Remove ValueWithKey struct

While using this library, I end up having lifetime issues with
`Config::get`. I've seen that current implementation forces the calleer
to match `key` lifetime to the output of the function.

My use case is, under some circumstances, return a suffixed version of
the config key. Something similar to:

```
        if some_condition == true {
            let key_name = format!("{}_suffix", key);
            self.config.get(&key_name)
        } else {
	    self.config.get(key)
	}
```

This code is noy compiling for me due to conflicting lifetimes. To avoid
this, I've started looking to the code and  I've found that `key` needed
this lifetime because of `ValueWithKey`. The purpouse of this struct
seems to be add more information to the errors that are returned to the
user.

To mitigate this lifetime coupling I've:

- Mapped the error on `Config::get` to include the originating key of
  the current error
- Remove all the code related with `ValueWithKey`

Author: gnieto

src/config.rs

@@ -10,7 +10,7 @@ use ser::ConfigSerializer;
 use source::Source;
 
 use path;
-use value::{Table, Value, ValueKind, ValueWithKey};
+use value::{Table, Value, ValueKind};
 
 #[derive(Clone, Debug)]
 enum ConfigKind {
@@ -151,7 +151,7 @@ impl Config {
         self.refresh()
     }
 
-    pub fn get<'de, T: Deserialize<'de>>(&self, key: &'de str) -> Result<T> {
+    pub fn get<'de, T: Deserialize<'de>>(&self, key: &str) -> Result<T> {
         // Parse the key into a path expression
         let expr: path::Expression = key.to_lowercase().parse()?;
 
@@ -161,7 +161,8 @@ impl Config {
         match value {
             Some(value) => {
                 // Deserialize the received value into the requested type
-                T::deserialize(ValueWithKey::new(value, key))
+                T::deserialize(value)
+                    .map_err(|e| e.extend_with_key(key))
             }
 
             None => Err(ConfigError::NotFound(key.into())),

src/de.rs

@@ -3,133 +3,7 @@ use error::*;
 use serde::de;
 use std::collections::{HashMap, VecDeque};
 use std::iter::Enumerate;
-use value::{Value, ValueKind, ValueWithKey, Table};
-
-// TODO: Use a macro or some other magic to reduce the code duplication here
-
-impl<'de> de::Deserializer<'de> for ValueWithKey<'de> {
-    type Error = ConfigError;
-
-    #[inline]
-    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
-    where
-        V: de::Visitor<'de>,
-    {
-        // Deserialize based on the underlying type
-        match self.0.kind {
-            ValueKind::Nil => visitor.visit_unit(),
-            ValueKind::Integer(i) => visitor.visit_i64(i),
-            ValueKind::Boolean(b) => visitor.visit_bool(b),
-            ValueKind::Float(f) => visitor.visit_f64(f),
-            ValueKind::String(s) => visitor.visit_string(s),
-            ValueKind::Array(values) => visitor.visit_seq(SeqAccess::new(values)),
-            ValueKind::Table(map) => visitor.visit_map(MapAccess::new(map)),
-        }
-    }
-
-    #[inline]
-    fn deserialize_bool<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        visitor.visit_bool(self.into_bool()?)
-    }
-
-    #[inline]
-    fn deserialize_i8<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        // FIXME: This should *fail* if the value does not fit in the requets integer type
-        visitor.visit_i8(self.into_int()? as i8)
-    }
-
-    #[inline]
-    fn deserialize_i16<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        // FIXME: This should *fail* if the value does not fit in the requets integer type
-        visitor.visit_i16(self.into_int()? as i16)
-    }
-
-    #[inline]
-    fn deserialize_i32<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        // FIXME: This should *fail* if the value does not fit in the requets integer type
-        visitor.visit_i32(self.into_int()? as i32)
-    }
-
-    #[inline]
-    fn deserialize_i64<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        visitor.visit_i64(self.into_int()?)
-    }
-
-    #[inline]
-    fn deserialize_u8<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        // FIXME: This should *fail* if the value does not fit in the requets integer type
-        visitor.visit_u8(self.into_int()? as u8)
-    }
-
-    #[inline]
-    fn deserialize_u16<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        // FIXME: This should *fail* if the value does not fit in the requets integer type
-        visitor.visit_u16(self.into_int()? as u16)
-    }
-
-    #[inline]
-    fn deserialize_u32<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        // FIXME: This should *fail* if the value does not fit in the requets integer type
-        visitor.visit_u32(self.into_int()? as u32)
-    }
-
-    #[inline]
-    fn deserialize_u64<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        // FIXME: This should *fail* if the value does not fit in the requets integer type
-        visitor.visit_u64(self.into_int()? as u64)
-    }
-
-    #[inline]
-    fn deserialize_f32<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        visitor.visit_f32(self.into_float()? as f32)
-    }
-
-    #[inline]
-    fn deserialize_f64<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        visitor.visit_f64(self.into_float()?)
-    }
-
-    #[inline]
-    fn deserialize_str<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        visitor.visit_string(self.into_str()?)
-    }
-
-    #[inline]
-    fn deserialize_string<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value> {
-        visitor.visit_string(self.into_str()?)
-    }
-
-    #[inline]
-    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value>
-    where
-        V: de::Visitor<'de>,
-    {
-        // Match an explicit nil as None and everything else as Some
-        match self.0.kind {
-            ValueKind::Nil => visitor.visit_none(),
-            _ => visitor.visit_some(self),
-        }
-    }
-
-    fn deserialize_enum<V>(
-        self,
-        name: &'static str,
-        variants: &'static [&'static str],
-        visitor: V,
-    ) -> Result<V::Value>
-    where
-        V: de::Visitor<'de>,
-    {
-        // FIXME: find a way to extend_with_key
-        visitor.visit_enum(EnumAccess{ value: self.0, name: name, variants: variants })
-    }
-
-    forward_to_deserialize_any! {
-        char seq
-        bytes byte_buf map struct unit newtype_struct
-        identifier ignored_any unit_struct tuple_struct tuple
-    }
-}
+use value::{Value, ValueKind, Table};
 
