Add support for passing a custom target specification. (#836)

* Add support for passing a custom target specification.

* Pass the target spec ias a dependency.

* Created a target_flag_value toolchain info field to avoid recalculating the value.

* Prevent passing both target_triple and target_json simultaneously.

* Streamline checks for None.

* Added unit tests for rust_toolchain rules.

* Rename test target spec to avoid collisions with the builtin.

* Regenerate documentation

* Rename the triple used in unit tests.

Co-authored-by: UebelAndre <github@uebelandre.com>
Co-authored-by: Marcel Hlopko <hlopko@google.com>

cargo/cargo_build_script.bzl

@@ -77,7 +77,7 @@ def _build_script_impl(ctx):
         # This isn't exactly right, but Bazel doesn't have exact views of "debug" and "release", so...
         "PROFILE": {"dbg": "debug", "fastbuild": "debug", "opt": "release"}.get(ctx.var["COMPILATION_MODE"], "unknown"),
         "RUSTC": toolchain.rustc.path,
-        "TARGET": toolchain.target_triple,
+        "TARGET": toolchain.target_flag_value,
         # OUT_DIR is set by the runner itself, rather than on the action.
     })
 
@@ -129,7 +129,7 @@ def _build_script_impl(ctx):
             script,
             ctx.executable._cargo_build_script_runner,
             toolchain.rustc,
-        ] + ctx.files.data,
+        ] + ctx.files.data + ([toolchain.target_json] if toolchain.target_json else []),
         transitive = toolchain_tools,
     )
 

docs/flatten.md

@@ -1085,7 +1085,8 @@ Run the test with `bazel build //hello_lib:hello_lib_test`.
 <pre>
 rust_toolchain(<a href="#rust_toolchain-name">name</a>, <a href="#rust_toolchain-allocator_library">allocator_library</a>, <a href="#rust_toolchain-binary_ext">binary_ext</a>, <a href="#rust_toolchain-cargo">cargo</a>, <a href="#rust_toolchain-clippy_driver">clippy_driver</a>, <a href="#rust_toolchain-debug_info">debug_info</a>,
                <a href="#rust_toolchain-default_edition">default_edition</a>, <a href="#rust_toolchain-dylib_ext">dylib_ext</a>, <a href="#rust_toolchain-exec_triple">exec_triple</a>, <a href="#rust_toolchain-opt_level">opt_level</a>, <a href="#rust_toolchain-os">os</a>, <a href="#rust_toolchain-rust_doc">rust_doc</a>, <a href="#rust_toolchain-rust_lib">rust_lib</a>, <a href="#rust_toolchain-rustc">rustc</a>,
-               <a href="#rust_toolchain-rustc_lib">rustc_lib</a>, <a href="#rust_toolchain-rustc_srcs">rustc_srcs</a>, <a href="#rust_toolchain-rustfmt">rustfmt</a>, <a href="#rust_toolchain-staticlib_ext">staticlib_ext</a>, <a href="#rust_toolchain-stdlib_linkflags">stdlib_linkflags</a>, <a href="#rust_toolchain-target_triple">target_triple</a>)
+               <a href="#rust_toolchain-rustc_lib">rustc_lib</a>, <a href="#rust_toolchain-rustc_srcs">rustc_srcs</a>, <a href="#rust_toolchain-rustfmt">rustfmt</a>, <a href="#rust_toolchain-staticlib_ext">staticlib_ext</a>, <a href="#rust_toolchain-stdlib_linkflags">stdlib_linkflags</a>, <a href="#rust_toolchain-target_json">target_json</a>,
+               <a href="#rust_toolchain-target_triple">target_triple</a>)
 </pre>
 
 Declares a Rust toolchain for use.
@@ -1153,6 +1154,7 @@ See @rules_rust//rust:repositories.bzl for examples of defining the @rust_cpuX r
 | <a id="rust_toolchain-rustfmt"></a>rustfmt |  The location of the <code>rustfmt</code> binary. Can be a direct source or a filegroup containing one item.   | <a href="https://bazel.build/docs/build-ref.html#labels">Label</a> | optional | None |
 | <a id="rust_toolchain-staticlib_ext"></a>staticlib_ext |  The extension for static libraries created from rustc.   | String | required |  |
 | <a id="rust_toolchain-stdlib_linkflags"></a>stdlib_linkflags |  Additional linker libs used when std lib is linked, see https://github.com/rust-lang/rust/blob/master/src/libstd/build.rs   | List of strings | required |  |
+| <a id="rust_toolchain-target_json"></a>target_json |  Override the target_triple with a custom target specification. For more details see: https://doc.rust-lang.org/rustc/targets/custom.html   | <a href="https://bazel.build/docs/build-ref.html#labels">Label</a> | optional | None |
 | <a id="rust_toolchain-target_triple"></a>target_triple |  The platform triple for the toolchains target environment. For more details see: https://docs.bazel.build/versions/master/skylark/rules.html#configurations   | String | optional | "" |
 
