Merge pull request #264 from azriel91/feature/225/externally-tagged-enums

Issue 255: Externally tagged enum deserialization

1 files changed, 391 insertions, 57 deletions

diff --git a/src/de.rs b/src/de.rs
index b5633ea..9334cd3 100644
--- a/src/de.rs
+++ b/src/de.rs
@@ -159,12 +159,35 @@ enum ErrorKind {
     /// type.
     Custom,
 
-    /// A struct was expected but something else was found
-    ExpectedString,
+    /// A tuple with a certain number of elements was expected but something
+    /// else was found.
+    ExpectedTuple(usize),
+
+    /// Expected table keys to be in increasing tuple index order, but something
+    /// else was found.
+    ExpectedTupleIndex {
+        /// Expected index.
+        expected: usize,
+        /// Key that was specified.
+        found: String,
+    },
+
+    /// An empty table was expected but entries were found
+    ExpectedEmptyTable,
 
     /// Dotted key attempted to extend something that is not a table.
     DottedKeyInvalidType,
 
+    /// An unexpected key was encountered.
+    ///
+    /// Used when deserializing a struct with a limited set of fields.
+    UnexpectedKeys {
+        /// The unexpected keys.
+        keys: Vec<String>,
+        /// Keys that may be specified.
+        available: &'static [&'static str],
+    },
+
     #[doc(hidden)]
     __Nonexhaustive,
 }
@@ -182,47 +205,8 @@ impl<'de, 'b> de::Deserializer<'de> for &'b mut Deserializer<'de> {
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Error>
         where V: de::Visitor<'de>,
     {
-        let mut tables = Vec::new();
-        let mut cur_table = Table {
-            at: 0,
-            header: Vec::new(),
-            values: None,
-            array: false,
-        };
 
-        while let Some(line) = self.line()? {
-            match line {
-                Line::Table { at, mut header, array } => {
-                    if !cur_table.header.is_empty() || cur_table.values.is_some() {
-                        tables.push(cur_table);
-                    }
-                    cur_table = Table {
-                        at: at,
-                        header: Vec::new(),
-                        values: Some(Vec::new()),
-                        array: array,
-                    };
-                    loop {
-                        let part = header.next().map_err(|e| {
-                            self.token_error(e)
-                        });
-                        match part? {
-                            Some(part) => cur_table.header.push(part),
-                            None => break,
-                        }
-                    }
-                }
-                Line::KeyValue(key, value) => {
-                    if cur_table.values.is_none() {
-                        cur_table.values = Some(Vec::new());
-                    }
-                    self.add_dotted_key(key, value, cur_table.values.as_mut().unwrap())?;
-                }
-            }
-        }
-        if !cur_table.header.is_empty() || cur_table.values.is_some() {
-            tables.push(cur_table);
-        }
+        let mut tables = self.tables()?;
 
         visitor.visit_map(MapVisitor {
             values: Vec::new().into_iter(),
@@ -237,6 +221,7 @@ impl<'de, 'b> de::Deserializer<'de> for &'b mut Deserializer<'de> {
         })
     }
 
+    // Called when the type to deserialize is an enum, as opposed to a field in the type.
     fn deserialize_enum<V>(
         self,
         _name: &'static str,
@@ -245,15 +230,34 @@ impl<'de, 'b> de::Deserializer<'de> for &'b mut Deserializer<'de> {
     ) -> Result<V::Value, Error>
         where V: de::Visitor<'de>
     {
-        if let Some(next) = self.next()? {
-            match next {
-                (_, Token::String { val, .. }) => {
-                    visitor.visit_enum(val.into_deserializer())
-                },
-                _ => Err(Error::from_kind(ErrorKind::ExpectedString))
+        let (value, name) = self.string_or_table()?;
+        match value.e {
+            E::String(val) => visitor.visit_enum(val.into_deserializer()),
+            E::InlineTable(values) => {
+                if values.len() != 1 {
+                    Err(Error::from_kind(ErrorKind::Wanted {
+                        expected: "exactly 1 element",
+                        found: if values.is_empty() {
+                            "zero elements"
+                        } else {
+                            "more than 1 element"
+                        },
+                    }))
+                } else {
+                    visitor.visit_enum(InlineTableDeserializer {
+                        values: values.into_iter(),
+                        next_value: None,
+                    })
+                }
             }
-        } else {
-            Err(Error::from_kind(ErrorKind::UnexpectedEof))
+            E::DottedTable(_) => visitor.visit_enum(DottedTableDeserializer {
+                name: name.expect("Expected table header to be passed."),
+                value: value,
+            }),
+            e @ _ => Err(Error::from_kind(ErrorKind::Wanted {
+                expected: "string or table",
+                found: e.type_name(),
+            })),
         }
     }
 
