Simplify node_launcher and fix signal propogation.

internal/node/node_launcher.sh

@@ -130,38 +130,35 @@ for ARG in "${ALL_ARGS[@]}"; do
   esac
 done
 
-# Note: Bash does not forward termination signals to any child process when
-# running in docker so need to manually trap and forward the signals
-_term() {
-  kill -TERM "$child" 2>/dev/null
-}
-
-_int() {
-  kill -INT "$child" 2>/dev/null
-}
+# The EXPECTED_EXIT_CODE lets us write bazel tests which assert that
+# a binary fails to run. Otherwise any failure would make such a test
+# fail before we could assert that we expected that failure.
+readonly EXPECTED_EXIT_CODE="TEMPLATED_expected_exit_code"
+if [ "${EXPECTED_EXIT_CODE}" -eq "0" ]; then
+  # Replace the current process (bash) with a node process.
+  # This means that stdin, stdout, signals, etc will be transparently
+  # handled by the node process.
+  # If we had merely forked a child process here, we'd be responsible
+  # for forwarding those OS interactions.
+  exec "${node}" "${NODE_OPTIONS[@]}" "${script}" "${ARGS[@]}"
+  # exec terminates execution of this shell script, nothing later will run.
+fi
 
 set +e
 "${node}" "${NODE_OPTIONS[@]}" "${script}" "${ARGS[@]}" <&0 &
-child=$!
-trap _term SIGTERM
-trap _int SIGINT
-wait "$child"
 RESULT="$?"
 set -e
 
-readonly EXPECTED_EXIT_CODE="TEMPLATED_expected_exit_code"
-if [ "${EXPECTED_EXIT_CODE}" -ne "0" ]; then
-  if (( ${RESULT} != ${EXPECTED_EXIT_CODE} )); then
-    echo "Expected exit code to be ${EXPECTED_EXIT_CODE}, but got ${RESULT}" >&2
-    if [ "${RESULT}" -eq "0" ]; then
-      # This exit code is handled specially by Bazel:
-      # https://github.com/bazelbuild/bazel/blob/486206012a664ecb20bdb196a681efc9a9825049/src/main/java/com/google/devtools/build/lib/util/ExitCode.java#L44
-      readonly BAZEL_EXIT_TESTS_FAILED = 3;
-      exit ${BAZEL_EXIT_TESTS_FAILED}
-    fi
-  else
-    exit 0
+if (( ${RESULT} != ${EXPECTED_EXIT_CODE} )); then
+  echo "Expected exit code to be ${EXPECTED_EXIT_CODE}, but got ${RESULT}" >&2
+  if [ "${RESULT}" -eq "0" ]; then
+    # This exit code is handled specially by Bazel:
+    # https://github.com/bazelbuild/bazel/blob/486206012a664ecb20bdb196a681efc9a9825049/src/main/java/com/google/devtools/build/lib/util/ExitCode.java#L44
+    readonly BAZEL_EXIT_TESTS_FAILED = 3;
+    exit ${BAZEL_EXIT_TESTS_FAILED}
   fi
+else
+  exit 0
 fi
 
-exit ${RESULT}
+exit ${RESULT}

internal/node/node_repositories.bzl

@@ -227,29 +227,17 @@ def _prepare_node(repository_ctx):
 
     # The entry points for node for osx/linux and windows
     if not is_windows:
-        # Sets process.env['PATH'] for node, npm & yarn and runs user script
-        # This extra step is needed as process.env['PATH'] needs to be set
-        # in some cases on osx/linux and in other cases PATH set in
-        # bin/node is sufficient. The first argument is the PATH to prepend.
-        repository_ctx.file("bin/node.js", content = """//Generated by node_repositories.bzl
-const {spawn} = require('child_process');
-process.env['PATH'] = `${process.argv[2]}:${process.env['PATH']}`;
-const proc = spawn(process.argv0, process.argv.slice(3), {stdio: [process.stdin, process.stdout, process.stderr]});
-proc.on('close', (code) => { process.exit(code); });
-""")
-
-        # Sets PATH and runs bin/node.js passing all arguments
+        # Sets PATH and runs the application
         repository_ctx.file("bin/node", content = """#!/usr/bin/env bash
 # Generated by node_repositories.bzl
 # Immediately exit if any command fails.
 set -e
 {get_script_dir}
 export PATH="$SCRIPT_DIR":$PATH
-"$SCRIPT_DIR/{node}" "$SCRIPT_DIR/{script}" "$SCRIPT_DIR" "$@"
+exec "$SCRIPT_DIR/{node}" $@"
 """.format(
             get_script_dir = GET_SCRIPT_DIR,
             node = node_exec_relative,
-            script = "node.js",
         ))
     else:
         # Sets PATH for node, npm & yarn and run user script