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[Clang][Comments] Add argument parsing for @throw @throws @exception
Doxygen allows for the @throw, @throws, and @exception commands to have an attached argument indicating the type being thrown. Currently, Clang's AST parsing doesn't support parsing out this argument from doc comments. The result is missing compatibility with Doxygen.
We would find it helpful if the AST exposed these thrown types as BlockCommandComment arguments so that we could generate better documentation.
This PR implements parsing of arguments for the @throw, @throws, and @exception commands. Each command can only have one argument, matching the semantics of Doxygen. We have also added unit tests to validate the functionality.
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@llvm/pr-subscribers-clang
Author: hdoc (hdoc)
Changes
Doxygen allows for the @throw, @throws, and @exception commands to have an attached argument indicating the type being thrown. Currently, Clang's AST parsing doesn't support parsing out this argument from doc comments. The result is missing compatibility with Doxygen.
We would find it helpful if the AST exposed these thrown types as BlockCommandComment arguments so that we could generate better documentation.
This PR implements parsing of arguments for the @throw, @throws, and @exception commands. Each command can only have one argument, matching the semantics of Doxygen. We have also added unit tests to validate the functionality.
Full diff: https://github.com/llvm/llvm-project/pull/84726.diff
4 Files Affected:
- (modified) clang/include/clang/AST/CommentCommands.td (+3-3)
- (modified) clang/include/clang/AST/CommentParser.h (+3)
- (modified) clang/lib/AST/CommentParser.cpp (+133)
- (modified) clang/unittests/AST/CommentParser.cpp (+234-1)
diff --git a/clang/include/clang/AST/CommentCommands.td b/clang/include/clang/AST/CommentCommands.td
index e839031752cdd8..06b2fa9b5531c6 100644
--- a/clang/include/clang/AST/CommentCommands.td
+++ b/clang/include/clang/AST/CommentCommands.td
@@ -132,9 +132,9 @@ def Tparam : BlockCommand<"tparam"> { let IsTParamCommand = 1; }
// HeaderDoc command for template parameter documentation.
def Templatefield : BlockCommand<"templatefield"> { let IsTParamCommand = 1; }
-def Throws : BlockCommand<"throws"> { let IsThrowsCommand = 1; }
-def Throw : BlockCommand<"throw"> { let IsThrowsCommand = 1; }
-def Exception : BlockCommand<"exception"> { let IsThrowsCommand = 1; }
+def Throws : BlockCommand<"throws"> { let IsThrowsCommand = 1; let NumArgs = 1; }
+def Throw : BlockCommand<"throw"> { let IsThrowsCommand = 1; let NumArgs = 1; }
+def Exception : BlockCommand<"exception"> { let IsThrowsCommand = 1; let NumArgs = 1;}
def Deprecated : BlockCommand<"deprecated"> {
let IsEmptyParagraphAllowed = 1;
diff --git a/clang/include/clang/AST/CommentParser.h b/clang/include/clang/AST/CommentParser.h
index e11e818b1af0a1..5884a25d007851 100644
--- a/clang/include/clang/AST/CommentParser.h
+++ b/clang/include/clang/AST/CommentParser.h
@@ -100,6 +100,9 @@ class Parser {
ArrayRef<Comment::Argument>
parseCommandArgs(TextTokenRetokenizer &Retokenizer, unsigned NumArgs);
+ ArrayRef<Comment::Argument>
+ parseThrowCommandArgs(TextTokenRetokenizer &Retokenizer, unsigned NumArgs);
+
BlockCommandComment *parseBlockCommand();
InlineCommandComment *parseInlineCommand();
diff --git a/clang/lib/AST/CommentParser.cpp b/clang/lib/AST/CommentParser.cpp
index 8adfd85d0160c3..c70fa1b05cb241 100644
--- a/clang/lib/AST/CommentParser.cpp
+++ b/clang/lib/AST/CommentParser.cpp
@@ -75,6 +75,25 @@ class TextTokenRetokenizer {
return *Pos.BufferPtr;
}
+ char peekNext(unsigned offset) const {
+ assert(!isEnd());
+ assert(Pos.BufferPtr != Pos.BufferEnd);
+ if (Pos.BufferPtr + offset <= Pos.BufferEnd) {
+ return *(Pos.BufferPtr + offset);
+ } else {
+ return '\0';
+ }
+ }
+
+ void peekNextToken(SmallString<32> &WordText) const {
+ unsigned offset = 1;
+ char C = peekNext(offset++);
+ while (!isWhitespace(C) && C != '\0') {
+ WordText.push_back(C);
+ C = peekNext(offset++);
+ }
+ }
+
void consumeChar() {
assert(!isEnd());
assert(Pos.BufferPtr != Pos.BufferEnd);
@@ -89,6 +108,29 @@ class TextTokenRetokenizer {
}
}
+ /// Extract a template type
+ bool lexTemplateType(SmallString<32> &WordText) {
+ unsigned IncrementCounter = 0;
+ while (!isEnd()) {
+ const char C = peek();
+ WordText.push_back(C);
+ consumeChar();
+ switch (C) {
+ default:
+ break;
+ case '<': {
+ IncrementCounter++;
+ } break;
+ case '>': {
+ IncrementCounter--;
+ if (!IncrementCounter)
+ return true;
+ } break;
+ }
+ }
+ return false;
+ }
+
/// Add a token.