 

docs/rust_repositories.md

@@ -34,7 +34,8 @@ A dedicated filegroup-like rule for Rust stdlib artifacts.
 <pre>
 rust_toolchain(<a href="#rust_toolchain-name">name</a>, <a href="#rust_toolchain-allocator_library">allocator_library</a>, <a href="#rust_toolchain-binary_ext">binary_ext</a>, <a href="#rust_toolchain-cargo">cargo</a>, <a href="#rust_toolchain-clippy_driver">clippy_driver</a>, <a href="#rust_toolchain-debug_info">debug_info</a>,
                <a href="#rust_toolchain-default_edition">default_edition</a>, <a href="#rust_toolchain-dylib_ext">dylib_ext</a>, <a href="#rust_toolchain-exec_triple">exec_triple</a>, <a href="#rust_toolchain-opt_level">opt_level</a>, <a href="#rust_toolchain-os">os</a>, <a href="#rust_toolchain-rust_doc">rust_doc</a>, <a href="#rust_toolchain-rust_lib">rust_lib</a>, <a href="#rust_toolchain-rustc">rustc</a>,
-               <a href="#rust_toolchain-rustc_lib">rustc_lib</a>, <a href="#rust_toolchain-rustc_srcs">rustc_srcs</a>, <a href="#rust_toolchain-rustfmt">rustfmt</a>, <a href="#rust_toolchain-staticlib_ext">staticlib_ext</a>, <a href="#rust_toolchain-stdlib_linkflags">stdlib_linkflags</a>, <a href="#rust_toolchain-target_triple">target_triple</a>)
+               <a href="#rust_toolchain-rustc_lib">rustc_lib</a>, <a href="#rust_toolchain-rustc_srcs">rustc_srcs</a>, <a href="#rust_toolchain-rustfmt">rustfmt</a>, <a href="#rust_toolchain-staticlib_ext">staticlib_ext</a>, <a href="#rust_toolchain-stdlib_linkflags">stdlib_linkflags</a>, <a href="#rust_toolchain-target_json">target_json</a>,
+               <a href="#rust_toolchain-target_triple">target_triple</a>)
 </pre>
 
 Declares a Rust toolchain for use.
@@ -102,6 +103,7 @@ See @rules_rust//rust:repositories.bzl for examples of defining the @rust_cpuX r
 | <a id="rust_toolchain-rustfmt"></a>rustfmt |  The location of the <code>rustfmt</code> binary. Can be a direct source or a filegroup containing one item.   | <a href="https://bazel.build/docs/build-ref.html#labels">Label</a> | optional | None |
 | <a id="rust_toolchain-staticlib_ext"></a>staticlib_ext |  The extension for static libraries created from rustc.   | String | required |  |
 | <a id="rust_toolchain-stdlib_linkflags"></a>stdlib_linkflags |  Additional linker libs used when std lib is linked, see https://github.com/rust-lang/rust/blob/master/src/libstd/build.rs   | List of strings | required |  |
+| <a id="rust_toolchain-target_json"></a>target_json |  Override the target_triple with a custom target specification. For more details see: https://doc.rust-lang.org/rustc/targets/custom.html   | <a href="https://bazel.build/docs/build-ref.html#labels">Label</a> | optional | None |
 | <a id="rust_toolchain-target_triple"></a>target_triple |  The platform triple for the toolchains target environment. For more details see: https://docs.bazel.build/versions/master/skylark/rules.html#configurations   | String | optional | "" |
 
 

rust/private/rustc.bzl

@@ -287,6 +287,7 @@ def collect_inputs(
         [toolchain.rustc] +
         toolchain.crosstool_files +
         ([build_info.rustc_env, build_info.flags] if build_info else []) +
+        ([toolchain.target_json] if toolchain.target_json else []) +
         ([] if linker_script == None else [linker_script]),
         transitive = [
             toolchain.rustc_lib.files,
@@ -430,7 +431,7 @@ def construct_arguments(
 
     args.add("--emit=" + ",".join(emit_with_paths))
     args.add("--color=always")
-    args.add("--target=" + toolchain.target_triple)
+    args.add("--target=" + toolchain.target_flag_value)
     if hasattr(attr, "crate_features"):
         args.add_all(getattr(attr, "crate_features"), before_each = "--cfg", format_each = 'feature="%s"')
     if linker_script:

rust/toolchain.bzl

@@ -196,12 +196,17 @@ def _rust_toolchain_impl(ctx):
         if not k in ctx.attr.opt_level:
             fail("Compilation mode {} is not defined in opt_level but is defined debug_info".format(k))
 
