Add rust_test to gn build, with working example.

.travis.yml

@@ -42,9 +42,10 @@ install:
  - gn args $BUILD_PATH --list
  - ccache -s
  # Travis hangs without -j2 argument to ninja.
- - ninja -j2 -C $BUILD_PATH mock_runtime_test deno_cc deno
+ - ninja -j2 -C $BUILD_PATH mock_runtime_test handlers_test deno_cc deno
 script:
  - $BUILD_PATH/mock_runtime_test
+ - $BUILD_PATH/handlers_test
  - $BUILD_PATH/deno_cc foo bar
  - $BUILD_PATH/deno meow
  - ./tools/lint.sh

BUILD.gn

@@ -34,6 +34,11 @@ rust_component("handlers") {
   extern = [ ":libc" ]
 }
 
+rust_test("handlers_test") {
+  source_root = "src/handlers.rs"
+  extern = [ ":libc" ]
+}
+
 executable("deno_cc") {
   sources = [
     "src/main.cc",

build_extra/rust/rust.gni

@@ -10,7 +10,11 @@ template("run_rustc") {
                              "source_root",
                              "deps",
                              "extern",
+                             "is_test",
                            ])
+    if (defined(invoker.testonly)) {
+      testonly = invoker.testonly
+    }
     if (defined(invoker.crate_name)) {
       crate_name = invoker.crate_name
     } else {
@@ -21,7 +25,6 @@ template("run_rustc") {
       source_root,
     ]
     outputs = []
-    depfile = "$target_out_dir/$target_name.d"
     script = "//third_party/v8/tools/run.py"
 
     args = [
@@ -29,10 +32,24 @@ template("run_rustc") {
       rebase_path(source_root, root_build_dir),
       "--crate-name=$crate_name",
       "--crate-type=$crate_type",
-      "--emit=dep-info=" + rebase_path(depfile, root_build_dir),
     ]
 
-    # We only use staticlib for the special "empty" lib.
+    if (defined(is_test) && is_test) {
+      # Test outputs are executables which should be in root_out_dir.
+      output = "$root_out_dir/$crate_name"
+      args += [
+        "--test",
+        "-o",
+        rebase_path(output, root_build_dir),
+      ]
+      outputs += [ output ]
+    } else {
+      # Non-test targets are handled differently.
+
+      # For unknown reasons emitting a depfile on tests doesn't work.
+      depfile = "$target_out_dir/$target_name.d"
+      args += [ "--emit=dep-info=" + rebase_path(depfile, root_build_dir) ]
+
       if (crate_type == "staticlib") {
         staticlib = "$target_out_dir/$crate_name.a"
         outputs += [ staticlib ]
@@ -50,6 +67,7 @@ template("run_rustc") {
         outputs += [ rlib ]
         args += [ "--emit=link=" + rebase_path(rlib, root_build_dir) ]
       }
+    }
 
     if (is_debug) {
       args += [ "-g" ]
@@ -99,6 +117,7 @@ template("rust_component") {
                              "extern",
                              "cfg",
                              "source_root",
+                             "testonly",
                            ])
     if (!defined(invoker.crate_type)) {
       crate_type = "rlib"
@@ -113,6 +132,7 @@ template("rust_component") {
                            [
                              "libs",
                              "deps",
+                             "testonly",
                            ])
     if (!defined(deps)) {
       deps = []
@@ -151,3 +171,18 @@ template("rust_executable") {
     }
   }
 }
+
+template("rust_test") {
+  run_rustc(target_name) {
+    crate_name = target_name
+    crate_type = "bin"
+    testonly = true
+    is_test = true
+    forward_variables_from(invoker,
+                           [
+                             "extern",
+                             "cfg",
+                             "source_root",
+                           ])
+  }
+}

src/handlers.rs

@@ -10,6 +10,11 @@ fn string_from_ptr(ptr: *const c_char) -> String {
     String::from(cstr.to_str().unwrap())
 }
 
+#[test]
+fn test_example() {
+    assert_eq!(2 + 2, 4);
+}
+
 #[no_mangle]
 pub extern "C" fn handle_code_fetch(
     module_specifier: *const c_char,