@@ -497,14 +501,21 @@ impl<'de> de::Deserializer<'de> for StrDeserializer<'de> {
 
 struct ValueDeserializer<'a> {
     value: Value<'a>,
+    validate_struct_keys: bool,
 }
 
 impl<'a> ValueDeserializer<'a> {
     fn new(value: Value<'a>) -> ValueDeserializer<'a> {
         ValueDeserializer {
             value: value,
+            validate_struct_keys: false,
         }
     }
+
+    fn with_struct_key_validation(mut self) -> Self {
+        self.validate_struct_keys = true;
+        self
+    }
 }
 
 impl<'de> de::Deserializer<'de> for ValueDeserializer<'de> {
@@ -553,6 +564,31 @@ impl<'de> de::Deserializer<'de> for ValueDeserializer<'de> {
             }
         }
 
+        if self.validate_struct_keys {
+            match &self.value.e {
+                &E::InlineTable(ref values) | &E::DottedTable(ref values) => {
+                    let extra_fields = values.iter()
+                        .filter_map(|key_value| {
+                            let (ref key, ref _val) = *key_value;
+                            if !fields.contains(&&(**key)) {
+                                Some(key.clone())
+                            } else {
+                                None
+                            }
+                        })
+                        .collect::<Vec<Cow<'de, str>>>();
+
+                    if !extra_fields.is_empty() {
+                        return Err(Error::from_kind(ErrorKind::UnexpectedKeys {
+                            keys: extra_fields.iter().map(|k| k.to_string()).collect::<Vec<_>>(),
+                            available: fields,
+                        }));
+                    }
+                }
+                _ => {}
+            }
+        }
+
         if name == spanned::NAME && fields == &[spanned::START, spanned::END, spanned::VALUE] {
             let start = self.value.start;
             let end = self.value.end;
@@ -585,7 +621,27 @@ impl<'de> de::Deserializer<'de> for ValueDeserializer<'de> {
     {
         match self.value.e {
             E::String(val) => visitor.visit_enum(val.into_deserializer()),
-            _ => Err(Error::from_kind(ErrorKind::ExpectedString))
+            E::InlineTable(values) => {
+                if values.len() != 1 {
+                    Err(Error::from_kind(ErrorKind::Wanted {
+                        expected: "exactly 1 element",
+                        found: if values.is_empty() {
+                            "zero elements"
+                        } else {
+                            "more than 1 element"
+                        },
+                    }))
+                } else {
+                    visitor.visit_enum(InlineTableDeserializer {
+                        values: values.into_iter(),
+                        next_value: None,
+                    })
+                }
+            }
+            e @ _ => Err(Error::from_kind(ErrorKind::Wanted {
+                expected: "string or inline table",
+                found: e.type_name(),
+            })),
         }
     }
 
@@ -697,6 +753,25 @@ impl<'de> de::Deserializer<'de> for DatetimeFieldDeserializer {
     }
 }
 
