version: v0.2.0

CHANGELOG.adoc

@@ -6,6 +6,12 @@
 
 == [Unreleased]
 
+== [v0.2.0] - 2022-11-25
+
+=== Added
+
+* parsing & deserialization
+
 == [v0.1.0] - 2022-11-18
 
 === Added

Cargo.toml

@@ -1,12 +1,14 @@
 [package]
 name = "serde_sjson"
-version = "0.1.0"
+version = "0.2.0"
 edition = "2021"
 keywords = ["serde", "serialization", "sjson"]
 description = "An SJSON serialization file format"
 categories = ["encoding", "parser-implementations"]
 
 [dependencies]
+nom = "7.1.1"
+nom_locate = "4.0.0"
 serde = { version = "1.0.147", default-features = false }
 
 [dev-dependencies]

src/de.rs

@@ -1,233 +1,734 @@
-pub struct Deserializer {}
+use nom::IResult;
+use serde::de::{EnumAccess, IntoDeserializer, VariantAccess};
+use serde::Deserialize;
 
-impl serde::Deserializer for Deserializer {
-    type Error;
+use crate::error::{Error, ErrorCode, Result};
+use crate::parser::*;
 
-    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
-    where
-        V: serde::de::Visitor<'de>,
-    {
-        todo!()
+pub struct Deserializer<'de> {
+    input: Span<'de>,
+    is_top_level: bool,
+}
+
+impl<'de> Deserializer<'de> {
+    #![allow(clippy::should_implement_trait)]
+    pub fn from_str(input: &'de str) -> Self {
+        Self {
+            input: Span::from(input),
+            is_top_level: true,
+        }
     }
 
-    fn deserialize_bool<V>(self, visitor: V) -> Result<V::Value, Self::Error>
-    where
-        V: serde::de::Visitor<'de>,
-    {
-        todo!()
+    fn parse(&mut self, f: &dyn Fn(Span) -> IResult<Span, Token>) -> Result<Token> {
+        f(self.input)
+            .map(|(span, token)| {
+                self.input = span;
+                token
+            })
+            .map_err(|err| self.error(ErrorCode::Message(err.to_string())))
     }
 
-    fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value, Self::Error>
-    where
-        V: serde::de::Visitor<'de>,
-    {
-        todo!()
+    fn next_token(&mut self) -> Result<Token> {
+        match parse_next_token(self.input) {
+            Ok((span, token)) => {
+                self.input = span;
+                Ok(token)
+            }
+            Err(err) => Err(self.error(ErrorCode::Message(err.to_string()))),
+        }
     }
 
-    fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value, Self::Error>
-    where
-        V: serde::de::Visitor<'de>,
-    {
-        todo!()
+    fn peek_token(&mut self) -> Result<Token> {
+        match parse_next_token(self.input) {
+            Ok((_, token)) => Ok(token),
+            Err(err) => Err(self.error(ErrorCode::Message(err.to_string()))),
+        }
     }
 
-    fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn error(&self, code: ErrorCode) -> Error {
+        Error::new(
+            code,
+            self.input.location_line(),
+            self.input.get_utf8_column(),
+            Some(self.input.fragment().to_string()),
+        )
+    }
+}
+
+pub fn from_str<'a, T>(input: &'a str) -> Result<T>
+where
+    T: Deserialize<'a>,
+{
+    let mut de = Deserializer::from_str(input);
+    let t = T::deserialize(&mut de)?;
+    if de.input.is_empty() || parse_trailing_characters(de.input).is_ok() {
+        Ok(t)
+    } else {
+        Err(de.error(ErrorCode::TrailingCharacters))
+    }
+}
+
+impl<'de, 'a> serde::de::Deserializer<'de> for &'a mut Deserializer<'de> {
+    type Error = Error;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        if self.is_top_level {
+            return Err(self.error(ErrorCode::ExpectedTopLevelObject));
+        }
+
+        match self.next_token()? {
+            Token::Boolean(val) => visitor.visit_bool::<Self::Error>(val),
+            Token::Float(val) => visitor.visit_f64(val),
+            Token::Integer(val) => visitor.visit_i64(val),
+            Token::Null => visitor.visit_unit(),
+            Token::String(val) => visitor.visit_str(&val),
+            _ => Err(self.error(ErrorCode::ExpectedValue)),
+        }
     }
 
-    fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_bool<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        if self.is_top_level {
+            return Err(self.error(ErrorCode::ExpectedTopLevelObject));
+        }
+
+        if let Ok(Token::Boolean(val)) = self.parse(&parse_bool) {
+            visitor.visit_bool(val)
+        } else {
+            Err(self.error(ErrorCode::ExpectedBoolean))
+        }
     }
 