+    if ctx.attr.target_triple and ctx.file.target_json:
+        fail("Do not specify both target_triple and target_json, either use a builtin triple or provide a custom specification file.")
+
     toolchain = platform_common.ToolchainInfo(
         rustc = ctx.file.rustc,
         rust_doc = ctx.file.rust_doc,
         rustfmt = ctx.file.rustfmt,
         cargo = ctx.file.cargo,
         clippy_driver = ctx.file.clippy_driver,
+        target_json = ctx.file.target_json,
+        target_flag_value = ctx.file.target_json.path if ctx.file.target_json else ctx.attr.target_triple,
         rustc_lib = ctx.attr.rustc_lib,
         rustc_srcs = ctx.attr.rustc_srcs,
         rust_lib = ctx.attr.rust_lib,
@@ -305,6 +310,11 @@ rust_toolchain = rule(
             ),
             mandatory = True,
         ),
+        "target_json": attr.label(
+            doc = ("Override the target_triple with a custom target specification. " +
+                   "For more details see: https://doc.rust-lang.org/rustc/targets/custom.html"),
+            allow_single_file = True,
+        ),
         "target_triple": attr.string(
             doc = (
                 "The platform triple for the toolchains target environment. " +

test/unit/toolchain/BUILD

@@ -0,0 +1,3 @@
+load(":toolchain_test.bzl", "toolchain_test_suite")
+
+toolchain_test_suite(name = "toolchain_test_suite")

test/unit/toolchain/toolchain-test-triple.json

@@ -0,0 +1,34 @@
+{
+  "arch": "x86_64",
+  "cpu": "x86-64",
+  "crt-static-respected": true,
+  "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128",
+  "dynamic-linking": true,
+  "env": "gnu",
+  "executables": true,
+  "has-elf-tls": true,
+  "has-rpath": true,
+  "llvm-target": "x86_64-unknown-linux-gnu",
+  "max-atomic-width": 64,
+  "os": "linux",
+  "position-independent-executables": true,
+  "pre-link-args": {
+    "gcc": [
+      "-m64"
+    ]
+  },
+  "relro-level": "full",
+  "stack-probes": {
+    "kind": "call"
+  },
+  "supported-sanitizers": [
+    "address",
+    "leak",
+    "memory",
+    "thread"
+  ],
+  "target-family": [
+    "unix"
+  ],
+  "target-pointer-width": "64"
+}

test/unit/toolchain/toolchain_test.bzl

@@ -0,0 +1,80 @@
+"""Unit tests for rust toolchains."""
+
+load("@bazel_skylib//lib:unittest.bzl", "analysistest", "asserts")
+load("//rust:toolchain.bzl", "rust_stdlib_filegroup", "rust_toolchain")
+
+def _toolchain_specifies_target_triple_test_impl(ctx):
+    env = analysistest.begin(ctx)
+    toolchain_info = analysistest.target_under_test(env)[platform_common.ToolchainInfo]
+
+    asserts.equals(env, None, toolchain_info.target_json)
+    asserts.equals(env, "toolchain-test-triple", toolchain_info.target_flag_value)
+    asserts.equals(env, "toolchain-test-triple", toolchain_info.target_triple)
+
+    return analysistest.end(env)
+
+def _toolchain_specifies_target_json_test_impl(ctx):
+    env = analysistest.begin(ctx)
+    toolchain_info = analysistest.target_under_test(env)[platform_common.ToolchainInfo]
+
+    asserts.equals(env, "toolchain-test-triple.json", toolchain_info.target_json.basename)
+    asserts.equals(env, "test/unit/toolchain/toolchain-test-triple.json", toolchain_info.target_flag_value)
+    asserts.equals(env, "", toolchain_info.target_triple)
+
+    return analysistest.end(env)
+
+toolchain_specifies_target_triple_test = analysistest.make(_toolchain_specifies_target_triple_test_impl)
+toolchain_specifies_target_json_test = analysistest.make(_toolchain_specifies_target_json_test_impl)
+
+def _toolchain_test():
+    rust_stdlib_filegroup(
+        name = "std_libs",
+        srcs = [],
+    )
+
+    native.filegroup(
+        name = "target_json",
+        srcs = ["toolchain-test-triple.json"],
+    )
+
+    rust_toolchain(
+        name = "rust_triple_toolchain",
+        binary_ext = "",
+        dylib_ext = ".so",
+        os = "linux",
+        rust_lib = ":std_libs",
+        staticlib_ext = ".a",
+        stdlib_linkflags = [],
+        target_triple = "toolchain-test-triple",
+    )
+
+    rust_toolchain(
+        name = "rust_json_toolchain",
+        binary_ext = "",
+        dylib_ext = ".so",
+        os = "linux",
+        rust_lib = ":std_libs",
+        staticlib_ext = ".a",
+        stdlib_linkflags = [],
+        target_json = ":target_json",
+    )
+
+    toolchain_specifies_target_triple_test(
+        name = "toolchain_specifies_target_triple_test",
+        target_under_test = ":rust_triple_toolchain",
+    )
+    toolchain_specifies_target_json_test(
+        name = "toolchain_specifies_target_json_test",
+        target_under_test = ":rust_json_toolchain",
+    )
+
+def toolchain_test_suite(name):
+    _toolchain_test()
+
+    native.test_suite(
+        name = name,
+        tests = [
+            ":toolchain_specifies_target_triple_test",
+            ":toolchain_specifies_target_json_test",
+        ],
+    )