Make AST generic over string values

This commit introduces a Text trait that is
used for representing text data in the AST.
This enables using the ast with &str references only,
with Cow, or just as now in an owned fashion (with String).

To prevent a wrapper type, the Text trait has an associated type 'Value'
that represents the actual value and has to be used in the AST nodes.

Author: theduke

src/common.rs

@@ -1,4 +1,4 @@
-use std::collections::BTreeMap;
+use std::{fmt, collections::BTreeMap};
 
 use combine::{parser, ParseResult, Parser};
 use combine::easy::Error;
@@ -9,15 +9,29 @@ use tokenizer::{Kind as T, Token, TokenStream};
 use helpers::{punct, ident, kind, name};
 use position::Pos;
 
+/// Text abstracts over types that hold a string value.
+/// It is used to make the AST generic over the string type.
+pub trait Text<'a>: 'a {
+    type Value: 'a + From<&'a str> + AsRef<str> + std::borrow::Borrow<str> + PartialEq + Eq + PartialOrd + Ord + fmt::Debug + Clone; 
+}
+
+impl<'a> Text<'a> for &'a str {
+    type Value = Self;
+}
 
-/// An alias for string, used where graphql expects a name
-pub type Name = String;
+impl<'a> Text<'a> for String {
+    type Value = String;
+}
+
+impl<'a> Text<'a> for std::borrow::Cow<'a, str> {
+    type Value = Self;
+}
 
 #[derive(Debug, Clone, PartialEq)]
-pub struct Directive {
+pub struct Directive<'a, T: Text<'a>> {
     pub position: Pos,
-    pub name: Name,
-    pub arguments: Vec<(Name, Value)>,
+    pub name: T::Value,
+    pub arguments: Vec<(T::Value, Value<'a, T>)>,
 }
 
 /// This represents integer number
@@ -32,23 +46,23 @@ pub struct Directive {
 pub struct Number(pub(crate) i64);
 
 #[derive(Debug, Clone, PartialEq)]
-pub enum Value {
-    Variable(Name),
+pub enum Value<'a, T: Text<'a>> {
+    Variable(T::Value),
     Int(Number),
     Float(f64),
     String(String),
     Boolean(bool),
     Null,
-    Enum(Name),
-    List(Vec<Value>),
-    Object(BTreeMap<Name, Value>),
+    Enum(T::Value),
+    List(Vec<Value<'a, T>>),
+    Object(BTreeMap<T::Value, Value<'a, T>>),
 }
 
 #[derive(Debug, Clone, PartialEq)]
-pub enum Type {
-    NamedType(Name),
-    ListType(Box<Type>),
-    NonNullType(Box<Type>),
+pub enum Type<'a, T: Text<'a>> {
+    NamedType(T::Value),
+    ListType(Box<Type<'a, T>>),
+    NonNullType(Box<Type<'a, T>>),
 }
 
 impl Number {
@@ -64,25 +78,27 @@ impl From<i32> for Number {
     }
 }
 
-pub fn directives<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Vec<Directive>, TokenStream<'a>>
+pub fn directives<'a, T>(input: &mut TokenStream<'a>)
+    -> ParseResult<Vec<Directive<'a, T>>, TokenStream<'a>>
+    where T: Text<'a>, 
 {
     many(position()
         .skip(punct("@"))
-        .and(name())
+        .and(name::<'a, T>())
         .and(parser(arguments))
         .map(|((position, name), arguments)| {
             Directive { position, name, arguments }
         }))
     .parse_stream(input)
 }
 
-pub fn arguments<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Vec<(String, Value)>, TokenStream<'a>>
+pub fn arguments<'a, T>(input: &mut TokenStream<'a>)
+    -> ParseResult<Vec<(T::Value, Value<'a, T>)>, TokenStream<'a>>
+    where T: Text<'a>,
 {
     optional(
         punct("(")
-        .with(many1(name()
+        .with(many1(name::<'a, T>()
             .skip(punct(":"))
             .and(parser(value))))
         .skip(punct(")")))
@@ -92,27 +108,29 @@ pub fn arguments<'a>(input: &mut TokenStream<'a>)
     .parse_stream(input)
 }
 
-pub fn int_value<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Value, TokenStream<'a>>
+pub fn int_value<'a, S>(input: &mut TokenStream<'a>)
+    -> ParseResult<Value<'a, S>, TokenStream<'a>>
+    where S: Text<'a>
 {
     kind(T::IntValue).and_then(|tok| tok.value.parse())
             .map(Number).map(Value::Int)
     .parse_stream(input)
 }
 
