Generate tsconfig once instead of on every webpack invocation

Avoids any potential race condition with parallel webpack invocations

script/generate-tsconfig.py

@@ -0,0 +1,43 @@
+import argparse
+import os
+import sys
+from lib.util import execute_stdout, scoped_cwd
+
+
+NPM = 'npm'
+if sys.platform in ['win32', 'cygwin']:
+    NPM += '.cmd'
+
+
+def main():
+    args = parse_args()
+    root_gen_dir = args.root_gen_dir[0]
+    generate_tsconfig(root_gen_dir)
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(description='Generate tsconfig')
+    parser.add_argument('--root_gen_dir', nargs=1)
+    args = parser.parse_args()
+    # validate args
+    if (args.root_gen_dir is None or
+            len(args.root_gen_dir) != 1 or
+            len(args.root_gen_dir[0]) == 0):
+        raise Exception("root_gen_dir argument was not specified correctly")
+    # args are valid
+    return args
+
+def generate_tsconfig(root_gen_dir, env=None):
+    if env is None:
+        env = os.environ.copy()
+
+    args = [NPM, 'run', 'web-ui-gen-tsconfig']
+
+    env["ROOT_GEN_DIR"] = root_gen_dir
+
+    dirname = os.path.abspath(os.path.join(__file__, '..', '..'))
+    with scoped_cwd(dirname):
+        execute_stdout(args, env)
+
+if __name__ == '__main__':
+    sys.exit(main())