gn build: Make sync script group output by revision

[thakis]

defaultdict

[pcc]

LGTM

llvm/utils/gn/build/sync_source_lists_from_cmake.py

 #!/usr/bin/env python
 
 """Helps to keep BUILD.gn files in sync with the corresponding CMakeLists.txt.
 
 For each BUILD.gn file in the tree, checks if the list of cpp files in
 it is identical to the list of cpp files in the corresponding CMakeLists.txt
 file, and prints the difference if not.
 
 Also checks that each CMakeLists.txt file below unittests/ folders that define
 binaries have corresponding BUILD.gn files.
 """
 
 from __future__ import print_function
 
+from collections import defaultdict
 import os
 import re
 import subprocess
 import sys
 
 
 def sync_source_lists():
     # Use shell=True on Windows in case git is a bat file.
     gn_files = subprocess.check_output(['git', 'ls-files', '*BUILD.gn'],
                                        shell=os.name == 'nt').splitlines()
 
     # Matches e.g. |   "foo.cpp",|, captures |foo| in group 1.
     gn_cpp_re = re.compile(r'^\s*"([^"]+\.(?:cpp|c|h|S))",$', re.MULTILINE)
     # Matches e.g. |   foo.cpp|, captures |foo| in group 1.
     cmake_cpp_re = re.compile(r'^\s*([A-Za-z_0-9./-]+\.(?:cpp|c|h|S))$',
                               re.MULTILINE)
 
-    changed = False
+    changes_by_rev = defaultdict(lambda: defaultdict(lambda: defaultdict(list)))
+
+    def find_gitrev(touched_line, in_file):
+        return subprocess.check_output(
+            ['git', 'log', '--format=%h', '-1', '-S' + touched_line, in_file],
+            shell=os.name == 'nt').rstrip()
+    def svnrev_from_gitrev(gitrev):
+        git_llvm = os.path.join(
+            os.path.dirname(__file__), '..', '..', 'git-svn', 'git-llvm')
+        return int(subprocess.check_output(
+            [sys.executable, git_llvm, 'svn-lookup', gitrev],
+            shell=os.name == 'nt').rstrip().lstrip('r'))
+
+    # Collect changes to gn files, grouped by revision.
     for gn_file in gn_files:
         # The CMakeLists.txt for llvm/utils/gn/secondary/foo/BUILD.gn is
-        # directly at foo/CMakeLists.txt.
+        # at foo/CMakeLists.txt.
         strip_prefix = 'llvm/utils/gn/secondary/'
         if not gn_file.startswith(strip_prefix):
             continue
         cmake_file = os.path.join(
                 os.path.dirname(gn_file[len(strip_prefix):]), 'CMakeLists.txt')
         if not os.path.exists(cmake_file):
             continue
 
         def get_sources(source_re, text):
             return set([m.group(1) for m in source_re.finditer(text)])
         gn_cpp = get_sources(gn_cpp_re, open(gn_file).read())
         cmake_cpp = get_sources(cmake_cpp_re, open(cmake_file).read())
 
         if gn_cpp == cmake_cpp:
             continue
 
-        changed = True
-        print(gn_file)
-        add = sorted(cmake_cpp - gn_cpp)
+        def by_rev(files, key):
+            for f in files:
+                svnrev = svnrev_from_gitrev(find_gitrev(f, cmake_file))
+                changes_by_rev[svnrev][gn_file][key].append(f)
+        by_rev(sorted(cmake_cpp - gn_cpp), 'add')
+        by_rev(sorted(gn_cpp - cmake_cpp), 'remove')
+
+    # Output necessary changes grouped by revision.
+    for svnrev in sorted(changes_by_rev.keys()):
+        print('gn build: Merge r{0} -- https://reviews.llvm.org/rL{0}'
+            .format(svnrev))
+        for gn_file, data in sorted(changes_by_rev[svnrev].items()):
+            print('  ' + gn_file)
+            add = data.get('add')
             if add:
-            print('add:\n' + '\n'.join('    "%s",' % a for a in add))
-        remove = sorted(gn_cpp - cmake_cpp)
+                print('    add:\n' + '\n'.join('    "%s",' % a for a in add))
+            remove = data.get('remove')
             if remove:
-            print('remove:\n' + '\n'.join(remove))
+                print('    remove:\n    ' + '\n    '.join(remove))
             print()
-    return changed
+        print()
+
+    return bool(changes_by_rev)
 
 
 def sync_unittests():
     # Matches e.g. |add_llvm_unittest_with_input_files|.
     unittest_re = re.compile(r'^add_\S+_unittest', re.MULTILINE)
 
     checked = [ 'clang', 'clang-tools-extra', 'lld', 'llvm' ]
     changed = False