-    fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_i64(visitor)
     }
 
-    fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_i64(visitor)
     }
 
-    fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_i64(visitor)
     }
 
-    fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        if self.is_top_level {
+            return Err(self.error(ErrorCode::ExpectedTopLevelObject));
+        }
+
+        if let Ok(Token::Integer(val)) = self.parse(&parse_integer) {
+            visitor.visit_i64(val)
+        } else {
+            Err(self.error(ErrorCode::ExpectedInteger))
+        }
     }
 
-    fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_i64(visitor)
     }
 
-    fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_i64(visitor)
     }
 
-    fn deserialize_char<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_i64(visitor)
     }
 
-    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_i64(visitor)
     }
 
-    fn deserialize_string<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_f64(visitor)
     }
 
-    fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        if self.is_top_level {
+            return Err(self.error(ErrorCode::ExpectedTopLevelObject));
+        }
+
+        if let Ok(Token::Float(val)) = self.parse(&parse_float) {
+            visitor.visit_f64(val)
+        } else {
+            Err(self.error(ErrorCode::ExpectedFloat))
+        }
     }
 
-    fn deserialize_byte_buf<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_char<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_str(visitor)
     }
 
-    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        if self.is_top_level {
+            return Err(self.error(ErrorCode::ExpectedTopLevelObject));
+        }
+
+        if let Ok(Token::String(val)) = self.parse(&parse_string) {
+            visitor.visit_str(&val)
+        } else {
+            Err(self.error(ErrorCode::ExpectedString))
+        }
     }
 
-    fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_string<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_str(visitor)
     }
 
-    fn deserialize_unit_struct<V>(
-        self,
-        name: &'static str,
-        visitor: V,
-    ) -> Result<V::Value, Self::Error>
+    fn deserialize_bytes<V>(self, _visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        unimplemented!()
     }
 
-    fn deserialize_newtype_struct<V>(
-        self,
-        name: &'static str,
-        visitor: V,
-    ) -> Result<V::Value, Self::Error>
+    fn deserialize_byte_buf<V>(self, _visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        unimplemented!()
     }
 
-    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        if self.is_top_level {
+            return Err(self.error(ErrorCode::ExpectedTopLevelObject));
+        }
+
+        if self.peek_token()? == Token::Null {
+            let _ = self.next_token()?;
+            visitor.visit_none()
+        } else {
+            visitor.visit_some(self)
+        }
     }
 
-    fn deserialize_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        if self.is_top_level {
+            return Err(self.error(ErrorCode::ExpectedTopLevelObject));
+        }
+
+        if let Ok(Token::Null) = self.parse(&parse_null) {
+            visitor.visit_unit()
+        } else {
+            Err(self.error(ErrorCode::ExpectedNull))
+        }
+    }
+
+    fn deserialize_unit_struct<V>(self, _name: &'static str, visitor: V) -> Result<V::Value>
+    where
+        V: serde::de::Visitor<'de>,
+    {
+        self.deserialize_unit(visitor)
+    }
+
+    fn deserialize_newtype_struct<V>(self, _name: &'static str, visitor: V) -> Result<V::Value>
+    where
+        V: serde::de::Visitor<'de>,
+    {
+        visitor.visit_newtype_struct(self)
+    }
+
+    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: serde::de::Visitor<'de>,
+    {
+        if self.is_top_level {
+            return Err(self.error(ErrorCode::ExpectedTopLevelObject));
+        }
+
+        if self.next_token()? != Token::ArrayStart {
+            return Err(self.error(ErrorCode::ExpectedArray));
+        }
+
+        let value = visitor.visit_seq(Separated::new(self))?;
+
+        if self.next_token()? == Token::ArrayEnd {
+            Ok(value)
+        } else {
+            Err(self.error(ErrorCode::ExpectedArrayEnd))
+        }
+    }
+
+    fn deserialize_tuple<V>(self, _len: usize, visitor: V) -> Result<V::Value>
+    where
+        V: serde::de::Visitor<'de>,
+    {
+        self.deserialize_seq(visitor)
     }
 
     fn deserialize_tuple_struct<V>(
         self,
-        name: &'static str,
-        len: usize,
+        _name: &'static str,
+        _len: usize,
         visitor: V,
-    ) -> Result<V::Value, Self::Error>
+    ) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_seq(visitor)
     }
 
