Tweak build_crubit.py to add support for --install-to flag.

Bug: 1329611
Change-Id: I260c0279d93d7cc036183c821bb0936ee1160ada
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3967741
Reviewed-by: Collin Baker <collinbaker@google.com>
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1061723}
NOKEYCHECK=True
GitOrigin-RevId: 401dc9c3876d8c9633b3e7085adccc555ee9434a

Author: anforowicz

README.md

@@ -110,14 +110,13 @@ Just run `tools/rust/build_rust.py` or `tools/rust/build_crubit.py`.
 ### Deploying
 
 `build_rust.py` by default copies the newly build executables/binaries into
-`//third_party/rust-toolchain`.  Currently a manual step is needed to copy
-Crubit binaries (note that the `_impl` suffix has been dropped from the binary
-name during the copy - this is expected):
+`//third_party/rust-toolchain`.
 
-```sh
-cp \
-    third_party/crubit/bazel-bin/rs_bindings_from_cc/rs_bindings_from_cc_impl \
-    third_party/rust-toolchain/rs_bindings_from_cc
+`build_crubit.py` will copy files into the directory specified in the
+(optional) `--install-to` cmdline parameter - for example:
+
+```
+$ tools/rust/build_crubit.py --install-to=third_party/rust-toolchain/bin/
 ```
 
 ### Testing

build_crubit.py

@@ -17,6 +17,7 @@
 import os
 import pipes
 import shutil
+import stat
 import string
 import subprocess
 import sys
@@ -50,7 +51,7 @@ def RunCommand(command, env=None, cwd=None, fail_hard=True):
 
 def CheckoutCrubit(commit, dir):
     """Checkout the Crubit repo at a certain git commit in dir. Any local
-  modifications in dir will be lost."""
+    modifications in dir will be lost."""
 
     print('Checking out crubit repo %s into %s' % (commit, dir))
 
@@ -121,6 +122,22 @@ def BuildCrubit(gcc_toolchain_path):
     RunCommand(args + extra_args, env=env, cwd=CRUBIT_SRC_DIR)
 
 
+def InstallCrubit(install_dir):
+    assert os.path.isdir(install_dir)
+
+    print('Installing crubit binaries to %s' % install_dir)
+
+    BAZEL_BIN_DIR = os.path.join(CRUBIT_SRC_DIR, "bazel-bin")
+    SOURCE_PATH = os.path.join(BAZEL_BIN_DIR, "rs_bindings_from_cc",
+                               "rs_bindings_from_cc_impl")
+    TARGET_PATH = os.path.join(install_dir, "rs_bindings_from_cc")
+    shutil.copyfile(SOURCE_PATH, TARGET_PATH)
+
+    # Change from r-xr-xr-x to rwxrwxr-x, so that future copies will work fine.
+    os.chmod(TARGET_PATH,
+             stat.S_IRWXU | stat.S_IRWXG | stat.S_IROTH | stat.S_IXOTH)
+
+
 def CleanBazel():
     RunCommand([BAZEL_EXE, "clean", "--expunge"], cwd=CRUBIT_SRC_DIR)
 
@@ -129,13 +146,36 @@ def ShutdownBazel():
     RunCommand([BAZEL_EXE, "shutdown"], cwd=CRUBIT_SRC_DIR)
 
 
+def WritableDir(d):
+    """ Utility function to use as `argparse` `type` to verify that the argument
+    is a writeable dir (and resolve it as an absolute path).  """
+
+    try:
+        real_d = os.path.realpath(d)
+    except Exception as e:
+        raise ArgumentTypeError(f"realpath failed: {e}")
+    if not os.path.isdir(real_d):
+        raise ArgumentTypeError(f"Not a directory: {d}")
+    if not os.access(real_d, os.W_OK):
+        raise ArgumentTypeError(f"Cannot write to: {d}")
+    return real_d
+
+
 def main():
     parser = argparse.ArgumentParser(
         description='Build and package Crubit tools')
     parser.add_argument('-v',
                         '--verbose',
                         action='count',
                         help='run subcommands with verbosity')
+    parser.add_argument(
+        '--install-to',
+        type=WritableDir,
+        help='skip Crubit git checkout. Useful for trying local changes')
+    parser.add_argument(
+        '--skip-clean',
+        action='store_true',
+        help='skip cleanup. Useful for retrying/rebuilding local changes')
     parser.add_argument(
         '--skip-checkout',
         action='store_true',
@@ -151,8 +191,13 @@ def main():
         CheckoutCrubit(CRUBIT_REVISION, CRUBIT_SRC_DIR)
 
     try:
-        CleanBazel()
+        if not args.skip_clean:
+            CleanBazel()
+
         BuildCrubit(args.gcc_toolchain)
+
+        if args.install_to:
+            InstallCrubit(args.install_to)
     finally:
         ShutdownBazel()