gn build: Add gn.py wrapper script that adds --dotfile= and --root= parameters

Since people weren't enthused about moving the .gn file to the toplevel in
D56419, here's a script to make gn at least somewhat more pleasant to invoke
(useful for gn clean, gn args --list, gn desc, etc).

Differential Revision: https://reviews.llvm.org/D56565

llvm-svn: 351064

1 files changed, 38 insertions, 0 deletions

diff --git a/llvm/utils/gn/gn.py b/llvm/utils/gn/gn.py
new file mode 100644
index 00000000000..f80873b3be8
--- /dev/null
+++ b/llvm/utils/gn/gn.py
@@ -0,0 +1,38 @@
+#!/usr/bin/env python
+"""Calls `gn` with the right --dotfile= and --root= arguments for LLVM."""
+
+# GN normally expects a file called '.gn' at the root of the repository.
+# Since LLVM's GN build isn't supported, putting that file at the root
+# is deemed inappropriate, which requires passing --dotfile= and -root= to GN.
+# Since that gets old fast, this script automatically passes these arguments.
+
+import os
+import subprocess
+import sys
+
+
+THIS_DIR = os.path.dirname(__file__)
+ROOT_DIR = os.path.join(THIS_DIR, '..', '..', '..')
+
+
+def main():
+    # Find real gn executable. For now, just assume it's on PATH.
+    # FIXME: Probably need to append '.exe' on Windows.
+    gn = 'gn'
+
+    # Compute --dotfile= and --root= args to add.
+    extra_args = []
+    gn_main_arg = next((x for x in sys.argv[1:] if not x.startswith('-')), None)
+    if gn_main_arg != 'help':  # `gn help` gets confused by the switches.
+        cwd = os.getcwd()
+        dotfile = os.path.relpath(os.path.join(THIS_DIR, '.gn'), cwd)
+        root = os.path.relpath(ROOT_DIR, cwd)
+        extra_args = [ '--dotfile=' + dotfile, '--root=' + root ]
+
+    # Run GN command with --dotfile= and --root= added.
+    cmd = [gn] + extra_args + sys.argv[1:]
+    sys.exit(subprocess.call(cmd))
+
+
+if __name__ == '__main__':
+    main()