-    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        if self.is_top_level {
+            self.is_top_level = false;
+
+            visitor.visit_map(Separated::new(self))
+        } else {
+            if self.next_token()? != Token::ObjectStart {
+                return Err(self.error(ErrorCode::ExpectedMap));
+            }
+
+            let value = visitor.visit_map(Separated::new(self))?;
+            if self.next_token()? == Token::ObjectEnd {
+                Ok(value)
+            } else {
+                Err(self.error(ErrorCode::ExpectedMapEnd))
+            }
+        }
     }
 
     fn deserialize_struct<V>(
         self,
-        name: &'static str,
-        fields: &'static [&'static str],
+        _name: &'static str,
+        _fields: &'static [&'static str],
         visitor: V,
-    ) -> Result<V::Value, Self::Error>
+    ) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_map(visitor)
     }
 
     fn deserialize_enum<V>(
         self,
-        name: &'static str,
-        variants: &'static [&'static str],
+        _name: &'static str,
+        _variants: &'static [&'static str],
         visitor: V,
-    ) -> Result<V::Value, Self::Error>
+    ) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        match self.next_token()? {
+            Token::String(val) => visitor.visit_enum(val.into_deserializer()),
+            Token::ObjectStart => {
+                let value = visitor.visit_enum(Enum::new(self))?;
+
+                if self.next_token()? == Token::ObjectEnd {
+                    Ok(value)
+                } else {
+                    Err(self.error(ErrorCode::ExpectedMapEnd))
+                }
+            }
+            _ => Err(self.error(ErrorCode::ExpectedEnum)),
+        }
     }
 
-    fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        if let Ok(Token::String(val)) = self.parse(&parse_identifier) {
+            visitor.visit_str(&val)
+        } else {
+            Err(self.error(ErrorCode::ExpectedString))
+        }
     }
 
-    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value>
     where
         V: serde::de::Visitor<'de>,
     {
-        todo!()
+        self.deserialize_any(visitor)
     }
 }
 