/// Returns true on success, false if there are no interesting tokens to
/// fetch from lexer.
@@ -149,6 +191,76 @@ class TextTokenRetokenizer {
addToken();
}
+ /// Extract a type argument
+ bool lexDataType(Token &Tok) {
+ if (isEnd())
+ return false;
+ Position SavedPos = Pos;
+ consumeWhitespace();
+ SmallString<32> NextToken;
+ SmallString<32> WordText;
+ const char *WordBegin = Pos.BufferPtr;
+ SourceLocation Loc = getSourceLocation();
+ StringRef ConstVal = StringRef("const");
+ bool ConstPointer = false;
+
+ while (!isEnd()) {
+ const char C = peek();
+ if (!isWhitespace(C)) {
+ if (C == '<') {
+ if (!lexTemplateType(WordText))
+ return false;
+ } else {
+ WordText.push_back(C);
+ consumeChar();
+ }
+ } else {
+ if (WordText.equals(ConstVal)) {
+ WordText.push_back(C);
+ consumeChar();
+ } else if (WordText.ends_with(StringRef("*")) ||
+ WordText.ends_with(StringRef("&"))) {
+ NextToken.clear();
+ peekNextToken(NextToken);
+ if (NextToken.equals(ConstVal)) {
+ ConstPointer = true;
+ WordText.push_back(C);
+ consumeChar();
+ } else {
+ consumeChar();
+ break;
+ }
+ } else {
+ NextToken.clear();
+ peekNextToken(NextToken);
+ if ((NextToken.ends_with(StringRef("*")) ||
+ NextToken.ends_with(StringRef("&"))) &&
+ !ConstPointer) {
+ WordText.push_back(C);
+ consumeChar();
+ } else {
+ consumeChar();
+ break;
+ }
+ }
+ }
+ }
+
+ const unsigned Length = WordText.size();
+ if (Length == 0) {
+ Pos = SavedPos;
+ return false;
+ }
+
+ char *TextPtr = Allocator.Allocate<char>(Length + 1);
+
+ memcpy(TextPtr, WordText.c_str(), Length + 1);
+ StringRef Text = StringRef(TextPtr, Length);
+
+ formTokenWithChars(Tok, Loc, WordBegin, Length, Text);
+ return true;
+ }
+
/// Extract a word -- sequence of non-whitespace characters.
