Build rust_test targets using a crate name different from the underlying lib (#2803)

This PR also makes `rust_test` put its compilation outputs in the same
directory as the `rust_library` rule (i.e. not in a `test-{hash}`
subdirectory anymore).

After this change both the `rust_library` and `rust_test` rules will put
all its compilation outputs in the same directory, but there won't be
any name collisions in non-sandboxed environments (see
#1427 for more context).

This is a partial rollback of
1018533
and
26344d4.

Author: felipeamp

docs/defs.md

@@ -567,9 +567,7 @@ rust_test(
 )
 ```
 
-Run the test with `bazel test //hello_lib:hello_lib_test`. The crate
-will be built using the same crate name as the underlying ":hello_lib"
-crate.
+Run the test with `bazel test //hello_lib:hello_lib_test`.
 
 ### Example: `test` directory
 

docs/flatten.md

@@ -1050,9 +1050,7 @@ rust_test(
 )
 ```
 
-Run the test with `bazel test //hello_lib:hello_lib_test`. The crate
-will be built using the same crate name as the underlying ":hello_lib"
-crate.
+Run the test with `bazel test //hello_lib:hello_lib_test`.
 
 ### Example: `test` directory
 

rust/private/rust.bzl

@@ -296,6 +296,7 @@ def _rust_test_impl(ctx):
 
     toolchain = find_toolchain(ctx)
 
+    crate_name = compute_crate_name(ctx.workspace_name, ctx.label, toolchain, ctx.attr.crate_name)
     crate_type = "bin"
     deps = transform_deps(ctx.attr.deps)
     proc_macro_deps = transform_deps(ctx.attr.proc_macro_deps + get_import_macro_deps(ctx))
@@ -309,13 +310,8 @@ def _rust_test_impl(ctx):
         # Target is building the crate in `test` config
         crate = ctx.attr.crate[rust_common.crate_info] if rust_common.crate_info in ctx.attr.crate else ctx.attr.crate[rust_common.test_crate_info].crate
 
-        output_hash = determine_output_hash(crate.root, ctx.label)
         output = ctx.actions.declare_file(
-            "test-%s/%s%s" % (
-                output_hash,
-                ctx.label.name,
-                toolchain.binary_ext,
-            ),
+            ctx.label.name + toolchain.binary_ext,
         )
 
         srcs, crate_root = transform_sources(ctx, ctx.files.srcs, getattr(ctx.file, "crate_root", None))
@@ -342,7 +338,7 @@ def _rust_test_impl(ctx):
 
         # Build the test binary using the dependency's srcs.
         crate_info_dict = dict(
-            name = crate.name,
+            name = crate_name,
             type = crate_type,
             root = crate.root,
             srcs = depset(srcs, transitive = [crate.srcs]),
@@ -368,13 +364,8 @@ def _rust_test_impl(ctx):
             crate_root = crate_root_src(ctx.attr.name, ctx.files.srcs, crate_root_type)
         srcs, crate_root = transform_sources(ctx, ctx.files.srcs, crate_root)
 
-        output_hash = determine_output_hash(crate_root, ctx.label)
         output = ctx.actions.declare_file(
-            "test-%s/%s%s" % (
-                output_hash,
-                ctx.label.name,
-                toolchain.binary_ext,
-            ),
+            ctx.label.name + toolchain.binary_ext,
         )
 
         data_paths = depset(direct = getattr(ctx.attr, "data", [])).to_list()
@@ -386,7 +377,7 @@ def _rust_test_impl(ctx):
 
         # Target is a standalone crate. Build the test binary as its own crate.
         crate_info_dict = dict(
-            name = compute_crate_name(ctx.workspace_name, ctx.label, toolchain, ctx.attr.crate_name),
+            name = crate_name,
             type = crate_type,
             root = crate_root,
             srcs = depset(srcs),
@@ -1342,9 +1333,7 @@ rust_test = rule(
         )
         ```
 
-        Run the test with `bazel test //hello_lib:hello_lib_test`. The crate
-        will be built using the same crate name as the underlying ":hello_lib"
-        crate.
+        Run the test with `bazel test //hello_lib:hello_lib_test`.
 
         ### Example: `test` directory
 

test/rust/src/lib.rs

@@ -12,5 +12,4 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#![crate_name = "hello_lib"]
 pub mod greeter;

test/unit/linkstamps/linkstamps_test.bzl

@@ -2,7 +2,7 @@
 
 load("@bazel_skylib//lib:unittest.bzl", "analysistest", "asserts")
 load("@rules_cc//cc:defs.bzl", "cc_library")
-load("//rust:defs.bzl", "rust_binary", "rust_common", "rust_library", "rust_test")
+load("//rust:defs.bzl", "rust_binary", "rust_library", "rust_test")
 load("//test/unit:common.bzl", "assert_action_mnemonic")
 
 def _is_running_on_linux(ctx):
@@ -20,13 +20,9 @@ def _supports_linkstamps_test(ctx):
     linkstamp_out = linkstamp_action.outputs.to_list()[0]
     asserts.equals(env, linkstamp_out.basename, "linkstamp.o")
     tut_out = tut.files.to_list()[0]
-    is_test = tut[rust_common.crate_info].is_test
     workspace_prefix = "" if ctx.workspace_name == "rules_rust" else "/external/rules_rust"
 
-    # Rust compilation outputs coming from a test are put in test-{hash} directory
-    # which we need to remove in order to obtain the linkstamp file path.
-    dirname = "/".join(tut_out.dirname.split("/")[:-1]) if is_test else tut_out.dirname
-    expected_linkstamp_path = dirname + "/_objs/" + tut_out.basename + workspace_prefix + "/test/unit/linkstamps/linkstamp.o"
+    expected_linkstamp_path = tut_out.dirname + "/_objs/" + tut_out.basename + workspace_prefix + "/test/unit/linkstamps/linkstamp.o"
     asserts.equals(
         env,
         linkstamp_out.path,