[clang-tidy] Update google todo checker with style guide changes.

The [Google style guide] now allows (and recommends) writing TODOs with
the following format:

```cpp
// TODO: bug reference - details about what needs to be done.
```

With this change the checker accepts the new style and suggests in in the
fix-it hint. The previous style is still accepted.

[Google style guide]: https://google.github.io/styleguide/cppguide.html#TODO_Comments

Author: qukhan

clang-tools-extra/clang-tidy/google/TodoCommentCheck.cpp

@@ -17,28 +17,37 @@ class TodoCommentCheck::TodoCommentHandler : public CommentHandler {
 public:
   TodoCommentHandler(TodoCommentCheck &Check, std::optional<std::string> User)
       : Check(Check), User(User ? *User : "unknown"),
-        TodoMatch("^// *TODO *(\\(.*\\))?:?( )?(.*)$") {}
+        TodoMatch("^// *TODO *((\\((.*)\\))?:?( )?|: *(.*) *- *)?(.*)$") {}
 
   bool HandleComment(Preprocessor &PP, SourceRange Range) override {
     StringRef Text =
         Lexer::getSourceText(CharSourceRange::getCharRange(Range),
                              PP.getSourceManager(), PP.getLangOpts());
 
-    SmallVector<StringRef, 4> Matches;
+    SmallVector<StringRef, 7> Matches;
     if (!TodoMatch.match(Text, &Matches))
       return false;
 
-    StringRef Username = Matches[1];
-    StringRef Comment = Matches[3];
+    const bool deprecated_style = !Matches[3].empty();
+    StringRef Username = deprecated_style ? Matches[5] : Matches[3];
+    StringRef Comment = Matches[6];
 
-    if (!Username.empty())
+    if (!Username.empty() && (deprecated_style || !Comment.empty()))
       return false;
 
-    std::string NewText = ("// TODO(" + Twine(User) + "): " + Comment).str();
+    if (Username.empty()) {
+      std::string NewText = ("// TODO: " + Twine(User) + " - " +
+                             (Comment.empty() ? "some details" : Comment))
+                                .str();
+
+      Check.diag(Range.getBegin(), "missing username/bug in TODO")
+          << FixItHint::CreateReplacement(CharSourceRange::getCharRange(Range),
+                                          NewText);
+    }
+
+    if (Comment.empty())
+      Check.diag(Range.getBegin(), "missing details in TODO");
 
-    Check.diag(Range.getBegin(), "missing username/bug in TODO")
-        << FixItHint::CreateReplacement(CharSourceRange::getCharRange(Range),
-                                        NewText);
     return false;
   }
 

clang-tools-extra/test/clang-tidy/checkers/google/readability-todo.cpp

@@ -2,22 +2,36 @@
 
 //   TODOfix this1
 // CHECK-MESSAGES: [[@LINE-1]]:1: warning: missing username/bug in TODO
-// CHECK-FIXES: // TODO(some user): fix this1
+// CHECK-FIXES: // TODO: some user - fix this1
 
 //   TODO fix this2
 // CHECK-MESSAGES: [[@LINE-1]]:1: warning: missing username/bug in TODO
-// CHECK-FIXES: // TODO(some user): fix this2
+// CHECK-FIXES: // TODO: some user - fix this2
 
 // TODO fix this3
 // CHECK-MESSAGES: [[@LINE-1]]:1: warning: missing username/bug in TODO
-// CHECK-FIXES: // TODO(some user): fix this3
+// CHECK-FIXES: // TODO: some user - fix this3
 
 // TODO: fix this4
 // CHECK-MESSAGES: [[@LINE-1]]:1: warning: missing username/bug in TODO
-// CHECK-FIXES: // TODO(some user): fix this4
+// CHECK-FIXES: // TODO: some user - fix this4
+
+// TODO: bug 12345 -
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: missing details in TODO
+
+// TODO: a message without a reference
+// CHECK-MESSAGES: [[@LINE-1]]:1: warning: missing username/bug in TODO
+// CHECK-FIXES: // TODO: some user - a message without a reference
 
 //   TODO(clang)fix this5
 
+// TODO: foo - shave yaks
+// TODO:foo - no space bewteen semicolon and username
+// TODO: foo- no space bewteen username and dash
+// TODO:    foo - extra spaces between semicolon and username
+// TODO: foo   - extra spaces between username and dash
+// TODO: b/12345 - use a b/ prefix
+// TODO: bug 12345 - use a space in username/bug reference
 // TODO(foo):shave yaks
 // TODO(bar):
 // TODO(foo): paint bikeshed