1 files changed, 73 insertions, 15 deletions

diff --git a/llvm/lib/Support/YAMLTraits.cpp b/llvm/lib/Support/YAMLTraits.cpp
index f8492c9..b9bbee7 100644
--- a/llvm/lib/Support/YAMLTraits.cpp
+++ b/llvm/lib/Support/YAMLTraits.cpp
@@ -341,11 +341,25 @@ void Input::scalarString(StringRef &S, QuotingType) {
 
 void Input::blockScalarString(StringRef &S) { scalarString(S, QuotingType::None); }
 
+void Input::scalarTag(std::string &Tag) {
+  Tag = CurrentNode->_node->getVerbatimTag();
+}
+
 void Input::setError(HNode *hnode, const Twine &message) {
   assert(hnode && "HNode must not be NULL");
   setError(hnode->_node, message);
 }
 
+NodeKind Input::getNodeKind() {
+  if (isa<ScalarHNode>(CurrentNode))
+    return NodeKind::Scalar;
+  else if (isa<MapHNode>(CurrentNode))
+    return NodeKind::Map;
+  else if (isa<SequenceHNode>(CurrentNode))
+    return NodeKind::Sequence;
+  llvm_unreachable("Unsupported node kind");
+}
+
 void Input::setError(Node *node, const Twine &message) {
   Strm->printError(node, message);
   EC = make_error_code(errc::invalid_argument);
@@ -436,9 +450,11 @@ bool Output::mapTag(StringRef Tag, bool Use) {
     // If this tag is being written inside a sequence we should write the start
     // of the sequence before writing the tag, otherwise the tag won't be
     // attached to the element in the sequence, but rather the sequence itself.
-    bool SequenceElement =
-        StateStack.size() > 1 && (StateStack[StateStack.size() - 2] == inSeq ||
-          StateStack[StateStack.size() - 2] == inFlowSeq);
+    bool SequenceElement = false;
+    if (StateStack.size() > 1) {
+      auto &E = StateStack[StateStack.size() - 2];
+      SequenceElement = inSeqAnyElement(E) || inFlowSeqAnyElement(E);
+    }
     if (SequenceElement && StateStack.back() == inMapFirstKey) {
       newLineCheck();
     } else {
@@ -461,6 +477,9 @@ bool Output::mapTag(StringRef Tag, bool Use) {
 }
 
 void Output::endMapping() {
+  // If we did not map anything, we should explicitly emit an empty map
+  if (StateStack.back() == inMapFirstKey)
+    output("{}");
   StateStack.pop_back();
 }
 
@@ -524,12 +543,15 @@ void Output::endDocuments() {
 }
 
 unsigned Output::beginSequence() {
-  StateStack.push_back(inSeq);
+  StateStack.push_back(inSeqFirstElement);
   NeedsNewLine = true;
   return 0;
 }
 
 void Output::endSequence() {
+  // If we did not emit anything, we should explicitly emit an empty sequence
+  if (StateStack.back() == inSeqFirstElement)
+    output("[]");
   StateStack.pop_back();
 }
 
@@ -538,10 +560,17 @@ bool Output::preflightElement(unsigned, void *&) {
 }
 
 void Output::postflightElement(void *) {
+  if (StateStack.back() == inSeqFirstElement) {
+    StateStack.pop_back();
+    StateStack.push_back(inSeqOtherElement);
+  } else if (StateStack.back() == inFlowSeqFirstElement) {
+    StateStack.pop_back();
+    StateStack.push_back(inFlowSeqOtherElement);
+  }
 }
 
 unsigned Output::beginFlowSequence() {
-  StateStack.push_back(inFlowSeq);
+  StateStack.push_back(inFlowSeqFirstElement);
   newLineCheck();
   ColumnAtFlowStart = Column;
   output("[ ");
@@ -680,6 +709,14 @@ void Output::blockScalarString(StringRef &S) {
   }
 }
 
+void Output::scalarTag(std::string &Tag) {
+  if (Tag.empty())
+    return;
+  newLineCheck();
+  output(Tag);
+  output(" ");
+}
+
 void Output::setError(const Twine &message) {
 }
 
@@ -693,7 +730,7 @@ bool Output::canElideEmptySequence() {
     return true;
   if (StateStack.back() != inMapFirstKey)
     return true;
-  return (StateStack[StateStack.size()-2] != inSeq);
+  return !inSeqAnyElement(StateStack[StateStack.size() - 2]);
 }
 
 void Output::output(StringRef s) {
@@ -703,9 +740,8 @@ void Output::output(StringRef s) {
 
 void Output::outputUpToEndOfLine(StringRef s) {
   output(s);
-  if (StateStack.empty() || (StateStack.back() != inFlowSeq &&
-                             StateStack.back() != inFlowMapFirstKey &&
-                             StateStack.back() != inFlowMapOtherKey))
+  if (StateStack.empty() || (!inFlowSeqAnyElement(StateStack.back()) &&
+                             !inFlowMapAnyKey(StateStack.back())))
     NeedsNewLine = true;
 }
 
@@ -725,16 +761,20 @@ void Output::newLineCheck() {
 
   outputNewLine();
 
-  assert(StateStack.size() > 0);
+  if (StateStack.size() == 0)
+    return;
+
   unsigned Indent = StateStack.size() - 1;
   bool OutputDash = false;
 
-  if (StateStack.back() == inSeq) {
+  if (StateStack.back() == inSeqFirstElement ||
+      StateStack.back() == inSeqOtherElement) {
     OutputDash = true;
-  } else if ((StateStack.size() > 1) && ((StateStack.back() == inMapFirstKey) ||
-             (StateStack.back() == inFlowSeq) ||
-             (StateStack.back() == inFlowMapFirstKey)) &&
-             (StateStack[StateStack.size() - 2] == inSeq)) {
+  } else if ((StateStack.size() > 1) &&
+             ((StateStack.back() == inMapFirstKey) ||
+              inFlowSeqAnyElement(StateStack.back()) ||
+              (StateStack.back() == inFlowMapFirstKey)) &&
+             inSeqAnyElement(StateStack[StateStack.size() - 2])) {
     --Indent;
     OutputDash = true;
   }
@@ -772,6 +812,24 @@ void Output::flowKey(StringRef Key) {
   output(": ");
 }
 
+NodeKind Output::getNodeKind() { report_fatal_error("invalid call"); }
+
+bool Output::inSeqAnyElement(InState State) {
+  return State == inSeqFirstElement || State == inSeqOtherElement;
+}
+
+bool Output::inFlowSeqAnyElement(InState State) {
+  return State == inFlowSeqFirstElement || State == inFlowSeqOtherElement;
+}
+
+bool Output::inMapAnyKey(InState State) {
+  return State == inMapFirstKey || State == inMapOtherKey;
+}
+
+bool Output::inFlowMapAnyKey(InState State) {
+  return State == inFlowMapFirstKey || State == inFlowMapOtherKey;
+}
+
 //===----------------------------------------------------------------------===//
 //  traits for built-in types
 //===----------------------------------------------------------------------===//