+struct DottedTableDeserializer<'a> {
+    name: Cow<'a, str>,
+    value: Value<'a>,
+}
+
+impl<'de> de::EnumAccess<'de> for DottedTableDeserializer<'de> {
+    type Error = Error;
+    type Variant = TableEnumDeserializer<'de>;
+
+    fn variant_seed<V>(self, seed: V) -> Result<(V::Value, Self::Variant), Self::Error>
+    where
+        V: de::DeserializeSeed<'de>,
+    {
+        let (name, value) = (self.name, self.value);
+        seed.deserialize(StrDeserializer::new(name))
+            .map(|val| (val, TableEnumDeserializer { value: value }))
+    }
+}
+
 struct InlineTableDeserializer<'a> {
     values: vec::IntoIter<(Cow<'a, str>, Value<'a>)>,
     next_value: Option<Value<'a>>,
@@ -724,6 +799,124 @@ impl<'de> de::MapAccess<'de> for InlineTableDeserializer<'de> {
     }
 }
 
+impl<'de> de::EnumAccess<'de> for InlineTableDeserializer<'de> {
+    type Error = Error;
+    type Variant = TableEnumDeserializer<'de>;
+
+    fn variant_seed<V>(mut self, seed: V) -> Result<(V::Value, Self::Variant), Self::Error>
+    where
+        V: de::DeserializeSeed<'de>,
+    {
+        let (key, value) = match self.values.next() {
+            Some(pair) => pair,
+            None => {
+                return Err(Error::from_kind(ErrorKind::Wanted {
+                    expected: "table with exactly 1 entry",
+                    found: "empty table",
+                }))
+            }
+        };
+
+        seed.deserialize(StrDeserializer::new(key))
+            .map(|val| (val, TableEnumDeserializer { value: value }))
+    }
+}
+
+/// Deserializes table values into enum variants.
+struct TableEnumDeserializer<'a> {
+    value: Value<'a>,
+}
+
+impl<'de> de::VariantAccess<'de> for TableEnumDeserializer<'de> {
+    type Error = Error;
+
+    fn unit_variant(self) -> Result<(), Self::Error> {
+        match self.value.e {
+            E::InlineTable(values) | E::DottedTable(values) => {
+                if values.len() == 0 {
+                    Ok(())
+                } else {
+                    Err(Error::from_kind(ErrorKind::ExpectedEmptyTable))
+                }
+            }
+            e @ _ => Err(Error::from_kind(ErrorKind::Wanted {
+                expected: "table",
+                found: e.type_name(),
+            })),
+        }
+    }
+
+    fn newtype_variant_seed<T>(self, seed: T) -> Result<T::Value, Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        seed.deserialize(ValueDeserializer::new(self.value))
+    }
+
+    fn tuple_variant<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.value.e {
+            E::InlineTable(values) | E::DottedTable(values) => {
+                let tuple_values = values
+                    .into_iter()
+                    .enumerate()
+                    .map(|(index, (key, value))| match key.parse::<usize>() {
+                        Ok(key_index) if key_index == index => Ok(value),
+                        Ok(_) | Err(_) => Err(Error::from_kind(ErrorKind::ExpectedTupleIndex {
+                            expected: index,
+                            found: key.to_string(),
+                        })),
+                    })
+                    // Fold all values into a `Vec`, or return the first error.
+                    .fold(Ok(Vec::with_capacity(len)), |result, value_result| {
+                        result.and_then(move |mut tuple_values| match value_result {
+                            Ok(value) => {
+                                tuple_values.push(value);
+                                Ok(tuple_values)
+                            }
+                            // `Result<de::Value, Self::Error>` to `Result<Vec<_>, Self::Error>`
+                            Err(e) => Err(e),
+                        })
+                    })?;
+
+                if tuple_values.len() == len {
+                    de::Deserializer::deserialize_seq(
+                        ValueDeserializer::new(Value {
+                            e: E::Array(tuple_values),
+                            start: self.value.start,
+                            end: self.value.end,
+                        }),
+                        visitor,
+                    )
+                } else {
+                    Err(Error::from_kind(ErrorKind::ExpectedTuple(len)))
+                }
+            }
+            e @ _ => Err(Error::from_kind(ErrorKind::Wanted {
+                expected: "table",
+                found: e.type_name(),
+            })),
+        }
+    }
+
+    fn struct_variant<V>(
+        self,
+        fields: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        de::Deserializer::deserialize_struct(
+            ValueDeserializer::new(self.value).with_struct_key_validation(),
+            "", // TODO: this should be the variant name
+            fields,
+            visitor,
+        )
+    }
+}
 
 impl<'a> Deserializer<'a> {
     /// Creates a new deserializer which will be deserializing the string
@@ -754,6 +947,53 @@ impl<'a> Deserializer<'a> {
         self.require_newline_after_table = require;
     }
 