-pub fn float_value<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Value, TokenStream<'a>>
+pub fn float_value<'a, S>(input: &mut TokenStream<'a>)
+    -> ParseResult<Value<'a, S>, TokenStream<'a>>
+    where S: Text<'a>
 {
     kind(T::FloatValue).and_then(|tok| tok.value.parse())
             .map(Value::Float)
     .parse_stream(input)
 }
 
-fn unquote_block_string(src: &str) -> Result<String, Error<Token, Token>> {
+fn unquote_block_string<'a>(src: &'a str) -> Result<String, Error<Token<'a>, Token<'a>>> {
     debug_assert!(src.starts_with("\"\"\"") && src.ends_with("\"\"\""));
     let indent = src[3..src.len()-3].lines().skip(1)
         .filter_map(|line| {
-            let trimmed = line.trim_left().len();
+            let trimmed = line.trim_start().len();
             if trimmed > 0 {
                 Some(line.len() - trimmed)
             } else {
@@ -144,7 +162,8 @@ fn unquote_block_string(src: &str) -> Result<String, Error<Token, Token>> {
     Ok(result)
 }
 
-fn unquote_string(s: &str) -> Result<String, Error<Token, Token>> {
+fn unquote_string<'a>(s: &'a str) -> Result<String, Error<Token, Token>> 
+{
     let mut res = String::with_capacity(s.len());
     debug_assert!(s.starts_with('"') && s.ends_with('"'));
     let mut chars = s[1..s.len()-1].chars();
@@ -183,67 +202,73 @@ pub fn string<'a>(input: &mut TokenStream<'a>)
     )).parse_stream(input)
 }
 
-pub fn string_value<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Value, TokenStream<'a>>
+pub fn string_value<'a, S>(input: &mut TokenStream<'a>)
+    -> ParseResult<Value<'a, S>, TokenStream<'a>>
+    where S: Text<'a>,
 {
     kind(T::StringValue).and_then(|tok| unquote_string(tok.value))
         .map(Value::String)
     .parse_stream(input)
 }
 
-pub fn block_string_value<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Value, TokenStream<'a>>
+pub fn block_string_value<'a, S>(input: &mut TokenStream<'a>)
+    -> ParseResult<Value<'a, S>, TokenStream<'a>>
+    where S: Text<'a>,
 {
     kind(T::BlockString).and_then(|tok| unquote_block_string(tok.value))
         .map(Value::String)
     .parse_stream(input)
 }
 
-pub fn plain_value<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Value, TokenStream<'a>>
+pub fn plain_value<'a, T>(input: &mut TokenStream<'a>)
+    -> ParseResult<Value<'a, T>, TokenStream<'a>>
+    where T: Text<'a>,
 {
     ident("true").map(|_| Value::Boolean(true))
     .or(ident("false").map(|_| Value::Boolean(false)))
     .or(ident("null").map(|_| Value::Null))
-    .or(name().map(Value::Enum))
+    .or(name::<'a, T>().map(Value::Enum))
     .or(parser(int_value))
     .or(parser(float_value))
     .or(parser(string_value))
     .or(parser(block_string_value))
     .parse_stream(input)
 }
 
-pub fn value<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Value, TokenStream<'a>>
+pub fn value<'a, T>(input: &mut TokenStream<'a>)
+    -> ParseResult<Value<'a, T>, TokenStream<'a>>
+    where T: Text<'a>,
 {
     parser(plain_value)
-    .or(punct("$").with(name()).map(Value::Variable))
+    .or(punct("$").with(name::<'a, T>()).map(Value::Variable))
     .or(punct("[").with(many(parser(value))).skip(punct("]"))
         .map(Value::List))
     .or(punct("{")
-        .with(many(name().skip(punct(":")).and(parser(value))))
+        .with(many(name::<'a, T>().skip(punct(":")).and(parser(value))))
         .skip(punct("}"))
         .map(Value::Object))
     .parse_stream(input)
 }
 
-pub fn default_value<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Value, TokenStream<'a>>
+pub fn default_value<'a, T>(input: &mut TokenStream<'a>)
+    -> ParseResult<Value<'a, T>, TokenStream<'a>>
+    where T: Text<'a>,
 {
     parser(plain_value)
     .or(punct("[").with(many(parser(default_value))).skip(punct("]"))
         .map(Value::List))
     .or(punct("{")
-        .with(many(name().skip(punct(":")).and(parser(default_value))))
+        .with(many(name::<'a, T>().skip(punct(":")).and(parser(default_value))))
         .skip(punct("}"))
         .map(Value::Object))
     .parse_stream(input)
 }
 
