feat: support keyword arguments with no definition on custom filters

crates/core/src/parser/filter.rs

@@ -24,6 +24,7 @@ pub struct ParameterReflection {
 pub trait FilterParametersReflection {
     fn positional_parameters() -> &'static [ParameterReflection];
     fn keyword_parameters() -> &'static [ParameterReflection];
+    fn keyword_group_parameters() -> &'static [ParameterReflection];
 }
 
 /// A trait that holds the information of a filter about itself, such as
@@ -42,6 +43,7 @@ pub trait FilterReflection {
 
     fn positional_parameters(&self) -> &'static [ParameterReflection];
     fn keyword_parameters(&self) -> &'static [ParameterReflection];
+    fn keyword_group_parameters(&self) -> &'static [ParameterReflection];
 }
 
 /// A trait that declares and holds the parameters of a filter.

crates/core/src/runtime/expression.rs

@@ -1,6 +1,7 @@
 use std::fmt;
 
 use crate::error::Result;
+use crate::model::Object;
 use crate::model::Scalar;
 use crate::model::Value;
 use crate::model::ValueCow;
@@ -9,26 +10,39 @@ use crate::model::ValueView;
 use super::variable::Variable;
 use super::Runtime;
 
+use std::collections::HashMap;
+
 /// An un-evaluated `Value`.
 #[derive(Debug, Clone, PartialEq)]
 pub enum Expression {
     /// Un-evaluated.
     Variable(Variable),
     /// Evaluated.
     Literal(Value),
+    /// Used for evaluating object literals,
+    ObjectLiteral(ObjectLiteral),
 }
 
+type ObjectLiteral = HashMap<String, Expression>;
+
 impl Expression {
     /// Create an expression from a scalar literal.
     pub fn with_literal<S: Into<Scalar>>(literal: S) -> Self {
         Expression::Literal(Value::scalar(literal))
     }
 
+    /// Creates an expression from an object literal (used when parsing filter
+    /// arguments)
+    pub fn with_object_literal(object_literal_expr: ObjectLiteral) -> Self {
+        Expression::ObjectLiteral(object_literal_expr)
+    }
+
     /// Convert into a literal if possible.
     pub fn into_literal(self) -> Option<Value> {
         match self {
             Expression::Literal(x) => Some(x),
             Expression::Variable(_) => None,
+            Expression::ObjectLiteral(_) => None,
         }
     }
 
@@ -37,6 +51,7 @@ impl Expression {
         match self {
             Expression::Literal(_) => None,
             Expression::Variable(x) => Some(x),
+            Expression::ObjectLiteral(_) => None,
         }
     }
 
@@ -48,6 +63,16 @@ impl Expression {
                 let path = x.try_evaluate(runtime)?;
                 runtime.try_get(&path)
             }
+            Expression::ObjectLiteral(ref obj_lit) => {
+                let obj = obj_lit
+                    .iter()
+                    .map(|(key, expr)| match expr.try_evaluate(runtime) {
+                        Some(result) => (key.into(), result.to_value()),
+                        None => (key.into(), Value::Nil),
+                    })
+                    .collect::<Object>();
+                Some(ValueCow::Owned(obj.to_value()))
+            }
         }
     }
 
@@ -57,8 +82,14 @@ impl Expression {
             Expression::Literal(ref x) => ValueCow::Borrowed(x),
             Expression::Variable(ref x) => {
                 let path = x.evaluate(runtime)?;
+
                 runtime.get(&path)?
             }
+            Expression::ObjectLiteral(obj_lit) => obj_lit
+                .iter()
+                .map(|(key, expr)| (key.into(), expr.evaluate(runtime).unwrap().to_value()))
+                .collect::<Object>()
+                .into(),
         };
         Ok(val)
     }
@@ -69,6 +100,7 @@ impl fmt::Display for Expression {
         match self {
             Expression::Literal(ref x) => write!(f, "{}", x.source()),
             Expression::Variable(ref x) => write!(f, "{}", x),
+            Expression::ObjectLiteral(ref x) => write!(f, "{:?}", x),
         }
     }
 }

crates/derive/src/filter_parameters.rs

@@ -83,6 +83,19 @@ impl<'a> FilterParameters<'a> {
             ));
         }
 
+        if fields.more_than_one_keyword_group_parameter() {
+            let grouped_keyword_fields = fields
+                .parameters
+                .iter()
+                .filter(|parameter| parameter.is_keyword_group())
+                .collect::<Vec<_>>();
+
+            return Err(Error::new_spanned(
+                grouped_keyword_fields.first(),
+                "Found more than one keyword_group parameter, this is not allowed.",
+            ));
+        }
+
         let name = ident;
         let evaluated_name = Self::parse_attrs(attrs)?
             .unwrap_or_else(|| Ident::new(&format!("Evaluated{}", name), Span::call_site()));
@@ -115,6 +128,16 @@ impl<'a> FilterParametersFields<'a> {
             .find(|parameter| !parameter.is_optional())
     }
 
