feat(value): Value literal macro

liquid-value/src/lib.rs

@@ -11,6 +11,8 @@ extern crate itertools;
 extern crate liquid_error;
 extern crate num_traits;
 
+mod macros;
+
 mod path;
 mod scalar;
 mod ser;

liquid-value/src/macros.rs

@@ -0,0 +1,242 @@
+/// A liquid_value::Value literal.
+///
+/// # Example
+///
+/// ```rust
+/// # #[macro_use]
+/// # extern crate liquid_value;
+/// #
+/// # fn main() {
+/// liquid_value!(5)
+///     .as_scalar().unwrap()
+///     .to_integer().unwrap();
+/// liquid_value!("foo")
+///     .as_scalar().unwrap()
+///     .to_str();
+/// liquid_value!([1, 2, 3])
+///     .as_array().unwrap();
+/// liquid_value!({"foo": 5})
+///     .as_object().unwrap();
+/// # }
+/// ```
+#[macro_export(local_inner_macros)]
+macro_rules! liquid_value {
+    ($($value:tt)+) => {
+        value_internal!($($value)+)
+    };
+}
+
+#[macro_export(local_inner_macros)]
+#[doc(hidden)]
+macro_rules! value_internal {
+    // Done with trailing comma.
+    (@array [$($elems:expr,)*]) => {
+        value_internal_vec![$($elems,)*]
+    };
+
+    // Done without trailing comma.
+    (@array [$($elems:expr),*]) => {
+        value_internal_vec![$($elems),*]
+    };
+
+    // Next element is `nil`.
+    (@array [$($elems:expr,)*] nil $($rest:tt)*) => {
+        value_internal!(@array [$($elems,)* value_internal!(nil)] $($rest)*)
+    };
+
+    // Next element is `true`.
+    (@array [$($elems:expr,)*] true $($rest:tt)*) => {
+        value_internal!(@array [$($elems,)* value_internal!(true)] $($rest)*)
+    };
+
+    // Next element is `false`.
+    (@array [$($elems:expr,)*] false $($rest:tt)*) => {
+        value_internal!(@array [$($elems,)* value_internal!(false)] $($rest)*)
+    };
+
+    // Next element is an array.
+    (@array [$($elems:expr,)*] [$($array:tt)*] $($rest:tt)*) => {
+        value_internal!(@array [$($elems,)* value_internal!([$($array)*])] $($rest)*)
+    };
+
+    // Next element is a map.
+    (@array [$($elems:expr,)*] {$($map:tt)*} $($rest:tt)*) => {
+        value_internal!(@array [$($elems,)* value_internal!({$($map)*})] $($rest)*)
+    };
+
+    // Next element is an expression followed by comma.
+    (@array [$($elems:expr,)*] $next:expr, $($rest:tt)*) => {
+        value_internal!(@array [$($elems,)* value_internal!($next),] $($rest)*)
+    };
+
+    // Last element is an expression with no trailing comma.
+    (@array [$($elems:expr,)*] $last:expr) => {
+        value_internal!(@array [$($elems,)* value_internal!($last)])
+    };
+
+    // Comma after the most recent element.
+    (@array [$($elems:expr),*] , $($rest:tt)*) => {
+        value_internal!(@array [$($elems,)*] $($rest)*)
+    };
+
+    // Unexpected token after most recent element.
+    (@array [$($elems:expr),*] $unexpected:tt $($rest:tt)*) => {
+        value_unexpected!($unexpected)
+    };
+
+    //////////////////////////////////////////////////////////////////////////
+    // TT muncher for parsing the inside of an object {...}. Each entry is
+    // inserted into the given map variable.
+    //
+    // Must be invoked as: value_internal!(@object $map () ($($tt)*) ($($tt)*))
+    //
+    // We require two copies of the input tokens so that we can match on one
+    // copy and trigger errors on the other copy.
+    //////////////////////////////////////////////////////////////////////////
+
+    // Done.
+    (@object $object:ident () () ()) => {};
+
+    // Insert the current entry followed by trailing comma.
+    (@object $object:ident [$($key:tt)+] ($value:expr) , $($rest:tt)*) => {
+        let _ = $object.insert(($($key)+).into(), $value);
+        value_internal!(@object $object () ($($rest)*) ($($rest)*));
+    };
+
+    // Current entry followed by unexpected token.
+    (@object $object:ident [$($key:tt)+] ($value:expr) $unexpected:tt $($rest:tt)*) => {
+        value_unexpected!($unexpected);
+    };
+
+    // Insert the last entry without trailing comma.
+    (@object $object:ident [$($key:tt)+] ($value:expr)) => {
+        let _ = $object.insert(($($key)+).into(), $value);
+    };
+
+    // Next value is `nil`.
+    (@object $object:ident ($($key:tt)+) (: nil $($rest:tt)*) $copy:tt) => {
+        value_internal!(@object $object [$($key)+] (value_internal!(nil)) $($rest)*);
+    };
+
+    // Next value is `true`.
+    (@object $object:ident ($($key:tt)+) (: true $($rest:tt)*) $copy:tt) => {