 impl<'de> de::Deserializer<'de> for Value {
     type Error = ConfigError;

src/ser.rs

@@ -3,7 +3,7 @@ use std::fmt::Display;
 use std::mem;
 
 use error::*;
-use value::{Value, ValueKind, ValueWithKey};
+use value::{Value, ValueKind};
 use Config;
 
 #[derive(Default, Debug)]

src/value.rs

@@ -542,58 +542,3 @@ impl Display for Value {
         write!(f, "{}", self.kind)
     }
 }
-
-pub struct ValueWithKey<'a>(pub Value, &'a str);
-
-impl<'a> ValueWithKey<'a> {
-    pub fn new(value: Value, key: &'a str) -> Self {
-        ValueWithKey(value, key)
-    }
-
-    pub fn into_bool(self) -> Result<bool> {
-        match self.0.into_bool() {
-            Ok(value) => Ok(value),
-            Err(error) => Err(error.extend_with_key(self.1)),
-        }
-    }
-
-    /// Returns `self` into an i64, if possible.
-    pub fn into_int(self) -> Result<i64> {
-        match self.0.into_int() {
-            Ok(value) => Ok(value),
-            Err(error) => Err(error.extend_with_key(self.1)),
-        }
-    }
-
-    /// Returns `self` into a f64, if possible.
-    pub fn into_float(self) -> Result<f64> {
-        match self.0.into_float() {
-            Ok(value) => Ok(value),
-            Err(error) => Err(error.extend_with_key(self.1)),
-        }
-    }
-
-    /// Returns `self` into a str, if possible.
-    pub fn into_str(self) -> Result<String> {
-        match self.0.into_str() {
-            Ok(value) => Ok(value),
-            Err(error) => Err(error.extend_with_key(self.1)),
-        }
-    }
-
-    /// Returns `self` into an array, if possible
-    pub fn into_array(self) -> Result<Vec<Value>> {
-        match self.0.into_array() {
-            Ok(value) => Ok(value),
-            Err(error) => Err(error.extend_with_key(self.1)),
-        }
-    }
-
-    /// If the `Value` is a Table, returns the associated Map.
-    pub fn into_table(self) -> Result<HashMap<String, Value>> {
-        match self.0.into_table() {
-            Ok(value) => Ok(value),
-            Err(error) => Err(error.extend_with_key(self.1)),
-        }
-    }
-}