+    fn tables(&mut self) -> Result<Vec<Table<'a>>, Error> {
+        let mut tables = Vec::new();
+        let mut cur_table = Table {
+            at: 0,
+            header: Vec::new(),
+            values: None,
+            array: false,
+        };
+
+        while let Some(line) = self.line()? {
+            match line {
+                Line::Table {
+                    at,
+                    mut header,
+                    array,
+                } => {
+                    if !cur_table.header.is_empty() || cur_table.values.is_some() {
+                        tables.push(cur_table);
+                    }
+                    cur_table = Table {
+                        at: at,
+                        header: Vec::new(),
+                        values: Some(Vec::new()),
+                        array: array,
+                    };
+                    loop {
+                        let part = header.next().map_err(|e| self.token_error(e));
+                        match part? {
+                            Some(part) => cur_table.header.push(part),
+                            None => break,
+                        }
+                    }
+                }
+                Line::KeyValue(key, value) => {
+                    if cur_table.values.is_none() {
+                        cur_table.values = Some(Vec::new());
+                    }
+                    self.add_dotted_key(key, value, cur_table.values.as_mut().unwrap())?;
+                }
+            }
+        }
+        if !cur_table.header.is_empty() || cur_table.values.is_some() {
+            tables.push(cur_table);
+        }
+        Ok(tables)
+    }
+
     fn line(&mut self) -> Result<Option<Line<'a>>, Error> {
         loop {
             self.eat_whitespace()?;
@@ -876,7 +1116,56 @@ impl<'a> Deserializer<'a> {
         }
     }
 
-    fn number(&mut self, Span { start, end}: Span, s: &'a str) -> Result<Value<'a>, Error> {
+    /// Returns a string or table value type.
+    ///
+    /// Used to deserialize enums. Unit enums may be represented as a string or a table, all other
+    /// structures (tuple, newtype, struct) must be represented as a table.
+    fn string_or_table(&mut self) -> Result<(Value<'a>, Option<Cow<'a, str>>), Error> {
+        match self.peek()? {
+            Some((_, Token::LeftBracket)) => {
+                let tables = self.tables()?;
+                if tables.len() != 1 {
+                    return Err(Error::from_kind(ErrorKind::Wanted {
+                        expected: "exactly 1 table",
+                        found: if tables.is_empty() {
+                            "zero tables"
+                        } else {
+                            "more than 1 table"
+                        },
+                    }));
+                }
+
+                let table = tables
+                    .into_iter()
+                    .next()
+                    .expect("Expected exactly one table");
+                let header = table
+                    .header
+                    .last()
+                    .expect("Expected at least one header value for table.");
+
+                let start = table.at;
+                let end = table
+                    .values
+                    .as_ref()
+                    .and_then(|values| values.last())
+                    .map(|&(_, ref val)| val.end)
+                    .unwrap_or_else(|| header.len());
+                Ok((
+                    Value {
+                        e: E::DottedTable(table.values.unwrap_or_else(Vec::new)),
+                        start: start,
+                        end: end,
+                    },
+                    Some(header.clone()),
+                ))
+            }
+            Some(_) => self.value().map(|val| (val, None)),
+            None => Err(self.eof()),
+        }
+    }
+
+    fn number(&mut self, Span { start, end }: Span, s: &'a str) -> Result<Value<'a>, Error> {
         let to_integer = |f| Value { e: E::Integer(f), start: start, end: end };
         if s.starts_with("0x") {
             self.integer(&s[2..], 16).map(to_integer)
@@ -1170,6 +1459,18 @@ impl<'a> Deserializer<'a> {
         Ok(result)
     }
 
