Recognize some enums in 'Value' deserialize.

Resolves #91.

src/value/de.rs

@@ -4,7 +4,7 @@ use std::cell::Cell;
 
 use serde::Deserialize;
 use serde::de::{self, Deserializer, IntoDeserializer};
-use serde::de::{Visitor, SeqAccess, MapAccess};
+use serde::de::{Visitor, SeqAccess, MapAccess, VariantAccess};
 
 use crate::Figment;
 use crate::error::{Error, Kind, Result};
@@ -396,7 +396,7 @@ impl<'de> Visitor<'de> for ValueVisitor {
     type Value = Value;
 
     fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.write_str("a config value")
+        f.write_str("any valid figment value")
     }
 
     visit_fn!(visit_bool: bool => Value::Bool);
@@ -438,11 +438,11 @@ impl<'de> Visitor<'de> for ValueVisitor {
         let mut raw_val: Option<RawValue> = None;
         while let Some(key) = map.next_key()? {
             if key == Value::FIELDS[0] {
-                id = Some(map.next_value().expect("value for key"));
+                id = Some(map.next_value()?);
             } else if key == Value::FIELDS[1] {
-                raw_val = Some(map.next_value().expect("value for key"));
+                raw_val = Some(map.next_value()?);
             }  else {
-                dict.insert(key, map.next_value().expect("value for key"));
+                dict.insert(key, map.next_value()?);
             }
         }
 
@@ -457,6 +457,11 @@ impl<'de> Visitor<'de> for ValueVisitor {
         Ok(dict.into())
     }
 
+    fn visit_enum<A: de::EnumAccess<'de>>(self, data: A) -> result::Result<Self::Value, A::Error> {
+        let (tag, variant) = data.variant::<String>()?;
+        Ok(crate::util::nest(&tag, variant.newtype_variant()?))
+    }
+
     fn visit_none<E: de::Error>(self) -> result::Result<Self::Value, E> {
         Ok(Empty::None.into())
     }

tests/yaml-enum.rs

@@ -0,0 +1,57 @@
+use serde::Deserialize;
+use figment::{Figment, providers::{Format, Yaml}};
+
+#[derive(Deserialize, PartialEq, Debug, Clone)]
+pub enum Trigger {
+    Start,
+    Inter { sec: u32 },
+    Triple(usize, usize, usize),
+    End(String),
+}
+
+#[derive(Deserialize, Debug, Clone)]
+pub struct Script {
+    pub triggers: Vec<Trigger>,
+}
+
+const YAML: &str = "
+triggers:
+  - !Start
+  - !Inter
+      sec: 5
+  - !Inter { sec: 7, }
+  - !Triple [1, 2, 3]
+  - !End Now
+";
+
+const YAML2: &str = "
+triggers:
+  - Start:
+  - Inter:
+      sec: 5
+  - !Inter { sec: 7, }
+  - Triple:
+    - 1
+    - 2
+    - 3
+  - End: Now
+";
+
+#[test]
+fn figment_yaml_deserize() {
+    let figment = Figment::new().merge(Yaml::string(YAML));
+    let script = figment.extract::<Script>().unwrap();
+    assert_eq!(script.triggers[0], Trigger::Start);
+    assert_eq!(script.triggers[1], Trigger::Inter { sec: 5 });
+    assert_eq!(script.triggers[2], Trigger::Inter { sec: 7 });
+    assert_eq!(script.triggers[3], Trigger::Triple(1, 2, 3));
+    assert_eq!(script.triggers[4], Trigger::End("Now".into()));
+
+    let figment = Figment::new().merge(Yaml::string(YAML2));
+    let script = figment.extract::<Script>().unwrap();
+    assert_eq!(script.triggers[0], Trigger::Start);
+    assert_eq!(script.triggers[1], Trigger::Inter { sec: 5 });
+    assert_eq!(script.triggers[2], Trigger::Inter { sec: 7 });
+    assert_eq!(script.triggers[3], Trigger::Triple(1, 2, 3));
+    assert_eq!(script.triggers[4], Trigger::End("Now".into()));
+}