-pub fn from_str<T>() -> crate::Result<T> {}
+struct Separated<'a, 'de: 'a> {
+    de: &'a mut Deserializer<'de>,
+    first: bool,
+}
+
+impl<'a, 'de: 'a> Separated<'a, 'de> {
+    fn new(de: &'a mut Deserializer<'de>) -> Self {
+        Self { de, first: true }
+    }
+}
+
+impl<'de, 'a> serde::de::SeqAccess<'de> for Separated<'a, 'de> {
+    type Error = Error;
+
+    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
+    where
+        T: serde::de::DeserializeSeed<'de>,
+    {
+        if self.de.peek_token()? == Token::ArrayEnd {
+            return Ok(None);
+        }
+
+        if !self.first && self.de.parse(&parse_separator)? != Token::Separator {
+            return Err(self.de.error(ErrorCode::ExpectedArraySeparator));
+        }
+
+        self.first = false;
+
+        // TODO: Shouldn't I check that this is a valid value?
+        seed.deserialize(&mut *self.de).map(Some)
+    }
+}
+
+impl<'de, 'a> serde::de::MapAccess<'de> for Separated<'a, 'de> {
+    type Error = Error;
+
+    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>>
+    where
+        K: serde::de::DeserializeSeed<'de>,
+    {
+        if matches!(self.de.peek_token()?, Token::ObjectEnd | Token::Eof) {
+            return Ok(None);
+        }
+
+        if !self.first && self.de.parse(&parse_separator)? != Token::Separator {
+            return Err(self.de.error(ErrorCode::ExpectedMapSeparator));
+        }
+
+        self.first = false;
+
+        // TODO: Shouldn't I check that this is a valid identifier?
+        seed.deserialize(&mut *self.de).map(Some)
+    }
+
+    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value>
+    where
+        V: serde::de::DeserializeSeed<'de>,
+    {
+        if self.de.next_token()? != Token::Equals {
+            return Err(self.de.error(ErrorCode::ExpectedMapEquals));
+        }
+
+        // TODO: Shouldn't I check that this is a valid value?
+        seed.deserialize(&mut *self.de)
+    }
+}
+
+struct Enum<'a, 'de: 'a> {
+    de: &'a mut Deserializer<'de>,
+}
+
+impl<'a, 'de> Enum<'a, 'de> {
+    fn new(de: &'a mut Deserializer<'de>) -> Self {
+        Self { de }
+    }
+}
+
+impl<'de, 'a> EnumAccess<'de> for Enum<'a, 'de> {
+    type Error = Error;
+    type Variant = Self;
+
+    fn variant_seed<V>(self, seed: V) -> Result<(V::Value, Self::Variant)>
+    where
+        V: serde::de::DeserializeSeed<'de>,
+    {
+        let val = seed.deserialize(&mut *self.de)?;
+
+        if self.de.next_token()? == Token::Equals {
+            Ok((val, self))
+        } else {
+            Err(self.de.error(ErrorCode::ExpectedMapEquals))
+        }
+    }
+}
+
+impl<'de, 'a> VariantAccess<'de> for Enum<'a, 'de> {
+    type Error = Error;
+
+    fn unit_variant(self) -> Result<()> {
+        Err(self.de.error(ErrorCode::ExpectedString))
+    }
+
+    fn newtype_variant_seed<T>(self, seed: T) -> Result<T::Value>
+    where
+        T: serde::de::DeserializeSeed<'de>,
+    {
+        seed.deserialize(self.de)
+    }
+
+    fn tuple_variant<V>(self, _len: usize, visitor: V) -> Result<V::Value>
+    where
+        V: serde::de::Visitor<'de>,
+    {
+        serde::Deserializer::deserialize_seq(self.de, visitor)
+    }
+
+    fn struct_variant<V>(self, _fields: &'static [&'static str], visitor: V) -> Result<V::Value>
+    where
+        V: serde::de::Visitor<'de>,
+    {
+        serde::Deserializer::deserialize_map(self.de, visitor)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::path::PathBuf;
+
+    use crate::error::{Error, ErrorCode};
+    use crate::from_str;
+
+    macro_rules! assert_value_ok {
+        ($type:ty, $json:expr) => {
+            assert_value_ok!($type, Default::default(), $json)
+        };
+        ($type:ty, $expected:expr, $json:expr) => {{
+            #[derive(Debug, serde::Deserialize, PartialEq)]
+            struct Value {
+                value: $type,
+            }
+
+            let expected = Value { value: $expected };
+
+            let json = format!("value = {}", $json);
+            let actual = from_str::<Value>(&json).unwrap();
+            assert_eq!(actual, expected);
+        }};
+    }
+
+    macro_rules! assert_ok {
+        ($type:ty, $expected:expr, $json:expr) => {{
+            let actual = from_str::<$type>($json).unwrap();
+            assert_eq!(actual, $expected);
+        }};
+    }
+
+    macro_rules! assert_value_err {
+        ($type:ty, $expected:expr, $json:expr) => {{
+            #[derive(Debug, serde::Deserialize, PartialEq)]
+            struct Value {
+                value: $type,
+            }
+
+            let json = format!("value = {}", $json);
+            let actual = from_str::<Value>(&json);
+            assert_eq!(actual, Err($expected));
+        }};
+    }
+
+    #[test]
+    fn deserialize_null() {
+        assert_value_ok!((), "null");
+
+        let err = Error::new(ErrorCode::ExpectedNull, 1, 8, Some(" foo".to_string()));
+        assert_value_err!((), err, "foo");
+    }
+
+    #[test]
+    fn deserialize_bool() {
+        assert_value_ok!(bool, true, "true");
+        assert_value_ok!(bool, false, "false");
+
+        let err = Error::new(ErrorCode::ExpectedBoolean, 1, 8, Some(" foo".to_string()));
+        assert_value_err!(bool, err, "foo");
+    }
+
+    #[test]
+    fn deserialize_integer() {
+        assert_value_ok!(i64, 0, "0");
+        assert_value_ok!(i64, -1, "-1");
+        assert_value_ok!(i64, i64::MAX, i64::MAX.to_string());
+        assert_value_ok!(i64, i64::MIN, i64::MIN.to_string());
+
+        assert_value_ok!(i8, 0, "0");
+        assert_value_ok!(i8, 102, "102");
+        assert_value_ok!(i8, -102, "-102");
+        assert_value_ok!(u8, 102, "102");
+        assert_value_ok!(i16, 256, "256");
+
+        let err = Error::new(ErrorCode::ExpectedInteger, 1, 8, Some(" foo".to_string()));
+        assert_value_err!(i64, err, "foo");
+    }
+
+    #[test]
+    fn deserialize_float() {
+        assert_value_ok!(f64, 0.0, "0");
+        assert_value_ok!(f64, 0.0, "0.0");
+        assert_value_ok!(f64, -1.0, "-1");
+        assert_value_ok!(f64, -1.0, "-1.0");
+        assert_value_ok!(f64, f64::MAX, f64::MAX.to_string());
+        assert_value_ok!(f64, f64::MIN, f64::MIN.to_string());
+    }
+
+    #[test]
+    fn deserialize_vec() {
+        assert_value_ok!(Vec<u64>, vec![1, 2, 3], "[1, 2, 3]");
+        assert_value_ok!(
+            Vec<u64>,
+            vec![1, 2, 3],
+            "\
+[
+    1
+    2
+    3
+]"
+        );
+    }
+
+    #[test]
+    fn deserialize_enum() {
+        #[derive(Debug, serde::Deserialize, PartialEq)]
+        enum Animal {
+            Mouse,
+            Dog { name: String },
+            Cat(u64),
+        }
+
+        assert_value_ok!(Animal, Animal::Mouse, "Mouse");
+        assert_value_ok!(Animal, Animal::Cat(9), "{ Cat = 9 }");
+        assert_value_ok!(
+            Animal,
+            Animal::Dog {
+                name: String::from("Buddy")
+            },
+            "{ Dog = { name = Buddy }}"
+        );
+    }
+
+    // Checks the example from
+    // https://help.autodesk.com/view/Stingray/ENU/?guid=__stingray_help_managing_content_sjson_html
+    #[test]
+    fn deserialize_stingray_example() {
+        #[derive(Debug, serde::Deserialize, PartialEq)]
+        struct Win32Settings {
+            query_performance_counter_affinity_mask: u64,
+        }
+
+        #[derive(Debug, serde::Deserialize, PartialEq)]
+        struct Settings {
+            boot_script: String,
+            console_port: u16,
+            win32: Win32Settings,
+            render_config: PathBuf,
+        }
+
+        let expected = Settings {
+            boot_script: String::from("boot"),
+            console_port: 14030,
+            win32: Win32Settings {
+                query_performance_counter_affinity_mask: 0,
+            },
+            render_config: PathBuf::from("core/rendering/renderer"),
+        };
+
+        let json = r#"
+// The script that should be started when the application runs.
+boot_script = "boot"
+
+// The port on which the console server runs.
+console_port = 14030
+
+// Settings for the win32 platform
+win32 = {
+    /* Sets the affinity mask for
+       QueryPerformanceCounter() */
+    query_performance_counter_affinity_mask = 0
+}
+
+render_config = "core/rendering/renderer"
+"#;
+
+        assert_ok!(Settings, expected, json);
+    }
+
+    #[test]
+    fn deserialize_missing_top_level_struct() {
+        let json = "0";
+        let err = Error::new(
+            ErrorCode::ExpectedTopLevelObject,
+            1,
+            1,
+            Some(json.to_string()),
+        );
+        let actual = from_str::<i64>(json);
+        assert_eq!(actual, Err(err));
+
+        let json = "1.23";
+        let err = Error::new(
+            ErrorCode::ExpectedTopLevelObject,
+            1,
+            1,
+            Some(json.to_string()),
+        );
+        let actual = from_str::<f64>(json);
+        assert_eq!(actual, Err(err));
+
+        let json = "true";
+        let err = Error::new(
+            ErrorCode::ExpectedTopLevelObject,
+            1,
+            1,
+            Some(json.to_string()),
+        );
+        let actual = from_str::<bool>(json);
+        assert_eq!(actual, Err(err));
+
+        let json = "null";
+        let err = Error::new(
+            ErrorCode::ExpectedTopLevelObject,
+            1,
+            1,
+            Some(json.to_string()),
+        );
+        let actual = from_str::<()>(json);
+        assert_eq!(actual, Err(err));
+    }
+}