bool lexWord(Token &Tok) {
if (isEnd())
@@ -295,6 +407,7 @@ Parser::parseCommandArgs(TextTokenRetokenizer &Retokenizer, unsigned NumArgs) {
Comment::Argument[NumArgs];
unsigned ParsedArgs = 0;
Token Arg;
+
while (ParsedArgs < NumArgs && Retokenizer.lexWord(Arg)) {
Args[ParsedArgs] = Comment::Argument{
SourceRange(Arg.getLocation(), Arg.getEndLocation()), Arg.getText()};
@@ -304,6 +417,23 @@ Parser::parseCommandArgs(TextTokenRetokenizer &Retokenizer, unsigned NumArgs) {
return llvm::ArrayRef(Args, ParsedArgs);
}
+ArrayRef<Comment::Argument>
+Parser::parseThrowCommandArgs(TextTokenRetokenizer &Retokenizer,
+ unsigned NumArgs) {
+ auto *Args = new (Allocator.Allocate<Comment::Argument>(NumArgs))
+ Comment::Argument[NumArgs];
+ unsigned ParsedArgs = 0;
+ Token Arg;
+
+ while (ParsedArgs < NumArgs && Retokenizer.lexDataType(Arg)) {
+ Args[ParsedArgs] = Comment::Argument{
+ SourceRange(Arg.getLocation(), Arg.getEndLocation()), Arg.getText()};
+ ParsedArgs++;
+ }
+
+ return llvm::ArrayRef(Args, ParsedArgs);
+}
+
BlockCommandComment *Parser::parseBlockCommand() {
assert(Tok.is(tok::backslash_command) || Tok.is(tok::at_command));
@@ -356,6 +486,9 @@ BlockCommandComment *Parser::parseBlockCommand() {
parseParamCommandArgs(PC, Retokenizer);
else if (TPC)
parseTParamCommandArgs(TPC, Retokenizer);
+ else if (Info->IsThrowsCommand)
+ S.actOnBlockCommandArgs(
+ BC, parseThrowCommandArgs(Retokenizer, Info->NumArgs));
else
S.actOnBlockCommandArgs(BC, parseCommandArgs(Retokenizer, Info->NumArgs));
diff --git a/clang/unittests/AST/CommentParser.cpp b/clang/unittests/AST/CommentParser.cpp
index c3479672ae2a3c..e01d654aa1cea2 100644
--- a/clang/unittests/AST/CommentParser.cpp
+++ b/clang/unittests/AST/CommentParser.cpp
@@ -1427,8 +1427,241 @@ TEST_F(CommentParserTest, Deprecated) {
}
}
+TEST_F(CommentParserTest, ThrowsCommandHasArg1) {
+ const char *Sources[] = {
+ "/// @throws int This function throws an integer",
+ ("/// @throws\n"
+ "/// int This function throws an integer"),
+ ("/// @throws \n"
+ "/// int This function throws an integer"),
+ ("/// @throws\n"
+ "/// int\n"
+ "/// This function throws an integer"),
+ ("/// @throws \n"
+ "/// int \n"
+ "/// This function throws an integer"),
+ };
+
+ for (size_t i = 0, e = std::size(Sources); i != e; i++) {
+ FullComment *FC = parseString(Sources[i]);
+ ASSERT_TRUE(HasChildCount(FC, 2));
+
+ ASSERT_TRUE(HasParagraphCommentAt(FC, 0, " "));
+ {
+ BlockCommandComment *BCC;
+ ParagraphComment *PC;
+ ASSERT_TRUE(HasBlockCommandAt(FC, Traits, 1, BCC, "throws", PC));
+ ASSERT_TRUE(HasChildCount(PC, 1));
+ ASSERT_TRUE(BCC->getNumArgs() == 1);
+ ASSERT_TRUE(BCC->getArgText(0) == "int");
+ }
+ }
+}
+
+TEST_F(CommentParserTest, ThrowsCommandHasArg2) {
+ const char *Sources[] = {
+ "/// @throws const int This function throws a const integer",
+ ("/// @throws\n"
+ "/// const int This function throws a const integer"),
+ ("/// @throws \n"
+ "/// const int This function throws a const integer"),
+ ("/// @throws\n"
+ "/// const int\n"
+ "/// This function throws a const integer"),
+ ("/// @throws \n"
+ "/// const int \n"
+ "/// This function throws a const integer"),
+ };
+
+ for (size_t i = 0, e = std::size(Sources); i != e; i++) {
+ FullComment *FC = parseString(Sources[i]);
+ ASSERT_TRUE(HasChildCount(FC, 2));
+
+ ASSERT_TRUE(HasParagraphCommentAt(FC, 0, " "));
+ {
+ BlockCommandComment *BCC;
+ ParagraphComment *PC;
+ ASSERT_TRUE(HasBlockCommandAt(FC, Traits, 1, BCC, "throws", PC));