+    /// Predicate that indicates the presence of more than one keyword group
+    /// argument
+    fn more_than_one_keyword_group_parameter(&self) -> bool {
+        self.parameters
+            .iter()
+            .filter(|parameter| parameter.is_keyword_group())
+            .count()
+            > 1
+    }
+
     /// Tries to create a new `FilterParametersFields` from the given `Fields`
     fn from_fields(fields: &'a Fields) -> Result<Self> {
         match fields {
@@ -256,6 +279,11 @@ impl<'a> FilterParameter<'a> {
         self.meta.mode == FilterParameterMode::Keyword
     }
 
+    /// Returns whether this is a keyword list field.
+    fn is_keyword_group(&self) -> bool {
+        self.meta.mode == FilterParameterMode::KeywordGroup
+    }
+
     /// Returns the name of this parameter in liquid.
     ///
     /// That is, by default, the name of the field as a string. However,
@@ -279,13 +307,15 @@ impl<'a> ToTokens for FilterParameter<'a> {
 enum FilterParameterMode {
     Keyword,
     Positional,
+    KeywordGroup,
 }
 
 impl FromStr for FilterParameterMode {
     type Err = String;
     fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
         match s {
             "keyword" => Ok(FilterParameterMode::Keyword),
+            "keyword_group" => Ok(FilterParameterMode::KeywordGroup),
             "positional" => Ok(FilterParameterMode::Positional),
             s => Err(format!(
                 "Expected either \"keyword\" or \"positional\". Found \"{}\".",
@@ -424,6 +454,15 @@ fn generate_construct_positional_field(
     }
 }
 
+/// Generates the statement that assigns the keyword list argument.
+fn generate_construct_keyword_group_field(field: &FilterParameter<'_>) -> TokenStream {
+    let name = &field.name;
+
+    quote! {
+        let #name = Expression::with_object_literal(keyword_as_map);
+    }
+}
+
 /// Generates the statement that evaluates the `Expression`
 fn generate_evaluate_field(field: &FilterParameter<'_>) -> TokenStream {
     let name = &field.name;
@@ -582,6 +621,13 @@ fn generate_impl_filter_parameters(filter_parameters: &FilterParameters<'_>) ->
         .iter()
         .filter(|parameter| parameter.is_keyword());
 
+    let keyword_group_fields = fields
+        .parameters
+        .iter()
+        .filter(|parameter| parameter.is_keyword_group());
+
+    let group_keyword_param_exists = keyword_group_fields.peekable().peek().is_some();
+
     let match_keyword_parameters_arms = fields
         .parameters
         .iter()
@@ -597,6 +643,55 @@ fn generate_impl_filter_parameters(filter_parameters: &FilterParameters<'_>) ->
             quote!{ let #field = #field.ok_or_else(|| ::liquid_core::error::Error::with_msg(concat!("Expected named argument `", #liquid_name, "`")))?; }
         });
 
