fix: emit empty scalars as "" instead of "~"

Fixes #36.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Upcoming
 
+**Bug fixes**
+- ([#37](https://github.com/Ethiraric/yaml-rust2/pull/37))
+  Parse empty scalars as `""` instead of `"~"`.
+
 ## v0.8.1
 
 **Bug fixes**

src/parser.rs

@@ -92,7 +92,7 @@ impl Event {
     /// Create an empty scalar.
     fn empty_scalar() -> Event {
         // a null scalar
-        Event::Scalar("~".to_owned(), TScalarStyle::Plain, 0, None)
+        Event::Scalar(String::new(), TScalarStyle::Plain, 0, None)
     }
 
     /// Create an empty scalar with the given anchor.

src/yaml.rs

@@ -662,7 +662,7 @@ impl Yaml {
             }
         }
         match v {
-            "~" | "null" => Yaml::Null,
+            "" | "~" | "null" => Yaml::Null,
             "true" => Yaml::Boolean(true),
             "false" => Yaml::Boolean(false),
             _ => {

tests/basic.rs

@@ -156,7 +156,7 @@ fn test_github_27() {
     let s = "&a";
     let out = YamlLoader::load_from_str(s).unwrap();
     let doc = &out[0];
-    assert_eq!(doc.as_str().unwrap(), "");
+    assert_eq!(*doc, Yaml::Null);
 }
 
 #[test]

tests/spec_test.rs

@@ -33,8 +33,8 @@ impl EventReceiver for YamlChecker {
             Event::SequenceEnd => TestEvent::OnSequenceEnd,
             Event::MappingStart(..) => TestEvent::OnMapStart,
             Event::MappingEnd => TestEvent::OnMapEnd,
-            Event::Scalar(ref v, style, _, _) => {
-                if v == "~" && style == TScalarStyle::Plain {
+            Event::Scalar(ref v, style, _, tag) => {
+                if (v == "~" || v.is_empty()) && style == TScalarStyle::Plain && tag.is_none() {
                     TestEvent::OnNull
                 } else {
                     TestEvent::OnScalar

tests/yaml-test-suite.rs

@@ -287,7 +287,6 @@ fn expected_events(expected_tree: &str) -> Vec<String> {
                 "-DOC ..." => "-DOC".into(),
                 s if s.starts_with("+SEQ []") => s.replacen("+SEQ []", "+SEQ", 1),
                 s if s.starts_with("+MAP {}") => s.replacen("+MAP {}", "+MAP", 1),
-                "=VAL :" => "=VAL :~".into(), // FIXME: known bug
                 s => s.into(),
             }
         })