src/error.rs

@@ -1,36 +1,39 @@
-use std::{fmt, io};
+use std::fmt;
 
 pub type Result<T> = std::result::Result<T, Error>;
 
+#[derive(PartialEq)]
 pub struct Error {
     inner: Box<ErrorImpl>,
 }
 
+#[derive(PartialEq)]
 struct ErrorImpl {
     code: ErrorCode,
-    line: usize,
+    line: u32,
     column: usize,
+    fragment: Option<String>,
 }
 
-// TODO: Remove once they are constructed
-#[allow(dead_code)]
+#[derive(PartialEq)]
 pub(crate) enum ErrorCode {
     // Generic error built from a message or different error
     Message(String),
-    // Wrap inner I/O errors
-    Io(io::Error),
-    Eof,
-    Syntax,
-    ExpectedTopLevelObject,
-    ExpectedBoolean,
-    ExpectedInteger,
-    ExpectedString,
-    ExpectedNull,
     ExpectedArray,
     ExpectedArrayEnd,
+    ExpectedArraySeparator,
+    ExpectedBoolean,
+    ExpectedEnum,
+    ExpectedFloat,
+    ExpectedInteger,
     ExpectedMap,
-    ExpectedMapEquals,
     ExpectedMapEnd,
+    ExpectedMapEquals,
+    ExpectedMapSeparator,
+    ExpectedNull,
+    ExpectedString,
+    ExpectedTopLevelObject,
+    ExpectedValue,
     TrailingCharacters,
 }
 
