Parse colon in plain scalar correctly when in a flow collection

Fixes #740.

src/exp.h

@@ -110,7 +110,7 @@ inline const RegEx& Value() {
   return e;
 }
 inline const RegEx& ValueInFlow() {
-  static const RegEx e = RegEx(':') + (BlankOrBreak() | RegEx(",}", REGEX_OR));
+  static const RegEx e = RegEx(':') + (BlankOrBreak() | RegEx(",]}", REGEX_OR));
   return e;
 }
 inline const RegEx& ValueInJSONFlow() {

test/integration/load_node_test.cpp

@@ -265,6 +265,52 @@ TEST(NodeTest, IncompleteJson) {
   }
 }
 
+struct SingleNodeTestCase {
+  std::string input;
+  NodeType::value nodeType;
+  int nodeSize;
+  std::string expected_content;
+};
+
+TEST(NodeTest, SpecialFlow) {
+  std::vector<SingleNodeTestCase> tests = {
+      {"[:]", NodeType::Sequence, 1, "[{~: ~}]"},
+      {"[a:]", NodeType::Sequence, 1, "[{a: ~}]"},
+      {"[:a]", NodeType::Sequence, 1, "[:a]"},
+      {"[,]", NodeType::Sequence, 1, "[~]"},
+      {"[a:,]", NodeType::Sequence, 1, "[{a: ~}]"},
+      {"{:}", NodeType::Map, 1, "{~: ~}"},
+      {"{a:}", NodeType::Map, 1, "{a: ~}"},
+      {"{:a}", NodeType::Map, 1, "{:a: ~}"},
+      {"{,}", NodeType::Map, 1, "{~: ~}"},
+      {"{a:,}", NodeType::Map, 1, "{a: ~}"},
+  };
+  for (const SingleNodeTestCase& test : tests) {
+    Node node = Load(test.input);
+    Emitter emitter;
+    emitter << node;
+    EXPECT_EQ(test.nodeType, node.Type());
+    EXPECT_EQ(test.nodeSize, node.size());
+    EXPECT_EQ(test.expected_content, std::string(emitter.c_str()));
+  }
+}
+
+TEST(NodeTest, IncorrectFlow) {
+  std::vector<ParserExceptionTestCase> tests = {
+    {"Incorrect yaml: \"{:]\"", "{:]", ErrorMsg::FLOW_END},
+    {"Incorrect yaml: \"[:}\"", "[:}", ErrorMsg::FLOW_END},
+  };
+  for (const ParserExceptionTestCase test : tests) {
+    try {
+      Load(test.input);
+      FAIL() << "Expected exception " << test.expected_exception << " for "
+             << test.name << ", input: " << test.input;
+    } catch (const ParserException& e) {
+      EXPECT_EQ(test.expected_exception, e.msg);
+    }
+  }
+}
+
 TEST(NodeTest, LoadTildeAsNull) {
   Node node = Load("~");
   ASSERT_TRUE(node.IsNull());