data |  Files needed by the build script.   |  <code>[]</code> |
+| <a id="cargo_build_script-tools"></a>tools |  Tools (executables) needed by the build script.   |  <code>[]</code> |
 | <a id="cargo_build_script-links"></a>links |  Name of the native library this crate links against.   |  <code>None</code> |
 | <a id="cargo_build_script-rustc_env"></a>rustc_env |  Environment variables to set in rustc when compiling the build script.   |  <code>{}</code> |
 | <a id="cargo_build_script-visibility"></a>visibility |  Visibility to apply to the generated build script output.   |  <code>None</code> |

docs/flatten.md

@@ -1396,8 +1396,8 @@ A test rule for performing `rustfmt --check` on a set of targets
 ## cargo_build_script
 
 <pre>
-cargo_build_script(<a href="#cargo_build_script-name">name</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-build_script_env">build_script_env</a>, <a href="#cargo_build_script-data">data</a>, <a href="#cargo_build_script-links">links</a>, <a href="#cargo_build_script-rustc_env">rustc_env</a>,
-                   <a href="#cargo_build_script-visibility">visibility</a>, <a href="#cargo_build_script-tags">tags</a>, <a href="#cargo_build_script-kwargs">kwargs</a>)
+cargo_build_script(<a href="#cargo_build_script-name">name</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-build_script_env">build_script_env</a>, <a href="#cargo_build_script-data">data</a>, <a href="#cargo_build_script-tools">tools</a>, <a href="#cargo_build_script-links">links</a>,
+                   <a href="#cargo_build_script-rustc_env">rustc_env</a>, <a href="#cargo_build_script-visibility">visibility</a>, <a href="#cargo_build_script-tags">tags</a>, <a href="#cargo_build_script-kwargs">kwargs</a>)
 </pre>
 
 Compile and execute a rust build script to generate build attributes
@@ -1468,7 +1468,8 @@ The `hello_lib` target will be build with the flags and the environment variable
 | <a id="cargo_build_script-version"></a>version |  The semantic version (semver) of the crate.   |  <code>None</code> |
 | <a id="cargo_build_script-deps"></a>deps |  The dependencies of the crate.   |  <code>[]</code> |
 | <a id="cargo_build_script-build_script_env"></a>build_script_env |  Environment variables for build scripts.   |  <code>{}</code> |
-| <a id="cargo_build_script-data"></a>data |  Files or tools needed by the build script.   |  <code>[]</code> |
+| <a id="cargo_build_script-data"></a>data |  Files needed by the build script.   |  <code>[]</code> |
+| <a id="cargo_build_script-tools"></a>tools |  Tools (executables) needed by the build script.   |  <code>[]</code> |
 | <a id="cargo_build_script-links"></a>links |  Name of the native library this crate links against.   |  <code>None</code> |
 | <a id="cargo_build_script-rustc_env"></a>rustc_env |  Environment variables to set in rustc when compiling the build script.   |  <code>{}</code> |
 | <a id="cargo_build_script-visibility"></a>visibility |  Visibility to apply to the generated build script output.   |  <code>None</code> |

test/cargo_build_script/BUILD.bazel

@@ -0,0 +1,25 @@
+"""Tests for the cargo_build_script rule"""
+
+load("//cargo:cargo_build_script.bzl", "cargo_build_script")
+load("//rust:rust.bzl", "rust_test")
+
+# Test that tools are built in the exec configuration.
+cargo_build_script(
+    name = "tools_exec_build_rs",
+    srcs = ["build.rs"],
+    build_script_env = {"TOOL": "$(execpath :tool)"},
+    tools = [":tool"],
+)
+
+genrule(
+    name = "tool",
+    srcs = [],
+    outs = ["tool-file"],
+    cmd = "touch $@",
+)
+
+rust_test(
+    name = "tools_exec",
+    srcs = ["tools_exec.rs"],
+    deps = [":tools_exec_build_rs"],
+)

test/cargo_build_script/build.rs

@@ -0,0 +1,7 @@
+fn main() {
+    // Pass the TOOL_PATH along to the rust_test so we can assert on it.
+    println!(
+        "cargo:rustc-env=TOOL_PATH={}",
+        std::env::var("TOOL").unwrap()
+    );
+}

test/cargo_build_script/tools_exec.rs

@@ -0,0 +1,9 @@
+#[test]
+pub fn test_tool_exec() {
+    let tool_path = env!("TOOL_PATH");
+    assert!(
+        tool_path.contains("-exec-"),
+        "tool_path did not contain '-exec-': {}",
+        tool_path
+    );
+}