+    /// Stores a value in the appropriate hierachical structure positioned based on the dotted key.
+    ///
+    /// Given the following definition: `multi.part.key = "value"`, `multi` and `part` are
+    /// intermediate parts which are mapped to the relevant fields in the deserialized type's data
+    /// hierarchy.
+    ///
+    /// # Parameters
+    ///
+    /// * `key_parts`: Each segment of the dotted key, e.g. `part.one` maps to
+    ///                `vec![Cow::Borrowed("part"), Cow::Borrowed("one")].`
+    /// * `value`: The parsed value.
+    /// * `values`: The `Vec` to store the value in.
     fn add_dotted_key(
         &self,
         mut key_parts: Vec<Cow<'a, str>>,
@@ -1191,12 +1492,12 @@ impl<'a> Deserializer<'a> {
             None => {}
         }
         // The start/end value is somewhat misleading here.
-        let inline_table = Value {
+        let table_values = Value {
             e: E::DottedTable(Vec::new()),
             start: value.start,
             end: value.end,
         };
-        values.push((key, inline_table));
+        values.push((key, table_values));
         let last_i = values.len() - 1;
         if let (_, Value { e: E::DottedTable(ref mut v), .. }) = values[last_i] {
             self.add_dotted_key(key_parts, value, v)?;
@@ -1384,8 +1685,23 @@ impl fmt::Display for Error {
             ErrorKind::EmptyTableKey => "empty table key found".fmt(f)?,
             ErrorKind::MultilineStringKey => "multiline strings are not allowed for key".fmt(f)?,
             ErrorKind::Custom => self.inner.message.fmt(f)?,
-            ErrorKind::ExpectedString => "expected string".fmt(f)?,
-            ErrorKind::DottedKeyInvalidType => "dotted key attempted to extend non-table type".fmt(f)?,
+            ErrorKind::ExpectedTuple(l) => write!(f, "expected table with length {}", l)?,
+            ErrorKind::ExpectedTupleIndex {
+                expected,
+                ref found,
+            } => write!(f, "expected table key `{}`, but was `{}`", expected, found)?,
+            ErrorKind::ExpectedEmptyTable => "expected empty table".fmt(f)?,
+            ErrorKind::DottedKeyInvalidType => {
+                "dotted key attempted to extend non-table type".fmt(f)?
+            }
+            ErrorKind::UnexpectedKeys { ref keys, available } => {
+                write!(
+                    f,
+                    "unexpected keys in table: `{:?}`, available keys: `{:?}`",
+                    keys,
+                    available
+                )?
+            }
             ErrorKind::__Nonexhaustive => panic!(),
         }
 
@@ -1429,8 +1745,11 @@ impl error::Error for Error {
             ErrorKind::EmptyTableKey => "empty table key found",
             ErrorKind::MultilineStringKey => "invalid multiline string for key",
             ErrorKind::Custom => "a custom error",
-            ErrorKind::ExpectedString => "expected string",
+            ErrorKind::ExpectedTuple(_) => "expected table length",
+            ErrorKind::ExpectedTupleIndex { .. } => "expected table key",
+            ErrorKind::ExpectedEmptyTable => "expected empty table",
             ErrorKind::DottedKeyInvalidType => "dotted key invalid type",
+            ErrorKind::UnexpectedKeys { .. } => "unexpected keys in table",
             ErrorKind::__Nonexhaustive => panic!(),
         }
     }
@@ -1509,6 +1828,21 @@ enum E<'a> {
     DottedTable(Vec<(Cow<'a, str>, Value<'a>)>),
 }
 
+impl<'a> E<'a> {
+    fn type_name(&self) -> &'static str {
+        match *self {
+            E::String(..) => "string",
+            E::Integer(..) => "integer",
+            E::Float(..) => "float",
+            E::Boolean(..) => "boolean",
+            E::Datetime(..) => "datetime",
+            E::Array(..) => "array",
+            E::InlineTable(..) => "inline table",
+            E::DottedTable(..) => "dotted table",
+        }
+    }
+}
+
 impl<'a> Value<'a> {
     fn same_type(&self, other: &Value<'a>) -> bool {
         match (&self.e, &other.e) {