+ ASSERT_TRUE(HasChildCount(PC, 1));
+ ASSERT_TRUE(BCC->getNumArgs() == 1);
+ ASSERT_TRUE(BCC->getArgText(0) == "const int");
+ }
+ }
+}
+
+TEST_F(CommentParserTest, ThrowsCommandHasArg3) {
+ const char *Sources[] = {
+ "/// @throws const int * This function throws a pointer to a const "
+ "integer\n",
+ ("/// @throws\n"
+ "/// const int * This function throws a pointer to a const integer"),
+ ("/// @throws \n"
+ "/// const int * This function throws a pointer to a const integer"),
+ ("/// @throws\n"
+ "/// const int *\n"
+ "/// This function throws a pointer to a const integer"),
+ ("/// @throws \n"
+ "/// const int *\n"
+ "/// This function throws a pointer to a const integer"),
+ };
+
+ for (size_t i = 0, e = std::size(Sources); i != e; i++) {
+ FullComment *FC = parseString(Sources[i]);
+ ASSERT_TRUE(HasChildCount(FC, 2));
+
+ ASSERT_TRUE(HasParagraphCommentAt(FC, 0, " "));
+ {
+ BlockCommandComment *BCC;
+ ParagraphComment *PC;
+ ASSERT_TRUE(HasBlockCommandAt(FC, Traits, 1, BCC, "throws", PC));
+ ASSERT_TRUE(HasChildCount(PC, 1));
+ ASSERT_TRUE(BCC->getNumArgs() == 1);
+ ASSERT_TRUE(BCC->getArgText(0) == "const int *");
+ }
+ }
+}
+
+TEST_F(CommentParserTest, ThrowsCommandHasArg4) {
+ const char *Sources[] = {
+ "/// @throws const int * const This function throws a const pointer to a "
+ "const integer",
+ ("/// @throws\n"
+ "/// const int * const This function throws a const pointer to a const "
+ "integer"),
+ ("/// @throws \n"
+ "/// const int * const This function throws a const pointer to a const "
+ "integer"),
+ ("/// @throws\n"
+ "/// const int * const\n"
+ "/// This function throws a const pointer to a const integer"),
+ ("/// @throws \n"
+ "/// const int * const\n"
+ "/// This function throws a const pointer to a const integer"),
+ };
+
+ for (size_t i = 0, e = std::size(Sources); i != e; i++) {
+ FullComment *FC = parseString(Sources[i]);
+ ASSERT_TRUE(HasChildCount(FC, 2));
+
+ ASSERT_TRUE(HasParagraphCommentAt(FC, 0, " "));
+ {
+ BlockCommandComment *BCC;
+ ParagraphComment *PC;
+ ASSERT_TRUE(HasBlockCommandAt(FC, Traits, 1, BCC, "throws", PC));
+ ASSERT_TRUE(HasChildCount(PC, 1));
+ ASSERT_TRUE(BCC->getNumArgs() == 1);
+ ASSERT_TRUE(BCC->getArgText(0) == "const int * const");
+ }
+ }
+}
+
+TEST_F(CommentParserTest, ThrowsCommandHasArg5) {
+ const char *Sources[] = {
+ "/// @throws int** This function throws a double pointer to an integer",
+ };
+
+ for (size_t i = 0, e = std::size(Sources); i != e; i++) {
+ FullComment *FC = parseString(Sources[i]);
+ ASSERT_TRUE(HasChildCount(FC, 2));
+
+ ASSERT_TRUE(HasParagraphCommentAt(FC, 0, " "));
+ {
+ BlockCommandComment *BCC;
+ ParagraphComment *PC;
+ ASSERT_TRUE(HasBlockCommandAt(FC, Traits, 1, BCC, "throws", PC));
+ ASSERT_TRUE(HasChildCount(PC, 1));
+ ASSERT_TRUE(BCC->getNumArgs() == 1);
+ ASSERT_TRUE(BCC->getArgText(0) == "int**");
+ }
+ }
+}
+
+TEST_F(CommentParserTest, ThrowsCommandHasArg6) {
+ const char *Sources[] = {
+ "/// @throws const char ** double pointer to a constant char pointer",
+ };
+
+ for (size_t i = 0, e = std::size(Sources); i != e; i++) {
+ FullComment *FC = parseString(Sources[i]);
+ ASSERT_TRUE(HasChildCount(FC, 2));
+
+ ASSERT_TRUE(HasParagraphCommentAt(FC, 0, " "));
+ {
+ BlockCommandComment *BCC;
+ ParagraphComment *PC;
+ ASSERT_TRUE(HasBlockCommandAt(FC, Traits, 1, BCC, "throws", PC));
+ ASSERT_TRUE(HasChildCount(PC, 1));
+ ASSERT_TRUE(BCC->getNumArgs() == 1);