-pub fn parse_type<'a>(input: &mut TokenStream<'a>)
-    -> ParseResult<Type, TokenStream<'a>>
+pub fn parse_type<'a, T>(input: &mut TokenStream<'a>)
+    -> ParseResult<Type<'a, T>, TokenStream<'a>>
+    where T: Text<'a>,
 {
-    name().map(Type::NamedType)
+    name::<'a, T>().map(Type::NamedType)
     .or(punct("[")
         .with(parser(parse_type))
         .skip(punct("]"))

src/format.rs

@@ -130,7 +130,9 @@ impl<'a> Formatter<'a> {
     }
 }
 
-pub(crate) fn format_directives(dirs: &[Directive], f: &mut Formatter) {
+pub(crate) fn format_directives<'a, T>(dirs: &[Directive<'a, T>], f: &mut Formatter) 
+    where T: ::common::Text<'a>,
+{
     for dir in dirs {
         f.write(" ");
         dir.display(f);
@@ -147,4 +149,16 @@ macro_rules! impl_display {
             }
         )+
     };
+
+    ('a $($typ: ident, )+) => {
+        $(
+            impl<'a, T> fmt::Display for $typ<'a, T> 
+                where T: Text<'a>,
+            {
+                fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                    f.write_str(&to_string(self))
+                }
+            }
+        )+
+    };
 }

src/helpers.rs

@@ -7,6 +7,8 @@ use combine::stream::easy::{Error, Errors, Info};
 use tokenizer::{TokenStream, Kind, Token};
 use position::Pos;
 
+use super::common::{Text};
+
 
 #[derive(Debug, Clone)]
 pub struct TokenMatch<'a> {
@@ -15,8 +17,10 @@ pub struct TokenMatch<'a> {
 }
 
 #[derive(Debug, Clone)]
-pub struct NameMatch<'a> {
-    phantom: PhantomData<&'a u8>,
+pub struct NameMatch<'a, T> 
+    where T: Text<'a>
+{
+    phantom: PhantomData<(&'a T)>,
 }
 
 #[derive(Debug, Clone)]
@@ -34,7 +38,9 @@ pub fn kind<'x>(kind: Kind) -> TokenMatch<'x> {
     }
 }
 
-pub fn name<'x>() -> NameMatch<'x> {
+pub fn name<'a, T>() -> NameMatch<'a, T> 
+    where T: Text<'a>
+{
     NameMatch {
         phantom: PhantomData,
     }
@@ -60,15 +66,15 @@ impl<'a> Parser for TokenMatch<'a> {
     }
 }
 
-pub fn punct<'x>(value: &'static str) -> Value<'x> {
+pub fn punct<'s>(value: &'static str) -> Value<'s> {
     Value {
         kind: Kind::Punctuator,
         value: value,
         phantom: PhantomData,
     }
 }
 
-pub fn ident<'x>(value: &'static str) -> Value<'x> {
+pub fn ident<'s>(value: &'static str) -> Value<'s> {
     Value {
         kind: Kind::Name,
         value: value,
@@ -97,17 +103,19 @@ impl<'a> Parser for Value<'a> {
     }
 }
 
-impl<'a> Parser for NameMatch<'a> {
+impl<'a, S> Parser for NameMatch<'a, S> 
+    where S: Text<'a>,
+{
     type Input = TokenStream<'a>;
-    type Output = String;
+    type Output = S::Value;
     type PartialState = ();
 
     #[inline]
     fn parse_lazy(&mut self, input: &mut Self::Input)
         -> ConsumedResult<Self::Output, Self::Input>
     {
         satisfy(|c: Token<'a>| c.kind == Kind::Name)
-        .map(|t: Token<'a>| t.value.to_string())
+        .map(|t: Token<'a>| -> S::Value { S::Value::from(t.value) } )
         .parse_lazy(input)
     }
 

src/lib.rs

@@ -25,7 +25,7 @@
 //! use graphql_parser::parse_query;
 //!
 //! # fn parse() -> Result<(), failure::Error> {
-//! let ast = parse_query("query MyQuery { field1, field2 }")?;
+//! let ast = parse_query::<&str>("query MyQuery { field1, field2 }")?;
 //! // Format canonical representation
 //! assert_eq!(format!("{}", ast), "\
 //! query MyQuery {
@@ -49,7 +49,7 @@
 //! use graphql_parser::parse_schema;
 //!
 //! # fn parse() -> Result<(), failure::Error> {
-//! let ast = parse_schema(r#"
+//! let ast = parse_schema::<String>(r#"
 //!     schema {
 //!         query: Query
 //!     }
@@ -64,7 +64,7 @@
 //!     type User {
 //!         name: String!,
 //!     }
-//! "#)?;
+//! "#)?.to_owned();
 //! // Format canonical representation
 //! assert_eq!(format!("{}", ast), "\
 //! schema {