[clang-tidy] Handle missing yaml module in run-clang-tidy.py

The Yaml module is missing on some systems and on many of clang buildbots. 
But the test for run-clang-tidy.py doesn't fail due to 'NOT' statement masking a python runtime error.

This patch conditionally imports and enables the yaml module only if it's present in the system. 
If not, then '-export-fixes' is disabled.

Differential Revision: https://reviews.llvm.org/D59734

llvm-svn: 357114

clang-tools-extra/clang-tidy/tool/clang-tidy-diff.py

@@ -36,11 +36,10 @@
 import threading
 import traceback
 
-yaml_imported = True
 try:
   import yaml
 except ImportError:
-  yaml_imported = False
+  yaml = None
 
 is_py2 = sys.version[0] == '2'
 
@@ -144,7 +143,7 @@ def main():
                       default='')
   parser.add_argument('-path', dest='build_path',
                       help='Path used to read a compile command database.')
-  if yaml_imported:
+  if yaml:
     parser.add_argument('-export-fixes', metavar='FILE', dest='export_fixes',
                         help='Create a yaml file to store suggested fixes in, '
                         'which can be applied with clang-apply-replacements.')
@@ -204,7 +203,7 @@ def main():
   max_task_count = min(len(lines_by_file), max_task_count)
 
   tmpdir = None
-  if yaml_imported and args.export_fixes:
+  if yaml and args.export_fixes:
     tmpdir = tempfile.mkdtemp()
 
   # Tasks for clang-tidy.
@@ -238,7 +237,7 @@ def main():
     # Run clang-tidy on files containing changes.
     command = [args.clang_tidy_binary]
     command.append('-line-filter=' + line_filter_json)
-    if yaml_imported and args.export_fixes:
+    if yaml and args.export_fixes:
       # Get a temporary file. We immediately close the handle so clang-tidy can
       # overwrite it.
       (handle, tmp_name) = tempfile.mkstemp(suffix='.yaml', dir=tmpdir)
@@ -253,7 +252,7 @@ def main():
   # Wait for all threads to be done.
   task_queue.join()
 
-  if yaml_imported and args.export_fixes:
+  if yaml and args.export_fixes:
     print('Writing fixes to ' + args.export_fixes + ' ...')
     try:
       merge_replacement_files(tmpdir, args.export_fixes)

clang-tools-extra/clang-tidy/tool/run-clang-tidy.py

@@ -47,7 +47,11 @@
 import tempfile
 import threading
 import traceback
-import yaml
+
+try:
+  import yaml
+except ImportError:
+  yaml = None
 
 is_py2 = sys.version[0] == '2'
 
@@ -199,9 +203,10 @@ def main():
                       'headers to output diagnostics from. Diagnostics from '
                       'the main file of each translation unit are always '
                       'displayed.')
-  parser.add_argument('-export-fixes', metavar='filename', dest='export_fixes',
-                      help='Create a yaml file to store suggested fixes in, '
-                      'which can be applied with clang-apply-replacements.')
+  if yaml:
+    parser.add_argument('-export-fixes', metavar='filename', dest='export_fixes',
+                        help='Create a yaml file to store suggested fixes in, '
+                        'which can be applied with clang-apply-replacements.')
   parser.add_argument('-j', type=int, default=0,
                       help='number of tidy instances to be run in parallel.')
   parser.add_argument('files', nargs='*', default=['.*'],
@@ -254,7 +259,7 @@ def main():
     max_task = multiprocessing.cpu_count()
 
   tmpdir = None
-  if args.fix or args.export_fixes:
+  if args.fix or (yaml and args.export_fixes):
     check_clang_apply_replacements_binary(args)
     tmpdir = tempfile.mkdtemp()
 
@@ -292,7 +297,7 @@ def main():
       shutil.rmtree(tmpdir)
     os.kill(0, 9)
 
-  if args.export_fixes:
+  if yaml and args.export_fixes:
     print('Writing fixes to ' + args.export_fixes + ' ...')
     try:
       merge_replacement_files(tmpdir, args.export_fixes)

clang-tools-extra/test/clang-tidy/run-clang-tidy.cpp

@@ -1,3 +1,4 @@
+// RUN: %run_clang_tidy --help
 // RUN: rm -rf %t
 // RUN: mkdir %t
 // RUN: echo "[{\"directory\":\".\",\"command\":\"clang++ -c %/t/test.cpp\",\"file\":\"%/t/test.cpp\"}]" | sed -e 's/\\/\\\\/g' > %t/compile_commands.json