Include compile_data targets in rustc_env location expansion for rust_test (#4000)

## Summary

Include `compile_data` targets in `rustc_env` location expansion for
`rust_test`.

## Problem

In `rust_test`, `$(location)` and `$(rootpath)` expansions in
`rustc_env` only search `data` targets. When a `compile_data` target is
referenced in `rustc_env` — for example to pass the path of a generated
file via `env!()` and `include_str!()` — the expansion fails because
`compile_data` targets are not in the search set.

This affects both `rust_test` code paths: the crate-wrapping path
(testing an existing `rust_library`) and the standalone path (test with
its own sources).

## Fix

Add `compile_data` targets to the `data_paths` depset passed to
`expand_dict_value_locations` in both `rust_test` code paths.

---

> **Note:** This PR was largely AI-generated using Claude Code, with
human review and guidance throughout.

---------

Co-authored-by: Tamas Vajk <tamas.vajk@databricks.com>

Author: tamasvajk

rust/private/rust.bzl

@@ -404,7 +404,7 @@ def _rust_test_impl(ctx):
             rustc_env.update(expand_dict_value_locations(
                 ctx,
                 ctx.attr.rustc_env,
-                deduplicate(getattr(ctx.attr, "data", [])),
+                deduplicate(getattr(ctx.attr, "data", []) + compile_data_targets.to_list()),
                 {},
             ))
         aliases = dict(crate.aliases)
@@ -461,7 +461,7 @@ def _rust_test_impl(ctx):
             rustc_env = expand_dict_value_locations(
                 ctx,
                 ctx.attr.rustc_env,
-                deduplicate(getattr(ctx.attr, "data", [])),
+                deduplicate(getattr(ctx.attr, "data", []) + getattr(ctx.attr, "compile_data", [])),
                 {},
             )
         else:

test/unit/compile_data_env/BUILD.bazel

@@ -0,0 +1,4 @@
+load(":compile_data_env_test.bzl", "compile_data_env_test_suite")
+
+############################ UNIT TESTS #############################
+compile_data_env_test_suite(name = "compile_data_env_test_suite")

test/unit/compile_data_env/compile_data_env_test.bzl

@@ -0,0 +1,111 @@
+"""Test that $(location) in rustc_env expands compile_data targets in rust_test."""
+
+load("@bazel_skylib//lib:unittest.bzl", "analysistest")
+load("@bazel_skylib//rules:write_file.bzl", "write_file")
+load("//rust:defs.bzl", "rust_library", "rust_test")
+load("//test/unit:common.bzl", "assert_env_value")
+
+def _find_action(tut, mnemonic):
+    for action in tut.actions:
+        if action.mnemonic == mnemonic:
+            return action
+    return None
+
+# ---------------------------------------------------------------------------
+# Test: standalone rust_test with generated compile_data in rustc_env
+# ---------------------------------------------------------------------------
+
+def _standalone_test_impl(ctx):
+    env = analysistest.begin(ctx)
+    tut = analysistest.target_under_test(env)
+    action = _find_action(tut, "Rustc")
+    if not action:
+        fail("No Rustc action found")
+    expected = "${pwd}/" + ctx.bin_dir.path + "/test/unit/compile_data_env/generated.txt"
+    assert_env_value(env, action, "GENERATED_PATH", expected)
+    return analysistest.end(env)
+
+standalone_compile_data_env_test = analysistest.make(_standalone_test_impl)
+
+# ---------------------------------------------------------------------------
+# Test: rust_test wrapping a crate with source compile_data in rustc_env
+# ---------------------------------------------------------------------------
+
+def _crate_wrap_test_impl(ctx):
+    env = analysistest.begin(ctx)
+    tut = analysistest.target_under_test(env)
+    action = _find_action(tut, "Rustc")
+    if not action:
+        fail("No Rustc action found")
+    assert_env_value(env, action, "DATA_PATH", "test/unit/compile_data_env/data.txt")
+    return analysistest.end(env)
+
+crate_wrap_compile_data_env_test = analysistest.make(_crate_wrap_test_impl)
+
+# ---------------------------------------------------------------------------
+# Subjects and test suite
+# ---------------------------------------------------------------------------
+
+def _test_subjects():
+    write_file(
+        name = "gen_file",
+        out = "generated.txt",
+        content = ["hello"],
+        newline = "unix",
+    )
+
+    # Standalone test: compile_data with a generated file
+    rust_test(
+        name = "standalone_test",
+        srcs = ["test.rs"],
+        compile_data = [":gen_file"],
+        edition = "2021",
+        rustc_env = {
+            "GENERATED_PATH": "$(execpath :gen_file)",
+        },
+    )
+
+    # Crate-wrap test: compile_data with a source file (not generated,
+    # to avoid triggering transform_sources which has a separate bug
+    # with crate= + generated compile_data)
+    rust_library(
+        name = "mylib",
+        srcs = ["lib.rs"],
+        edition = "2021",
+    )
+
+    rust_test(
+        name = "crate_wrap_test",
+        crate = ":mylib",
+        compile_data = ["data.txt"],
+        edition = "2021",
+        rustc_env = {
+            "DATA_PATH": "$(rootpath data.txt)",
+        },
+    )
+
+def compile_data_env_test_suite(name):
+    """Entry-point macro called from the BUILD file.
+
+    Args:
+        name: Name of the macro.
+    """
+    _test_subjects()
+
+    standalone_compile_data_env_test(
+        name = "standalone_compile_data_env_test",
+        target_under_test = ":standalone_test",
+    )
+
+    crate_wrap_compile_data_env_test(
+        name = "crate_wrap_compile_data_env_test",
+        target_under_test = ":crate_wrap_test",
+    )
+
+    native.test_suite(
+        name = name,
+        tests = [
+            ":standalone_compile_data_env_test",
+            ":crate_wrap_compile_data_env_test",
+        ],
+    )

test/unit/compile_data_env/data.txt

@@ -0,0 +1 @@
+hello

test/unit/compile_data_env/lib.rs

@@ -0,0 +1 @@
+pub fn lib() {}

test/unit/compile_data_env/test.rs

@@ -0,0 +1,2 @@
+#[test]
+fn test() {}