@@ -38,19 +41,25 @@ impl fmt::Display for ErrorCode {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             ErrorCode::Message(msg) => f.write_str(msg),
-            ErrorCode::Io(err) => fmt::Display::fmt(err, f),
-            ErrorCode::Eof => f.write_str("unexpected end of input"),
-            ErrorCode::Syntax => f.write_str("syntax error"),
-            ErrorCode::ExpectedTopLevelObject => f.write_str("expected object at the top level"),
-            ErrorCode::ExpectedBoolean => f.write_str("expected a boolean value"),
-            ErrorCode::ExpectedInteger => f.write_str("expected an integer value"),
-            ErrorCode::ExpectedString => f.write_str("expected a string value"),
-            ErrorCode::ExpectedNull => f.write_str("expected null"),
             ErrorCode::ExpectedArray => f.write_str("expected an array value"),
             ErrorCode::ExpectedArrayEnd => f.write_str("expected an array end delimiter"),
-            ErrorCode::ExpectedMap => f.write_str("expected an object value"),
-            ErrorCode::ExpectedMapEquals => f.write_str("expected a '=' between key and value"),
+            ErrorCode::ExpectedArraySeparator => {
+                f.write_str("expected comma or newline between array entries")
+            }
+            ErrorCode::ExpectedBoolean => f.write_str("expected a boolean value"),
+            ErrorCode::ExpectedEnum => f.write_str("expected string or object"),
+            ErrorCode::ExpectedFloat => f.write_str("expected floating point number"),
+            ErrorCode::ExpectedInteger => f.write_str("expected an integer value"),
+            ErrorCode::ExpectedMap => f.write_str("expected an object"),
             ErrorCode::ExpectedMapEnd => f.write_str("expected an object end delimiter"),
+            ErrorCode::ExpectedMapEquals => f.write_str("expected a '=' between key and value"),
+            ErrorCode::ExpectedMapSeparator => {
+                f.write_str("expected comma or newline between object entries")
+            }
+            ErrorCode::ExpectedNull => f.write_str("expected null"),
+            ErrorCode::ExpectedString => f.write_str("expected a string value"),
+            ErrorCode::ExpectedTopLevelObject => f.write_str("expected object at the top level"),
+            ErrorCode::ExpectedValue => f.write_str("expected a value"),
             ErrorCode::TrailingCharacters => f.write_str("unexpected trailing characters"),
         }
     }
@@ -80,10 +89,11 @@ impl fmt::Debug for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
-            "Error({:?}, line: {}, column: {})",
+            "Error({:?}, line: {}, column: {}, fragment: {:?})",
             self.inner.code.to_string(),
             self.inner.line,
-            self.inner.column
+            self.inner.column,
+            self.inner.fragment,
         )
     }
 }
@@ -97,6 +107,7 @@ impl serde::de::Error for Error {
             code: ErrorCode::Message(msg.to_string()),
             line: 0,
             column: 0,
+            fragment: None,
         });
         Self { inner }
     }
@@ -111,6 +122,7 @@ impl serde::ser::Error for Error {
             code: ErrorCode::Message(msg.to_string()),
             line: 0,
             column: 0,
+            fragment: None,
         });
         Self { inner }
     }
@@ -119,9 +131,14 @@ impl serde::ser::Error for Error {
 impl std::error::Error for Error {}
 
 impl Error {
-    pub(crate) fn new(code: ErrorCode, line: usize, column: usize) -> Self {
+    pub(crate) fn new(code: ErrorCode, line: u32, column: usize, fragment: Option<String>) -> Self {
         Self {
-            inner: Box::new(ErrorImpl { code, line, column }),
+            inner: Box::new(ErrorImpl {
+                code,
+                line,
+                column,
+                fragment,
+            }),
         }
     }
 }

src/lib.rs

@@ -1,7 +1,8 @@
-// mod de;
+mod de;
 mod error;
+mod parser;
 mod ser;
 
-// pub use de::{from_str, Deserializer};
+pub use de::{from_str, Deserializer};
 pub use error::{Error, Result};
 pub use ser::{to_string, Serializer};