+    let keyword_group_fields_handling_blocks = fields
+        .parameters
+        .iter()
+        .filter(|parameter| parameter.is_keyword_group())
+        .map(generate_construct_keyword_group_field)
+        .collect::<Vec<_>>();
+
+    let keyword_not_found_in_params_block = if group_keyword_param_exists {
+        // If there is a parameter that indicates all keywords should be grouped
+        // in an object, we generate an empty matching arm to prevent an error from
+        // being returned when a parsed keyword argument is not defines as a param.
+        quote! {
+            {}
+        }
+    } else {
+        // If there is no parameter that indicates all keywords should be grouped,
+        // an error is returned when a keyword argument is found but has not being
+        // declared.
+        quote! {
+            {
+                return ::std::result::Result::Err(::liquid_core::error::Error::with_msg(format!("Unexpected named argument `{}`", keyword)))
+            }
+        }
+    };
+
+    let assign_grouped_keyword_block = if group_keyword_param_exists {
+        keyword_group_fields_handling_blocks
+            .first()
+            .unwrap()
+            .clone()
+    } else {
+        quote! {}
+    };
+
+    let keywords_handling_block = quote! {
+        let mut keyword_as_map: std::collections::HashMap<String, liquid_core::runtime::Expression> = std::collections::HashMap::new();
+        #(let mut #keyword_fields = ::std::option::Option::None;)*
+        #[allow(clippy::never_loop)] // This is not obfuscating the code because it's generated by a macro
+        while let ::std::option::Option::Some(arg) = args.keyword.next() {
+            keyword_as_map.insert(arg.0.into(), arg.1.clone());
+            match arg.0 {
+                #(#match_keyword_parameters_arms)*
+                keyword => #keyword_not_found_in_params_block
+            }
+        }
+        #assign_grouped_keyword_block
+        #(#unwrap_required_keyword_fields)*
+    };
+
     quote! {
         impl<'a> ::liquid_core::parser::FilterParameters<'a> for #name {
             type EvaluatedFilterParameters = #evaluated_name<'a>;
@@ -606,18 +701,10 @@ fn generate_impl_filter_parameters(filter_parameters: &FilterParameters<'_>) ->
                 if let ::std::option::Option::Some(arg) = args.positional.next() {
                     return ::std::result::Result::Err(#too_many_args);
                 }
-
-                #(let mut #keyword_fields = ::std::option::Option::None;)*
-                #[allow(clippy::never_loop)] // This is not obfuscating the code because it's generated by a macro
-                while let ::std::option::Option::Some(arg) = args.keyword.next() {
-                    match arg.0 {
-                        #(#match_keyword_parameters_arms)*
-                        keyword => return ::std::result::Result::Err(::liquid_core::error::Error::with_msg(format!("Unexpected named argument `{}`", keyword))),
-                    }
-                }
-                #(#unwrap_required_keyword_fields)*
+                #keywords_handling_block
 
                 Ok( #name { #comma_separated_field_names } )
+
             }
 
             fn evaluate(&'a self, runtime: &'a dyn ::liquid_core::runtime::Runtime) -> ::liquid_core::error::Result<Self::EvaluatedFilterParameters> {
@@ -692,6 +779,12 @@ fn generate_impl_reflection(filter_parameters: &FilterParameters<'_>) -> TokenSt
         .filter(|parameter| parameter.is_keyword())
         .map(generate_parameter_reflection);
 
+    let kwg_params_reflection = fields
+        .parameters
+        .iter()
+        .filter(|parameter| parameter.is_keyword_group())
+        .map(generate_parameter_reflection);
+
     let pos_params_reflection = fields
         .parameters
         .iter()
@@ -707,6 +800,10 @@ fn generate_impl_reflection(filter_parameters: &FilterParameters<'_>) -> TokenSt
             fn keyword_parameters() -> &'static [::liquid_core::parser::ParameterReflection] {
                 &[ #(#kw_params_reflection)* ]
             }
+
+            fn keyword_group_parameters() -> &'static [::liquid_core::parser::ParameterReflection] {
+                &[ #(#kwg_params_reflection)* ]
+            }
         }
     }
 }

crates/derive/src/parse_filter/filter_reflection.rs

@@ -15,15 +15,18 @@ fn generate_reflection(filter_parser: &ParseFilter<'_>) -> Result<TokenStream> {
     let impl_filter_reflection =
         filter_parser.generate_impl(quote! { ::liquid_core::parser::FilterReflection });
 
-    let (positional_parameters, keyword_parameters) = if let Some(parameters_struct_name) =
+    let (positional_parameters, keyword_parameters, keyword_group_parameters) = if let Some(
+        parameters_struct_name,
+    ) =
         parameters_struct_name
     {
         (
             quote_spanned! {parameters_struct_name.span()=> <#parameters_struct_name as ::liquid_core::parser::FilterParametersReflection>::positional_parameters() },
             quote_spanned! {parameters_struct_name.span()=> <#parameters_struct_name as ::liquid_core::parser::FilterParametersReflection>::keyword_parameters() },
+            quote_spanned! {parameters_struct_name.span()=> <#parameters_struct_name as ::liquid_core::parser::FilterParametersReflection>::keyword_group_parameters() },
         )
     } else {
-        (quote! { &[] }, quote! { &[] })
+        (quote! { &[] }, quote! { &[] }, quote! { &[] })
     };
 
     Ok(quote! {
@@ -42,6 +45,10 @@ fn generate_reflection(filter_parser: &ParseFilter<'_>) -> Result<TokenStream> {
             fn keyword_parameters(&self) -> &'static [::liquid_core::parser::ParameterReflection] {
                 #keyword_parameters
             }
+
+            fn keyword_group_parameters(&self) -> &'static [::liquid_core::parser::ParameterReflection] {
+                #keyword_group_parameters
+            }
         }
     })
 }