+ ASSERT_TRUE(BCC->getArgText(0) == "const char **");
+ }
+ }
+}
+
+TEST_F(CommentParserTest, ThrowsCommandHasArg7) {
+ const char *Sources[] = {
+ "/// @throws Error<T> error of type Error<T>",
+ };
+
+ for (size_t i = 0, e = std::size(Sources); i != e; i++) {
+ FullComment *FC = parseString(Sources[i]);
+ ASSERT_TRUE(HasChildCount(FC, 2));
+
+ ASSERT_TRUE(HasParagraphCommentAt(FC, 0, " "));
+ {
+ BlockCommandComment *BCC;
+ ParagraphComment *PC;
+ ASSERT_TRUE(HasBlockCommandAt(FC, Traits, 1, BCC, "throws", PC));
+ ASSERT_TRUE(HasChildCount(PC, 3)); // Extra children because <T> is parsed
+ // as a series of TextComments
+ ASSERT_TRUE(BCC->getNumArgs() == 1);
+ ASSERT_TRUE(BCC->getArgText(0) == "Error<T>");
+ }
+ }
+}
+
+TEST_F(CommentParserTest, ThrowsCommandHasArg8) {
+ const char *Sources[] = {
+ "/// @throws Error<Container<T>> nested templates",
+ };
+
+ for (size_t i = 0, e = std::size(Sources); i != e; i++) {
+ FullComment *FC = parseString(Sources[i]);
+ ASSERT_TRUE(HasChildCount(FC, 2));
+
+ ASSERT_TRUE(HasParagraphCommentAt(FC, 0, " "));
+ {
+ BlockCommandComment *BCC;
+ ParagraphComment *PC;
+ ASSERT_TRUE(HasBlockCommandAt(FC, Traits, 1, BCC, "throws", PC));
+ ASSERT_TRUE(HasChildCount(PC, 1));
+ ASSERT_TRUE(BCC->getNumArgs() == 1);
+ ASSERT_TRUE(BCC->getArgText(0) == "Error<Container<T>>");
+ }
+ }
+}
+
+TEST_F(CommentParserTest, ThrowsCommandHasArg9) {
+ const char *Sources[] = {
+ "/// @throws Error<Ts...> variadic templates",
+ };
+
+ for (size_t i = 0, e = std::size(Sources); i != e; i++) {
+ FullComment *FC = parseString(Sources[i]);
+ ASSERT_TRUE(HasChildCount(FC, 2));
+
+ ASSERT_TRUE(HasParagraphCommentAt(FC, 0, " "));
+ {
+ BlockCommandComment *BCC;
+ ParagraphComment *PC;
+ ASSERT_TRUE(HasBlockCommandAt(FC, Traits, 1, BCC, "throws", PC));
+ ASSERT_TRUE(HasChildCount(PC, 1));
+ ASSERT_TRUE(BCC->getNumArgs() == 1);
+ ASSERT_TRUE(BCC->getArgText(0) == "Error<Ts...>");
+ }
+ }
+}
+
} // unnamed namespace
} // end namespace comments
} // end namespace clang
-
Before I do an in-depth review i think supporting arguments to @throw etc makes a lot of sense.
However, I don't think we want to have a type-id parser in the comment parser. The grammar is complicated, and the approach seems brittle and hard to maintain.
Given use cases, I think it's sufficient to consider anything before a space as part of a type.
You can try to support things like foo<const bar> just by balancing <>, but I really don't think we want to parse arbitrary types (including function types, arrays, lambdas, etc) as types that you can throw.
If people want to throw "unsigned int" exceptions, well... it won't work. I think it's a reasonable tradeoff. 99% of exceptions are going to be class types.
In the long term, if we really want to support arbitrary constructs there, I think it would take a more robust approach such as the one that was proposed here (and subsequently abandoned)
@cor3ntin we appreciate the feedback. Likewise, we agree that the home-grown parser just for parsing type-ids in comments is less than ideal. We had some alternative approaches in mind, like using an instance of clang::Lexer, but went with our original approach at first.
I've refactored the PR and reduced the functionality to the subset you requested. I think that makes more sense from a maintainability perspective, as you highlighted. Please review the PR when you get a chance. Thank you.
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