+        value_internal!(@object $object [$($key)+] (value_internal!(true)) $($rest)*);
+    };
+
+    // Next value is `false`.
+    (@object $object:ident ($($key:tt)+) (: false $($rest:tt)*) $copy:tt) => {
+        value_internal!(@object $object [$($key)+] (value_internal!(false)) $($rest)*);
+    };
+
+    // Next value is an array.
+    (@object $object:ident ($($key:tt)+) (: [$($array:tt)*] $($rest:tt)*) $copy:tt) => {
+        value_internal!(@object $object [$($key)+] (value_internal!([$($array)*])) $($rest)*);
+    };
+
+    // Next value is a map.
+    (@object $object:ident ($($key:tt)+) (: {$($map:tt)*} $($rest:tt)*) $copy:tt) => {
+        value_internal!(@object $object [$($key)+] (value_internal!({$($map)*})) $($rest)*);
+    };
+
+    // Next value is an expression followed by comma.
+    (@object $object:ident ($($key:tt)+) (: $value:expr , $($rest:tt)*) $copy:tt) => {
+        value_internal!(@object $object [$($key)+] (value_internal!($value)) , $($rest)*);
+    };
+
+    // Last value is an expression with no trailing comma.
+    (@object $object:ident ($($key:tt)+) (: $value:expr) $copy:tt) => {
+        value_internal!(@object $object [$($key)+] (value_internal!($value)));
+    };
+
+    // Missing value for last entry. Trigger a reasonable error message.
+    (@object $object:ident ($($key:tt)+) (:) $copy:tt) => {
+        // "unexpected end of macro invocation"
+        value_internal!();
+    };
+
+    // Missing colon and value for last entry. Trigger a reasonable error
+    // message.
+    (@object $object:ident ($($key:tt)+) () $copy:tt) => {
+        // "unexpected end of macro invocation"
+        value_internal!();
+    };
+
+    // Misplaced colon. Trigger a reasonable error message.
+    (@object $object:ident () (: $($rest:tt)*) ($colon:tt $($copy:tt)*)) => {
+        // Takes no arguments so "no rules expected the token `:`".
+        value_unexpected!($colon);
+    };
+
+    // Found a comma inside a key. Trigger a reasonable error message.
+    (@object $object:ident ($($key:tt)*) (, $($rest:tt)*) ($comma:tt $($copy:tt)*)) => {
+        // Takes no arguments so "no rules expected the token `,`".
+        value_unexpected!($comma);
+    };
+
+    // Key is fully parenthesized. This avoids clippy double_parens false
+    // positives because the parenthesization may be necessary here.
+    (@object $object:ident () (($key:expr) : $($rest:tt)*) $copy:tt) => {
+        value_internal!(@object $object ($key) (: $($rest)*) (: $($rest)*));
+    };
+
+    // Munch a token into the current key.
+    (@object $object:ident ($($key:tt)*) ($tt:tt $($rest:tt)*) $copy:tt) => {
+        value_internal!(@object $object ($($key)* $tt) ($($rest)*) ($($rest)*));
+    };
+
+    //////////////////////////////////////////////////////////////////////////
+    // The main implementation.
+    //
+    // Must be invoked as: value_internal!($($value)+)
+    //////////////////////////////////////////////////////////////////////////
+
+    (nil) => {
+        ::liquid_value::Value::Nil
+    };
+
+    (true) => {
+        ::liquid_value::Value::scalar(true)
+    };
+
+    (false) => {
+        ::liquid_value::Value::scalar(false)
+    };
+
+    ([]) => {
+        ::liquid_value::Value::Array(value_internal_vec![])
+    };
+
+    ([ $($tt:tt)+ ]) => {
+        ::liquid_value::Value::Array(value_internal!(@array [] $($tt)+))
+    };
+
+    ({}) => {
+        ::liquid_value::Value::Object(Default::default())
+    };
+
+    ({ $($tt:tt)+ }) => {
+        ::liquid_value::Value::Object({
+            let mut object = ::liquid_value::Object::new();
+            value_internal!(@object object () ($($tt)+) ($($tt)+));
+            object
+        })
+    };
+
+    ($other:ident) => {
+        $other
+    };
+
+    // Any Serialize type: numbers, strings, struct literals, variables etc.
+    // Must be below every other rule.
+    ($other:expr) => {
+        ::liquid_value::to_value($other).unwrap()
+    };
+}
+
+#[macro_export]
+#[doc(hidden)]
+macro_rules! value_internal_vec {
+    ($($content:tt)*) => {
+        vec![$($content)*]
+    };
+}

tests/conformance.rs

@@ -3,6 +3,9 @@ extern crate liquid;
 extern crate regex;
 extern crate serde_yaml;
 
+#[macro_use]
+extern crate liquid_value;
+
 #[macro_use]
 mod test_helper;
 mod conformance_ruby;