src/parser.rs

@@ -0,0 +1,305 @@
+use nom::branch::alt;
+use nom::bytes::complete::{escaped, tag, take_until};
+use nom::character::complete::{
+    alpha1, alphanumeric1, char, digit1, none_of, not_line_ending, one_of,
+};
+use nom::combinator::{cut, eof, map, map_res, opt, recognize, value};
+use nom::multi::{many0_count, many1_count};
+use nom::number::complete::double;
+use nom::sequence::{delimited, pair, preceded, terminated, tuple};
+use nom::IResult;
+use nom_locate::LocatedSpan;
+
+pub(crate) type Span<'a> = LocatedSpan<&'a str>;
+
+#[derive(Clone, Debug, PartialEq)]
+pub(crate) enum Token {
+    ArrayEnd,
+    ArrayStart,
+    Boolean(bool),
+    Eof,
+    Equals,
+    Float(f64),
+    Integer(i64),
+    Null,
+    ObjectEnd,
+    ObjectStart,
+    Separator,
+    String(String),
+}
+
+fn horizontal_whitespace(input: Span) -> IResult<Span, char> {
+    one_of(" \t")(input)
+}
+
+fn whitespace(input: Span) -> IResult<Span, char> {
+    one_of(" \n\r\t")(input)
+}
+
+fn null(input: Span) -> IResult<Span, ()> {
+    value((), tag("null"))(input)
+}
+
+fn separator(input: Span) -> IResult<Span, &str> {
+    map(alt((tag(","), tag("\n"))), |val: Span| *val.fragment())(input)
+}
+
+fn bool(input: Span) -> IResult<Span, bool> {
+    alt((value(true, tag("true")), value(false, tag("false"))))(input)
+}
+
+fn integer(input: Span) -> IResult<Span, i64> {
+    map_res(recognize(tuple((opt(char('-')), digit1))), |val: Span| {
+        val.fragment().parse::<i64>()
+    })(input)
+}
+
+fn float(input: Span) -> IResult<Span, f64> {
+    double(input)
+}
+
+fn identifier(input: Span) -> IResult<Span, &str> {
+    let leading = alt((alpha1, tag("_")));
+    let trailing = many0_count(alt((alphanumeric1, tag("_"))));
+    let ident = pair(leading, trailing);
+
+    map(recognize(ident), |val: Span| *val.fragment())(input)
+}
+
+fn string_content(input: Span) -> IResult<Span, &str> {
+    // TODO: Handle Unicode escapes
+    map(
+        alt((
+            escaped(none_of("\n\\\""), '\\', one_of(r#""rtn\"#)),
+            tag(""),
+        )),
+        |val: Span| *val.fragment(),
+    )(input)
+}
+
+fn delimited_string(input: Span) -> IResult<Span, &str> {
+    preceded(char('"'), cut(terminated(string_content, char('"'))))(input)
+}
+
+fn string(input: Span) -> IResult<Span, &str> {
+    alt((identifier, delimited_string))(input)
+}
+
+fn line_comment(input: Span) -> IResult<Span, &str> {
+    map(
+        preceded(tag("//"), alt((not_line_ending, eof))),
+        |val: Span| *val.fragment(),
+    )(input)
+}
+
+fn block_comment(input: Span) -> IResult<Span, &str> {
+    map(
+        delimited(tag("/*"), take_until("*/"), tag("*/")),
+        |val: Span| *val.fragment(),
+    )(input)
+}
+
+fn comment(input: Span) -> IResult<Span, &str> {
+    alt((line_comment, block_comment))(input)
+}
+
+fn optional(input: Span) -> IResult<Span, ()> {
+    let whitespace = value((), whitespace);
+    let comment = value((), comment);
+    let empty = value((), tag(""));
+    let content = value((), many1_count(alt((whitespace, comment))));
+
+    alt((content, empty))(input)
+}
+
+pub(crate) fn parse_next_token(input: Span) -> IResult<Span, Token> {
+    preceded(
+        opt(optional),
+        alt((
+            // Order is important here.
+            // Certain valid strings like "null", "true" or "false" need to be
+            // matched to their special value.
+            // Integer-like numbers need to be matched to that, but are valid floats, too.
+            value(Token::Eof, eof),
+            value(Token::Separator, separator),
+            value(Token::ObjectStart, tag("{")),
+            value(Token::ObjectEnd, tag("}")),
+            value(Token::ArrayStart, tag("[")),
+            value(Token::ArrayEnd, tag("]")),
+            value(Token::Equals, tag("=")),
+            value(Token::Null, null),
+            map(bool, Token::Boolean),
+            map(integer, Token::Integer),
+            map(float, Token::Float),
+            map(string, |val| Token::String(val.to_string())),
+        )),
+    )(input)
+}
+
+pub(crate) fn parse_trailing_characters(input: Span) -> IResult<Span, ()> {
+    value((), optional)(input)
+}
+
+pub(crate) fn parse_null(input: Span) -> IResult<Span, Token> {
+    preceded(optional, value(Token::Null, null))(input)
+}
+
+pub(crate) fn parse_separator(input: Span) -> IResult<Span, Token> {
+    preceded(
+        opt(horizontal_whitespace),
+        value(Token::Separator, separator),
+    )(input)
+}
+
+pub(crate) fn parse_bool(input: Span) -> IResult<Span, Token> {
+    preceded(optional, map(bool, Token::Boolean))(input)
+}
+
+pub(crate) fn parse_integer(input: Span) -> IResult<Span, Token> {
+    preceded(optional, map(integer, Token::Integer))(input)
+}
+
+pub(crate) fn parse_float(input: Span) -> IResult<Span, Token> {
+    preceded(optional, map(float, Token::Float))(input)
+}
+
+pub(crate) fn parse_identifier(input: Span) -> IResult<Span, Token> {
+    preceded(
+        optional,
+        map(identifier, |val| Token::String(val.to_string())),
+    )(input)
+}
+
+pub(crate) fn parse_string(input: Span) -> IResult<Span, Token> {
+    preceded(optional, map(string, |val| Token::String(val.to_string())))(input)
+}
+
+#[cfg(test)]
+mod test {
+    use nom::error::{Error, ErrorKind};
+    use nom::Err;
+
+    use super::*;
+
+    macro_rules! assert_ok {
+        ($input:expr, $parser:ident, $remain:expr, $output:expr) => {{
+            let res = super::$parser(Span::from($input));
+            assert_eq!(
+                res.map(|(span, res)| { (*span, res) }),
+                Ok(($remain, $output))
+            );
+        }};
+    }
+
+    macro_rules! assert_err {
+        ($input:expr, $parser:ident, $kind:expr) => {{
+            {
+                let input = Span::from($input);
+                assert_eq!(
+                    super::$parser(input),
+                    Err(Err::Error(Error::new(input, $kind)))
+                );
+            }
+        }};
+    }
+
+    #[test]
+    fn parse_optional() {
+        assert_ok!("\n", whitespace, "", '\n');
+        assert_ok!("\t", whitespace, "", '\t');
+        assert_ok!("  ", whitespace, " ", ' ');
+        assert_ok!("/* foo bar */", comment, "", " foo bar ");
+        assert_ok!("// foo", comment, "", " foo");
+        assert_ok!("// foo\n", comment, "\n", " foo");
+
+        assert_ok!("", optional, "", ());
+        assert_ok!("\t\n", optional, "", ());
+        assert_ok!("\n\t", optional, "", ());
+        assert_ok!("// foo", optional, "", ());
+        assert_ok!("\n\t// foo\n\t/* foo\n\tbar */\n", optional, "", ());
+    }
+
+    #[test]
+    fn parse_integer() {
+        assert_ok!("3", integer, "", 3);
+        assert_ok!("12345", integer, "", 12345);
+        assert_ok!("-12345", integer, "", -12345);
+        assert_ok!("12345   ", integer, "   ", 12345);
+
+        assert_err!("   12345", integer, ErrorKind::Digit);
+
+        assert_ok!("    12345", parse_integer, "", Token::Integer(12345));
+        assert_ok!("\n12345", parse_integer, "", Token::Integer(12345));
+        assert_ok!("\t12345", parse_integer, "", Token::Integer(12345));
+    }
+
+    #[test]
+    fn parse_float() {
+        assert_ok!("3", float, "", 3.0);
+        assert_ok!("3.0", float, "", 3.0);
+        assert_ok!("3.1415", float, "", 3.1415);
+        assert_ok!("-123.456789", float, "", -123.456789);
+        assert_err!("   1.23", float, ErrorKind::Float);
+        assert_ok!("1.23   ", float, "   ", 1.23);
+    }
+
+    #[test]
+    fn parse_raw_string() {
+        assert_ok!("foo", identifier, "", "foo");
+        assert_ok!("foo123", identifier, "", "foo123");
+        assert_ok!("foo_bar", identifier, "", "foo_bar");
+        assert_ok!("_foo", identifier, "", "_foo");
+        assert_ok!("foo bar", identifier, " bar", "foo");
+
+        assert_err!("123", identifier, ErrorKind::Tag);
+        assert_err!("1foo", identifier, ErrorKind::Tag);
+        assert_err!("\"foo\"", identifier, ErrorKind::Tag);
+    }
+
+    #[test]
+    fn parse_delimited_string() {
+        assert_ok!(r#""""#, delimited_string, "", "");
+        assert_ok!(r#""foo""#, delimited_string, "", "foo");
+        assert_ok!(r#""\"foo""#, delimited_string, "", r#"\"foo"#);
+        assert_ok!(r#""foo bar""#, delimited_string, "", "foo bar");
+        assert_ok!(r#""foo123""#, delimited_string, "", "foo123");
+        assert_ok!(r#""123foo""#, delimited_string, "", "123foo");
+        assert_ok!(r#""foo\"bar""#, delimited_string, "", "foo\\\"bar");
+
+        assert_err!("foo\"", delimited_string, ErrorKind::Char);
+
+        {
+            let input = Span::from("\"foo");
+            assert_eq!(
+                delimited_string(input),
+                Err(Err::Failure(Error::new(
+                    unsafe { Span::new_from_raw_offset(4, 1, "", ()) },
+                    ErrorKind::Char
+                )))
+            );
+        }
+
+        {
+            let input = Span::from("\"foo\nbar\"");
+            assert_eq!(
+                delimited_string(input),
+                Err(Err::Failure(Error::new(
+                    unsafe { Span::new_from_raw_offset(4, 1, "\nbar\"", ()) },
+                    ErrorKind::Char
+                )))
+            );
+        }
+    }
+
+    #[test]
+    fn parse_line_comment() {
+        assert_ok!("// foo", line_comment, "", " foo");
+        assert_ok!("// foo\n", line_comment, "\n", " foo");
+    }
+
+    #[test]
+    fn parse_block_comment() {
+        assert_ok!("/* foo */", block_comment, "", " foo ");
+        assert_ok!("/*\n\tfoo\nbar\n*/", block_comment, "", "\n\tfoo\nbar\n");
+    }
+}

src/ser.rs

@@ -33,7 +33,7 @@ impl Serializer {
 
     fn ensure_top_level_struct(&self) -> Result<()> {
         if self.level == 0 {
-            return Err(Error::new(ErrorCode::ExpectedTopLevelObject, 0, 0));
+            return Err(Error::new(ErrorCode::ExpectedTopLevelObject, 0, 0, None));
         }
 
         Ok(())